Principles, concepts, and practices in prosthodontics—1989

SECTION

EDITOR

Principles, Academy PREFACE

concepts,

of Denture

and practices

in prosthodontics-1989

Prosthetics

TO THE SEVENTH

EDITION

This edition is the latest. of a continuing effort by the Academy of Denture Prosthetics to update the principles, concepts, and practices in prosthodontics. The seventh edition is a major revision with input from 11 organizations in contrast to three for the sixth edition. Suggestions for revision of existing statements and for new statements were received from the Academy of Denture Prosthetics, the American Academy of Crown and Bridge Prosthodontics, the American Academy of Esthetic Dentistry, American Academy of Implant Dentistry, American Academy of Maxillofacial Prosthetics, American Academy of Periodontology, the American College of Prosthodontists, the Midwest Academy of Prosthodontics, Northeastern Gnathological Society, the Northeastern Prosthodontic Society, and the Pacific Coast Society of Prosthodontists. Some organizations, such as the Academy of Denture Prosthetics, sought input from each member; others worked by committee. All suggestions were edited by the Committee of the Academy of Denture Prosthetics before submission to the participating organizations for revision and refinement. Finally, these suggestions were again edited and submitted to the membership of the Academy of Denture Prosthetics for approval. A minimum of 85% affirmative votes by voting fellows was required for publication of the statements. The Academy of Denture Prosthetics is indebted to all of the participating organizations. In particular, the suggestion for the new format was developed by the American College of Prosthodontists. In addition, the section on Legal Considerations was developed by Dr. Burton R. Pollack, who is an attorney and dentist, from the School of Dental Medicine, State University of New York, Stony Brook, N. Y. Support for the committee activities came from the Editorial Council of the Journal of Prosthetic Dentistry, the Federation of Prosthodontic Organizations, and the Education and Research Foundation of Prosthodontics. Each contributing organization funded its own committee activities. The purposes of the Principles, Concepts, and Practices in Prosthodontics-1989 are:

The first study was prepared in 1957 under the leadership of Drs. Luzerne G. Jordan, Frank M. Lott, and Russell W. Tenth.’ ‘The five successive publications were under the auspices of fellows of the Academy: Drs. George Hughes, 0. M. Dresen, Victor H. Sears, Leroy E. Kurth, S. Howard Payne, Chester K. Perry, Richard Kingery, Victor L. Steffel, Arthur E. Aull, 0. C. Applegate, Davis Henderson, Henry E. Ebel, I. Kehneth Adisman, Charles Bolender, and Jack Preston.2-6 Members of the Principles, Concepts, and Practices Committee for the seventh edition were Dr. Dale E. Smith, Chairman, Dr. Arthur 0. Rahn, and Dr. Ned B. Van Roekel. Drs. Louis J. Boucher, Francis V. Panno, and George E. Smutko were consultants to the committee. RESPECTFULLY

SUBMII-TED

BY:

Dr. Dale E. Smith, Chairman PRINCIPLES,

CONCEPTS, AND PRACTICES COMMITTEE:

Louis J. Boucher, Francis V. Panno, Arthur 0. Rahn, George E. Smutko, Ned B. Van Roekel, Dale E. Smith

PRINCIPLES, PRACTICES

CONCEPTS, AND IN PROSTHODONTICS-1989

Guide and index to PCP statements Definitions Gathering diagnostic information Diagnosis and treatment planning Prognosis Prerestorative treatment Treatment of oral structures Reevaluation and refinement of treatment plan Prosthetic treatment I. Basic to most areas of prosthodontics II. Fixed partial dentures III. Removable partial dentures IV. Maxillofacial prosthetics V. Complete dentures VI. Implant restorations Materials and devices I. Articulators Interim rest.orations Auxiliary personnel and work authorization Legal considerations

88 89 89 90 90 90 91 91 91 94 96 loo 102 105 106 106 107 107 107

DEFINITIONS’ 1. To provide for the practicing prosthodontist and generaldentist a reference of principles, concepts, and practices that are currently accepted by leading prosthodontists 2. To provide a current standard of acceptable practice standards in the absence of scientific research to prove all principles, concepts, and practices in prosthetic dentistry 3. To assist predoctoral and postdoctoral students of prosthodontics, particularly the graduate student, in assessing the value of various ideas that are presented during their educational experience 88

1. Prosthodontics is the branch of dentistry pertaining to the restoration and maintenance of oral function, comfort, appearance, and health of the patient by the restoration of natural teeth and/or the replacement of missing teeth and contiguous oral and maxillofacial tissuel3 with artificial substitutes. 2. Fixed prosthodontics is the branch of prosthodontics concerned with the replacement and/or restoration of teeth by artificial substitutes that are not removable from the mouth. 3. Removable prosthodontics is the branch of prosthodontics concerned with the replacement of teeth and contiguous structures JANUARY

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for edentulous or partially edentulous patients by artificial substitutes that are removable from the mouth. 4. Maxillofacial prosthetics is the branch of prosthcdontics concerned with the restoration and/or replacement of stomatognathic and associated facial structures by artificial substitutes that may or may not be removable. 5. Implant prosthodontics is the phase of dentistry concerning the restorative phase following implant placement.

GATHERING DIAGNOSTIC INFORMATION 1. At the first appointment, the patient should be encouraged to describe previous medical and dental experiences. To interpret the patient’s concerns, the dentist must be attentive and record the patient’s concerns and expectations. 2. A diagnosis may require information from one or more of the following sources: medical and dental histories, a clinical examination, radiographic surveys, diagnostic casts, consultations with other health practitioners, and tests that may include pretreatmentprocedures such as a diagnostic prosthesis, trial prosthesis, and surgery. 3. A standardized examination form for recording data may be used during the examination. The oral cavity, visible pharynx, paraoral structures, and associated lymph nodes should be examined. Patients with special needs may require additional diagnostic procedures such as speech analysis, psychosocial assessment, occlusal analysis, diagnostic sounding procedures, sialography, photographs, and other testing mechanisms. 4. A list of questions about prior dental experience may guide the patient to provide information not otherwise elicited in an openended discussion. 5. The dentist should consider the patient a potential carrier of contagious disease and follow current guidelines of the American Dental Association (ADA) and the U.S. Centers for Disease Control during patient care. 6. For patients with orofacial defecta, a psychosocial evaluation may be a valuable aid for diagnosis and treatment plan development. 7. All patients with natural teeth should receive a thorough, systematic periodontal examination including a clinical and radiographic examination, pocket depth probing, and an evaluation of periodontal status.

DIAGNOSIS PLANNING

AND TREATMENT

1. Diagnosis is the determination of the nature of a disease. 2. In-depth knowledge of anatomy, embryology, histology, physiology, microbiology, pathology, psychology, biochemistry, pharmacology, and the physiology of oral function are factors that improve diagnostic capabilities. 3. The dentist should identify and record any active disease process and any defects created by disease. When indicated, the dentist should refer the patient to appropriate professionals for further diagnosis or treatment. 4. Maxillofacial defects may be congenital, acquired, or developmental. 5. Structures that provide valuable support, stability, and retenr tion for a maxillofacial prosthesis should be preserved. 6. Normal growth patterns should be understood so that deviations can be recognized and evaluated. 7. Mechanisms of the healing process of the oral and perioral hard and soft tissues should be understood. 8. Inflammation may cause changes in the appearance and function of the oral mucosa. 9. Assessment of the following information is essential to the periodontal aspects of the examination: (a) Gross periodontal pathosis including evaluation of topography of the gingiva and related structures (b) The existence and degree of gingival inflammation (c) Periodontal pocket depth to determine the attachment THE JOURNAL

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level and to provide information on the health of the subgingival area (d) Presence and distribution of bacterial plaque and calculus (e) Degree of tooth mobility (f) An adequate number of diagnostic quality radiographs (g) Documentation of loss of attached gingiva 10. Exploratory surgical procedures should be referred to the appropriate surgeon. 11. Drug effects and interactions must be understood by both patient and dentist. 12. The oral mucosa is altered under a removable denture that has been worn. 13. Bruxism may produce destructive changes in the supporting tissues of removable dentures. 14. Because a favorable response to loading by a prosthesis has been observed in both dense and porotic bone, bone density as seen radiographically does not always indicate a response to additional loading. 15. Bone resorption may be caused by many factors. 16. Aging causes changes in body tissues, organs, and functions, which may affect patient response to a prosthesis. 17. Dimensional loss of the bony foundation supporting dentures may lead to loss of the vertical dimension of occlusion. 18. The determination of the vertical dimension of occlusion is generally a matter of judgment. Commonly used methods and guidelines include the following: (a) A measurement of 3 mm less than physiologic rest dimension (b) An evaluation of the closest speaking space (c) Proprioception or choice by patient (d) Swallowing on soft wax cones (e) Relative parallelism of ridges (f) General appearance of the midface profile 19. The vertical dimension of rest is a postural position that is subject to change. 20. A record of the maxillomandibular relationship when the mandible is in its terminal hinge position is considered a necessary component of a comprehensive diagnosis. 21. Altering the vertical dimension of occlusion requires critical judgment. When an existing vertical dimension is to be altered, a trial period at the new position may be used to ascertain that the new position is physiologically acceptable. 22. In maximum intercuspation, all posterior teeth should contact simultaneously. Deflective occlusaI contacts may cause altered mandibular positions. 23. The occlusion of any patient that was established by prosthodontic procedures should be periodically reevaluated. 24. Correctly mounted diagnostic casts usually are necessary for diagnosis and treatment planning. 25. The treatment planning, mouth preparation, and design of removable partial dentures are professional responsibilities to be accomplished by the dentist before the master casts are made and given to a dental technician or dental laboratory for fabrication of a framework. 26. The dental surveyor assists in contour analysis of hard and soft tissues of the dental arch. 27. Criteria for selection of removable partial denture abutment teeth include the following: (a) Crown-root ratio of the teeth (b) Number of roots (c) Form and curvature of roots (d) Alveolar support (amount of bone) (e) Tooth inclination (position in the arch) (f) Mobility (periodontal health) (g) Stress evaluation (h) Previous response to stress (i) Restorability of the tooth (i) Occlusal relationships 89

ACADEMY

(k) Crown contour (1) Plaque control (m) Impending functional demands 28. Treatment planning procedures for patients who are to be treated with biocompatible dental implants should include diagnostic casts articulated with a trial arrangement of artificial teeth on trial denture bases. A presurgical prosthodontic diagnosis is essential for site location and proper angle of implant placement. 29. Systemic conditions affecting the etiology, pathogenesis, and treatment of periodontal disease have the potential for altering the state of periodontal health and should be identified for adequate treatment planning. 30. When possible, optimal periodontal health should be established before completing the definitive restorative and prosthetic treatment. After a thorough examination of the patient, a periodontal diagnosis is useful in establishing a logical plan of treatment. Referral to a periodontist may be helpful. 31. The decision to treat a patient with fixed or removable partial dentures is largely dependent on the number, location, condition, and supporting structures of the abutment teeth and the size and contour of the edentulous spaces.

PROGNOSIS 1. A prognosis is an opinion or judgment given in advance of treatment concerning the prospects for success of therapy and usefulness of the restoration or treatment. 2. The prognosis for a restoration and the natural dentition is positively influenced by oral hygiene and plaque control. 3. The oral cavity should be healthy before placement of definitive restorations. 4. Proper selection of materials and the skillful execution of treatment enhances treatment success. 5. Tissue tolerance and adaptability of the patient affects the prognosis of the tissue-borne prosthesis. 6. Compatibility of clinician and patient and the manner of the clinician during treatment influence treatment success. 7. General health and nutrition may influence the patient’s ability to use any prosthesis. 8. Psychological factors may pose insurmountable obstacles to denture wearing. 9. Success in wearing a prosthesis is more likely to be compromised as physical defects become larger.

PRERESTORATIVE

TREATMENT

and local 1. Many signs of systemic disorders, such as diabetes, avitaminosis, or hormonal imbalances, may manifest themselves by altering the oral mucosa. This may indicate the need for supportive therapy before prosthodontic treatment is initiated. 2. Prosthodontic patients with unfavorable tissue response and senescent individuals, in particular, may benefit from dietary counseling. 3. The success of a removable prosthesis is enhanced by proper preparation of the remaining oral structures. 4. It is important to recognize the importance of conditioning the oral mucosa and orofacial musculature for patients requiring removable prostheses. 5. The emotional status of the patient may influence the success of prosthodontic treatment. 6. Gagging stimulated by dentures may have a psychologic component. A. Systemic

B. Patient

education

1. Informed patients are usually more receptive and cooperative than uninformed patients. 2. A program of education, instruction, and discussion about dental care should continue during the entire treatment period, including recall visits. 90

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3. Both oral and printed information help patients understand and accept treatment goals. 4. Successful dental treatment is enhanced if the patient practices thorough oral hygiene. It is the dentist’s responsibility to teach such procedures and the patient’s responsibility to perform them. 5. It is desirable to speak of “prosthodontic treatment” instead of focusing attention solely on the fabrication of the denture. 6. Patients should be educated as to both the value and the shortcomings of complete dentures. 7. Patients should be informed that residual ridge resorption occurs in varying, unpredictable degrees and that this will affect the adaptation and function of their dentures. 8. Treatment with dentures is individual and cannot be standardized. 9. Patients should be warned of the hazards of “do-it-yourself’ denture-relining kits and their use should be discouraged. 10. A prospective patient should be informed that neuromuscular adaptation contributes to success in wearing a removable prosthesis. 11. For patients who have had radiation therapy to the head or neck, plaque control instructions and frequent periodic prophylaxis should be part of care. A thorough oral examination is essential. Fluorides should be self-administered daily. 12. Patient education and disease control should include the following: (a) Teaching about diagnosis, etiology, and consequences of disease (b) Training in personal plaque control and care of prosthetic restorations 13. Before completion of treatment, patients should be given the following information: (a) The prognosis, both periodontally and prosthetically, is influenced by diet, systemic factors, and their ability to maintain a plaque-free environment. (b) Even with proper professional and personal care, periodontal disease may recur. (c) When teeth that are retained after periodontal therapy have a doubtful prognosis, the longevity of the restoration could be compromised. When possible, such teeth should be extracted before or during periodontal therapy.

TREATMENT

OF ORAL STRUCTURES

1. Each treatment procedure should be directed toward preservation of the oral tissues and normal functions to the extent possible. 2. Pathosis of hard and soft oral tissues should be corrected when possible before missing structures are replaced with a prosthesis. Treatment procedures (not in order of priority) may include the following: (a) Periodontal therapy (b) Oral surgery procedures, including placement of implants (c) Occlusal corrections (d) Operative dentistry (e) Endodontics (f) Orthodontics (g) Crowns and/or fixed partial dentures to restore satisfactory functional relationships 3. Traumatic occlusion should be appropriately treated. Treatment may include interocclusal splints, occlusal restorations, selective occlusal adjustments, surgery, orthodontics, muscle exercise, or other corrective methods. 4. Before an impression is made for a removable prosthesis, a program of tissue conditioning should be considered when soft tissue is inflamed, irritated, or distorted. 5. If the examination shows the presence of periodontal disease, a periodontal consultation should usually follow. 6. Periodontal pathosis should be treated and periodontal health stabilized before the final preparation of abutment teeth. JANUARY

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7. When a patient is referred to a periodontist, the prosthodontic treatment plan under consideration should accompany the written referral request. The periodontist should be advised of the criteria remaining teeth must meet if they are to be retained as part of a prosthodontic treatment plan. 8. Plans for periodontal treatment may include the following: (a) Instruction in daily oral hygiene (b) Removal of supragingival and subgingival calculus (c) Smoothing of root surface irregularities where appropriate (d) Posttreatment evaluation of periodontal health and reinforcement of daily oral hygiene and plaque control care when needed (e) Recontouring supporting bone (f) Reorganizing or augmentation of unattached gingiva (g) Extraction (before periodontal therapy) of teeth that lack proper supporting structures, crown form, or position and would compromise the prognosis of a prosthesis 9. Treatment options when the periodontal condition is more severely involved may include the following: (a) Pocket reduction through the use of soft- and hard-tissue surgical procedures (b) Grafting procedures to enhance lost periodontal tissues and to provide an adequate zone of attached gingiva, particularly around teeth to be prepared for a prosthodontic treatment (c) Occlusal therapy to reduce occlusal trauma (d) Minor tooth movement 10. Postoperative patient care is the joint responsibility of the periodontist and the prosthodontist, if the patient is treated by both specialists.

REEVALUATION AND REFINEMENT TREATMENT PLAN

OF

1. After prerestorative treatment is completed, the treatment plan should be reevaluated and modified as indicated by the patient response to the following: (a) Education (b) Efforts to eradicate or control disease (c) Exploratory and trial procedures 2. Upon completion of active periodontal therapy, supportive care, including regular reevaluations of the periodontal status, reinforcement of personal oral hygiene, and removal of any etiologic factors is critical to the long-range maintenance of periodontal patient health.

PROSTHETIC

TREATMENT

I. Basic to most areas of prosthodontics A. Design, fabrication,

and classification

1. The selection and final arrangement of artificial teeth are the responsibility of the dentist in consultation with the patient. 2. Artificial teeth should be arranged for minimal inhibition of the tongue and so that the shape of the palatal vault will not be substantially altered. 3. The external form of a prosthesis should be compatible with the function of the oral musculature and their overlying tissue. 4. Patient experience with an existing prosthesis should be evaluated carefully before extensive preprosthetic surgery is considered. 5. The relationship of the tuberosities relative to the retromolar pads is best visualized with diagnostic casts articulated in centric relation at an acceptable vertical dimension of occlusion. 6. There should be accommodation for the coronoid process during the normal functioning range of mandibular movement in the retrozygomatic area of the maxillary denture base. 7. To control lateral stress to an abutment tooth as much as possible, the retainer should be designed to direct forces along the long axis of the tooth. THE

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8. The prosthodontist should know and understand the physical and chemical properties of all of the materials used in the practice of prosthodontics. 9. Dimensional changes occur in resin materials during processing procedures. 10. Dimensional changes in dentures can occur from differences in coefficients of thermal expansion of gypsum products, resins, and metal flasks. Dentures should be processed with techniques that minimize these changes. 11. Four areas of concern in the fabrication of any new prosthesis are comfort, function, esthetics, and phonetics. 12. The design and fabrication of all restorations, both provisional and definitive, should be compatible with maintaining the health of the periodontium. Areas of concern include margin placement, marginal adaptation, contour of the restoration, and occlusal relationships. The prosthodontic design should consider crown-root ratio, length of the edentulous space, root configuration, size, and contour of the anterior edentulous ridge, occlusal-gingival dimension, size and configuration of the clinical crown, occlusal scheme present, and materials to be used. B. Tooth preparation

and soft tissue management

1. The mucosa in edentulous regions may assume an altered surface form and texture as a result of being covered by denture bases. 2. Surgery may be desirable to alter ridge contours, reduce,pendulous tissues, and reposition tissue attachments. 3. Surgery may be indicated to improve maxillomandibular ridge relationships. 4. When a maxillary tuberosity approximates the retromolar pad or is pendulous, it may be reduced to provide the desired interarch distance, a more stable denture base, or to permit proper orientation of the occlusal plane. 5. Irritated, inflamed, or distorted mucosa should be treated so that it is in a state of maximum health before final impressions are made. 6. Tissue conditioning is more effective when the occlusion is corrected, the proper vertical dimension of occlusion is restored, the denture borders are properly extended, and the conditioner is properly placed and changed as required. 7. Tissue conditioning materials placed on the tissue surface of a surgical prosthesis can help to compensate for tissue alterations resulting from surgery. 8. Before dentures are placed, areas on the tissue surface of the denture that transmit excessive pressure on the tissues should be identified and relieved. 9. Inflammatory papillary hyperplasia may require surgical removal before definitive treatment to prepare a maxillary arch to accept dentures. 10. Patients should be informed that meticulous plaque control is essential to the success of prosthodontic restorations and should be instructed in the proper maintenance of oral health. 11. When oral surgery procedures are indicated to reduce tuberosities, tori, or other hard or soft tissue interferences, the diagnostic cast or a duplicate of it may be recontoured to the desired shape and/or a clear plastic template constructed to aid the surgeon in achieving the desired residual ridge contour. 12. Augmentation and/or revision should be considered for a residual ridge presenting unfavorable gingival contours for pontic placement. C. Impressions

1. A correctly designed and contoured custom impression tray will facilitate making impressions for the fabrication of fixed or removable partial dentures, complete dentures, and implant prostheses when certain types of impression materials are used. 2. Impression trays for final impressions should remain dimensionally stable throughout the impression- and cast-making procedure.

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3. Preliminary impressions made with modeling plastic impression compound may he altered hy trimming and/or adding material so that they may be used as final impression trays. 4. Displacement or deformation of soft and pendulous tissues should not occur during final impression making. 5. The borders of the final impression should represent the extension and contours to be produced in the processed denture. 6. Maximum extension of denture bases within physiologic limits is helpful to distribute forces to the supporting structures, augment retention and stability, and minimize accumulation of food particles under the bases. 7. Displacement of soft tissues during the making of an impression may be partially controlled through the placement of relief in the tray, by escape holes in the tray, and/or control of the viscosity of the impression materials. 8. When plaster of paris, zinc oxide-eugenol paste, or similar materials are used for final impressions for the fabrication of complete or removable partial dentures, sufficient space between the impression tray and the mucosa should be present. 9. When gagging is a problem while impressions are being made, placing the patient in an upright or forward position and/or the judicious application of a topical or infiltration anesthetic agent to the posterior palatal area and the posterior part of the tongue can aid in managing the problem. 10. Manufacturer’s instructions for each impression material should be carefully followed for optimum results. 11. The making of impressions for diagnostic casts may provide useful knowledge about the patient, including unusual sensitivities of the mucosa structures, the tendency toward gagging, tolerance to oral procedures, and favorable and unfavorable tongue movements. D. Casts

1. All materials used in prosthcdontics should be carefully selected. The materials should meet ADA specifications where possible and should be used in accord with manufacturers’ instructions. 2. Impression materials, gypsum products, and other die materials should be mutually compatible to produce accurate dies and C&S.

3. Cast formation should be accomplished immediately after the impression-making procedure or within the time recommended by the manufacturer of each material. 4. The manufacturers’ recommendations regarding the powderto-water ratio should be followed when cast materials are mixed. 5. Impressions should not be inverted on the same mix of stone when casts are formed, that is, either a two-pour or a boxing technique should be used. 6. The cast produced from an impression should accurately record all of the details captured in the impression, including the border contours. 7. Ordinary plaster of paris is not a suitable material for the construction of master casts. 8. When it is mandatory that a cast made of gypsum materials be hydrated, the cast should be soaked in slurry water instead of tap water to avoid disintegration of the cast’s surface. 9. Diagnostic casts are helpful for diagnosis, treatment planning, patient education, and as a permanent record of the status of the dentition. 10. Accurately mounted diagnostic casts with and without the patient’s removable prostheses may be necessary as an adjunct to proper diagnosis. 11. Unaltered diagnostic casts may be an important part of the patient’s treatment record. 12. Suitable means should be used to prevent the record base and other materials from adhering to or distorting casts. 13. Diagnostic waxing, tooth arrangement, or other preliminary procedures on articulated casts are helpful in diagnosis, treatment planning, and fabrication of final restorations. 14. Mounting of any cast in an articulator should be accomplished 92

using procedures and materials that minimize dimensional changes between the mounted cast and the member of the articulator. 15. Vacuum mixing and correct water-to-powder ratios are essential in mixing the final cast materials. 16. Casts should be properly trimmed according to their intended use. 17. The accuracy of casts made from impressions may be checked with an occlusal index made in the mouth. E. Maxillomandibular

records and registratiorw

1. Temporomandibular joints are capable of three-dimensional movementa. 2. A record of the maxillomandibular relationship when the mandible is in centric relation is a necessary component of comprehensive diagnosis. 3. When posterior teeth are missing and mastication has occurred only on the anterior teeth, an eccentric functional relation of the mandible to the maxilla may have occurred and should be recognized before jaw relation records are made. 4. Unilateral loss of posterior teeth may alter the relationship of the condyle to the glenoid fossa. The proper conditioning or positioning of the condyles should be accomplished, where possible, through prosthodontic services. 5. As used in dentistry, the term vertical dimension refers to the length of the patient’s facial profile as it may be established by raising and lowering the mandible in relation to the maxillae (opening or closing the jaws). 6. The term rest vertical dimension refers to the length of the patient’s facial profile when the mandible is in its rest position in relation to the maxillae. 7. Mandibular rest position is a postural position and is subject to the same physiologic and pathologic factors as posture elsewhere in the body. Thus, it is subject to change and may not be constant throughout life. 8. The interocclusal distance, when added to the vertical dimension of occlusion, equals the rest vertical dimension. 9. Although the interocclusal distance is relatively stable, it can vary with time, but variations are usually small. 10. Patients can best assume mandibular rest position when sitting erect in a chair without a headrest or back support or when standing erect. 11. In the absence of occlusal interference or pathosis, the mandible normally tends to return to its physiologic rest position after most functional movement. 12. Opposing teeth or occlusion rims should not be in contact when the mandible is in its physiologic rest position. 13. Reference points placed on the face r!nay aid in registering vertical jaw relationships. 14. It can be difficult to properly assess the correct vertical dimension of occlusion before the arrangement of the teeth on the denture base. 15. The alteration of the vertical dimension of occlusion requires critical judgment. The use of interim diagnostic restorations at the altered vertical dimension may be indicated. 16. Tissue changes that occur when dentures are worn may cause a loss of the vertical dimension of occlusion. 17. When parts of the natural dentition are missing, some vertical dimension of occlusion may be lost. 18. Recording maxillomandibular relations is best accomplished when the patient is relaxed. 19. Centric relation serves as a reference for analysis of an existing occlusion and for the type of occlusion to be established during treatment. 20. Centric relation is individual to each patient. 21. On an articulator, centric relation at one vertical dimension of occlusion may not be the same as at another occlusal vertical dimension unless a transverse horizontal axis determination has been made. JANUARY

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22. A new centric relation record should be made if it becomes necessary to alter the originally established vertical dimension of occlusion unless a transverse horizontal axis determination has been made. 23. Because recording of maxillomandibular relations is best accomplished when the mandible is relaxed, patients should be trained to relax the muscles controlling the mandible before centric relation records are made. 24. Head position influences the recording of centric relation. 25. Centric relation records should be made with minimum closing pressure. 26. Centric relation records should be repeatable. 27. Eccentric jaw relation records are made to adjust the guiding elements of an articulator. 28. The recording of centric relation for a removable prosthesis requires rigid and accurately fitted bases that resist warpage during clinical use. 29. Properly adapted record bases should be stable on the casts and incorporate an accurate index on the occlusion rim into which they may be related for mounting casts on an articulator. 30. Record bases should not be adapted to severe undercuts on the casts; this might warp the bases or damage the casts when they are removed. 31. Shellac-type record bases are susceptible to deformation. 32. Thick record bases may interfere with the accurate recording of jaw relations. 33. Occlusion rims should be made of a material that is easily softened and molded to the desired form, is easily attached to the record base, becomes sufficiently rigid when cooled to serve as a temporary occlusal surface, and permits resoftening in selected areas. 34. The labial, buccal, and lingual contours of occlusion rims may influence the results when jaw relation records are made. This consideration is especially important when phonetic determinations are used. 35. The recording of jaw relations may be more accurately accomplished when the design of the occlusion rims conforms to the positions and dimensions originally occupied by the natural teeth and their investing tissues. 36. If an average-value facebow is used, interocclusal centric relation records should be kept to a minimum thickness. 37. Such factors as the nature and extent of prosthodontic therapy and the health of the stomatognathic system, instead of statistical averages, determine the need for recording condylar movement to set condylar guidance. 38. A remount procedure on a suitable articulator with new maxillomandibular records is an effective method of identifying occlusal discrepancies before placement of a prosthesis. F. Occlusion

1. Because occlusal relationships are not static, the neuromuscular reflexes may change in response to changes in the occlusal position. 2. The occlusion of all prosthodontically treated patients should receive scheduled reevaluation. 3. Opposing tooth contacts should be planned to allow free movement throughout the functional range of the mandible. 4. Artificial posterior teeth should be arranged to provide equalized contact in centric relation with no interference in eccentric excursion. 5. The factors of articulation directly under the control of the dentist during complete denture fabrication are: anterior guidance, plane of occlusion, cusp height, and compensating curve. 6. Occlusion and articulation of artificial teeth should be physiologically compatible with the remaining natural teeth and other parts of the masticatory system. 7. In centric occlusion, all posterior teeth should contact simultaneously. THE

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8. Orthodontic procedures may play an important role in the correction of some occlusal disharmonies. 9. The occlusion should be analyzed and necessary occlusal alterations accomplished before final impressions are made and a prosthesis is fabricated. 10. Attempts to create artificial occlusal surfaces in the partially edentulous patient should be preceded by the elimination of occlusal discrepancies in the natural teeth. 11. A thorough examination of the occlusion of the remaining natural teeth should include properly mounted diagnostic casts. 12. Contact of the teeth during speech may indicate insufficient interocclusal distance. 13. Physiologic stimulation of teeth and ridge structures is advisable. Excessive forces or dysfunction can be harmful and destructive. 14. Eccentric occlusions can be developed to meet the patient’s physical and neuromuscular requirements. 15. An acceptable vertical dimension of occlusion contributes to optimum function, acceptable interocclusal distance, comfort, satisfactory speech, and good appearance. 16. Extreme caution should be exercised when performing procedures that will change the vertical dimension of occlusion. If the existing vertical dimension of occlusion is to be altered, a trial period at the new position is recommended to ascertain that a physiologically acceptable position has been established. 17. Incisal guidance is important in establishing anterior tooth position and the occlusal patterns of posterior restorations. 18. The absence of harmony between the intercuspal position and centric relation may cause prosthodontic failure. 19. The occlusion of all new dentures should be refined after processing. 20. Abnormal swallowing closures do not necessarily terminate at centric relation. 21. Provision of food escapeways in artificial posterior teeth adds to chewing effectiveness. 22. Occlusal morphology and cuspal patterns should be developed to satisfy the patient’s needs instead of to fulfill a stereotyped concept of cuspal form. 23. The protrusive movement has two elements that should be considered in articulation: condylar inclination, which is established by the patient, and incisal guidance, which is determined by the dentist’s judgment and the patient’s esthetic demands and functional needs. and verification procedures 1. Mandibular artificial posterior teeth should be positioned neither more distal than the anterior border of the retromolsr pad nor on the distal incline of the residual ridge. 2. When only the anterior teeth in a partially edentulous arch remain, the artificial posterior teeth should be arranged on a record base and tried in the patient’s mouth to verify the jar relations, occlusion, and appearance. G. Try-in

H. Esthetic

considerations

1. Natural anterior teeth may become more uniform in color as their incisal edges become worn. They may not present the same incisal edge translucency found in most artificial teeth. 2. Natural anterior teeth often have a lower color value and acquire a smoother surface as the patient ages. 3. Facial templates or facial measurements may be helpful in arranging artificial teeth. 4. Photographs, diagnostic casts, and radiographs made before complete extractions are valuable guides to satisfactory esthetics. 5. Irregular or asymmetric arrangement of artificial anterior teeth may enhance the natural appearance of prosthetic restorations. 6. Compromises between esthetics and function should be assessed and discussed with the patient before treatment is started. 7. Preextraction records, which become part of the patient’s 93

ACADEMY

record before any remaining natural teeth are removed, may be helpful during future treatment. 8. A preextraction protile record of the face is best made while the teeth are in maximum contact. 9. The dentist is responsible for esthetics. His work authorization to the technician should give specific instructions regarding esthetic factors. 10. Tooth color selection should be communicated to the dental technician through appropriate terminology. 11. Dental treatment rooms and the dental laboratory need similar light conditions for optimum shade matching. 12. The esthetic features of the restorations should be observed in artificial and natural light. 13. Shade selection should be under conditions that simulate natural daylight. 14. Resin denture base materials should optimally reproduce the color and characteristics of the patient’s oral tissues that are being replaced. 15. The incisal length of maxillary anterior teeth should be determined esthetically and phonetically by arranging the teeth on the record base. 16. The natural appearance of replacement teeth may be enhanced if various tooth colors and molds are used in an artistic arrangement of the anterior teeth. 17. Reflective surface and texture are critical to attaining a shade match. 18. Modification of standard artificial teeth may improve the appearance of a removable prosthesis, especially for mature patients. 19. The dentist needs a working knowledge of the science of color to match the colors of natural teeth. 20. Esthetic requirements of a patient should be met with due consideration for the periodontal health of the tissues and proper function. Rigid esthetic requirements that conflict with functional requirements may preclude treatment. I. Initial placement of restorations (insertion) 1. Adequate time should be allowed for the appointment involving initial placement of restorations so that the patient fully comprehends the importance of his or her responsibilities in the success of the restorations. 2. The tissue surface of each denture base should be evaluated and corrected, if necessary, before occlusal evaluation and placement. 3. At the preliminary placement of the prosthesis, all areas should be checked with pressure indicator material, and all interfering regions should be assessed for selective relief. 4. Written instructions to the patient regarding home care and maintenance of the prostheses and oral tissues are positive reinforcements of verbal instructions and a future informational reference. 5. The patient should be recalled for necessary adjustments at an appropriate interval after the initial placement of a removable prosthesis. 6. Explanation of common sensations and effects of wearing a prosthesis should precede initial placement of the prosthesis. J. Care after placement 1. Prosthodontic treatment is a continuous service that does not end with the placement of the oral or facial prosthesis. 2. The patient should be impressed with the need for routine examinations to evaluate the occlusion and assessthe response of the oral environment to the prosthetic restoration. 3. Proper diet should be emphasized to all prosthodontic patients. 4. The patient’s name, date, articulator number, condylar settings, and other pertinent data should be indelibly recorded on articulated diagnostic casts, treatment casts, and dies, which should

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be retained by the dentist. The records are a valuable aid in further treatment and for medicolegal reasons. 5. Care after placement should include regular supportive (maintenance) periodontal care and care of the prosthetic restorations. K. Interim and immediate restorations 1. After surgery and appropriate healing, the original prosthesis may require revision or replacement. 2. Some temporomandibular joint symptoms may be alleviated by properly constructed interim restorations. 3. Placing tissue-conditioning materials on the tissue surface of a surgical prosthesis is an acceptable method of compensating for tissue changes after surgery. 4. A transitional removable partial denture may be considered as a temporary treatment modality before immediate complete dentures to help the patient adapt to wearing a prosthesis. 5. Immediate restorations generally are considered provisional, to be followed later by definitive treatment.

II. Fixed partial

dentures

A. Diagnostic procedures 1. For most fixed partial dentures, the patient’s diagnostic casts should be mounted in a semiadjustable or fully adjustable articulator capable of accepting eccentric excursive and centric relation records. 2. The maxillary cast should be mounted in the articulator with the aid of a facebow. 3. Pantographic tracings may provide additional diagnostic information concerning the patient’s jaw movements. 4. Casts mounted in an articulator should be evaluated: (a) To determine anteroposterior and lateral excursive interferences (b) To select the appropriate path of placement (c) To decide whether to alter the vertical dimension of occlusion to provide the desired plane of occlusion (d) To determine the types of dental restorations needed (e) To aid in pontic selection (f) To accomplish trial equilibration procedures 5. A diagnostic wax-up of proposed restorations is indicated in some situations: (a) To provide useful information relative to the intended esthetic result (b) To indicate the amount of tooth reduction required (c) To aid in fabrication of provisional restorations (d) To provide a visual aid during treatment-planning discussions with the patient (e) To plan occlusion 6. A second set of mounted casts may be used for trial tooth preparation. 7. A customized incisal guide table may be developed by using the mounted diagnostic casts. B. Tooth preparation 1. Preparation of a tooth should be planned and executed so that adequate retention and resistance form are developed. 2. The addition of boxes, grooves, or pinholes to a preparation may provide increased resistance to dislodgment of a cast metal restoration. 3. Sufficient tooth structure must be removed to preserve the integrity of the restoration, provide the desired esthetic result, and allow the restoration to be fabricated without being overcontoured. The amount of tooth reduction needed will vary depending on the restorative material being used. (a) Occlusal reduction for a cast metal restoration should be a minimum 1 to 1.5 mm for the lingual cusps of the maxillary teeth and buccal cusps of the mandibular teeth. (b) Preparation of the occlusal surfaces should replicate as

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nearly as possible the anatomy of the cusps and grooves to avoid over or under reduction of the tooth. (c) Adequate peripheral reduction, especially near the margins, increases the rigidity of the casting. (d) Boxes, grooves, ledges, and occlusal shoulders may be used to increase the rigidity of a casting. 4. Supragingival placement of the margins of cast restorations may be desirable if the requirements for retention and resistance form and esthetics are satisfied. (a) If subgingival margin placement is necessary, an adequate zone of attached gingiva should be present. (b) Whenever possible, the margins of a restoration should be accessible to the dentist for finishing and to the patient for cleaning. (c) The finish line should be placed on enamel if possible. In some situations, it may be necessary to locate the finish line on cementurn, dentin, amalgam, or gold. Placing the finish line on composite resin should be avoided. (d) There should be no occlusal margins in an area of occlusal function. (e) During tooth preparation, the formation of a well-defined finish line such as the knife-edge, chamfer, chamfer with a bevel, shoulder, and shoulder with a bevel is desirable. (f) The type of restorative material used and the location of the tooth being restored may dictate the choice of finish line. 5. Tooth preparation should be accomplished with minimal pulpal trauma. The use of an air and water coolant is recommended during tooth reduction with rotary instruments. 6. Endodonticahy treated teeth may require the use of a core buildup or a dowel and core to obtain the desired retention and resistance form. 7. Periodontal health should be established before or in concert with the restorative treatment. Preservation of the supporting structures should be a primary consideration in the design and fabrication of fixed partial dentures. Teeth should be prepared in relation to healthy tissue. The gingival terminus should not violate the epithelial attachment. C. Impression making 1. An impression material should be selected because its physical, chemical, and working properties are best suited for the clinical problem being treated. 2. Impression materials used should meet the specifications of the ADA Council on Dental Materials, Instruments, and Equipment. 3. The use of a full-arch custom tray may facilitate making impressions when elastomeric impression materials are used. 4. Gingival displacement may be accomplished by using mechanical, chemical, or electrosurgical methods. (a) Gingiva should be healthy and free of inflammation before final tooth preparation. (b) Care must be exercised to avoid violating the integrity of the epithelial attachment no matter what method of gingival retraction is employed. (c) Epinephrine-impregnated cords should not be used on patients with certain types of cardiovascular disease, hyperthyroidism, or a history of epinephrine hypersensitivity. (d) Electrosurgical gingival preparation should not be used on patients with cardiac pacemakers. 5. Careful management of the interface between tooth and periodontium is integral to the preservation of periodontal health. Ideally, an impression should not extend subgingivally; however, certain clinical situations may necessitate subgingival margin placement. Invasive techniques to displace gingival tissue should be minimally traumatic. D. Interocclusal records 1. The time lapse between securing an interocclusal

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record and its

use in mounting caste in an articulator should be consistent with minimizing inaccuracies inherent in the recording material being used. 2. A separate appointment for making interocclusal records after the working casts have been recovered from the impressions will permit verification of the records while the patient is present. 3. Numerous materials and techniques will enable accurate reproduction of interocclusal relationships. Personal preference and clinical circumstances will dictate which methods are used. 4. Interocclusal records trimmed so that only cusp-tip indentations remain facilitate accurate positioning of the caste in the record before their mounting in an articulator. 5. When limited numbers of teeth are being restored, the interocclusal registration may be made with the remaining unprepared teeth in contact. The recording medium should avoid increasing the vertical dimension of occlusion and thus possibly incorporating an inaccuracy into the mounting. 6. Interocclusal registration made with the teeth out of contact should be recorded bilaterally. The dentist should guide the patient to the desired centric relation or lateral excursive position. 7. An occlusal programmer or jig provides a vertical stop at the desired degree of vertical opening and assists in positioning the condyles in their appropriate positions. 8. Lateral excursive recordings may be made by guiding the patient in a lateral movement until the opposing arches are in a cusp tip to cusp tip relationship; that relationship is then captured with the recording medium. 9. At least two registrations should be used to verify the accuracy of the centric relation mounting of the mandibular cast in the articulator. 10. When a significant edentulous segment exists, an interocclusal record to relate the casts for a fixed partial denture should be made by using a stabilized record base fabricated on the master cast. 11. Making interocclusal registrations, positioning the casts in the registration, and mounting them in the articulator are the responsibility of the dentist. E. Provisional restorations 1. Provisional restorations should incorporate the same qualities as the final restoration, including marginal integrity, esthetics, form, and function, while maintaining the health of the abutment teeth and supporting structures. 2. Many acceptable materials are available for fabricating provisional restorations. The position of the tooth in the arch, the type of tooth preparation, the expected length of service, and whether it is a single unit or a fixed partial denture will influence the choice of material. F. Occlusal considerations 1. A cusp-marginal ridge occluaal relationship is found in most adult natural occlusions. This type of occlusal morphology may be used in the fabrication of either single or multiple cast restorations. 2. A cusp-fossa occlusal scheme is rarely found in natural teeth. It is often advocated when multiple adjacent and opposing teeth are being restored with cast restorations to direct the forces of occlusion in a more axial direction. 3. A group-function occlusion may distribute the occlusal load on the working side in lateral excursions. 4. The functionally generated path technique is an effective way of developing a group-function occlusion in cast restorations. 5. A mutually protected occlusion may be indicated when there are periodontally healthy anterior teeth, an Angle class I jaw relationship, and the posterior teeth are not in a reverse occlusion in which the maxillary and mandibular buccal cusps interfere with each other in a lateral excursive movement. 6. In a mutually protected occlusion, only the anterior teeth are in contact in any excursive position of the mandible. Maximum in-

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tercuspation is coincident with centric relation and the occlusal forces are directed along the long axis of the posterior teeth. The anterior teeth protect the posterior teeth in eccentric movements and the posterior teeth protect the anterior teeth in the intercuspal position. 7. Lateral excursive contacts on the balancing side are considered undesirable in either a group-function or mutually protected occlusion. 8. Care must be exercised in the fabrication of anterior restorations so that the vertical and horizontal overlap and the configuration of the lingual surfaces of tb.e maxillary restorations are in harmony with the patient’s functional movements. 9. When the vertical dimension of occlusion is to be increased or decreased, it is advisable to have a trial period of several weeks to several months during which the patient is allowed to function at the desired vertical dimension of occlusion before the definitive restorations are fabricated. and verification 1. After removal of the provisional restorations, the prepared teeth should be examined carefully to assure that they are free from temporary cement or any other debris before placement of the definitive restoration is attempted. 2. A binocular microscope may be used to examine the internal surfaces of cast restorations to make sure that they are free of small bubbles, investment, or deposits of veneering material before placement on the prepared tooth is attempted. 3. A disclosing medium may be used on the internal surface of a casting to locate discrepancies that prevent the restoration from seating completely on the prepared tooth. 4. Proximal contact areas of fixed restorations should be firm yet allow the passing of dental floss to maintain good oral hygiene. 5. Pontics designed to contact the residual ridge should do so in a passive manner. 6. The apical form of the pontic should be designed and adjusted to allow the patient to adequately perform oral hygiene procedures. 7. Equilibration of occlusion discrepancies of definitive restorations should be carried out by using relatively smooth rotary instruments and a thin marking medium. 8. Articulating strips of different colors can be used as an aid to help differentiate between centric and lateral excursive interferences during equilibration of the definitive restorations. 9. The use of a remount procedure may facilitate occlusal equilibration of the definitive restorations when numerous teeth are being restored. 10. When access allows, margins of cast restorations should be refined on the tooth with the restoration in place. 11. To achieve the maximum esthetic result with ceramic restorations, the dentist should perform final surface characterization, contouring, and shade modification with the patient present. 12. Fixed partial dentures replacing anterior teeth should provide lip support and satisfy the patient’s esthetic, phonetic, and functional requirements. 13. The trial fitting procedure should include procedures that verify complete seating of the castings and marginal integrity and that verify proper embrasure spaces and contour for periodontal health. 14. It may be helpful to have individual units indexed from an intraoral try-in before soldering. G. Casting try-in

H. Cementation

1. Before cementation, the metal should be repolished and the porcelain polished or reglazed in areas where adjustments have been made. 2. Trial placement of the restoration with a temporary cement may be indicated to assesstissue and patient response. 3. The cement selected should meet the specifications of the

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American Dental Association Council on Dental Materials, Instruments, and Equipment. 4. Different types of cements are available for final placement of a restoration. The dentist should select the cement with physical, chemical, and working properties best suited to each clinical situation. 5. The tooth should be cleansed, isolated, and dried; where indicated, a cavity varnish should be applied before final cementation. 6. The manufacturer’s instructions for manipulating the cement should be strictly followed. 7. When multiple individual restorations are to be placed, each restoration should be cemented individually to assure complete seating. 8. After the cement has set, all of the extraneous material should be removed so that none remains to act as a gingival irritant. 9. The occlusion should be reexamined after cementation and equilibrated, if necessary. 10. Patients should be thoroughly instructed regarding oral hygiene procedures, aids, and devices to facilitate interproximal and pontic tissue surface cleansing. 11. The patient should be given an appointment for follow-up care after placement of the restoration. I. Periodic

recall examination

1. Periodic recall after placement should be an essential part of fixed prosthodontic therapy. Early detection of potential problems through recall examination after placement may prevent failure of the restorations.

III.

Removable

A. Refining

partial

diagnostic

dentures

procedures

and preparatory

treatment

1. The occlusion of the teeth should be compatible with normal function of the stomatognathic system. It may be necessary to treat the patient with occlusal splints, occlusal adjustment, or orthodontics to restore proper harmony between the musculature, the temporomandibular joints, and the occlusion of the teeth. 2. The patient’s periodontal health is an important consideration in treating a patient with a removable partial denture. 3. Diagnostic casts mounted in an articulator assist in locating elements of the removable partial denture that relate to esthetics, design, and function. Spatial requirements for rest placement and preparation can be evaluated. 4. Diagnostic casts are necessary in evaluating the degree of mouth preparation and tooth modification required for removable partial denture framework design. 5. Planned mouth preparation and tooth modification may be done on the diagnostic cast before actual patient preparation and can serve as a guide for subsequent intraoral procedures. 6. A dental surveyor must be used to locate undercuts and guide surfaces in relation to the planned path of placement on the diagnostic cast. 7. Guiding surfaces are parallel surfaces that will contact a rigid part of the removable partial denture. Adequate guiding surfaces should be planned to establish the path of placement and dislodgment. Properly prepared guiding surfaces contribute to the retention and stability of the removable partial denture. 8. Because diagnostic casts are made by using stock trays and a viscous impression material, they may not be a reliable guide to soft tissue reflections, anatomy, and contour (for example, vestibular depth, frenum movement). B. Design, fabrication,

and classification

1. The treatment planning, mouth preparation, and designing of removable partial dentures are professional responsibilities to be accomplished by the dentist before master casts are presented to a dental laboratory to accomplish various steps in the fabrication of the prosthesis.

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2. The classification of a partially edentulous arch should permit immediate visualization of the type of arch being considered. It should also permit immediate differentiation between the toothborne and the tooth- and tissue-supported removable partial denture. 3. Philosophies of removable partial denture support are based on principles of broad or selective distribution of occlusal forces. 4. The basic purposes of the component parts of removable partial dentures are: to provide support by means of rests on abutment teeth and by denture bases on edentulous ridge areas; to provide primary retention by direct retainers; and to provide selective force transmission through placement of rigid components of the removable partial denture. 5. A removable partial denture should restore arch integrity, thereby preventing further change of both maxillary and mandibular arches. 6. An important consideration in removable partial denture design is to maintain and improve the health of the remaining teeth and supporting structures. Impingement of any part of the prosthesis on gingival tissues should be avoided. 7. When a removable partial denture is supported by both natural teeth and the residual ridge(s), the design should use both supporting units to their greatest potential. 8. In some instances, support and stabilization are as significant as retention in the design of a removable partial denture. 9. Retention of a removable partial denture is important for patient management, particularly for the first months after placement of the denture. 10. Removable partial dentures should be constructed to transmit occlusal forces to the abutment tooth nearly parallel to its long axis. 11. The design, contour, and finish of a removable partial denture should minimize the retention or impaction of food. 12. A survey of both the diagnostic and the master casts is essential for removable partial denture fabrication. 13. One method of stress distribution to abutment teeth is to use multiple abutments. 14. An isolated premolar adjacent to a distal extension base may not be an adequate primary abutment for a removable partial denture. The prognosis can be improved by splinting with a fixed partial denture. 15. Forces that produce torque on abutment teeth and the alveolar residual ridge should be controlled and minimized in the design of direct retainers for distal extension removable partial dentures. 16. A removable partial denture with distal extension bases may use stress directors to minimize stress distribution on abutment teeth. 17. Major connectors should be designed to have sufficient rigidity to distribute forces throughout the dental arch. 18. Most removable partial dentures move during function. The extent and direction of movement are influenced by the supporting structures, design of the prosthesis, and the accuracy of fit of the framework and the bases. 19. A removable partial denture base that derives part of its support from the residual ridge should not displace the underlying mucosa except during masticatory function. 20. In tooth- and tissue-supported removable partial dentures, denture bases should provide optimum support during occlusal loading. 21. The form of the denture base for a mandibular distal extension removable partial denture should be similar to that required for a complete denture. Modification may be dictated by the path of placement. 22. In surveying a cast for a removable partial denture, the relationship of the vertical spindle of the surveyor to the cast indicates the most desirable path for placement and removal of the completed restoration.

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23. Abutment teeth should be prepared by modifying unfavorable contours and preparing guiding surfaces and rest seats before the impression for the master cast is made. 24. Fixed restorations used as abutments for removable partial dentures should incorporate guiding surfaces, rest seats, and stabilizing and retentive areas. 25. Fixed restorations that are to be integrated with removable prostheses should be surveyed in the wax pattern stage and verified after casting, after veneering, and before cementing. 26. Indirect retainers establish a positional reference point for the removable partial denture and provide better stress distribution by transferring forces to structures other than the abutment teeth. 27. A direct retainer (clasp) should be passive when the removable partial denture is in place and at rest. 28. Intracoronal or extracoronal retainers may be used in combination with stress-directing devices in extension base removable partial dentures. 29. Whenever possible, retainer elements should be kept at the same height relative to survey lines on opposing tooth surfaces so that unfavorable forces on abutments will be minimized. 30. Each direct retainer (clasp) requires reciprocation to reduce movement of the abutment tooth during placement and dislodgment of the removable partial denture. 31. For a direct retainer to be effective, components of the framework must contact the abutment tooth at three points or areas encircling more than 180 degrees of the tooth. 32. A direct retainer (clasp) design that will minimize the display of metal should be chosen when appearance is a consideration. 33. The undercut gauge indicates the amount of infrabulge at the site selected and the distance the retentive clasp arm must flex or deform to pass over the greatest contour of the tooth. 34. Direct retainers (clasps) should not engage undercuts that require deflection beyond the yield strength of the metal being used. 35. Multiple occlusal rests and other supportive elements may provide a more advantageous transfer and distribution of forces to the existing natural teeth. 36. Occlusal and incisal rests are important supporting elements of removable partial dentures and, thereby, help to resist horizontal and vertical forces applied to the prostheses. Other components that contact teeth above the survey line may also provide stability. 37. The major connector should be located so that gingival impingement will be avoided and its contact will be compatible with structures that move during function. 38. Direct measurements of the distance between the active floor of the mouth and the lingual gingival tissues are essential to selection and placement of mandibular major connectors. 39. Major connectors join the denture base(s) to other parts of removable partial denture and help distribute functional forces. 40. The angle formed by the occlusal rest and the vertical minor connector should be slightly less than 90 degrees. 41. The use of permanent soft denture base material for definitive removable partial denture fabrication is not recommended. 42. Mandibular labial bar major connectors may be used when lingual inclinations of remaining teeth contraindicate the use of a conventional lingual major connector. 43. A hinged continuous labial bar may be indicated in patients with missing key abutments, unfavorable tooth contours, unfavorable soft tissue contours, and teeth with questionable prognosis. 44. The use of porcelain teeth should be limited to instances in which the opposing occlusal surfaces will not be subject to accelerated functional wear. 45. Acrylic resin teeth should be considered for use in removable partial dentures when there is aberrant spacing in the edentulous area. 46. The flexibility of a clasp varies with its length, thickness, width, curvature, taper, form in cross section, metallurgical composition, and handling during fabrication.

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47. It is the dental technician’s responsibility to follow the dentist’s work authorization or design and to fabricate the removable partial denture framework so that it accurately fits the undamaged master cast. If these criteria are met and the framework does not fit the mouth, the fault lies with errors occurring before technical fabrication. 48. The metal framework of a removable partial denture must not prevent the contact of natural teeth in occlusion unless an increase in vertical dimension is planned. 49. Overdenture abutments can provide support for removable partial dentures. 50. An overdenture abutment supporting a removable partial overdenture may contact the metal framework or the acrylic resin of the denture base. 51. The use of acrylic resin contact with overdenture abutments in removable partial overdentures has several advantages: the abutment tooth may be recontoured or shortened and the denture base readapted with autopolymerizing or visible light-curved resin; a coping can be placed at a later date and the denture base readapted; there are fewer problems in making an altered cast impression or relining the denture base; and the denture base can be adapted to the abutment tooth under some degree of occlusal loading of the artificial teeth. C. Tooth preparation

and

soft tissue

management

1. The occlusal rest should be spoon-shaped and deeper in ite central portion. Surface angles of the preparation should be rounded and the preparation highly polished. 2. Spoon-shaped occlusal rest seats prepared in sound enamel are satisfactory to support a removable partial denture. 3. A rest seat on an anterior tooth should be placed on a recontoured lingual or incisal surface so that the resultant force is directed parallel to the long axis of the tooth. When recontouring is not feasible, a restoration that incorporates a rest seat may be required. 4. Rest seats must be strong enough to endure functional stress, preferably be prepared in enamel or a metallic restoration, provide a vertical contact for the metal framework, be rounded, and conform to the existing coronal anatomy. The rest seat preparation should be sufficiently deep to prevent rest fractures. The opposing dentition may require modification to provide space for adequate rest thickness. 5. If possible, rests should not be located on habitual occlusal contacts. 6. Cingulum rest seats may be prepared in teeth having a naturally accentuated cingulum. 7. Cingulum rest seats should have an outline that blends into tooth contours. 8. Incisal rest seats should be shaped as a rounded groove extending onto the labial surface of an anterior tooth and gingivally on the lingual surface. Incisal rest seats are used principally on mandibular anterior teeth. 9. An occlusal strap rest is a continuous occlusal rest extending through prepared central grooves of a group of natural teeth to provide stabilization of the dentition. 10. Teeth to be used as abutments for a removable partial denture should have favorable contours or be recontoured or restored as needed. Some tooth alteration is usually necessary for patients who initially receive removable partial dentures. 11. Heights of contour may be altered and guiding surfaces created to aid in retention and stability of the removable partial denture. 12. Guiding surfaces should be aligned to the, path of insertion, curved buccolingually to follow tooth form, straight occlusogingivally, and dispersed in the arch as much as possible. 13. Guiding planes should be completed on the unrestored abutment teeth before crowns or other teeth are constructed. Thus, they serve as a guide for crown contours. 98

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14. Line angles of crowded anterior teeth that will receive a lingual plate or continuous clasp, proximal line angles of tipped or rotated teeth, and buccal and lingual surfaces of tipped teeth may be recontoured to permit better framework placement. 15. The fixed splinting of teeth to be used as abutments for removable partial dentures may be indicated when the bone support of the abutment(s) is unfavorable or when rigid retainers are planned. 16. Fixed splinting of teeth may aid in counteracting forces that result in torque of abutment teeth. 17. Contiguous teeth and those separated by an edentulous space may be splinted together to provide more support for the removable partial denture. 18. Natural tooth surfaces that have been modified must be highly polished and should receive fluoride treatment. 19. Soft tissues that have been distorted and displaced by a previous removable partial denture should be returned to normal health and contour before impressions are made for a new removable partial denture. 20. Plans for correcting discrepancies in the plane of occlusion should be noted during the diagnosis and incorporated into the treatment plan. 21. Tooth contours on removable partial denture abutment teeth may be altered in certain situations through the use of composite resins or metal castings bonded to acid-etched enamel. D. Final

impressions

1. When properly used, reversible and irreversible hydrocolloids and elastomeric impression materials may be acceptable for removable partial denture impressions. 2. One concept of impression making uses a secondary impression (altered cast removable partial denture impression) to record the supporting tissues of the denture base. Mandibular distal extension removable partial dentures usually require a secondary impression technique or relining procedure to improve the stability and support of the prostheses. 3. One potential complication of the altered cast impression procedure is incorrect or incomplete seating of the framework in the mouth or on the cast. 4.’ Final impressions should be carefully inspected to verify that all critical soft and hard tissue areas are accurately recorded, that voids are not present in rest seats, and that the impression material has not separated from the tray. 5. The impression tray must be carefully positioned and held without movement until the impression material completely sets. 6. Hydrocolloid impressions should be poured immediately after removal from the mouth. 7. Most final impressions should be cleaned of saliva and other debris, disinfected, and poured in improved stone immediately after removal from the mouth. A few impression materials require a delay in pouring. 8. When the posterior teeth are missing, the final impression of the partially edentulous mandibular arch should include the retromolar pad. 9. A posterior palatal seal on a removable partial denture with full palatal coverage may prevent the ingress of food and aid in retention during forceful expulsion of air through the mouth. E. Casts

1. The master cast must be an exact replica of the oral structures. It should be dense, clear of debris, without critical voids, and possess an adequate base. 2. Master casts for removable partial dentures should be disinfected. 3. Master casts should be produced with an improved dental stone that is compatible with the material used for making the impression. 4. Duplicate casts are helpful to communicate removable partial JANUARY

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denture design to the technician. Diagnostic casts are not recommended for this purpose if restorative procedures or recontouring have significantly altered the contours of teeth subsequent to the making of the diagnostic impressions. 5. The design of the removable partial denture framework should be drawn either on the master cast or on a duplicate of the master cast to transmit this information to the technician. 6. If needed for proper occlusion and framework relationships, an opposing cast mounted in an articulator should be provided to the technician as a guide in waxing the framework. 7. At its thinnest area, a master cast should be at least 8 mm thick. 8. All casts submitted to the laboratory for framework fabrication should be trimmed so that the base is flat, the walls are vertical, and the land areas are definite; mandibular casts should have flat, smooth lingual land areas. 9. Accurate casts that have been neatly trimmed, carefully designed, surveyed, blocked out, and tripoded may instill a desire for the highest quality work from the technician. F. Framework try-in 1. Initial seating of the framework should be gentle and slow to allow minor repositioning of the abutments. 2. All parts of the framework must be completely seated. 3. Vertical elements of the framework for tooth- and tissue-supported removable partial dentures must be physiologically adjusted to minimize undesirable stress on abutment teeth during prosthesis movement. 4. Occlusal surfaces of the framework must be in harmony with the occlusion of the natural teeth. 5. Most removable partial denture frameworks require some adjustment to achieve their optimal fit. Fitting can best be accomplished by using a disclosing medium. 6. Retentive clasp arms of removable partial dentures may not be passive unless the framework is completely seated. 7. Extracoronal or intracoronal attachment removable partial dentures capable of vertical movement under stress should be adjusted to optimal occlusion before the vertical movement of the attachment occurs. G. Maxillomandibular records 1. Before beginning preparation of abutment and related teeth, an accurate occlusal record used to mount diagnostic casts in an artitular at the proper vertical dimension may be helpful. 2. The recording of maxillomandibular relation records for distal extension removable partial dentures requires accurately adapted denture bases attached to the framework;which correctly relates to the remaining teeth. 3. Interocclusal registrations should be made with the natural teeth in contact at maximum intercuspation in patients for whom the existing occlusion is physiologic and the prognosis is good. 4. Interocclusal registrations should be made in centric relation before a definitive occlusal pattern or arrangement is developed for patients who show evidence of traumatogenic occlusion. 5. Maxillomandibular records for distal extension removable partial dentures should be made with minimal pressure. 6. A semiadjustable articulator is adequate to develop tooth arrangement for most removable partial dentures. 7. In tooth- and tissue-supported removable partial dentures, the recording of maxillomandibular relationships is best performed by using record bases attached to frameworks that are fabricated after an altered cast impression procedure. 8. The vertical dimension of occlusion established for the removable partial denture must be coincident with the remaining natural dentition. H. Occlusion 1. To articulate THE

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the occlusion DENTISTRY

of a removable

partial

denture should be developed with the remaining natural teeth at the correct vertical dimension of occlusion. 2. Contact only in maximum intercuspation is usually required in removable partial dentures opposing natural dentitions. 3. The occlusal surfaces of opposing natural teeth may require adjustment before removable partial denture service is provided. 4. Nonworking side contacts usually are undesirable for removable partial dentures opposing natural teeth or another removable partial denture. 5. Generally, no part of the removable prosthesis should interfere with complete closing contact or eccentric movements of the remaining natural dentition. 6. Dentitions that include removable partial dentures provide less masticating efficiency than natural dentitions with similar contact areas. 7. Processed removable partial dentures may be returned to the articulator before removal from the master cast to adjust for processing changes. This procedure reestablishes and verifies the intended vertical dimension of occlusion. 8. Distal extension removable partial dentures may be remounted in the articulator to refine centric and eccentric occlusal contacts. This adjustment should follow base modification by using indicator paste. 9. Short-span tooth-supported removable partial dentures may have the static and dynamic occlusal relationships perfected in the patient’s mouth. 10. Occlusal relationships of tooth-supported removable partial dentures may be perfected in the patient’s mouth if opposed by natural teeth or another partial denture. I. Try-in of the waxed removable partial denture 1. A try-in with the artificial teeth arranged in wax attached to the framework is usually necessary. 2. The accuracy of the articulator mounting should be verified at the try-in appointment. 3. The appearance of the removable partial denture should be satisfactory to both patient and dentist. 4. Anterior artifical teeth should be tried in the mouth to verify their size, shade, position, and acceptability to the patient. 5. When esthetics is a primary concern, it may be helpful to have a relative or friend of the patient present at the try-in appointment. a relative or friend of the patient present at the try-in appointment. 6. Waxing for proper esthetic form and for physiologic function should be accomplished before processing of the denture base material. 7. The artificial teeth should be positioned for optimal centric relation and eccentric contacts. 8. The centric relation should be verified after the accuracy of the vertical dimension of occlusion has been determined. J. Esthetic considerations 1. The effect on appearance should be considered in designing direct retainers for removable partial dentures. 2. Artificial teeth adjacent to abutment teeth may be contoured to accommodate retainers. 3. In the partially edentulous patient with a well-formed anterior residual alveolar ridge, anterior teeth that are adapted to the ridge with no labial denture base may provide optimum appearance. K. Initial denture placement 1. Denture base border extension and thickness should be verified during placement. 2. The denture bases and major connector should be checked with disclosing medium to justify areas of undesirable pressure. 3. The occlusion may require adjustment to provide planned contacts in maximum intercuspation and lateral excursions. 99

4. Verbal or written home care instructions with demonstrations are recommended. 5. When undercut areas prevent the seating of the denture bases of removable partial dentures, judicious adjustment is required. The tissue surfaces of posterior bases are relieved so that border extent can be maintained. Anterior bases are shortened and contoured to blend with the remaining tissues to avoid an unnatural appearance. 6. Removable partial denture frameworks must be fully seated on the supporting structures before occlusal adjustment. L. Care after denture

placement

1. The proper maintenance of the prosthesis and the supporting structures is a major factor in the success of a removable partial denture. 2. Most patients who have removable partial dentures should be reexamined at least semiannually and more frequently, if indicated. 3. Written instructions aid in educating patients effectively. 4. Properly designed brushes and appropriate instructions should be provided to patients to facilitate cleansing of removable partial dentures and supporting teeth. 5. Application of fluoride to the natural teeth by using the prosthesis or on individual applicator as a carrier may be indicated. 6. Instructions for cleansing and stimulation around abutment teeth and the remaining natural teeth are essential. 7. Removable partial dentures usually should be removed from the mouth when the patient goes to bed. 8. Distal extension removable partial dentures should be examined periodically to evaluate ridge resorption, stability, occlusion, and framework displacement. Variations from optimum should be corrected. M. Interim

restorations

1. Interim removabie partial dentures may facilitate residual ridge remodeling and help maintain the vertical dimension of occlusion after removal of posterior teeth. 2. Interim removable partial dentures can be used for diagnostic purposes in determining proper vertical dimension of occlusion, esthetic and phonetic requirements, and to assessthe patient’s ability to cooperate and cope with the wearing of a prosthesis.

IV. Maxillofacial A. Scope of manillofacial

prosthetics prosthesis

1. In a society that values appearance, those who lack eyes, ears, a nose, facial and mandibular tissues, or who exhibit severe scar tissue and malformed parts of the face, neck, and oral cavity may become less socially acceptable. Although developmental defects afford ample time for behavioral adjustments to be made, sudden traumatic and surgical defecta may diminish the patient’s quality of life. Rehabilitation of the maxillofacial patient into society requires a broad knowledge of prosthodontics, plus the capacity for compassionate patient management. B. Refining

diagnostic

procedures

1. The maxillofacial prosthodontist is an integral member of the interdisciplinary team that treats individuals with oral, cranial, and facial defects. 2. The evaluation of a patient’s requirements for maxillofacial care generally comprises dental, medical, and surgical histories; psychosocial assessment; speech evaluation; and clinical examination. Diagnostic aids include articulated maxillary and mandibular casts and oral radiographs. Maxiliofacial patients may require radiographs of related facial structures. 3. When possible, all prospective patients for head and neck surgery who are potential candidates for any maxillofacial prosthesis, should be seen by the maxillofacial prosthodontist for diagnosis and pretreatment evaluation before surgery, radiation therapy, or chemotherapy.

100

4. The prosthetic prognosis for patients after irradiation is less favorable because of changes in supporting structures. Consideration must be given to trismus, fibrosis, xerostomia, hypogeusia, radiation caries, soft tissue fragility, and osteoradionecrosis. 5. Corrective surgery may be indicated to improve function, comfort, and natural appearance for patients requiring maxillofacial prostheses. 6. All dental structures that may provide valuable retention, and support of a maxillofacial prosthesis should be preserved. 7. Facial prostheses are indicated when no further reconstructive plastic surgery is to be performed or an immediate or provisional prosthesis is needed after resective surgery. 8. The ideal material for facial prostheses should be biologically compatible, flexible, translucent, able to retain extrinsic and intrinsic color, eazy to clean, lightweight, durable, color stable, inexpensive, easy to fabricate, and finishable to a fine edge. 9. The palatal lift prosthesis is indicated for palatal incompetency and elevates the middle segment of the soft palate to approximate the posterior and lateral walls of the pharynx. 10. A palatal lift prosthesis may increase the activity and range of motion of the incompetent soft palate. 11. A speech-aid prosthesis is indicated to correct a palatopharyngeal deficiency or incompetency when surgical repair is deferred or contraindicated. 12. An obturator feeding aid may assist in the normal feeding of a cleft palate infant and can be discontinued when the infant can eat normally without it. 13. The preparation of a patient for a obturator prosthesis may require supportive dental treatment, including restorations for the remaining dentition of both dental arches to achieve proper support and retention of the prosthesis. 14. After a hemimandibulectomy including the condyle, the patient should be instructed in exercises or have a mandibular resection prosthesis with a guide fabricated in an attempt to minimize deviation of the mandible toward the resected side on closure. 15. The prognosis for edentulous mandibulectomy patients becomes less favorable as the size of the resection increases. 16. A prosthesis placed at the time of surgery can aid the patient’s immediate postoperative convalescence. 17. A surgical obturator is generally delivered during the surgical procedure for resection of the maxillae. 18. Certain oroantral and oronasal palatal defects require simple coverage by the prosthesis base; others need obturation by extension of the prosthesis base to enhance retention, stability, and support of the completed restoration. 19. A custom conformer prosthesis, which can be sequentially increased in size, may be required to enlarge the contracted socket before an acceptable artificial eye can be constructed. 20. Maxillofacial prosthesis may be transitional restorations until definitive surgery is performed. C. Design features

and considerations

1. A maxillofacial prosthesis should be designed and fabricated so that the residual anatomic structures will perform the functions of speech, respiration, mastication, and deglutition with minimal impediment. 2. Maximum tissue coverage supported by residual bone is desirable for maxillofacial prostheses. 3. A surgical obturator prosthesis should be lightweight, strong, easy to repair and alter, and easy for the patient to place and remove. 4. Sometimes the patient’s existing complete maxillary denture may be converted into an acceptable surgical obturator prosthesis. 5. The use of hollow extensions is indicated when the weight of the prosthesis will compromise retention and place undue stress on the surrounding tissues. 6. Resilient, flexible materials that extend into desirable undercut areas of nasal or palatal cavities may be used for added retention of the prosthesis. IANUARY

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7. The use of resilient or adaptive lining materials may be indicated for maintaining prostheses during growth, development, and postsurgical healing. 8. The pharyngeal part of a speech-aid prosthesis should extend to the level of maximum muscle activity in the nasopharynx. Normally, this will be slightly above the anterior tubercle of the first cervical vertebra or on the palatal plane in the adult patient. 9. The palatal extension section can be made of a cast metal bar traversing the soft palate anteroposteriorly and ending in a retention loop midway in the nasopharyngeal cavity. 10. Speech-aid prostheses should be fabricated in maxillary, palatal, and pharyngeal sections. Each section may require refitting and use by the patient before succeeding sections are made. 11. A facial prosthesis should be formed so that peripheral borders are thin, translucent, and blend with facial anatomy to conceal the edges of the prosthesis. 12. The use of auxiliary aid for retention of maxillofacial prostheses such as resilient material into undercuts, spectacle frames, intermaxillary springs, sectional swivel hinges, magnets, implants, and adhesives should be considered on an individual basis. 13. To obtain retention from the remaining abutment tooth, a mandibular resection prosthesis should include multiple retainers. When minimal retentive undercut areas are available, swinglock or facioliigual continuous retainers may be employed. 14. When possible, contours of facial prostheses should harmonize with the natural contralateral side and remaining areas of the face from full-face, superior, and inferior views. 15. Intrinsic tinting of the facial prosthesis within the tolerance of the material will provide the most stable color. 16. The degree to which satisfactory appearance can be realized in maxillofacial restorations may be limited by unfavorable anatomic relationships. 17. Direct retainers for maxillofacial prostheses should have strong stabilizing characteristics and enhance retention on abutment teeth. 18. Orthodontic bands with buccal tubes or appropriately contoured crown preparations on permanent or deciduous teeth can be used to retain a maxillofacial prosthesis. 19. The auditory meatus of an auricular prosthesis should align with the natural auditory meatus to assure normal hearing. 20. An orbital prosthesis can be fabricated for placement after orbital resection. 21. A surgical obturator prosthesis improves speech, mastication, and deglutition; maintains packings of skin grafts in position; and may improve patient morale. 22. The use of acrylic resin artificial teeth for maxillofacial prostheses is usually advisable. 23. Even though the long spans and extended denture bases covered by removable partial dentures that incorporate maxillofacial prostheses pose special design problems, the basic principles of support, stability, and retention remain the same as for conventional removable partial dentures. D. Tooth alterations in enamel 1. In maxillofacial prosthetics, judiciously recontouring enamel to improve esthetics, preparing guide planes, removing interferences, preparing rest seats, correcting occlusal disharmonies, and using methods to augment retention are basically the same as for conventional removable partial dentures. 2. In developmental deformities, tooth positions may be more aberrant than normal and thus require an overdenture design after coronal reduction and complete coping coverage have been completed. 3. Although the remaining teeth and alveolar bone are of greater relative value in the maxillofacial patient, motivation for plaque control and good oral hygiene is often less than desirable. 4. In situations involving chronic tissue abuse with lack of proper THE JOURNAL

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oral hygiene and routine dental care, the dentist should exercise caution in the use of tissue-conditioner relines, particularly where they may contact highly sensitive respiratory mucosa. E. Final impressions 1. Impression procedures for extraoral and intraoral defects are influenced by the character of the remaining tissues. 2. Impressions for diagnostic caste of maxillofacial prosthetic patientc may require recording structures not normally included in impressions for conventional prosthodontic patients. 3. Because of their drying and irritating effects on oral mucosa, metallic oxide and plaster impression materials are contraindicated for many irradiated patients 4. A complete or sectional facial impression may be indicated for the fabrication of an orbital prosthesis. 5. A sectional facial impression is acceptable in the fabrication of an auricular or nasal prosthesis. 6. The maxillofacial patient should be seated in a nearly upright position while the facial impression is being made. 7. Complete and sectional facial impressions may be made with irreversible hydrocolloid material supported with a plaster of paris backing. 8. The form and position of the pharyngeal section of any speech aid is determined by visual inspection, speech evaluation, and the patient’s response. 9. The impression of the nasopharynx for the fabrication of any speech-aid prosthesis should be made during speech, postural movements, and swallowing. 10. Usually, an impression material that can be physiologically molded is the best for making impressions of the nasopharyngeal regions. 11. Because the lateral wall and the scar band of the maxillaryresected patient are dynamic, functional impression materials, for example, dental impression wax, may be needed for an improved border seal. F. Master casts 1. Master casts for maxillofacial patients require the same considerations and qualities as removable partial denture casts. G. Framework try-in 1. Framework try-in and maxillomandibular recording procedures are similar to those for removable partial dentures. 2. Additional care is required in making jaw relation records on large mobile record bases to avoid displacement of the record base during registration. 3. Discontinuity defects of the mandible require special skills, methods, materials, and patience when jaw relation registrations are attempted. 4. When there is loss of mandibular continuity, some movements of the remaining mandible can be recorded. Currently, no articulating instrument is capable of accepting all these functional records and their aberrations. 5. Mandibular resections may hinder repeating centric relation position. Thus, an acceptable functional jaw record is one with a consistent pattern of duplicable relationships made without tension or force. H. Wax try-in 1. Wax try-in procedures are similar to those for complete and removable partial dentures. 2. Processed acrylic resin bases have value for early testing of fit, comfort, retention, and stability of prostheses associated with maxillofacial defects. 3. A clay or wax sculpture with a properly aligned artificial eye should be used for trial fittings of an orbital prosthesis before final processing. 101

ACADEMY

V. Complete

I. Occlusion

1. Changes in the tissues supporting a maxillofacial prosthesis may be more rapid than in those supporting a more conventional prosthesis. Therefore, the occlusion and base adaptation must be reevaluated frequently and corrected by selective grinding of the occlusion or refitting the base of the prosthesis. 2. All occlusal patterns in maxillofacial reconstructions must be physiologically compatible with the patient’s residual anatomic structures and functional capabilities. 3. Occlusal stress should be minimized for the irradiated patient requiring complete dentures. Acrylic resin teeth with a reduced occlusal contact area may be indicated. 4. Altering the cusp angle of posterior teeth may influence the stability of the prosthesis placed on an edentulous resected maxilla or mandible. 5. It may be necessary to accept an occlusion that is not bilaterally balanced in eccentric occluding positions for an edentulous maxilla or mandible. 6. When needed, occlusal ramps or platforms may be placed on the opposing maxillary prosthesis to direct the resected mandible into a more desirable maxillomandibular relationship. J. Initial

placement

1. Initial placement procedures are similar to those for removable partial dentures, There should be special emphasis on patient education. 2. Placement of a surgical obturator prosthesis for maxillary resections may eliminate the need for or facilitate early removal of a nasogastric tube. 3. Placement of a surgical obturator prosthesis may help to shorten the patient’s hospital recovery period. 4. Extensions of the prosthesis should be evaluated and adjusted to acceptable positions. K. Initial

care after placement

1. After placement, the focus is on the care and cleaning of the prosthesis and on maintaining the health of the remaining oral structures. 2. Speech therapy is often necessary after placement of any speech aid prosthesis for a cleft palate patient. 3. Speech-aid prostheses for patients with soft palate defects may require an adjustment in the size and contour of the pharyngeal section, because wearing the prosthesis may stimulate palatopharyngeal changes. 4. It may be necessary to place tissue-conditioning material in a newly placed prosthesis before refitting with more permanent materials. 5. Rehabilitation of the maxillofacial patient after surgery may require speech assessment, psychosocial evaluations, physical therapy, and vocational guidance. 6. Patients with oral neoplasms frequently have a history of mouth neglect and poor oral hygiene. Preventive dentistry and education in good oral hygiene are necessary components of effective aftercare. 7. Facial prostheses require periodic replacement because of tissue changes and the unstable properties of available materials. 8. Adhesives used for retention of facial prostheses should be nonirritating and nontoxic to the skin and mucous membrane, sufficiently flexible to move with surrounding tissues, compatible with the material of the facial prosthesis and the patient’s skin, strong enough to retain the prosthesis, easily cleaned from tissue and prosthesis, stable, and incapable of supporting bacterial growth. 9. Frequent reevaluation for maxillofacial patients is necessary because of possible rapid tissue and occlusal changes often associated with unstable restorative materials frequently used. 10. Surgical obturator prostheses provided for a maxillary resection must be relined periodically during the healing period to assure patient comfort and function.

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A. Refining

OF DENTURE

PROSTHETICS

dentures

diagnostic

procedures

1. Many signs of systemic disorders, such as diabetes or avitaminosis, manifest themselves in mucosal structures; these may indicate the need for other therapy before prosthodontic treatment. 2. Nutritional guidance should be a part of treatment for many complete denture patients. 3. Psychologic maladjustment may result from the association of denture wearing with advancing age. 4. Patients with psychotic tendencies may use their maladjustments to dentures to avoid traumatic interpersonal situations with friends, relatives, and others. 5. Prosthodontic treatment for patients who have had radiation therapy in or about the oral cavity should be carefully considered in reference t.o time of treatment, radiation methods, and radiation dosage. 6. Most irradiated patients can wear removable prostheses if the effects of radiation therapy are not severe and the patient follows instructions for the use of the prosthesis. 7. The risk of osteoradionecrosis is greater in the mandible than in the maxillae. 8. Evaluation of the patient’s arch form, cross-sectional shape of the alveolar ridges, retromylohyoid extensions and tongue position are important physical criteria for establishing a prognosis. 9. Relief or alteration of the denture base to accommodate undercuts associated with root eminences of overdenture abutments may cause reduced retention, stability, and border seal. 10. Patients for whom overdentures are planned should be informed that overdentures may be less stable and retentive than fixed or removable partial dentures. 11. Endodontic treatment of an overdenture abutment is usually required so that the tooth can be reduced sufficiently to allow esthetic placement of the artificial tooth. 12. Overdentures should only be considered if the patient can achieve and maintain satisfactory oral hygiene. B. Design features

and considerations

1. The space available for complete dentures is controlled in part by the oral and circumoral structures surrounding the space and their movements in function. 2. Maximum coverage and intimate contact of the denture foundation area are essential for the support of a complete denture prosthesis. 3. The dentist should establish a posterior palatal seal for the maxillary complete denture either in the impression procedure or by proper alteration of the master cast. 4. The posterior palatal seal should extend bilaterally through the pterygomaxillary notch areas. 5. Palatal relief should not be routinely placed in the maxillary complete denture. 6. Artificial anterior porcelain teeth should not be used with posterior artificial acrylic resin teeth, but anterior artificial acrylic resin teeth may be used with posterior artificial porcelain teeth. 7. Intimate tissue contact and border seal permit atmospheric pressure to serve as an important physical factor in complete denture retention. 8. Neuromuscular control contributes to complete denture retention and stability. It becomes increasingly effective in the experienced denture patient. 9. Optimum denture retention at denture placement can aid the patient in learning the neuromuscular control needed to effectively use complete dentures. 10. Anatomic regions that resist resorptive changes most effectively should be covered to promote long-term support and minimize changes in the relation of the denture to the maxillae or mandible. Horizontal portions of the hard palate, the retromolar pad, and the buccal shelf are examples of such areas. JANUARY

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11. In preparing overdenture abutments, it is important to reduce the crown-root ratio to prevent undue lateral stresses and to provide ample room for artificial teeth. 12. For overdentures, sufficient attached gingivae should be present around the abutments, and the moving denture base should not impinge on or cause strangulation of the tissue of the free gingival margin. 13. The angle of emergence of the coping or attachment of an overdenture abutment tooth should be compatible with gingival health and maintenance of hygiene. 14. Although retentive devices can enhance overdenture retention, they may not be essential for successful patient care. 15. When available, canines are the most desirable teeth to support overdentures. 16. The clinical crown length of an overdenture abutment should be 2 to 3 mm above the proximal gingival margin to avoid migration of the gingival tissue. 17. For overdenture abutments, the tooth reduction on the labial or buccal surfaces should be sufficient to allow esthetic positioning of the artificial teeth. 18. Overdenture abutments aid in providing support and stability to a prosthesis. 19. Overdenture abutments provide a degree of tactile sense, which aids proprioception. 20. Overdenture abutments assist in preserving alveolar bone. C. Soft tissue management

1. Patients who are already using dentures should remove them for a time before final impressions are made and before new dentures are placed. Factors to consider in determining the length of time for complete tissue rest include the patient’s age, the condition of the supporting tissue, the length of time the prosthesis has been worn continuously, and the thickness of the mucoperiosteum. 2. Before impressions are made of tissues that have been supporting a removable prosthesis, the tissues should be returned to a physiologic status through tissue conditioning, massage, and/or complete rest. 3. Residual ridge resorption under complete dentures may alter occlusal relationships, which can further hasten ridge resorption. 4. For overdenture abutments, periodontal health should be established and maintained. Proper education of the patient in the maintenance of the teeth and denture are important. Daily, the patient should clean the teeth under the denture and apply fluoride. D. Impressions

1. There is a relationship between the requirements for an adequate impression and the contemplated external form of the prosthesis. Before the impression procedure is started, a concept of the completed denture border form should be developed. This is determined from the diagnostic cast and by visual and digital examination of the denture-bearing area, including the tongue’s influence on the level of the floor of the mouth. 2. A maxillary preliminary impression should completely fill the labial and buccal vestibules and extend posteriorly beyond the hard palate and into the pterygomaxillary notches. A preliminary mandibular impression should include the entire residual ridge and the retromolar pad and extend lingually into the floor of the mouth including the retromylohoid fossa. The distobuccal extensions should include the external oblique ridges and should approach the anterior borders of the rami. 3. Final impressions should record the entire denture foundation area to be covered by the denture base. 4. The foveae palatinae are anatomic landmarks that can be used as one aid in determining the posterior limit of the maxillary denture. 5. The location of the junction of the movable and immovable soft THE JOURNAL

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palate is used to determine the posterior extension of a complete maxillary denture. 6. The curved borders of the labial, buccal, and lingual areas of final impressions represent the extension and contours to be reproduced in the processed prosthesis. 7. Areas of the impression tray that may exert excessive pressure on the denture foundation area should be determined and relieved before an impression is made. 8. Impressions of edentulous arches should record the form of healthy tissue at rest and extend to the physiologic limit of border tissues to maintain a border seal and to assure the distribution of functional stresses over the greatest area of support. 9. The complete denture final impression provides for intimate tissue contact and border seal of the denture base, excluding ingress of air between the denture base and soft tissue. These physical factors permit atmospheric pressure to serve as the primary physical factor in complete denture retention. 10. Selective pressure complete denture impressions permit the recording of certain anatomic regions with minimal pressure and other areas with mild pressure. This promotes less positive contact of the denture base with anatomic regions that are not ideal stressbearing areas because of the friable nature of the mucosa or the susceptibility to pressure-induced resorption. E. Casts

1. Complete denture impressions should be boxed before pouring master casts. 2. Type II dental stone has adequate physical properties for complete denture casts. 3. Complete denture casts should have a clearly defined land area. F. Record bases, occlusion rims, and maxillomandibular

records

1. The incisal length of maxillary occlusion rims should be established after the desired contour of the facial surfaces has been set. 2. To prevent displacement of the complete denture bases, it is particularly important that the centric relation record be made with a minimum of closing pressure. 3. Mechanical recording devices are more accurate when neuromuscular control is good, the residual ridges are ample, and the soft tissues are not highly displaceable. 4. Methods for recording maxillomandibular relationships include the following: (a) Interocclusal records (b) Mechanical devices (c) Chew-in techniques (d) Cephalometric radiographs 5. The recording of centric relation at the correct vertical dimension of occlusion is one of the most important factors in complete denture construction. 6. Centric relation is a desirable position to record and transfer to an articulator during the fabrication of complete dentures. 7. Centric relation should be recorded at the correct vertical dimension of occlusion unless casts are mounted on the transverse horizontal hinge axis on an appropriate articulator. 8. The vertical dimension of occlusion usually should be estalished before the centric relation record is made. 9. Centric relation records should be verified regardless of the posterior tooth form that is used. 10. A facebow is important when any change in the vertical dimension of occlusion is anticipated during therapy. Such changes in vertical dimension include the following: (a) Compensation for interocclusal record thickness (b) Excuraive movements when cusped teeth are used (c) Alterations in the vertical dimension of occlusion, including occlussl adjustment 11. An anatomic average transverse horizontal axis is generally acceptable for tissue-supported or tooth- and tissue-supported

103

ACADEMY

prostheses in determining posterior reference points for a facebow record. G. Complete

denture

occlusion

1. To prevent deflective occlusal contacts, the cuspal inclines of artificial teeth may require selective alteration. 2. A universally accepted concept of articulation and occlusal form for complete dentures has yet to be scientifically established. Several concepts for eccentric occlusal relationships may be used with success. 3. A reduction in the vertical dimension of occlusion as a result of either a loss of supporting tissues or wear of teeth shifts the mandibular jaw position and occlusion anteriorly. 4. The vertical and horizontal jaw relations of the natural teeth should be evaluated before immediate denture service is initiated. 5. When a vertical overlap of the anterior teeth is necessary, sufficient horizontal overlap is desirable to prevent interference by the teeth when the patient is speaking and masticating. 6. The occlusal plane should be located according to mechanical requirements for stability of the dentures, masticating efficiency, preservation of the supporting structures, anatomic landmarks, esthetics, and phonetics. 7. The stability of the denture bases supporting artificial teeth is important in maintaining a previously created balanced articulation. 8. Bilateral eccentric contact can be developed with anatomic or nonanatomic posterior teeth. 9. To evaluate changes in occlusion caused by processing, complete dentures may be returned to the articulator before removal from the cast. 10. Incorrect vertical dimension of occlusion increases the potential for bone resorption beneath immediate or conventional complete dentures. 11. Malocclusion increases the potential for ridge resorption in the prosthodontically restored edentulous patient. 12. Occlusal discrepancies may result from the dimensional changes of materials used to process resin dentures. 13. Complete dentures should not be relined until existing malocclusion, which frequently occurs after residual ridge resorption, has been corrected. 14. The proper use of a semiadjustable articulator is advantageous in complete denture construction. 15. An adequate occlusal scheme can be developed for complete dentures on a semiadjustable articulator. 16. Before fabrication of single complete dentures, the opposing natural teeth should be restored or recontoured to favorable occlusal

H. Try-in

and verification

procedures

1. Any treatment sequence for complete dentures should include a try-in of artificial teeth with stable denture bases to evaluate the vertical and horizontal maxillomandibular relationships, esthetics, and phonetics. The patient and, when possible, a family member or friend should participate in the evaluation. 2. It is difficult to properly assessthe correct vertical dimension of occlusion before all teeth are arranged on the denture base. 3. Enunciation of sounds is diagnostically more accurate with trial dentures than with wax rims. 4. Aging, physical limitations, previous dental history, and lack of neuromuscular coordination may combine to render the absolute verification of maxillomandibular relationships impossible. 5. Verification of centric relation and securing eccentric records should follow verification of the accuracy of the vertical dimension of occlusion. 6. After the try-in appointment, teeth should be repositioned for optimal contacts in the centric relation and eccentric positions with care to avoid altering the appearance of the dentures.

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I. Complete

denture

OF DENTURE

PROSTHETICS

materials

1. To minimize distortion, previously processed acrylic resin denture bases should not be heated above 165’ F. 2. Processed resilient denture base materials may be of value for patients demonstrating persistent soreness and inability to wear well-constructed dentures with hard resin bases. 3. Using porcelain teeth in complete dentures that oppose natural teeth or gold restorations may cause undesirable wear of the opposing teeth. 4. The dentist should understand the role of the various denture base materials and their influence on supporting tissues. J. Esthetic

considerations

1. The relationship of artificial teeth to each other in the arch affects the apparent size and color of individual teeth. Placing a tooth more anterior in the arch creates the illusion of a lighter shade and a larger tooth. Placing the tooth more posterior in the arch creates the illusion of a darker shade and a smaller tooth. 2. The level of the occlusal plane in the mandibular premolar area is usually at or slightly below the commissure of the lips. 3. Posterior teeth of a natural-appearing length should be used whenever the interridge distance permits. 4. A common defect in facial appearance results from positioning the maxillary anterior artificial teeth too far palatally. K. Initial

placement

1. Complete dentures should be remounted in a semiadjustable or a fully adjustable articulator for correction of occlusal discrepancies after initial adjustment of the tissue surface of the denture. 2. Mounting the completed restoration in an articulator with a proven interocclusal record is an accurate method of developing final mandibular position and occlusion; it is more accurate than intraoral occlusal correction. 3. During the initial placement of complete dentures, the dentist should evaluate border extensions, border seal, retention, and esthetic values. Areas where the denture exerts excessive pressure on the denture foundation area should be located and relieved. 4. Surfaces of porcelain teeth that have been ground during occlusal adjustment should be polished. 5. To reinforce previous educational efforts, the patient should receive verbal and/or written instructions at the initial placement appointment regarding the wearing and care of dentures and cleansing procedures for the supporting tissues. 6. To maintain good tissue health, complete dentures should be removed from the mouth at least several hours during each 24-hour period. This is best accomplished during sleep. 7. A record of the vertical dimension of occlusion should be made at initial denture placement for future reference. 8. Patients should not be given removable restorations before occlusal discrepancies are eliminated. 9. Instructions to overdenture patients must emphasize the importance of meticulous daily cleansing of retained overdenture abutment teeth, and the importance of the daily use of fluoride (nonacidulated) in the denture over the abutment teeth. L. Care after placement

1. Some adjustments of the tissue surfaces of processed resin dentures should be expected during the early wearing period. 2. Complete denture treatment should include provision for adjustment appointments after initial placement of the dentures. 3. Complete denture patients should be informed that they should be examined at least annually to determine the health of oral tissues and the condition of dentures. The importance of these factors should be stressed to each patient. 4. Patients should be advised and reminded that complete dentures require periodic adjustment and eventually will require modification, which may include relining or remaking if proper tissue adaptation and occlusion are to be maintained. JANUARY

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5. When dentures are initially placed and at subsequent appointments, the dentist should emphasize the importance of maintaining adequate hygiene of both the mucosa and the dentures. 6. Dietary recommendations for the patient during the adjustment period are advisable. 7. The form of the denture-bearing area for complete dentures continues to change throughout life. 8. Residual ridge resorption under complete dentures causes malocclusion. 9. The possible deleterious effects of a complete maxillary denture opposed by mandibular anterior natural teeth and a distal-extension removable partial denture should be carefully explained to the patient. The need for frequent examination, continuing treatment when necessary, and removal of both dentures before sleeping should be emphasized. 10. The proper relining of complete dentures requires skill and meticulous care. 11. Alteration of the vertical dimension of occlusion should not occur during relining unless it is required to restore proper vertical dimension. 12. Relining of complete dentures must include restoration of proper occlusion. This may require a clinical remount procedure after the reline and before seating the denture. 13. The overdenture patient must be seen for regular, frequent recalls to reevaluate and reinforce oral hygiene practices, correct any new or recurrent periodontal problems, restore carious lesions, and adjust the denture adaptation to the teeth and tissues. M. Immediate

and interim

restorations

1. Immediate or transitional dentures are the desired method of treatment for introducing patients to complete dentures. They should be constructed only after the patient has been informed of the requirements of immediate denture service. Where indicated, an interim or transitional partial denture may facilitate the patient’s adjustment to complete dentures. 2. Properly constructed and adjusted immediate dentures aid the healing response of the denture-bearing tissues. 3. Unnecessary removal of bone should be avoided when teeth are extracted for placement of immediate dentures. 4. Immediate denture treatment is time-consuming and exacting. 5. The patient should return to the dental office at stated intervals after the immediate denture has been placed so that border extensions, occlusion, and tissue irritation can be evaluated and needed corrections made. 6. The immediate denture or one that has been constructed soon after extraction of the remaining teeth must be maintained with additions and subtractions for the entire healing period. Eventually, relining, rebasing, or refabrication of the denture will be necessary. 7. The use of successive temporary relines for immediate complete dentures is recommended to maintain support, stability, comfort, and function during the healing period before definitive relining or secondary denture treatment. 8. When it is desirable to duplicate the arrangement of the natural teeth, the teeth should be removed from the cast one at a time so that remaining adjacent and contralateral teeth serve as guides for positioning of each artificial tooth. 9. The vertical and horizontal jaw relations established by the natural teeth should be evaluated before implemention of immediate denture service. 10. Because swelling and edema follow placement of immediate dentures, malocclusion should be corrected after swelling and edema have subsided. 11. In the interim immediate denture procedure, all remaining teeth commonly are extracted at denture placement. 12. An interim complete denture used during the healing period has several advantages over the conventional immediate denture. (a) Final impressions and jaw relation records for definitive dentures are obtained after healing. THE

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(b) A wax try-in is possible for the definitive denture. (c) The patient can retain the interim denture to serve in an emergency. 13. An interim prosthesis may need to be relined or remade shortly after placement to compensate for changes in the denture foundation area. 14. In immediate denture treatment, the use of interim dentures for initial placement and during the healing period is recommended. Better quality secondary dentures can be constructed on completely healed supporting tissues. 15. Before fabrication of a conventional immediate denture is begun, all posterior teeth are extracted except those necessary to provide adequate occlusal contacts to maintain the interarch distance. 16. A transparent surgical template may be used as a guide to the amount of surgery required during placement of immediate dentures.

VI. Implant A. Diagnostic

restorations information

1. The clinical evaluation of a patient requiring implant prosthodontic treatment should include dental, medical, and surgical histories. Speech and psychological testing may also be needed. 2. Unrealistic expectations may affect the prognosis in implant patients. 3. Radiographic examination may require intraoral, panoramic, cephalometric, and tomographic imaging techniques. 4. Age does not appear to be a factor in the successof dental implants. B. Diagnosis

1. A need for an implant-supported prosthesis should be established as an alternative to conventional denture therapy. 2. Patients who are to be treated for endosseous dental implants should have diagnostic casts articulated with a trial arrangement of artificial teeth on trial denture bases. A presurgical prosthodontic evaluation analysis is essential for site, number, and position of the implants. 3. The type of implant for use in a patient must be selected relative to the quality and quantity of osseous tissue available to support the implant. 4. An analysis should be made of attached and nonattached gingiva surrounding implant sites, and consideration should be given to the adequacy of attached gingiva at the permucosal site of implant posts. 5. Prosthodontic treatment must be planned before implant surgery. C. Prognosis

1. The patient should be informed of benefits, risks, time, cost of treatment, and alternative treatments. 2. Meticulous sterile surgical techniques are essential to the initial and long-term success of any dental implant system. 3. Alveolar bone surrounding osseointegrated implants has the potential to maintain slower resorptive patterns than alveolar bone supporting conventional tissue-borne prostheses. 4. Replacement teeth should not be arranged for appearance in a position that could cause an unfavorable force distribution and compromise oral hygiene. 5. Future health changes could change the prognosis for survival of an implant restoration. D. Prerestoratiue

treatment

1. The oral structures, dentulous or edentulous, should be in a state of optimal health. 2. Any systemic disorder must be recognized and evaluated relative to dental implant success.

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3. Before proceeding with treatment, patient response to educational-efforts should be assessed. 4. If an interdisciplinary team provides treatment, one member (usually the restorative dentist) must supervise and direct treatment. E. Prosthodontic

treatment

1. Dental implants may be classified as subperiosteal, endodontic, endosteal, transosteal, intramucosal inserts, supraperiosteal or subperiosteal augmentation. 2. Fixed, removable, fixed-removable, and overdenture prostheses can be used with dental implants. The prosthesis must match the implant capabilities. 3. Casts for diagnosis and/or custom implant design and fabrication may be obtained by the following means (a) Conventional intraoral impressions (b) Surgical degloving followed by a bone impression (c) Computerized axial tomography to produce a computer generated model 4. Direct impressions of the alveolar bone must be made with nonirritating materials. All particles of impression material must be removed from the bone surface and tissue after removal of the impression. 5. A totally implant-supported prosthesis does not depend upon soft tissue for support. The impressions need only extend to regions necessary for landmark identification. 6. An implant- and tissue-supported prosthesis uses soft tissue areas for support, therefore, an impression should be made according to accepted principles for optimal support, extension, and stability for tissue-borne prostheses. 7. It is the dentist’s responsibility to design the implant-supported restoration. 8. An immobile occlusal record base facilitates obtaining accurate and verifiable maxillomandibular relation records. 9. Fixed, fixed-removable, removable partial, removable complete dentures, and overdentures in implant dentistry have varied occlusal requirements. The occlusion should be developed to reflect the prosthodontic capabilities of the dentist, the available support, and the needs of the patient. 10. Occlusal patterns should be developed to direct forces to the regions selected for stress distribution. 11. All implant-supported restorations should seat passively over implant abutments. 12. Overdentures supported completely by implants may not require border extensions or palatal coverage to the same extent as conventional complete dentures. 13. The patient must be informed of the need for continued regular maintenance. 14. Diligent home care is necessary with periodic professional maintenance. F. Materials and devices

1. The dentist should be aware of the implant type, number, design, and stress distribution to the surrounding tissues when planning the prosthesis. 2. Materials and techniques must be biocompatible. G. Interim

restorations

1. Immediate restorations on endosseous implants may or may not be placed dependent upon modality and concepts. 2. Interim restorations may consist of removable complete dentures, removable partial dentures, or fixed prostheses depending upon the implant supported and system used. 3. Interim dentures for osseointegrated dental implant patients should be periodically relined with soft lining material during the healing period to prevent trauma to the implant sites.

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MATERIALS

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PROSTAETICS

AND DEVICES

A. Articulators

1. An articulator is a mechanical device that represents temporomandibular joints and the jaw members to which maxillary and mandibular casts may be attached to simulate some or all of the mandibular movements.7 2. The ideal articulator should be capable of reproducing all the patient’s jaw movements during function and parafunction and should maintain the mounted relationship of the opposing casts. 3. The use of an articulator is essential in most types of prosthodontic care. 4. An articulator is no more accurate in reproducing mandibular movements than the records employed to adjust the instrument. 5. The types of articulators can be classified as simple hinge, average value, semiadjustable, fully adjustable, and fossae molded. 6. Simple hinge articulators can be accurate in centric occlusion when caste are mounted at the correct vertical dimension of occlusion. Eccentric positions cannot be reproduced; changes in the vertical dimension of occlusion accomplished on the articulator invalidate the centric occlusion. 7. Average value articulators have the same limitations as simple hinge articulators, but will permit minor changes in vertical dimension of occlusion if a traverse horizontal-axis facebow is accepted by the articulator and utilized. Eccentric positions only approximate the patient’s eccentric positions. 8. Semiadjustable articulators used with a kinematic face-bow and eccentric records allow centric relation records to be mounted at an increased vertical dimension, minor changes in vertical dimension, and a closer approximation of the patient’s mandibular movement at the end points of eccentric movement than when an average value articulator is used. 9. A fully adjustable articulator or fossae molded articulator, when provided with the proper kinematic records and programming, will encompass all of the features of the semiadjustable articulator. It also will closely approximate the patient’s mandibular movement on all points along its eccentric movements. 10. Casts mounted in an articulator provide important data to analyze, diagnose, and plan treatment. 11. Verification of the relationship of the casts mounted in the articulator is a prerequisite to developing accurate occlusal contacts of completed restorations. 12. The adjustable guidances of an articulator should permit alteration to harmonize with the recorded and/or anticipated mandibular movements. 13. The anterior guide of an articulator should be adjustable and/or have a provision for custom guide fabrication. 14. A facebow record should be used for mounting the maxillary cast on an articulator that will accept an axis transfer. 15. An occlusal scheme developed on any articulator should be clinically evaluated in the mouth before a prosthesis is finalized or luted in place. 16. A fully adjustable articulator or technique giving equivalent accuracy is desirable when extensive fixed occlusal restorations are planned. 17. The dentist should know the limitations of the articulator being used and how to compensate for them. 18. A third point of reference is important in a facebow transfer because it: (a) Permits subsequent remounts of the maxillary cast in the same position (b) Permits use of previously recorded condylar path settings (c) Allows the maxillary cast to be oriented in the articulator in the same relation to the horizontal axis as the maxillary arch is to a similar plane selected on the patient (d) Permits the application of anatomic average values as condylar path settings when such settings are adequate

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RESTORATIONS

1. An interim restoration is a dental prosthesis used for a short interval for esthetics, mastication, occlusal support, convenience, or to condition the patient to accept definitive prosthodontic therapy. 2. Some temporomandibular joint symptoms may be alleviated by properly constructed interim restorations. 3. Tissue-conditioning materials placed on the tissue surface of surgical prostheses can compensate for tissue changes after surgery. 4. Transitional removable partial dentures may be used to facilitate osseous healing and to help maintain the vertical dimension of occlusion after posterior teeth have been removed. 5. Interim restorations may be desirable before placement of endosseous implants: (a) To maintain function and appearance during postsurgical healing phase (b) To aid in presurgical planning of the location and angulation of implants 6. Interim restorations should be used in 6xed prosthodontics when the vertical dimension must be restored and dental esthetic requirements determined. 7. An interim prosthesis may be constructed to aid in stabilizing the dentition during periodontal treatment. 8. Interim restorations should meet all guidelines for restorations with regard to periodontal health, esthetics, and function. They should stabilize the occlusion and position of the remaining teeth. Where lost vertical dimension of occlusion is to be restored, the interim restoration can verify this occlusal dimension so that it can be restored in harmony with oral facial function.

AUXILIARY PERSONNEL, WORK AUTHORIZATION, AND LABORATORY UTILIZATION A. Auxiliary personnel 1. Clear, concise communication among all members of the dental health team enhances the quality of the dental service received by a patient. 2. Auxiliary personnel may aid the dentist in obtaining diagnostic information for treatment planning purposes. 3. Delegation of specific procedures to qualified auxiliaries is acceptable where legally permissible; however, the dentist is responsible for treatment within the framework of liability established by the governing jurisdiction. 4. The dentist is responsible for the quality of the completed prosthesis even when parts of the fabrication are delegated to a dental laboratory. 5. The dental technician is a valuable member of the prosthodontic team. Communication between the technician and the dentist enhances the patient’s treatment. 6. The skills and training of the dental technician should be recognized and properly used as an adjunct to improve the quality of the finished restorations. 7. The dentist is required to use auxiliary personnel in compliance with state dental practices. 8. The dentist should be in the office when auxiliary personnel perform intraoral procedures as permitted by state laws. 9. The dentist should recognize special needs of patients and, when necessary, refer them to qualified specialists for treatment. 10. Cooperation and communication between the dentist and the oral and maxillofacial surgeon is essential for preprosthetic surgery procedures. 11. Prosthodontists, as well as the dental assistants and dental technicians, should prevent contagious disease contact and transmission. They should be immunized, sterilize instruments, impressions, and casts; disinfect environmental surfaces; and use gloves, protective eye wear, and face masks.

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12. When indicated, a dentist, physician, or nutritionist provide the patient with nutritional advice. B. Specific to mazillofacial prosthetics 1. Facial prostheses may be fabricated with patient prosthetist under the supervision of a prosthodontist.

should

contact by a

C. Work authorization and laboratory utilization 1. A properly executed work authorization can be an effective way for the dentist to communicate with the dental laboratory technician. 2. All work delegated to a commercial dental laboratory should be accompanied by a detailed written work authorization that complies with the applicable state dental laws. 3. Specific work authorization by the dentist is essential to provide quality control during the laboratory phase of prosthesis fabrication. 4. The dentist should provide a completed work authorization form that states the specifications of materials that will best meet the needs of the patient. When artificial teeth are involved, the specification should include manufacturer, material, shade, mold, and design. 5. Accurate interocclusal records are essential to properly mount casts in an articulator and are the dentist’s responsibility. 6. The dentist must provide the laboratory with adequate diagnostic caste, mounted casts, or (as a minimum) complete arch casts with a stable interocclusal record. Master casts should have dies trimmed and finish lines marked by the dentist. 7. Removable prostheses should be returned to the dentist for wax trial evaluation before they are completed. 8. The dentist is responsible for selection and final position of artificial teeth. 9. The flasking of a removable prosthesis in artificial stone or other suitable material should be done in sections to facilitate separation of the prosthesis from the investment material. 10. When a fixed restoration is to be placed in conjunction with a removable partial denture, the design of both should be coordinated by using a diagnostic cast to design the restorations. 11. The dentist should request that the metal ceramic framework be waxed to full contour as directed by diagnostic waxing and be cut back to allow proper veneering control. 12. Whenever the cast metal portion of any prosthesis is complicated, a framework try-in should be requested. Framework try-ins of extensive ceramic restorations should be routine. 13. Direct dentist-technician communication is necessary when working with ceramic restorations, and an appropriate method of communication should be employed to facilitate final shading and staining.

LEGAL

CONSIDERATIONS

A. Basic to all prosthodontics 1. The laws of each jurisdiction are different and, although this is written with generic law in mind, laws that apply to specific jurisdictions may be obtained from a local attorney. B. The dentist-patient relationship 1. Contract law governs the relationship of the dentist and the patient. 2. A contract is an agreement between competent parties to perform, or not to perform, some legal act. 3. Except in special situations, usually not related to the dentistpatient relationship, the terms of a contract need not be in writing to be enforceable. 4. The written contract serves as evidence that an agreement between the parties was reached. 5. The terms of a contact may be expressed or implied.

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6. Terms that usually are expressed include the fee, nature of the treatment to be performed, the time in which the treatment is to be completed, payment arrangements, and other specific items. 7. There are many additional implied terms (duties) that attach to the doctor-patient relationship. 8. In jurisdictions in which cases have attempted to attach implied warranties of fit and satisfaction, the courts have ruled against such warranty. 9. The courts have consistently held that the fee paid for the fabrication of a prosthesis is for the service required to complete it, and not for the physical prosthesis. However, guarantees made by the dentist would constitute an express term in the contract. 10. Unwarranted claims about the outcome of care that could be interpreted as guarantees are unethical and in some jurisdictions illegal. 11. Guarantees may result in loss of a suit based on breach of contqact rather than on malpractice. 12. In a breach of contract suit, negligence need not be shown. 13. In many jurisdictions, unless an express guarantee is made by the care provider, breach of contract suite brought against health providers are held to the same rules of law as suits of malpractice. 14. Many suits alleging malpractice are initiated because the dentist brought an action against the patient to collect the fee. C. The standard

of care

1. The standard of care to which dentists are held by courts in malpractice casesis to provide care using the same degree of knowledge, education, and training that a reasonably prudent dentist would provide in the same or similar community. 2. In general, because of rules of evidence, it is difficult to use texts, guidelines of professional organizations, or what is taught in a dental school as a means of establishing the standard to which a defendant dentist will be held. 3. Consistent with the definition of the standard of care, specialists usually are held to the standards of other specialists, and general practitioners are usually held to the standards of other general practitioners. 4. If one holds oneself as a specialist, although a generalist, the courts are likely to apply the standards of a specialist. 5. Another risk for the generalist (depending on the quality of treatment provided) is that if it can be shown that other generalists in the same community would have referred the patient to a specialist, not having made the referral could constitute negligence. 6. Generally, it is desirable to limit treatment to aspects of dentistry in which the dentist is qualified and competent. The dentist should make appropriate referrals on a timely basis and maintain his skills and knowledge consistent with the advances in his field of practice. D. Consent

1. It is firmly established that if a doctor treats a patient without informed consent, he or she ma,y be liable for damages, even if the treatment benefited the patient. 2. In the landmark cast of Canterbury versus Spence, decided in 1972, the court indicated that for consent to be valid it must be informed. Guidelines were established by which to judge whether the consent was truly informed. 3. During the past decade, most courts have adopted the Canterbury view, either in whole or in part. 4. The question that remains is: How much must the patient be told for the consent to meet the test of being informed? The states are divided on this issue. The traditional standard of informed consent determines by expert testimony what other practitioners in the same community disclose to their patients when faced with a similar treatment. The defendant practitioner is held to that measure of disclosure.

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5. Another standard of informed consent is the “reasonable perThere are two divergent views expressed by the courts using this standard: the objective test and the subjective test. In the former, the measure is: How much would any reasonable person have to be told to make an intelligent decision? In the latter: How much should the specific patient be told? 6. Much of the problem of informed consent centers around disclosure of risks. 7. In jurisdictions that adhere to the reasonable person standard, the general rule is that risks are “material” and should be disclosed. 8. A “material risk” is defined as one that may influence the patient’s decision. 9. A legislature may adopt any option to define informed consent. As an example, New York, by statute, chose the professional community standard. 10. Many courts have distinguished between total lack of consent and inadequate disclosure in obtaining consent. The former may be considered as assault and battery. In the latter, the dentist is negligent for failing to obtain informed consent. 11. In an emergency, where immediate care must be provided to protect the health or life of an injured person, and where consent cannot be obtained, consent is implied by law. 12. Documentation of consent, if it was obtained, plays a major role in the outcome of a legal procedure. 13. The documentation that consent was obtained depends on the mode of practice by the dentist. 14. In general, the more invasive the procedure and the greater the risk to the patient, the more documentation becomes important. 15. Consent may range from a note made on the patient’s record to a note made on the record initialed by the patient, or to the patient signing a separate form with a copy placed in the patient’s record folder. 16. The dentist must weigh the legal risks against the resources of the practice in time, personnel, and effort in documenting that consent was granted. 17. The best the practitioner can do, with respect to legal risks, is to take precautions to weight the odds in his or her favor.

son standard.”

E. Patient

records

1. In some jurisdictions, the law requires that accurate records of the diagnosis and treatment of a patient be maintained as part of care. 2. In the eyes of the law, good records are as important in patient care as the diagnosis and treatment. 3. Failure to keep accurate records may result in penalties imposed by the state if the requirement to maintain records is mandated by law, a finding of negligence by a court in a civil suit brought by a patient, or loss of a malpractice suit because the defendent dentist was unable to document the care provided. 4. Entries on the patient’s treatment record may become public information. Keep in mind that the record may eventually be seen and subject to review by the patient and his or her attorney. 5. For complete protection, if the records are required for the defense of an allegation of malpractice, they should be kept indefinitely. 6. A reasonable rule of thumb is to retain records of adults for 10 years after the last treatment visit. 7. In the case of minors, the records should be kept for 10 years after they reach majority. 8. Except when acting under the order of court, never part with the original record, radiographs, consultation reports, or any other document relating to care of a patient. 9. Entries in the record should be made in black ink or ballpoint pen. 10. Entries should be initialed or signed in offices where more than one person is permitted to write on patient’s records.

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11. Errors should not be blocked out so they cannot be read. 12. A single line should be drawn through the error and the word “error” written above. The correction should be made on the next available line. 13. What does not belong on the patient’s record is sometimes as important as what should be on it. Subjective notes as to the patient’s mental state should be avoided. 14. In many jurisdictions, the patient may have access to dental records. If you are sued, do not record conversations with any attorney or representatives of the insurance company on the treatment record. Place such notes in a separate file. 15. It is best not to include financial information on the treatment record. Such data should be kept separately. 16. Never tamper with the records. Fraud may be suspected if treatment records appear to have been tampered with. 17. The patient’s record is a legal document. F. Associates and employees 1. In partnership practice, each innocent partner may be held accountable for the negligent act of any other partner. 2. Corporate practice usually relieves an innocent shareholder from liability for the negligent acts of other shareholders. Only the negligent individual and the corporation may be held liable. 3. An employer is liable to an injured party for the negligent acts of an employee. 4. An employee of a dentist becomes the agent of the dentist in dealing with patients. 5. When a hygienist, assistant, or secretary-receptionist makes assurances to a patient regarding the treatment to be provided by the employer-dentist, the dentist is bound by such assurances. 6. Employees should be informed of the responsibilities that flow from their relationship with their employer and cautioned about statements made to patients. G. Managing the dificult patient and issues of abandonment 1. There are situations in which discontinuing treatment is the only reasonable alternatives to predictable failure in care; for example, when patient fails to cooperate in his or her care, to keep appointments, or to live up to financial agreements. If the dentist cannot function effectively under such circumstances, the patient should be so informed. 2. To help health practitioners avoid being found guilty of abandonment, the courts have provided the following guidelines:

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(a) Treatment should not be discontinued when the health of the patient is placed at risk. (b) The patient should be given adequate time to secure the services of a substitute dentist. (cl Cooperation in the treatment should be assured by the substitute dentist. (d) All records and radiographs relating to the patient’s treatment should be made available to the substitute dentist upon request. 3. In notifying the patient of an intention to discontinue treatment, remember that it is in the patient’s best interest and that the patient should be advised to seek the services of another dentist. 4. After telling the patient of a decision to discontinue treatment, a certified letter with return receipt required should be sent. The letter should state what the patient was told and assure cooperation with the substitute dentist. 5. It is best to let the patient select the new dentist. REFERENCES 1. The Academyof DentureProsthetics.Principles,concepts,and practices in prosthodontista.J PROSTHET DENT 1959;9:528-38. 2. The Academyof DentureProsthetics.Principles,concepts,and practices in prosthodontics.J PROSTHET DENT 1960,10:804-6. 3. The Academyof DentureProsthetics.Principles,concepts,and practices in prosthodontics.J PROSTHET DENT lS63;13:283-94. 4. The Academyof DentureProsthetics.Principles,concepts,and practices in prosthodontics-1967. J PROSTHET DENT 1968;19:180-98. 5. The Academyof DentureProsthetics.Principles,concepts,and practices in prosthodontics-1977.J PROSTHET DENT 1977;37:204-21. 6. The Academyof Denture Prosthetics.Principles,concepts,and practices in prosthodontics-1982. J PROSTHEYTDENT 1982;48:467-84. 7. The Academyof DentureProsthetics.Glossaryof prosthodonticterms.J PROSTHET DENT 1987;58:713-62.

REPRINTS Reprints

of the seventh edition

of the Principles,

Con-

cepts, and Practices in Prosthodontics are available from the Education and Research Foundation of Prosthodontics. Send to Dr. John B. Holmes, 279 Sandringham North, Moraga, CA 94556.

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