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Tooth-supported complete dentures: Description and clinical evaluation of a simplified technique
Tooth-supported clinical
complete
evaluation
dentures:
of a simplified
Description
and
technique
Robert M. Morrow, lieutenant Colonel, USAF (DC),* Joseph M. Powell, Major, USAF (DC),** William S. Jameson, lieutenant Colonel, USAF (DC),*** Leonard G. Jewson, lieutenant Colonel, USAF (DC),**** and Kenneth D. Rudd, Colonel, USAF (DC)***** Wilford Hall USAF Hospital, Aerospace Lackland Air Force Base, Texas
Medical
Division
(AFSC),
I
t has been estimated1 that twenty million Americans are totally edentulous and ten million more are edentulous in one arch. Nearly two thirds of all Americans over the age of 75 years are edentulous. In one study* of the reasons for removal of teeth in an oral surgery practice among middle-income families, 20 per cent were clinically sound teeth but removed for “prosthetic” reasons. These statistics indicate a need for increased efforts in preventive dentistry by all members of the dental profession in order to significantly reduce the number of persons who become edentulous. Patients with many teeth that are hopeless are often candidates for complete dentures. They may, however, have 1, 2, or 3 retainable teeth. Frequently, these few teeth are removed because they are considered inadequate to support partial dentures, and complete dentures are constructed. However, such patients can benefit from tooth-supported complete dentures. TOOTH-SUPPORTED
COMPLETE
DENTURES
The variety of methods3-5 for using natural teeth to support and stabilize complete dentures indicates an awareness of the need for effective techniques that will permit the retention of teeth inadequate to support the usual prostheses. The techniques using natural teeth vary in complexity. In some instances, the denture is constructed for insertion directly onto the remaining recontoured, but unprotected, natural teeth and, undoubtedly, many are successful. The disadvantages Read before the Academy *Training **Assistant ***Assistant ****Staff,
Officer
Prosthetics
Project
Officer,
in Honolulu,
Hawaii.
Department
of Prosthodontics.
Chief, Area Dental Laboratory. Chairman, Department of Prosthodontics. Department
*****Consultant
414
of Denture
and Research
cJf Periodontics.
in Prosthodontics
to the Surgeon, USAFE.
Volume 22 Number 4
Tooth-supported
complete
dentures
415
of this technique include the susceptibility of the unprotected abutment teeth to caries, the possibility of wear between the denture and abutment teeth, and e\pr-n the possibility of denture breakage while in service. Gold copings cemented on prepared abutment teeth prior to denture construe,tion provide increased protection against caries and can contribute to an impro\4 esthetic result. The preparation reduces the size of the abutment teeth and enabks the replacements on the denture to approximate the size and contour of the uljprepared teeth. Successful endodontic therapy for abutment teeth further aids m achieving this objective, and facilitates the development of improved clinical crown / root ratios. As with unprepared teeth, complete dentures constructed for insertion over abutment copings are subject to wear between the gold coping and the acrylic resin of the denture base, with a resultant shorter service life. Milleti advocates the use of gold copings on abutment teeth and corresponding gold copings within the completed denture. His method provides caries protection and metal-to-metal bearing surfaces between the denture and abutment copings. The effects are the minimizing of wear between abutment copings and the dentun:, reduction in breakage, and more effective stress distribution to supporting structures. In a modification of this technique, a cast metal base, rather than individual denture copings, is incorporated within the denture. G Both methods have recei\.rd extensive use at our facility with excellent results.
DISADVANTAGES OF TOOTH-SUPPORTED COMPLETE DENTURES Disadvantages of both methods are the time requirement and the increased cost associated with fabricating cast gold denture copings, or cast gold or chrome-cobalt alloy denture bases. In addition, the flasking and packing procedures are more complicated than for routine complete dentures, and any subsequent rebasing or relining of the denture is more difficult. Increased cost and complex laboratory requirements often are negative influences on the use of a given procedure, regarrlless of its clinical validity. The purpose of this project was to evaluate eclectically the current techniques for constructing tooth-supported complete dentures and To attempt to simplify the clinical and laboratory procedures incident to the technique. A clinical study involving the objective determination of pocket depths and rhe horizontal mobility of abutments was included to aid in evaluation.
METHODS AND MATERIALS Careful evaluation of the advantages of placing gold copings over prepared endodontically treated teeth resulted in their use throughout the study, but with some design modifications. Reduced caries susceptibility, increased potential for improving crown/root ratios and esthetics, as well as better stress distribution to abutment teeth, justify the additional clinical and laboratory procedures for placement of copings. Although possessing considerable merit, metal bases or copings within the denture base require additional laboratory procedures that significantly increase costs. Laboratory expense can be reduced and positive contributions with metal ba.sc-vs and denture copings can be retained by using prefabricated chrome-cobalt bearings processed with the denture base.
416
Morrow
et al.
Fig . 1. The chrome-cobalt bearing provides the occlusal surface of the abutment coping.
Fig. 2. A waxing
tool is used to shape uniform
J. Pros. Dent. October, 1969
metal-to-metal
indentations
contact
between
in coping patterns.
the denture
and
Tooth-supported CHROME-COBALT
complete dentures
417
BEARINGS
Some chrome-cobalt castings serve as metal bearing surfaces between the abutment copings and the denture base (Fig. 1). They are hemispherical in shape and have an upper surface that is roughened by coating it with retentive crystals to permit its retention within the denture base resin. The convex surface of each bearing is designed so it will function in a corresponding concavity placed in the occlusai surface of the coping on the abutment tooth, The radius of curvature for the denture bearing is slightly less than the one for the indentation in the tooth coping. The difference in curvature between the surface of the denture bearing and the curvature of the coping indentation permits a centralized contact to be made between the bearing surfaces, and this allows some freedom of rotation. Uniformity of coping indentations was assured by constructing a special waxing tool (Fig. 2) This tool is used to make indentations of known curvatures in the occlusal surfaces of wax patterns for the abutment copings. The denture bearings are cast in :I chrome-cobalt alloy. * The technique for constructing the denture support bearings and the waxing tool is to be described in a later article. CONSTRUCTING
THE DENTURE
The clinical success of tooth-supported complete dentures is predicated on thorough examination, accurate diagnosis, and a carefully formulated treatment plan. In addition to a thorough visual and digital examination of the oral cavity, a radiographic survey and a history are essential. The patient’s oral hygiene status should be determined, and corrective measures should be instituted as they are indicated. Maintenance of an adequate oral hygiene level is a prerequisite to success. Hopeless teeth should be identified and prospective abutment teeth evaluated systematically from four viewpoints: periodontal, endodontic, positional consideration, and caries susceptibility. Ideally, abutment teeth should present minimal periodontal involvement, but this situation seldom prevails, Apparent horizontal mobility can be reduced by shortening the length of the clinical crown, and pocket depths often can be reduced by appropriate periodontal procedures. Normally, the periodontal treatment is completed after the hopeless teeth have been removed and prior to the initiation of endodontic therapy. Endodontic treatment of abutment teeth is recommended because it facilitates the development of more favorable clinical crown/root ratios, allows for an improved esthetic result, and often permits the use of tilted or malposed abutment teeth. The positional consideration of prospective abutment teeth includes the determination of their number and distribution in the dental arch. Patients with four or less retainable teeth in an arch should be considered for tooth-supported dentures. When an arch has more than four retainable teeth, other treatment approaches mav be indicated. Ideally, abutments should be equally distributed bilaterally, e.g., .a cuspid and a second premolar on the left and a cuspid and a second premolar on the right. Two abutment teeth in an arch are common and typified by a cuspid or a premolar on each side. Cuspids and single-rooted premolars frequently are selected *Ticonium,
type 100, C.M.P.
Industries,
Inc., Albany,
N. Y.
418
Morrow
et al.
as abutments because they are amenable to endodontic Extensive caries involvement of a prospective abutment unless the abutment tooth is restorable.
J. Pros. Dent. October, 1969
and periodontal treatment. may contraindicate its use
TREATMENT SEQUENCE After the identification of hopeless teeth and selection of abutments, immediateinsertion removable partial dentures are constructed. They are inserted at the time of surgery and worn by the patient throughout the healing period. Modifications often are necessary during this phase of treatment in order to maintain adequate adaptation and patient comfort. The indicated periodontal and endodontic procedures can be completed during the healing period, which reduces the total treatment period. Upon completion of all prerequisite procedures, the abutment teeth are prepared. They should be reduced adequately, both axially and occlusogingivally, to achieve the objectives of abutment preparation. These objectives are as follows: (1) reduction of clinical crown/root ratio, (2) adequate removal of tooth structure to facilitate improved esthetics, (3) planning of tooth structure removal to permit the use of tilted or malposed abutments, (4) contouring of abutment form to permit axial loading of the abutment tooth during function, and (5) development of accurate preparation margins.
MAKING THE COPINGS Prepared teeth should be conical in shape and have the occlusal surface flattened. Chamfer-type margins should be extended immediately below the free gingival margin. Impressions of the prepared teeth are made by using rubber base or reversible hydrocolloid impression materials. The impression adapted for removable dies is poured in an improved stone. After the setting, the dies are removed and the margins are indicated by “ditching.” The wax patterns are carved and the occlusal indentation is made with the waxing tool while the pattern is mounted in a surveyor. Then the patterns are sprued, invested, burned out, and cast in a type III gold alloy. The polished castings are fitted in the mouth by using disclosing wax. Endodontically treated abutment teeth are coated with a fluoride caries-preventing solution prior to cementing the copings. After cementation, a border-molded impression is made of the copings and the residual alveolar ridges in a rubber base material carried to the mouth in a relieved resin tray. Opposing arch impressions are made at this time, and improved stone is poured into the boxed impressions. The abutments on the cast are blocked out with wax prior to constructing autopolymerizing (cold-curing) resin baseplates. Denture bearings are placed in each abutment indentation on the cast and sealed in position with baseplate wax, and the cast is coated with a tinfoil substitute. A cold-curing soft resin is placed in undercut areas, and the baseplate is completed by adding a hard type of cold-curing resin over the denture bearings and the soft resin in order to build up the desired thickness. The denture bearings retained in the baseplate contribute to the support and stability of the baseplate during the jaw relation recording procedures. Jaw relation records are obtained and verified, and the casts are mounted in an articulator by the use of a face-bow transfer.
Volume 22 Number 4
Tooth-supported
Fig. 3. Resin denture abutment.
teeth are hollowed
complete
out so they can be placed
dentures
over the bearin:
419
ac~i tl,,.
The mold and shade of the teeth are selected, and the anterior teeth are po~itioned in the presence of the patient by the dentist. Baseplate resin is removed in the region of the abutment teeth to permit the setting of denture teeth for a try-in. The denture bearings are retrieved from thr. resin that is removed from the baseplates by heating the resin and taking them out as the resin softens. These same denture bearings are returned to the master cast an{! sealed in position with sticky wax. Resin denture teeth of the proper size and shad!are hollowed with a bur until they can be properly positioned over the abutment-~ (Fig. 3). They are waxed to the bearings and the occlusion is adjusted prior to thi* try-in. Either anatomic or monoplane posterior teeth can be used. When constructinrc a complete denture opposed by natural teeth, the occlusion is developed by thrb functionally generated path technique. After the try-in, the wax dentures are sealed to the casts, the occlusion is PC-Yfected, and the denture patterns are waxed. The wax is eliminated and the dentures bearings are retrieved from the wax. Then the bearings are cleaned in boiling watt:! and cemented to the casts with oxyphosphate of zinc cement (Fig. 4). The uppt~’ surfaces of the bearings are opaqued* prior to coating the casts with a tinfoil substitute. The denture flanges are tinted by placing tinting polymers on the facial surface% of the stone in the cope (the upper half of the flask). Heat-curing polymer of thus proper color is sifted into the abutment indentations of the upper part of the flask. and saturated with a monomer. Denture base resin amenable to the single closurca technique is mixed and placed into the mold, and the flasks are slowly closed in zr hand compress. The dentures are subjected to the proper curing cycle, at the end o! which they are bench cooled, retrieved from the flasks, and mounted in the artic:;*Justi
Opaque,
H. D. Justi Division,
Williams
Gold Refining
Co., Inc., Philadelphia,
Pa
420
Morrow
J. Pros. Dent. October, 1969
et al.
Fig. 4. The chrome-cobalt the denture base resin.
bearings
(arrows)
are cemented
to the abutments
prior
to packing
lator for the correction of processing changes. Then the corrected dentures are removed from the cast and polished (Fig. 5) . Disclosing wax is used at the time of insertion to locate contacts between the abutment teeth and the acrylic resin of the denture base. Abutment contacts should exist only between the convex surface of the bearing and the concave bearing surface of the coping on the tooth. Inasmuch as contacts between the lateral walls of the abutments and the denture are undesirable, they are removed by grinding from the resin of the denture when the need is indicated by the disclosing wax. The completed dentures are subjected to the usual checks associated with the insertion of dentures, and special emphasis is placed upon maintenance instructions. The need for an adequate oral hygiene program is reemphasized to the patient, stressing the correlation between the oral hygiene and the service life of the prosthesis. Disclosing tablets are used to indicate areas that require additional cleansing, and the patient is instructed to use narrow gauze strips to clean the abutment teeth effectively. The need for follow-up care is discussed, and post-insertion visits are scheduled.
CLINICAL EVALUATION Tooth-supported complete dentures were constructed in the manner described for nine patients involving twenty abutment teeth. Six of the tooth-supported dentures were made for the maxillary arch, and three for the mandibular arch. Five of the test dentures were opposed by natural teeth and four were opposed by a softtissueborne complete denture. Both monoplane and anatomic occlusal patterns were used. Functionally generated path occlusions were developed for the dentures
Tooth-supported
Fig. 5. The bearings are visible in a completed
complete dentures
421
denture.
opposed by natural teeth. All abutment teeth were either cuspids or premolars that had been endodontically treated. Seven of the nine dentures were supported by two abutment teeth, and two by three abutment teeth. When two abutments were used, they were distributed bilaterally, whereas when three were used, two were on one side of the arch and one on the other. Mobility of teeth and depth of the periodontal pockets are parameters that are frequently used to assess periodontal health. When two or three teeth support a complete denture, there may be a physiologically incompatible application of force to the abutment teeth, with a concomitant alteration in mobility and pocket depth values. The objective of this study was to determine the effect of a tooth-supported denture on the horizontal mobility and the pocket depth of the supporting abutment teeth. The horizontal mobility of each abutment tooth was measured with a periodontometer, as described by O’Leary and Rudd.7 Pocket depths were recorded by a staff periodontist for each tooth at eight positions. Fiducial recordings were obtained for these parameters at the time of tooth coping cementation after prerequisite endodontic and periodontal therapy. In addition to the initial recordings, postinsertion measurements were obtained during the first, second, third, and fourth postinsertion weeks, and then at monthly intervals. The shortest period of observation was 80 days following insertion of the denture and the longest was 221 days. The average postinsertion observation period was 147 days. All but four pcriodontometer measurements were made by the same dentist. Measurement perjods were scheduled at the same hour throughout the study. The measuring gauge used to indicate the mobility of the teeth was stabilized in the mouth with acrylic resin clutches. A 500 gram force was applied to the facial and lingual surfaces of the teeth> and the resultant deflections of the measuring gauge were noted (Fig. 6). Index
422
Morrow
J. Pros. Dent. October, 1969
et al.
Fig. 6. The periodontometer
in place on the patient.
Table
mobility
I. Mean
abutment
Before
No. of teeth
Table II. Mean pocket depth
20
placement
1
Before
(mm.) placement 2.1
before and after placement End of test period 15.1
15.3
20
No. of teeth
(mm./lOO)
before and after placement (
End of test period 2.3
)
Percentage
of denture change
1.3 Decrease
of denture 1 Percentage
change
9.0 Increase
marks were placed on the teeth in a diagnostic cast in order to facilitate the application of force at the same point on the tooth at the time of each measurement. The total horizontal mobility was determined by adding the facial and lingual deflections. Two facial and lingual measurements were made and the average horizontal mobility was recorded according to the schedule.
RESULTS The horizontal mobility of the 20 abutment teeth did not vary significantly from the fiducial recordings throughout the test period (Table I). No difference in mo-
Volume 22 Number 4
Tooth-supported
complete
dentures
423
bility behavior was noted between the abutment-supported dentures opposed by complete dentures and abutment-supported dentures opposed by natural teeth. Tlrc number of patients treated was not large enough to permit evaluation of mobilit) differences, if any, related to the type of occlusion used. The depths of the pockets also tended to remain near the fiducial levels (‘1 able II). One patient had an acute periodontal abscess, which significantly increased the pocket depth and mobility of that abutment. Subjective observations by the patients with respect to comfort, esthetics, and masticatory performance were uniformly favorable. Two dentures were brokru during the study; one was dropped onto a hard surface, and the other developed a fracture line across the labial flange, but both were repaired satisfactorily.
SUMMARY AND CONCLUSIONS A method for constructing tooth-supported complete dentures was described and the results of a clinical evaluation were discussed. In addition to those advantages inherent to tooth-supported dentures, the simplified construction technique eliminated the need for cast metal bases or denture copings. Also, the small size of the metal casting in the denture permitted its unobtrusive placement within the denture and facilitated an esthetic result, The uniformity of the chrome-cobalt bearings, and the waxing tool improve the stress distribution, and made possible the construction of duplicate dentures with minimal additional time and materials. Horizontal mobility and pocket depth were recorded for 20 abutments in 9 patients following the insertion of dentures constructed by the described method. The horizontal mobility for abutment-teeth supported complete dentures tended to remain at or below fiducial levels throughout the test period. With only a slight variation, pocket depths remained consistent with initial levels. Patient acceptance of the tooth-supported dentures was uniformly excellent, as manifested by few postinsertion complaints and steady improvement in masticator-y performance. One denture fractured when dropped on the floor, and another developed a fracture line in a thin labial flange; otherwise there were no incidents of denture failure dlle to breakage. The principal disadvantage of the technique was related to the need ~OJ prerequisite periodontic, endodontic, and surgical procedures that, in turn, lengthenrd the treatment period and increased the cost. This factor should be equated reaiistitally with the ultimate service to the patient. Based on the objective clinical evalultion, the tooth-supported complete denture remains an effective, preventive prosthodontic procedure.
References 1. Selected Dental Findings in Adults by Age, Race, and Sex, National Center for Health Statistics, Series 11, Number 7, 1960-1962, Washington, D. C., U. S. Department of Health, Education, and Welfare, 1962. 2. Krogh, H. W.: Permanent Tooth Mortality. A Clinical Study of Loss, J. A. D. A. 57: 670-675, 1958. 3. Brill, N.: Adaptation and the Hybrid Prosthesis, J. PROS. DENT. 5: 811-824, 1955. 4. Miller, P. A.: Complete Dentures Supported by Natural Teeth, J. PROS. DENT. 8: 921928, 1958. 5. Dolder, E. J.: The Bar Joint Mandibular Denture, J. PROS. DENT. 11: 689-707, 1961.
424
Morrow
et al.
J. Pros. Dent. October, 1969
6. Morrow, R. M., Feldmann, E. E., Rudd, K. D., and Trovillion, H. M.: Tooth Supported Compete Dentures: An Approach to Preventive Prosthodontics, J. PROS. DENT. Pending publication. 7. O’Leary, T. J., and Rudd, K. D.: An Instrument for Measuring Horizontal Tooth Mobility, J. Am. Sot. Periodontist 1: 249-254, 1963.
206
EASTRIDGE SAN ANTONIO,
DR.
TEX. 78227
complete
evaluation
dentures:
of a simplified
Description
and
technique
Robert M. Morrow, lieutenant Colonel, USAF (DC),* Joseph M. Powell, Major, USAF (DC),** William S. Jameson, lieutenant Colonel, USAF (DC),*** Leonard G. Jewson, lieutenant Colonel, USAF (DC),**** and Kenneth D. Rudd, Colonel, USAF (DC)***** Wilford Hall USAF Hospital, Aerospace Lackland Air Force Base, Texas
Medical
Division
(AFSC),
I
t has been estimated1 that twenty million Americans are totally edentulous and ten million more are edentulous in one arch. Nearly two thirds of all Americans over the age of 75 years are edentulous. In one study* of the reasons for removal of teeth in an oral surgery practice among middle-income families, 20 per cent were clinically sound teeth but removed for “prosthetic” reasons. These statistics indicate a need for increased efforts in preventive dentistry by all members of the dental profession in order to significantly reduce the number of persons who become edentulous. Patients with many teeth that are hopeless are often candidates for complete dentures. They may, however, have 1, 2, or 3 retainable teeth. Frequently, these few teeth are removed because they are considered inadequate to support partial dentures, and complete dentures are constructed. However, such patients can benefit from tooth-supported complete dentures. TOOTH-SUPPORTED
COMPLETE
DENTURES
The variety of methods3-5 for using natural teeth to support and stabilize complete dentures indicates an awareness of the need for effective techniques that will permit the retention of teeth inadequate to support the usual prostheses. The techniques using natural teeth vary in complexity. In some instances, the denture is constructed for insertion directly onto the remaining recontoured, but unprotected, natural teeth and, undoubtedly, many are successful. The disadvantages Read before the Academy *Training **Assistant ***Assistant ****Staff,
Officer
Prosthetics
Project
Officer,
in Honolulu,
Hawaii.
Department
of Prosthodontics.
Chief, Area Dental Laboratory. Chairman, Department of Prosthodontics. Department
*****Consultant
414
of Denture
and Research
cJf Periodontics.
in Prosthodontics
to the Surgeon, USAFE.
Volume 22 Number 4
Tooth-supported
complete
dentures
415
of this technique include the susceptibility of the unprotected abutment teeth to caries, the possibility of wear between the denture and abutment teeth, and e\pr-n the possibility of denture breakage while in service. Gold copings cemented on prepared abutment teeth prior to denture construe,tion provide increased protection against caries and can contribute to an impro\4 esthetic result. The preparation reduces the size of the abutment teeth and enabks the replacements on the denture to approximate the size and contour of the uljprepared teeth. Successful endodontic therapy for abutment teeth further aids m achieving this objective, and facilitates the development of improved clinical crown / root ratios. As with unprepared teeth, complete dentures constructed for insertion over abutment copings are subject to wear between the gold coping and the acrylic resin of the denture base, with a resultant shorter service life. Milleti advocates the use of gold copings on abutment teeth and corresponding gold copings within the completed denture. His method provides caries protection and metal-to-metal bearing surfaces between the denture and abutment copings. The effects are the minimizing of wear between abutment copings and the dentun:, reduction in breakage, and more effective stress distribution to supporting structures. In a modification of this technique, a cast metal base, rather than individual denture copings, is incorporated within the denture. G Both methods have recei\.rd extensive use at our facility with excellent results.
DISADVANTAGES OF TOOTH-SUPPORTED COMPLETE DENTURES Disadvantages of both methods are the time requirement and the increased cost associated with fabricating cast gold denture copings, or cast gold or chrome-cobalt alloy denture bases. In addition, the flasking and packing procedures are more complicated than for routine complete dentures, and any subsequent rebasing or relining of the denture is more difficult. Increased cost and complex laboratory requirements often are negative influences on the use of a given procedure, regarrlless of its clinical validity. The purpose of this project was to evaluate eclectically the current techniques for constructing tooth-supported complete dentures and To attempt to simplify the clinical and laboratory procedures incident to the technique. A clinical study involving the objective determination of pocket depths and rhe horizontal mobility of abutments was included to aid in evaluation.
METHODS AND MATERIALS Careful evaluation of the advantages of placing gold copings over prepared endodontically treated teeth resulted in their use throughout the study, but with some design modifications. Reduced caries susceptibility, increased potential for improving crown/root ratios and esthetics, as well as better stress distribution to abutment teeth, justify the additional clinical and laboratory procedures for placement of copings. Although possessing considerable merit, metal bases or copings within the denture base require additional laboratory procedures that significantly increase costs. Laboratory expense can be reduced and positive contributions with metal ba.sc-vs and denture copings can be retained by using prefabricated chrome-cobalt bearings processed with the denture base.
416
Morrow
et al.
Fig . 1. The chrome-cobalt bearing provides the occlusal surface of the abutment coping.
Fig. 2. A waxing
tool is used to shape uniform
J. Pros. Dent. October, 1969
metal-to-metal
indentations
contact
between
in coping patterns.
the denture
and
Tooth-supported CHROME-COBALT
complete dentures
417
BEARINGS
Some chrome-cobalt castings serve as metal bearing surfaces between the abutment copings and the denture base (Fig. 1). They are hemispherical in shape and have an upper surface that is roughened by coating it with retentive crystals to permit its retention within the denture base resin. The convex surface of each bearing is designed so it will function in a corresponding concavity placed in the occlusai surface of the coping on the abutment tooth, The radius of curvature for the denture bearing is slightly less than the one for the indentation in the tooth coping. The difference in curvature between the surface of the denture bearing and the curvature of the coping indentation permits a centralized contact to be made between the bearing surfaces, and this allows some freedom of rotation. Uniformity of coping indentations was assured by constructing a special waxing tool (Fig. 2) This tool is used to make indentations of known curvatures in the occlusal surfaces of wax patterns for the abutment copings. The denture bearings are cast in :I chrome-cobalt alloy. * The technique for constructing the denture support bearings and the waxing tool is to be described in a later article. CONSTRUCTING
THE DENTURE
The clinical success of tooth-supported complete dentures is predicated on thorough examination, accurate diagnosis, and a carefully formulated treatment plan. In addition to a thorough visual and digital examination of the oral cavity, a radiographic survey and a history are essential. The patient’s oral hygiene status should be determined, and corrective measures should be instituted as they are indicated. Maintenance of an adequate oral hygiene level is a prerequisite to success. Hopeless teeth should be identified and prospective abutment teeth evaluated systematically from four viewpoints: periodontal, endodontic, positional consideration, and caries susceptibility. Ideally, abutment teeth should present minimal periodontal involvement, but this situation seldom prevails, Apparent horizontal mobility can be reduced by shortening the length of the clinical crown, and pocket depths often can be reduced by appropriate periodontal procedures. Normally, the periodontal treatment is completed after the hopeless teeth have been removed and prior to the initiation of endodontic therapy. Endodontic treatment of abutment teeth is recommended because it facilitates the development of more favorable clinical crown/root ratios, allows for an improved esthetic result, and often permits the use of tilted or malposed abutment teeth. The positional consideration of prospective abutment teeth includes the determination of their number and distribution in the dental arch. Patients with four or less retainable teeth in an arch should be considered for tooth-supported dentures. When an arch has more than four retainable teeth, other treatment approaches mav be indicated. Ideally, abutments should be equally distributed bilaterally, e.g., .a cuspid and a second premolar on the left and a cuspid and a second premolar on the right. Two abutment teeth in an arch are common and typified by a cuspid or a premolar on each side. Cuspids and single-rooted premolars frequently are selected *Ticonium,
type 100, C.M.P.
Industries,
Inc., Albany,
N. Y.
418
Morrow
et al.
as abutments because they are amenable to endodontic Extensive caries involvement of a prospective abutment unless the abutment tooth is restorable.
J. Pros. Dent. October, 1969
and periodontal treatment. may contraindicate its use
TREATMENT SEQUENCE After the identification of hopeless teeth and selection of abutments, immediateinsertion removable partial dentures are constructed. They are inserted at the time of surgery and worn by the patient throughout the healing period. Modifications often are necessary during this phase of treatment in order to maintain adequate adaptation and patient comfort. The indicated periodontal and endodontic procedures can be completed during the healing period, which reduces the total treatment period. Upon completion of all prerequisite procedures, the abutment teeth are prepared. They should be reduced adequately, both axially and occlusogingivally, to achieve the objectives of abutment preparation. These objectives are as follows: (1) reduction of clinical crown/root ratio, (2) adequate removal of tooth structure to facilitate improved esthetics, (3) planning of tooth structure removal to permit the use of tilted or malposed abutments, (4) contouring of abutment form to permit axial loading of the abutment tooth during function, and (5) development of accurate preparation margins.
MAKING THE COPINGS Prepared teeth should be conical in shape and have the occlusal surface flattened. Chamfer-type margins should be extended immediately below the free gingival margin. Impressions of the prepared teeth are made by using rubber base or reversible hydrocolloid impression materials. The impression adapted for removable dies is poured in an improved stone. After the setting, the dies are removed and the margins are indicated by “ditching.” The wax patterns are carved and the occlusal indentation is made with the waxing tool while the pattern is mounted in a surveyor. Then the patterns are sprued, invested, burned out, and cast in a type III gold alloy. The polished castings are fitted in the mouth by using disclosing wax. Endodontically treated abutment teeth are coated with a fluoride caries-preventing solution prior to cementing the copings. After cementation, a border-molded impression is made of the copings and the residual alveolar ridges in a rubber base material carried to the mouth in a relieved resin tray. Opposing arch impressions are made at this time, and improved stone is poured into the boxed impressions. The abutments on the cast are blocked out with wax prior to constructing autopolymerizing (cold-curing) resin baseplates. Denture bearings are placed in each abutment indentation on the cast and sealed in position with baseplate wax, and the cast is coated with a tinfoil substitute. A cold-curing soft resin is placed in undercut areas, and the baseplate is completed by adding a hard type of cold-curing resin over the denture bearings and the soft resin in order to build up the desired thickness. The denture bearings retained in the baseplate contribute to the support and stability of the baseplate during the jaw relation recording procedures. Jaw relation records are obtained and verified, and the casts are mounted in an articulator by the use of a face-bow transfer.
Volume 22 Number 4
Tooth-supported
Fig. 3. Resin denture abutment.
teeth are hollowed
complete
out so they can be placed
dentures
over the bearin:
419
ac~i tl,,.
The mold and shade of the teeth are selected, and the anterior teeth are po~itioned in the presence of the patient by the dentist. Baseplate resin is removed in the region of the abutment teeth to permit the setting of denture teeth for a try-in. The denture bearings are retrieved from thr. resin that is removed from the baseplates by heating the resin and taking them out as the resin softens. These same denture bearings are returned to the master cast an{! sealed in position with sticky wax. Resin denture teeth of the proper size and shad!are hollowed with a bur until they can be properly positioned over the abutment-~ (Fig. 3). They are waxed to the bearings and the occlusion is adjusted prior to thi* try-in. Either anatomic or monoplane posterior teeth can be used. When constructinrc a complete denture opposed by natural teeth, the occlusion is developed by thrb functionally generated path technique. After the try-in, the wax dentures are sealed to the casts, the occlusion is PC-Yfected, and the denture patterns are waxed. The wax is eliminated and the dentures bearings are retrieved from the wax. Then the bearings are cleaned in boiling watt:! and cemented to the casts with oxyphosphate of zinc cement (Fig. 4). The uppt~’ surfaces of the bearings are opaqued* prior to coating the casts with a tinfoil substitute. The denture flanges are tinted by placing tinting polymers on the facial surface% of the stone in the cope (the upper half of the flask). Heat-curing polymer of thus proper color is sifted into the abutment indentations of the upper part of the flask. and saturated with a monomer. Denture base resin amenable to the single closurca technique is mixed and placed into the mold, and the flasks are slowly closed in zr hand compress. The dentures are subjected to the proper curing cycle, at the end o! which they are bench cooled, retrieved from the flasks, and mounted in the artic:;*Justi
Opaque,
H. D. Justi Division,
Williams
Gold Refining
Co., Inc., Philadelphia,
Pa
420
Morrow
J. Pros. Dent. October, 1969
et al.
Fig. 4. The chrome-cobalt the denture base resin.
bearings
(arrows)
are cemented
to the abutments
prior
to packing
lator for the correction of processing changes. Then the corrected dentures are removed from the cast and polished (Fig. 5) . Disclosing wax is used at the time of insertion to locate contacts between the abutment teeth and the acrylic resin of the denture base. Abutment contacts should exist only between the convex surface of the bearing and the concave bearing surface of the coping on the tooth. Inasmuch as contacts between the lateral walls of the abutments and the denture are undesirable, they are removed by grinding from the resin of the denture when the need is indicated by the disclosing wax. The completed dentures are subjected to the usual checks associated with the insertion of dentures, and special emphasis is placed upon maintenance instructions. The need for an adequate oral hygiene program is reemphasized to the patient, stressing the correlation between the oral hygiene and the service life of the prosthesis. Disclosing tablets are used to indicate areas that require additional cleansing, and the patient is instructed to use narrow gauze strips to clean the abutment teeth effectively. The need for follow-up care is discussed, and post-insertion visits are scheduled.
CLINICAL EVALUATION Tooth-supported complete dentures were constructed in the manner described for nine patients involving twenty abutment teeth. Six of the tooth-supported dentures were made for the maxillary arch, and three for the mandibular arch. Five of the test dentures were opposed by natural teeth and four were opposed by a softtissueborne complete denture. Both monoplane and anatomic occlusal patterns were used. Functionally generated path occlusions were developed for the dentures
Tooth-supported
Fig. 5. The bearings are visible in a completed
complete dentures
421
denture.
opposed by natural teeth. All abutment teeth were either cuspids or premolars that had been endodontically treated. Seven of the nine dentures were supported by two abutment teeth, and two by three abutment teeth. When two abutments were used, they were distributed bilaterally, whereas when three were used, two were on one side of the arch and one on the other. Mobility of teeth and depth of the periodontal pockets are parameters that are frequently used to assess periodontal health. When two or three teeth support a complete denture, there may be a physiologically incompatible application of force to the abutment teeth, with a concomitant alteration in mobility and pocket depth values. The objective of this study was to determine the effect of a tooth-supported denture on the horizontal mobility and the pocket depth of the supporting abutment teeth. The horizontal mobility of each abutment tooth was measured with a periodontometer, as described by O’Leary and Rudd.7 Pocket depths were recorded by a staff periodontist for each tooth at eight positions. Fiducial recordings were obtained for these parameters at the time of tooth coping cementation after prerequisite endodontic and periodontal therapy. In addition to the initial recordings, postinsertion measurements were obtained during the first, second, third, and fourth postinsertion weeks, and then at monthly intervals. The shortest period of observation was 80 days following insertion of the denture and the longest was 221 days. The average postinsertion observation period was 147 days. All but four pcriodontometer measurements were made by the same dentist. Measurement perjods were scheduled at the same hour throughout the study. The measuring gauge used to indicate the mobility of the teeth was stabilized in the mouth with acrylic resin clutches. A 500 gram force was applied to the facial and lingual surfaces of the teeth> and the resultant deflections of the measuring gauge were noted (Fig. 6). Index
422
Morrow
J. Pros. Dent. October, 1969
et al.
Fig. 6. The periodontometer
in place on the patient.
Table
mobility
I. Mean
abutment
Before
No. of teeth
Table II. Mean pocket depth
20
placement
1
Before
(mm.) placement 2.1
before and after placement End of test period 15.1
15.3
20
No. of teeth
(mm./lOO)
before and after placement (
End of test period 2.3
)
Percentage
of denture change
1.3 Decrease
of denture 1 Percentage
change
9.0 Increase
marks were placed on the teeth in a diagnostic cast in order to facilitate the application of force at the same point on the tooth at the time of each measurement. The total horizontal mobility was determined by adding the facial and lingual deflections. Two facial and lingual measurements were made and the average horizontal mobility was recorded according to the schedule.
RESULTS The horizontal mobility of the 20 abutment teeth did not vary significantly from the fiducial recordings throughout the test period (Table I). No difference in mo-
Volume 22 Number 4
Tooth-supported
complete
dentures
423
bility behavior was noted between the abutment-supported dentures opposed by complete dentures and abutment-supported dentures opposed by natural teeth. Tlrc number of patients treated was not large enough to permit evaluation of mobilit) differences, if any, related to the type of occlusion used. The depths of the pockets also tended to remain near the fiducial levels (‘1 able II). One patient had an acute periodontal abscess, which significantly increased the pocket depth and mobility of that abutment. Subjective observations by the patients with respect to comfort, esthetics, and masticatory performance were uniformly favorable. Two dentures were brokru during the study; one was dropped onto a hard surface, and the other developed a fracture line across the labial flange, but both were repaired satisfactorily.
SUMMARY AND CONCLUSIONS A method for constructing tooth-supported complete dentures was described and the results of a clinical evaluation were discussed. In addition to those advantages inherent to tooth-supported dentures, the simplified construction technique eliminated the need for cast metal bases or denture copings. Also, the small size of the metal casting in the denture permitted its unobtrusive placement within the denture and facilitated an esthetic result, The uniformity of the chrome-cobalt bearings, and the waxing tool improve the stress distribution, and made possible the construction of duplicate dentures with minimal additional time and materials. Horizontal mobility and pocket depth were recorded for 20 abutments in 9 patients following the insertion of dentures constructed by the described method. The horizontal mobility for abutment-teeth supported complete dentures tended to remain at or below fiducial levels throughout the test period. With only a slight variation, pocket depths remained consistent with initial levels. Patient acceptance of the tooth-supported dentures was uniformly excellent, as manifested by few postinsertion complaints and steady improvement in masticator-y performance. One denture fractured when dropped on the floor, and another developed a fracture line in a thin labial flange; otherwise there were no incidents of denture failure dlle to breakage. The principal disadvantage of the technique was related to the need ~OJ prerequisite periodontic, endodontic, and surgical procedures that, in turn, lengthenrd the treatment period and increased the cost. This factor should be equated reaiistitally with the ultimate service to the patient. Based on the objective clinical evalultion, the tooth-supported complete denture remains an effective, preventive prosthodontic procedure.
References 1. Selected Dental Findings in Adults by Age, Race, and Sex, National Center for Health Statistics, Series 11, Number 7, 1960-1962, Washington, D. C., U. S. Department of Health, Education, and Welfare, 1962. 2. Krogh, H. W.: Permanent Tooth Mortality. A Clinical Study of Loss, J. A. D. A. 57: 670-675, 1958. 3. Brill, N.: Adaptation and the Hybrid Prosthesis, J. PROS. DENT. 5: 811-824, 1955. 4. Miller, P. A.: Complete Dentures Supported by Natural Teeth, J. PROS. DENT. 8: 921928, 1958. 5. Dolder, E. J.: The Bar Joint Mandibular Denture, J. PROS. DENT. 11: 689-707, 1961.
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6. Morrow, R. M., Feldmann, E. E., Rudd, K. D., and Trovillion, H. M.: Tooth Supported Compete Dentures: An Approach to Preventive Prosthodontics, J. PROS. DENT. Pending publication. 7. O’Leary, T. J., and Rudd, K. D.: An Instrument for Measuring Horizontal Tooth Mobility, J. Am. Sot. Periodontist 1: 249-254, 1963.
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EASTRIDGE SAN ANTONIO,
DR.
TEX. 78227