Overview of articulation materials and methods for the prosthodontic patient

Overview of articulation materials and methods for the prosthodontic patient D o n n a L. D i x o n , D M D ,

MA a

Birmingham, Ala.

Statement o f problem. Many methods and materials are available tbr registering the centric relation position, with various degrees of accuracy. Once the centric relation position is recorded, many instruments arc available for cast articulation. These articulators range from simple to complex devices that generate dif ferent mandibular movements depending oll the sophistication of the instrument. Purpose. This review evaluated the methods and materials used to record the centric relation position and eccentric maxillomandibular relations, and to compare the articulators available tbr mounting casts. Methods. A MEDLINE search was completed (from 1966-present) along with personal searches of selected journals to find additional publications that addressed these materials, methods of registration, and available instrumentation. Conclusion. Potential applications of this review are as tbllows: (1) to allow the reader to examine the various methods for recording the centric relation position that have been studied and described, and (2) to observe how the accuracy of recording materials have changed over time. The reader will also realize the types of simple and complex articulators that exist, along with the different degrees of simulated mandibular movements that may be accomplished. (J Prosthet Dent 2000;83:235-47.)

Recording the centric relation position is of utmost importance in the prosthetic reconstruction of edentulous and partially edentulous patients. Historically, this position (and eccentric maxillomandibular positions) have been recorded using many methods and materials. Furthermore, articulators used for mounting diagnostic and worldng casts have varied over time. The purpose o f this article is to provide an overview o f the literature relating to the methods and materials used to record the centric and eccentric relation positions, and to further review the past and present instrumentation used to articulate casts with generated records. Much of the historical aspect o f this article was previously published by Lang and Kelsey in 1972.1 This overview was completed after a M E D L I N E search from 1966 to the present, along with personal searches o f selected journals. DEFINITIONS

OF CENTRIC

RELATION

The centric relation record is the most important and the most difficult maxillomandibular relation Presented at the Ninth Annual Comprehensive Review in Prosthodontics, University of Michigan Continuing Education Program, Ann Arbor, Mich., October 1998. aStudent, Cumberland School of Law, Samford University. FEBRUARY 2000

record to make. 2 Centric relation is defined as a maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion o f their respective disks, with the complex and the anterior-superior position against the shapes o f the articular eminencies. This position is independent o f tooth contact and clinically discernible when the mandible is directed superiorly and anteriorly. It is restricted to a purely rotary movement about a transverse horizontal axis. 3 Historically, the term centric relation has many meanings. Sheppard 4 and Shanahan 5 believed that the centric relation position o f the mandible to the maxillae occurred when a person swallowed. Baer 6 believed that this position was coincident with the physiologic rest position. Page 7 and Rader 8 thought that there was no practical way o f locating this position. Shpuntoff and Shpuntoff 9 wrote an article regarding the determination o f the centric relation position using EMG. They suggested that a single channel high gain differential E M G may be used to determine the physiologic rest position and centric position. When studying 215 adults they found the characteristic E M G coincided with the centric relation position in these persons. They suggested that the ma W methods o f recording the centric relation position may be studied and compared using the E M G technique. THE JOURNAL OF PROSTHETIC DENTISTRY 235

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Hickey 1° reported that the centric relation position is the only position in which even occlusal contact can be established in all other mandibular positions. Thus, he believed that recording this position is necessary when fabricating complete dentures. Kingery 11 explained that there are 2 requirements o f a centric relation record: (1) it must record a correct horizontal relationship o f the mandible to the maxillae, and (2) equilibration o f vertical contacts o f the denturesupporting areas must occur. If disease o f the joint is not present, this relationship is reproducible. Centric relation, in a healthy person, is t h o u g h t o f as ligamentous position. All muscles attached to the mandible must be relaxed to achieve a repeatable centric relation record. There are 3 requirements for maldng such a centric relation record: (1) to record the horizontal relation o f the mandible to the maxilla, (2) to apply equal vertical pressure, and (3) to keep the completed record in a condition where it will not distort until the casts have been mounted. It is necessary that the recording medium is a constant consistency. In addition, the medium must not resist the forces exerted by the muscles} It has been emphasized that centric relation is not a resting mandibular position, but that it definitely is repeatable.10,12 Such records should be made at the appropriate vertical dimension o f occlusion. 1° RECORD

BASES

Graser 13 and Klein and Soni 14 agreed that the jaw relation record is only as accurate as the bases on which the recording is made. Elder is stated that record bases must: (1) have borders that are adapted similarly to the finished base; (2) be rigid; (3) be dimensionally stable; (4) be fabricated quickly, easily, and without undue expense; (5) not have an undesirable color; and (6) be able to be used as a base for setting denture teeth. In 1966 Tucker 16 added other requirements to Elder's list o f 6 and stated that these bases must: take advantage of desirable undercuts, not abrade the casts on removal and replacement, and bond with the material used to block out the undercuts. Elahi and Abdullah 17 examined the effect of 5 fabrication techniques on the dimensional stability o f record bases. The most discrepancy noted at the midpalatal area o f the base to the maxillary casts occurred with the technique where the autopolymerizing resin was applied to the cast and then was immersed in water in a pressure pot undisturbed fbr 3 minutes. The least discrepancy in the midpalatal area occurred with a technique where a humidor with m o n o m e r vapor was used during the polymerization process. In 1994, Loney 18 described a technique for making stabilized record bases for implant-retained overdentures. The technique involved the use o f elastomeric caps that are incorporated into the record base, which 236

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could be used for retention o f the base over the implant components. Therefore, this simplifies the registration o f the jaw relationship by generating stability. Graser 13 described a procedure for maldng completed bases for complete denture jaw relation records. H e stated that it is easier to record the maxillomandibular relation with these bases because they have the retention and stability of the completed denture, and further explained that a disadvantage to using completed bases is that there is an increase in time and expense. RECORD

CATEGORIES

Centric relation records may be grouped into 4 categories: (1) direct interocclusal records, (2) intraoral and extraoral graphic recordings, (3) functional recordings, and (4) cephalometrics. 19 Direct recordings The direct interocclusal recording is also referred to as the physiologic m e t h o d 2 or the static recording method. 12 In the 1700s Pfaff first described the technique. 20 It is necessary that patients' proprioceptors and tactical sense are functioning normally to make an accurate record using this method. It is also necessary that the dentist's visual acuity and sense of touch are functioning normally. Three factors that influence interocclusal direct records are as follows: (1) the amount of pressure exerted on the displaceable tissue in the joints and the equalization of such pressure; (2) the patient's comfort that, in turn, depends on the stability of the record bases; and (3) the number o f reference points used to make the record. For instance, a record made by using cusp tips is more acceptable than one where only wax or monoplane teeth are used. Such direct records are indicated when the maxilla and mandible are abnormally related and supporting tissues are displaceable, when an abnormally large tongue is present, and when abnormal mandibular movements occur. 2 Hickey 10 wrote that these records were easy to make and that he preferred this type o f record because of its simplicity. The direct interocclusal record was the most commonly used recording method until the end of the 19th century. 19 Hanau 21 was one o f the first people concerned with pressure equalization when completing direct interocclusal records. When writing about pressure equalization, he coined the term Realeff This word is formed by the beginning letters o f "resilient and like effect." Wright 22 and Block 23 agreed that no pressure should be applied when making a record using the direct method. Schuyler, 24 Payne, 2~ and Trapozzano 26 stated that light pressure should be used when making a direct record. Greene 27 invented a pressometer in an attempt to equalize the pressure when recording the centric relation position by the direct method. Kingery 11 discussed 2 fundamental principles that contribute to the success o f the direct recording VOLUME 83 NUMBER 2

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method: the dentist's ability to recognize the centric relation position, and understanding that the recording medium directly influences the pressure developed in the recording and the subsequent equilibration o f the recording. Akerly28 described a direct tripodal method o f recording centric relation, which was a minimum pressure technique that could be quicldy and accurately verified. Akerly28 stated that a series o f 3 chromecobalt tacks must be placed in the mandibular occlusion rim. The jaw relation record was then completed, and the tacks made an indentation into the maxillary occlusion rim as the registration was made. Shanahan 29 used a physiologic approach to recording the centric relation position. H e placed cones o f soft wax on the mandibular occlusion rim, and the patient was asked to swallow repeatedly. H e believed that, during swallowing, the t o n g u e forced the mandible into the centric relation position. The cones o f soft wax were then moved and centric relation was recorded using his method. Graphic recordings The second type o f recording is the graphic method, which records a tracing o f the mandibular movements in 1 plane. The apex o f a tracing made in this manner indicates the most retruded relationship o f the mandible to the maxilla; and, from this retruded relationship, lateral movements may take place. These m e t h o d s may be accomplished either intraorally or extraorally, depending on where the recording device is placed. Extraoral tracings are also referred to by 2 other names: gothic arch tracings and arrow point tracings. These tracings are larger than intraoral tracings; therefore the apex is more easily seen. The earliest graphic recording techniques were based on studies completed by Balkwill. 3° The first needlepoint tracing was completed by Hesse 31 and this technique was improved about 20 years later by Gysi. 31 Gysi's tracer was an extraoral tracer. 32 Sears used the Gysi tracer with lubricated rims for the movements to be accomplished more easily. Sears 33 placed the needlepoint tracer on the mandibular rim, and on the maxillary rim he placed the plate. H e cemented the rims together for removal. Stansbery 34 then introduced a technique that used a curved plate m o u n t e d on the maxillary rim. The central bearing screw was attached to a mandibular curved plate; and, after the extraoral tracing was completed, plaster was introduced between the plates to form a biconcave registration. Hall 3s also used this type o f technique; however, he used compound instead of plaster. Phillips 36 recognized that lateral movements would cause interferences o f the occlusion rims and this could result in a distorted record. H e developed a plate for the maxillary occlusion rim and a tripoded ballbearing mounted on a jackscrew for the mandibular occlusion FEBRUARY 2000

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rim. The occlusion rims were removed; and, after the patient had produced what he thought to be an appropriate extraoral tracing, he softened the compound and inserted this between the trial bases. This innovation by Phillips was called the "central bearing point." As stated earlier, this central bearing point produced equalization o f pressure on the supporting tissues. When completing a graphic tracing, it is important that 12 factors are considered: 1. The record bases may become displaced if the central bearing point becomes "off-center" when the mandible moves into excursive positions; 2. if a central bearing device is not used, more resistance to horizontal movements occurs with the occlusion rims; 3. it is difficult is locate the center o f the arches (so that the forces may be centralized); 4. when a patient's tissues are easily displaced, it is difficult to achieve a stabilized record base; 5. ridges that have no vertical height also cause difficulty in stabilization o f a record base; 6. large tongues result in difficulties in record base stabilization; 7. recording devices may not be compatible with normal physiologic mandibular movements; 8. the tracing is considered unacceptable with a blunted apex, only sharp or pointed apexes are considered acceptable; 9. if double tracings occur, this usually indicates that the movements wcrc not coordinated or recordings were made at a different vertical dimensions o f jaw separation (if double tracings occur, then it is necessary to make additional tracings); 10. it is necessary to perform the graphic tracing at the predetermined vertical dimension o f occlusion; 11. graphic methods record eccentric relations; and 12. such graphic methods o f recording are thought to be the most accurate visual means o f recording centric relations with a mechanical instrument. However, all graphic tracings are not totally accurate. 2 Hanau 37 did not believe that the graphic recording was the most accurate record, but he finally conceded that the Gysi tracing was satisfactory to verify records and still believed that universal usage o f these recordings was not appropriate. Intraoral tracing devices are referred to as combination central bearing points with needlepoint tracings) 2 Yurkstas and Kapur 38 wrote about the intraoral tracing procedure. They referred to the many objections or criticisms o f this procedure by prosthodontists. Trapozzano 26 was one person who criticized the procedure. H e did not believe that central bearing points equalize pressure. T r a p o z z a n o said that this equalization o f pressure will result only if 2 conditions are present, namely, normal ridge relationships, which result in an ability to place the central bearing point in the center o f 237

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the foundational basis, and firm mucosa. Payne 25 stated that any type o f apparatus placed intraorally may cause discrepancy in recordings. Yurkstas and Kapur 38 evaluated the reproducibility o f the wax record and the intraoral tracing. Thirty-five edentulous patients participated in their study and their occlusal vertical dimensions remained constant throughout the experiment. These authors emphasized that many variables occur that can affect the results o f a recording procedure. In the wax recording procedure, it was found that the consistency, the hardness of the wax, the bilateral homogeneity, the a m o u n t o f occlusal contact, and the presence (or absence of) anterior freedom significantly influence the dentist's ability to duplicate the records. For the intraoral tracing procedure, the central bearing point location, the inclination o f the central bearing point in relation to the tracing plate, and the inclination o f the tracing plate relative to the underlying bearing surfaces all play important parts in being able to duplicate the records. The results o f this study led Yurkstas and Kapur to reco m m e n d that centric relation records be made with accurate record bases, under little pressure, and that the pressure be centralized and distributed equally to the underlying tissues. Later, in the 1940s and 1950s, the central bearing point was used to produce a gothic arch tracing. Hardy 39 and Pleasure 4° described the use o f the CoNe Balancer. Hardy 39 and Porter 41 used a round bur to make a depression at the apex o f the intraoral tracing, and this enabled the patient to hold the bearing point into the depression while the plaster was injected and subsequently setting. Silverman 42 decided that he would solve the problem o f obtaining an "exact" centric relation by incorporating a biting point on an intraoral centric bearing device, along with his method o f measuring the vertical dimension by means o f tattooing the alveolar ridges. H e mounted the bridge portion o f the intraoral central bearing device on the mandibular wax occlusion rim, and the stylist portion was attached to the maxillary record base. The wax rim was removed from the record base. H e stated that the central bearing device was centered in approximately the second premolar to first molar area, to avoid tipping the bases. The patient then was told to bite or repeatedly tap the upper pin against the mandibular base. H e did not ask the patient to close lightly. In fact, the patient was told to bite very hard, with dynamic pressure. Because such a hard biting force was used, he believed that the closing musculature placed the mandible in the most retruded functional position. After the patient occluded with this pressure, a mark was made on the disk, and this is what was called the "biting point." The biting point was accentuated with a round bur, permitting the patient to lock into this depression. Silverman n o t e d that the 238

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resultant biting point was at the apex o f the gothic arch tracing with some persons, anterior to the apex with some, and postcrior to the apex with others. The record that he made with the indentation point was used for mounting purposes whether it corresponded to the gothic arch apex. Boos 43 stated that the centric relation position is not always at the apex o f the gothic arch tracing. In 1962, Walker 44 completed a study of 2 methods o f recording the centric relation position. The 2 methods were physiologic (or swallowing method) and graphic (or needlepoint tracing method). For the graphic method, he used an extraoral stylist attached to the maxillary occlusion rim. H e considered that the jaws were in centric relation when the stylist was at the apex o f the tracing. The physiologic method used the act o f swallowing to register the centric relation position; and, to obtain this record, metal studs were embedded in the mandibular occlusion rim. An analyzing instrument was used to measure the differences between the various relationships recorded at 5 points in space. Twenty-one cdcntulous subjects participated. The graphic method did not locate the mandible in the same position as did the swallowing or physiologic method. The mandible was tbund to be in a more posterior relationship to the maxillae when recordings were made using the graphic method. Walker studied the physiologic position because Niswonger 45 stated that during swallowing, the mandible travels from rest position to the centric relation position and back to the rest position again. Those who did not believe in recording centric relation during swallowing or by using the physiologic method were known as "mechanistics. ''44 Some people in the mechanistic school o f thought believed that it was unscientific to record centric relation w i t h o u t finding the hinge axis o f the mandible.46, 47 The conclusion that Walker 44 reached was that swallowing was unreliable for the registration for centric relation; however, swallowing could be valuable when determining various habitual positions of the patients' mandibles. In 1976 H u n t and Yoxsimer 48 described the displaceability of occlusion rims (with attached clutches) when completing a pantographic tracing. These authors described the technique o f using "vacustatics" to stabilize the clutches. In 1967 Schoen and Stewart 49 conducted an experiment to compare the accuracy o f interim (autopolymerized) record bases and permanent (heat polymerized) bases regarding differences in generated centric relation records. In this study, an intraoral tracing was made with an interim base and the other with a permanent base (on the same patient). Five patients who wear dentures participated. Results indicated that there were no significant differences in jaw relationship records obtained by using either interim or permanent record bases. VOLUME 83 NUMBER 2

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In 1996 Obrez and Stohler 5° completed a clinical study of the effect of masticatory muscle pain on the maxillomandibular relation and range o f mandibular motion. Five healthy adults participated in this study. Muscle pain was induced by infusion of 5% hypertonic saline solution into the central portion o f the masseter muscle. Isotonic saline solution was used as a control and the subjects were blinded to the type o f substance given. This study demonstrated that the gothic arch tracings in healthy volunteers with induced tonic masticatory muscle pain were reversibly altered. It was also suggested that pain has a bearing on the static and dynamic occlusal contact relationships. The experimental muscle pain also significantly affected the location o f the posterior mandibular position in which the border movements were accomplished. In 1998 Obrez and Ttirp sl further questioned the validity o f maxillomandibular relation records made in the presence o f facial pain. Functional recordings Functional or "chew-in" records were another m e t h o d described to record centric relation. These were first discussed in the dental literature around 1910. All functional methods o f recording centric relation require a stable record base. If this record base is dislodged, the record will be inaccurate. Patients must have good neuromuscular coordination to participate in such a recording procedure, and they must also be capable o f following instructions. 2 Needles 52 mounted studs on maxillary occlusion rims, and these studs engraved arrow tracings into compound rims on the mandibular arch. After the rims were removed from the oral cavity, they were reassembled with the functional grooves in place. Patterson s3 was also known for promoting the use o f functional records. Patterson prepared a trough in the maxillary and mandibular occlusion rims, and these troughs were filled with a plaster mixture. Again, the patient was asked to move his mandible, and continue the motion until the appropriate curvature had been formed on the rims. This was said to equalize pressure and provide uniform contacts in all excursive movements. Meyer s4 also developed a functional technique in which soft wax occlusion rims were used and wax paths were formed in these rims during functional movements. Then, a plaster index was made o f this wax path, and teeth were set opposing this generated plaster index. In the 1930s, House~5, ~6 described a technique of recording mandibular movement and registering the centric relation position using an engraving method. To complete the functional registration using the House technique, shellac trial denture bases with attached wax occlusion rims were made. A preliminary jaw relation record was obtained and the maxillary cast and occlusion rim was mounted on the House articulator. Wax was FEBRUARY 2000

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then placed in the premolar and molar regions bilaterally on the mandibular occlusion rim. It was then replaced by a block of impression compound. These compound blocks had an occlusal surface simulating an average curve o f Spee and curve o f Wilson. Four triangularshaped studs with cutting edges were then placed in the maxillary wax occlusion rims opposite these blocks. The new occlusion rims were then inserted intraorally and the patients carried out mandibular movements. During these movements, the studs engraved 4 separate needlepoint gothic arch recordings into the blocks of compound. This was called a "chew-in" recording. One of the casts was then remounted. According to the new gothic arch recording, the condylar elements o f the articulator were adjusted. Swanson 57 suggested that the House technique was desirable but it needed some improvements such as (1) an accurate recording o f the terminal hinge axis with a face-bow, (2) the jaw relation records made on intimately adapted denture bases or on the final impressions, (3) using the central bearing screw when performing the chew-in recordings so that the vertical dimension o f occlusion could be maintained, (4) the recording made with a soft material rather than a hard material, and (5) the recordings used with an articulator capable o f simulating jaw movement and with fossae that could be molded. Swanson 57 t h e n described a procedure where he improved on the House technique using the TMJ technique. The TMJ ldnematic face-bow (TMJ Instrument Co, Santa Ana, Calif.) was used to locate the hinge axis, the recording plates were attached to impressions rather than stabilized trial denture bases, and a central beating screw was incorporated. A recording was made, and the molded fossae with the TMJ articulator (TMJ Instrument Co) were then formed from the generated gothic arch tracings. In 1972, Hemphill et a158 recognized that many variables enter into recording procedures. They examined the Needles-House and Patterson techniques o f functionally generated recordings to determine whether any differences in centrie relation registrations occurred if the recording surfaces contacted with equal pressure at thc beginning o f the procedure or if they were recorded with unequal pressure bilaterally at the beginning. Ninc patients participated in this study. Three sets o f acrylic resin record bases were made for each patient. Functional registrations were then made with unequal pressure on thc recording surfaces; and, using tubes and calipers, measurements were completed on tight and left sides o f the rims. From this study, it was apparent that clinical procedures used for registering tentativc jaw relation records must be carefully evaluated for equalized pressure because neither o f the 2 methods studied corrected the error that was experimentally induced. 239

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One of the most famous promoters of functional records was Boos. 43 He developed the gnathodynamometer. Using this instrument, he determined the vertical and horizontal position where maximum biting force could be generated. This instrument was mounted on the mandibular occlusion rim, and it had a central bearing point that occluded against a plate on the maxillary rim. Plaster registrations were also used intraorally with the gnathodynamometer in place and with the patient exerting biting pressure. Boos claimed that the optimum occlusal position and the position of the maximum biting force are coincident. He believed that all registrations should be made under this biting force with displacement of the soft tissue. He thought that this displacement would also occur in function.59,60 In 1959 Boos 61 wrote that centric relation records should be made with no pressure or torsion. He advocated the use of materials such as piaster or zinc oxide eugenol paste. He said that wax or compound would tend to tip or displace the mandible because these materials required that force be exerted to obtain an appropriate recording. Cephalometric

recordings

Pyott and Schaeffer62 described the use of cephalometrics to record centric relation. These radiographs were used to determine centric relation and the appropriate vertical dimension of occlusion. This practice, however, never gained widespread usage.

Muscle Conditioning In 1956 Boos 63 prescribed an exercise to condition the muscles of mastication; thus, enabling the patient to relax before jaw relation records were completed. An article by Nasr and Griffiths64 also described a procedure in which exercise therapy was used before recording jaw relationships. The purpose of exercise therapy, they explained, was to eliminate habitual eccentric reflexes and to train the patients to close in the centric relation position. The exercise appliances they described were either an acrylic resin splint or a modified denture that the patient wore. The exercise consisted of hyperextending the mouth and touching the posterior border of the maxillary denture with the tip of the tongue. This exercise was supposed to be repeated several times over a 3-minute period. They further stated that the exercise should be repeated 3 times daily. These authors reported that this should be continued for 2 to 7 weeks; and, by doing so, the patient learned to close h i s / h e r jaws in the centric relation position. Recording of this position supposedly became easy for both the patient and the dentist. TIME OF RECORDING In 1975 Shafgah et al65 showed the position of the condyles in centric relation for dentulous patients was 240

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different when examined in the morning and again in the evening. Because Shafgah et al6s demonstrated this, in 1992 Latta 66 began an investigation to evaluate the effect of circadian periodicity on the ability to reproduce centric relation records for the edentulous patient. Thirty patients participated in the study, and they were divided into 3 groups. Their dentures were remounted twice on the same day. The dentures for 10 patients were remounted twice in the evening; the dentures for 10 patients were remounted twice in the afternoon; and, for 10 patients, the dentures were remounted once in the morning and again in the afternoon. Significant differences between time groups occurred; therefore this demonstrated that circadian periodicity affects the recording of centric relation for edentulous patients. This may imply that dentures made in the morning would occlude best in the morning, and those made in the afternoon would occlude best in the afternoon. RECORDS FOR THE PARTIALLY EDENTULOUS PATIENT For removable partial denture fabrication, it is not always necessary to make a jaw relation record. If the casts can be hand articulated, then this appointment may be eliminated. When a jaw relation recording appointment is necessary, however, this recording must be completed free from any pressure. Pressure would cause compression of the patients' tissues with resultant record base displacement. This displacement, in turn, would cause errors in mounting the casts. 67 In 1954 Beckett 68 wrote an article regarding occlusal registrations for removable partial dentures. He stated that the vertical dimension of occlusion is greater in the finished partial dentures than that observed when the record is made. He decided that this was because the occlusion rims used to make the recording displace the resilient mucosa, thereby increasing the vertical dimension of occlusion. He decided that all removable partial denture occlusion relations would belong to 1 of 4 types. These types are classified as type A, B, C, and D. Type A partially edentulous patients exhibit sufficient occlusal contacts to allow the dentist to articulate the maxillary and mandibular casts without occlusion rims; type B patients do not exhibit sufficient occlusal contacts for articulation of the maxillary and mandibular casts without occlusion rims; type C patients exhibit occlusal contacts for establishing the correct vertical dimension of occlusion, but insufficient occlusal contacts exist to allow articulation of the casts without occlusion rims; and, type D patients exhibit no occlusal contacts between opposing teeth for establishing the vertical dimension of occlusion, and occlusion rims must be used for recording the centric relation position. Beckett suggested that plaster be used for centric VOLUME 83 NUMBER 2

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relation records. He advocated that occlusal pressure should be transmitted to the teeth adjacent to the distal extension areas of the occlusion rims with occlusal rests to eliminate soft tissue displacement. In 1978 Akerly69 described a technique that used both the altered cast impression for a distal extension removable partial denture and the functional occlusal registration to record the jaw relation position. Freilich et al 7° discussed principles tbr selecting the type of interocclusal record for articulation of partially edentulous casts. Other authors71, 72 have suggested that a tripod of 3 widely spaced contacts should exist between 2 casts when mounting them. Freilich et al7° stated that when malting an interocclusal record for a partially edentulous patient, it is important to provide support or stability that the casts of the remaining dentition do not have. These authors described using an occlusion rim made on the partially edentulous cast that is then made to function as a substitute for the tooth stops with the record base in the mouth. The baseplate wax or the occlusion rim may be used alone to record the imprints of the opposing teeth; but, most often, other materials are placed on the occlusion rim for the recording of the jaw relationship. They mentioned that this recording material is often Aluwax (Aluwax Dental Products Co, Grand Rapids, Mich.). They described a situation in which an occlusion rim may be present in 1 arch opposing a distal extension segment. Some type of rigid-setting recording material may then be introduced to contact the occlusion rim on i arch and the edentulous ridge on the other. This material should be soft when introduced intraorally.73-75 A material used in this manner has been termed a "mucostatic recording material. "70 In 1976 Lundquist and Fiebiger 75 discussed ways of mounting maxillary and mandibular partially edentulous diagnostic casts based on Kennedy's classification system. Methods discussed for mounting casts for the Class I and II patient were based on patients who had no periodontal involvement of the anterior teeth. These authors described placing a leaf gauge between the anterior teeth while guiding the patient's mandible toward the centric relation position. When this position was found, record bases were inserted intraorally, and a plaster recording medium was used to register the position. In Class II patients, the authors advocated that acrylic resin be placed over the dentulous side while making the record. With Class III partially edentulous patients, the authors discussed that the preferred method for registering the jaw relationship was using acrylic resin over the teeth present and the leaf gauge. If an extensive edentulous space is present, however, record bases must also be used with some type of plaster recording material. With Class IV patients, or with may othcr class, including periodontally involved or missing anterior teeth, FEBRUARY 2000

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the authors discussed that the material of choice to be used is dependent on the neuromuscular control of the patient and the location and number of rcmaining teeth. They stated that impression plaster or acrylic resin are the materials of choice if good neuromuscular control is prcscnt. If this control is not apparent, then some type of thermoplastic material should be used. They also mentioned that it is necessary to verify all centric relation records. RECORDS FOR THE MAXILLOFACIAL

PATIENT In 1975 Curtis et al76 wrote regarding the maxillofacial patient and the special problems the dentist may encounter in attempting to record jaw relationships. These authors stated that 2 factors may affect maxillofacial patients: (1) radiation therapy and (2) the physiologic trauma that cancer patients face after therapy. After radiation treatment, a gradual reduction in the blood supply to the muscles and joint structures may occur, and an increased fibrosis of these structures may follow. Trismus and restricted movements of the mandible may ensue. This may complicate the use of any type of intraoral tracing device and may limit the border movements of the mandible. They further explained that in cleft palate patients, the recording base may move upward in the anterior area under pressure. In maxillectomy patients, the base would also move, however, it would move upward on the side of the defect. Because the magnitude of this displacement of the bases may vary, the dentist may encounter differing problems regarding stability of the base and the necessity to equalize the pressure during the jaw relationship recording procedure. With maxillary deficiencies, it was noted that mandibular movement restrictions are not typically present. However, with mandibular resection patients, movement restrictions are apparent. They stated that with completion of a lateral mandibular resection, the remaining portion of the mandible will drift toward the area of resection and the remaining portion will also retrude and rotate. Lingual cusps on the nonsurgical side of the mandible will be retruded inferiorly. The normal hinge movement of the mandible parallel to the sagittal plane is no longer possible with these patients. Force of closure and tactile discrimination is also compromised. To test thcse clinical observations, the authors examined patients with mandibulectomies and lateral resections. Because this was a pilot study, definite conclusions were not possible. This study suggested that these patients cannot make definitive protrusive or lateral excursive movements. Their functional movements form a diagonal pathway of closure to maximum intercuspation. Perhaps the unilateral action of the suprahyoid musculature may account for this pattern of mandibular movement. 241

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ECCENTRIC INTEROCCLUSAL RECORDS Eccentric interocclusal records are defined as a registration o f any maxillomandibular position other than centric relationship. 3 Rahn 2 stated that methods for recording eccentric relation positions may be classified similar to the methods used for recording the centric relation position: (1) functional or "chew-in" procedures; (2) graphic methods; and, (3) tactile or interocclusal record methods. He further wrote that the best time to make eccentric records is after all the artificial teeth have been arranged fbr try-in and the centric relation record has been verified. Eccentric interocclusal records made with soft materials tend to generate a steeper condylar inclination than records obtained with a more resistant material. In 1929 Gysi77 wrote that lateral records made with either wax or c o m p o u n d are unreliable, and such records could lead to great errors during prosthesis fabrication. Craddock 78 found that interocclusal records made on the same edentulous patient by the same dentist were more consistent than records made on the same patient by different dentists. However, the differences were still great. H e also n o t e d that eccentric records made with wax on dentulous patient were unreliable and almost worthless. Eight factors contribute to the accuracy o f eccentric records: 1. the distance that the condyles translate when the record is being made; 2. the resistance o f the recording material; 3. the stability o f the record bases; 4. the ability o f the patient to cooperate; 5. the adjustability of the articulator; 6. the dimensional accuracy of the recording material; 7. the interpretation o f the record and articulator manipulation by the dentist; and, 8. the accuracy with which the articulator calibration may be interpreted. 79 Frazier et a179 initiated a study to determine the repeatability o f eccentric records by the dentist, to evaluate the consistency o f records made by 3 different dentists on the same patient, and to evaluate the consistency o f articulator adjustment by 4 dentists using the same articulator with the same interocclusal eccentric record. Ten patients participated, and complete maxillary and mandibular dentures were fhbricated for them by 5 dentists. Each dentist treated 2 patients. A plaster interocclusal recording material was used in the procedure to m o u n t the casts in a centric relation position. The artificial teeth were arranged for try-in and the centric relation record was verified. The dentist who made the dentures then made 3 protrusive, 3 right lateral, and 3 left lateral interocclusal records using plaster. Then, the 2 other dentists made 3 protrusive, 1 right lateral, and 1 left lateral plaster record for the 242

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same patient within a 2-hour period. After the records were made, each dentist adjusted the articulator to accept the records; and, the calibrations were rcad and recorded by a dental assistant. The data were collected and statistically analyzed. Results from this study indicated that each dentist was very consistent with himself for a given patient but was not as consistent with other dentists making records for the same patient. Inconsistencies that occur in the making o f eccentric records are primarily caused by the record making itself and not the dentist's ability to adjust the articulator. It was suggested that interocclusal eccentric records are repeatable enough to render them useful as a basis o f treatment for the edentulous patient. ACCURACY OF RECORDING MATERIALS Berman 80 questioned the accuracy of interocclusal records made with dental waxes. H e tested various waxes and found that all offered some resistance to closure, and that this resistance was inappropriate. H e advocated the use o f zinc oxide eugenol impression paste to make jaw relation records for fabrication o f complete denture prostheses. In 1986, Lassila 8] compared several interocclusal recording materials in an attempt to find the most suitable material tbr making interocclusal records. The materials studied were silicone putty, polyether elastomer, zinc oxide eugenol (ZOE) paste, eugenol-free zinc oxide paste, acrylic resin, and baseplate wax. Resistance to closure, volumetric changes of the materials during polymerization, and dimensional stability during storage were studied. H e noted that resistance o f the acrylic resin increased rapidly in the beginning, although polymerization was not completed tbr a while. Silicone was found to be very highly resistant to closure. The author stated that silicone therefore was not very suitable fbr interocclusal registrations for gingiva-supported prostheses. He stated that wax is difficult to use because its resistance to closure is very high even at temperatures near its melting point. H e mentioned that acrylic resin and zinc oxide paste were sticky, and this adhesive property could be a problem with interocclusal registration for fixed restorations; however, with removable prostheses, this stickiness may be advantageous. H e stated that, if it was necessary to store recording materials betbre mounting, this may be problematic. ZOE materials may be stored in stable conditions; however, ZOE is susceptible to changes in relative humidity. 82 The elastomeric recording materials, he said, remain stable for a long time, and their contraction due to volatility is slight if they are stored in tightly sealed plastic bags. If these elastomers encounter moisture, considerable dimensional change may occur. 81 In 1992 Breeding and Dixon 8a studied the compression resistance o f 4 interocclusal recording materials. During this investigation the deformation o f differVOLUME 83 NUMBER 2

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ent thickness o f 3 polyvinyl siloxanes and 1 polyether interocclusal recording material was studied when these materials were subjected to a consistent compressive force. All the recording materials were compressed clinically significant distances during the constant load. One o f the polyvinyl siloxanes was significantly more resistant to compression than the other materials at the thickness o f 5, 10, and 20 mm. In 1994 Millstein and Hsu 84 examined 5 brands o f polyvinyl siloxanes recording materials regarding their dimensional stability and associated weight change. All brands studied were found to be accurate and dimensionally stable over a 48-hour period. The negligible weight change did not affect the dimensional stability o f the materials. In 1994 Chai et a185 studied the surface hardness and dimensional stability o f several intermaxillary registration materials. These authors found that the dimensional stability o f a polyether registration material was significantly lower than that o f the vinyl (poly)siloxane materials tested. The dimensional change o f all the materials was considered acceptable. RECORDING

MATERIALS

AND

MOUNTING ERRORS In 1981 Mullick et a186 stated that an ideal interocclusal material and technique combination for making intraoral recordings would allow the placement o f fabricated prostheses intraorally with no occlusal adjustment. He wrote that the reasons for occlusal inaccuracies, caused by the interocclusal record, may be divided into 3 main groups: (1) anatomic and physiologic characteristics o f the patient, (2) dentist induced causes, and (3) properties o f the material used to make the record along with technical manipulation o f the record during use. The purpose o f the Mullick et a186 study was to determine the vertical assembly error in mounting dentulous casts on an articulator as affected by (1) materials, (2) distance between prepared and opposing teeth, and (3) dentist variability. Stone casts obtained from a patient with a complete dentition were mounted on an articulator. All posterior teeth, except for those in the maxillary left quadrant, were prepared on the cast to simulate full veneer crown preparations. Vertical displacements o f the casts on either the right or left side were measured in increments o f 0.0001 inch. Aluwax Z O E paste, 4 types o f silicone putties, and i polyether material were placed bilaterally between the casts and the articulator and the instrument was closed to incisal pin contact. Measurements were made 5 minutes later. The first measurement was made before record removal, the second measurement was made after the records were removed, trimmed, and the casts were replaced into the trimmed record. Three dentists repeated the test 10 times fbr each material on both the right and left sides. The Aluwax paste (Aluwax Dental Products Co) was the most variable and least reliable o f FEBRUARY 2000

all materials studied. The 5 elastomers consistently resulted in the least amount o f errors, and the 2 thicknesses of elastomeric records studied resulted in significantly different mounting discrepancies. In another study o f cast mounting errors, Mfiller et a187 examined vertical errors in mounting dentulous casts on an articulator as affected by 3 variables: interocclusal registration material, storage time o f completed interocclusal records, and points from which the measurements were made. Maxillary and mandibular casts, with posterior tooth preparations, were mounted on an articulator. The anterior guide pin was raised 3 m m to create an interocclusal space between the posterior teeth. The following interocclusal recording materials were tested: impression compound, impression compound combined with Z O E paste, baseplate wax, baseplate wax combined with Z O E paste, a polyether material, Z O E paste, and gypsum. Materials were placed between the casts at a constant closing pressure. A Condymeter instrument (SAM, Munich, Germany) was used to make measurements representing deviations from the original position o f the casts. This device is designed to measure 3-dimensional changes in jaw relationships with 3 gauges m o u n t e d at 90-degree angles at each condyle o f a modified SAM articulator (SAM). After storage o f the records (30 minutes, 6 hours, and 24 hours) other measurements were made with the Condymeter instrument (SAM). It was decided that for clinical procedures, all materials tested may cause not only vertical but also 3-dimensional dislocation of mounted casts. If anterior teeth are present, and the jaw relation will be registered at the maximal intercuspation position, then a material should be chosen that creates only a small deviation at the molar region. In addition, the polyether material tested was the material o f choice for this situation because no clinically significant differences were found among the storage periods tested. Furthermore, it was suggested that a corrected wax also creates an acceptable deviation if used after a short storage time o f 30 minutes or less. Breeding et a188 developed a method to measure the 3-dimensional accuracy o f interocclusal recording materials with a computerized axiograph. This m e t h o d was then used to compare the accuracy o f 3 interocclusal recording materials: acrylic resin, thermoplastic material, and polyvinyl siloxane. The thermoplastic resin generated mounting errors that were significantly greater than those errors generated by the other 2 materials tested. ARTICULATOR

CLASSIFICATION

In 1963, Weinberg 89 classified articulators in 4 categories: arbitrary, positional, semiadjustable, and fully adjustable. H e explained that when an arbitrary articulator is used, individual variations are not taken into consideration. A general curve o f the occlusal plane is 243

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established with these instruments. Weinberg 89 mentioned the Stansbery m e t h o d when describing positional articulators. Users o f such an articulator believe that the static or positional relationship o f the mandible in centric relation, protrusive, and each lateral position may be obtained. Positional articulators, he explained, are designed primarily for fabrication o f complete dentures. One example o f a semiadjustable instrument is the H a n a u model H articulator (Teledyne Waterpik, Fort Collins, Colo.). A face-bow transfer and centric relation record are used to orient casts on this type o f articulator. These instruments are also primarily designed for complete denture fabrication. Weinberg stated that because o f the relative mobility o f complete denture bases, a semiadjustable articulator is adequate; however, fixed restorations require a greater degree o f accuracy in the lateral excursive movements than complete dentures. It was suggested that shortcomings o f semiadjustable articulators must be understood, and more adjustable instruments would be indicated for fabrication o f fixed prostheses to reduce the degree o f occlusal correction necessary during intraoral insertion. Articulators were also classified at The 1972 International Prosthodontic Workshop on Complete Denture Occlusion. 1 Class 1 instruments were called holding instruments. It was stated that these are capable o f accepting a single static registration only, and are suited for maximum intercuspation restorations. It was explained that class 2 instruments permit horizontal and vertical motions but do not orient the motion to the temporomandibular joint. These instruments were said to be useful for the mounted position; however, the eccentric movements these instruments offer provide no advantage because they are not registered and are therefore inaccurate. Class 3 instruments were described as those that simulate condylar pathways by using averages or mechanical equivalents for all or part o f the motion. These instruments were said to allow joint orientation o f the casts, and may be either arcon or nonarcon articulators. Such articulators, it was explained, fulfill the requirements for complete denture fabrication. Class 4 articulators were described as instruments that accept 3-dimensional dynamic registrations, and allow joint orientation o f casts. These articulators were called the instruments o f choice for complete intraoral reconstructions. CHOOSING

AN ARTICULATOR

Celenza 90 described an articulator as a mechanical holding device that is most conveniently used when relating opposing casts. H e suggested 2 simple, general categories to classify the different types o f articulators: those that permit eccentric movements, and those that do not. H e stated that, if centric relation is the registration position used, then an articulator that 244

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accepts a face-bow transfer should also be used because all centric relation positions fall on the terminal arc. When using a noneccentric movement articulator, it is necessary to adjust all eccentric pathways intraorally. Registration o f the centric relation position must be used as a starting reference position with eccentric m o v e m e n t instruments. Celenza 90 stated that a reason for using an i n s t r u m e n t that allows eccentric movements is so that occlusal adjustments may be minimized and to preserve anatomic details o f the teeth. H e referred to eccentric movement articulators as "precision" articulators and stated that these instruments duplicate all eccentric pathways so a precision centric position may be developed and maintained, and so eccentric "irritants" will not be introduced. H e said that there is n o d o u b t many patients benefit from the occlusal arrangements g e n e r a t e d from such articulators; however, he also m e n t i o n e d that many patients do well without them. Celenza 9° stated that, when selecting an articulator, the dentist first must determine the type o f occlusal scheme to be used. H e also stated that, if maximum intercuspation is to be used for restoration o f the patient's occlusion, then it is necessary to only make a registration o f that position with the remaining teeth in contact. Thus, worldng casts are not joint-oriented because this is not a b o r d e r position. H o w e v e r , if the centric relation position is recorded, it would advantageous to use a joint-oriented technique for mounting (such as a faceb o w transfer). H c suggested that, if this is accomplished, eccentric pathways should bc dynamically registered with a pantograph, a stereograph, interocclusal record m e t h o d , d e t e r m i n e d by mechanical equivalents, or adjusted entirely intraorally. If this is to be done, Celcnza suggested a fully adjustable articulator because he believed 3-dimensional eccentric registrations reduce chairside adjustment o f occlusion. Celenza stated that a "centric relation system" should be used in c o m p l e t e d e n t u r e fabrication techniques; however, it is inappropriate to complete precise 3-dimensional eccentric registrations because o f tissue resiliency. H o b o et a191 also offered several rules for matching the articulator with the dental treatment to be performed. They stated that for most single restorations, a fixed condylar path instrument will produce an acceptable result, namely, a nonadjustable articulator. They t h o u g h t it was desirable to have a shallow condylar inclination, preferably approximately 20 degrees, because the error produced with such a condylar inclination will usually bc negative. Therefore, there will be greater tolerance in excursive movements than necessary. I f the practitioner is knowledgeable regarding occlusion errors that may occur using this type o f instrument, such errors may be quickly adjusted chairside. They stated that when multiple restorations or VOLUME 83 NUMBER 2

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fixed partial dentures are fabricated, there is a greater need for accuracy in instrumentation. I f it is not necessary to restore vertical dimension o f occlusion, and if no occlusal disease or immediate mandibular lateral translation is present, then a semiadjustable articulator may be used for such restorations. It is necessary to use lateral interocclusal records to set the condylar inclinations on these semiadjustable instruments. These authors suggested that a fully adjustable articulator, coupled with the use o f a hinge axis transfkr and a pantographic tracing or a 3-dimensional intraoral recording, be used for extensive restorative treatments. This includes restoration o f opposing quadrants, reconstruction o f the entire occlusion, or for patients with significant immediate mandibular lateral translation occurring during eccentric movements. Use o f a fully adjustable i n s t r u m e n t is particularly desirable when restoration o f vertical dimension o f occlusion is necessary or when there is occlusal disease present. They did not suggest that a small nonadjustable hinge articulator be used at any time. In 1963 Weinberg 92 described a gnathologic type of instrument where 3-dimensional guidance of the working condyle is reproduced. H e stated that this is the instrument of choice among the fully adjustable articulators, and this articulator can be adjusted with accurate 3dimensional pantographs or with eccentric interocclusal records. H e stated that the semiadjustable articulators are clinically adequate for complete denture fabrication, and he explained that this type of instrument is based on clinical averages. H e further explained that to reduce the amount of intraoral correction necessary with restorations, the use of a fully adjustable instrument that will accept lateral interocclusal records may be necessary. Stuart 93 stated that the use o f a particular articulator was not the only factor in successfully achieving an optimal occlusion. He referred to optimal occlusion as "organic occlusion." H e described the Stuart articulator (C.E. Stuart Gnathological Instruments, Ventura, Calif.), which uses frictionless condylar recordings, and said that this instrument had the same potential for movement as the jaws. H e believed that the use o f frictional devices to record mandibular movements was inappropriate. The mandibular m o v e m e n t recorder used with the Stuart articulator is known as a pantograph. Stuart referred to his articulator as an "analog computer." By using this articulator, the static and moving relations o f the mandible may be replicated. The development o f occlusion with this articulator allows the mandible to position itself where the patient's muscles, joints, and nerves dictate, without regard for tooth guidance. H e stated that Stuart articulators provide reliable and accurate preservation o f the centric relation position because o f the rigidity o f the instrument. H e believed that full interdigitation o f the cusps must occur in the centric relation position. H e FEBRUARY 2000

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also believed that an articulator is only valuable if it is used with accurate casts, appropriate interocclusal records, and proper jaw-writing records. Guichet 94 believed a dentist should never consider restoration of the occlusion out o f harmony with the condylar paths o f movement. H e stated that when the restoration o f a patient involves at least the last 2 or 3 teeth in a quadrant, the Denar pantograph and fully adjustable articulator offers treatment advantages. H e stated that w h e n occlusal restoration o f a patient involves only 1 or a few teeth, such restoration can usually be developed by relying on anatomic guidelines established by the noninvolved teeth with a functionally generated path technique, or by using minimal laboratory procedures with appropriate chairside adjustment on insertion o f the restoration. L u n d e e n 9~ described the Lee pantograph system (Panadent, Grand Terrace, Calif.) that was used to record condylar border movements o f several hundred subjects. From these data, a computer analysis method analyzed the movement patterns o f 163 subjects and reported that the average protrusive condylar pathway angle was 45 degrees. The average lateral balancing side pathway was 55 degrees, and the Bennett movement average was 0.75 mm. H e described a simplified mandibular movement recorder that was not used to directly program an articulator. H e stated that articulator adjustments may be accomplished very quicldy by the use o f preformed condylar motion analogs. In 1973 Bellanti 96 completed a study to measure the discrepancies that can exist in articulator capability due to incomplete m o v e m e n t simulation. H e concluded that semiadjustable articulators produce errors that may result in more than a minimal amount o f eccentric occlusal adjustment, or uncontrolled amounts o f disclusion o f fabricated fixed prostheses. H e suggested that an articulator is needed with a wide range o f intercondylar width adjustment, and with adjustable fossa walls to accurately reproduce the effects o f the immediate mandibular lateral translation. SUMMARY Different methods and materials have been used to record the centric relation position and eccentric maxillomandibular relationships. The accuracy and stability of these methods and materials varies, and has been extensively evaluated over time and reported in the dental literature. The variation in articulators has also been discussed in the literature regarding the degree that these instruments are capable of simulating jaw movements, and the instrument complexity required to complete different types o f prosthetic restorations. Future research must focus on the changes in dental materials and instrumentation that are continually developing for recording maxillomandibular relation positions and mounting casts for prosthodontic rehabilitations. 245

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REFERENCES 1. Lang BR, Kelsey CC, editors. Articulators and articulation: international prosthodontic workshop on complete denture occlusion. Ann Arbor: University of Michigan; 1972. 2. Rahn AO, Heartwe]l CM. Textbook of complete dentures. 5th ed. Philadelphia: Lea & Febiger; 1993. 3. The Academy of Prosthodontics. The glossary of prosthodontic terms. 7th edition. J Prosthet Dent 1999;81:39-110. 4. Sheppard ]M. The bracing position, centric occlusion, and centric relation. J Prosthet Dent 1959;9:11-20. 5. Shanahan TE. Physiologic vertical dimension and centric relation. J Prosthet Dent 1956;6:741-7. 6. Baer PN. Analysis of physiologic rest position, centric relation, centric occlusion. J Periodontol 1956;27:181-3. 7. Page HL. A critical appraisal of centric relation. D Digest 1953:59:342-5. 8. Rader AF. Centric relation is obsolete. J Prosthet Dent 1955;5:333-7. 9. Shpuntoff H, Shpuntoff W. A study of physiologic rest position and centric position by electromyography. J Prosthet Dent 1956;6:621-8. 10. Hickey JC. Centric relation--a must for complete dentures. Dent Clin North Am 1965;58:587-600. 11. Kingery RH. A review of some of the problems associated with centric relation. J Prosthet Dent 1952;2:307-19. 12. Zarb GA, Bolender CL, Carlsson GE. goucher's prosthodontic treatment for edentulous patients. 1 lth ed. St Louis: Mosby; 1997. 13. Graser GN. Completed bases for removable dentures. J Prosthet Dent 1978;39:232-6. 14. Klein IE, Soni A. Stabilized record bases for complete dentures. J Prosthet Dent 1979;42:584-7. 15. Elder ST. Stabilized baseplates. J Prosthet Dent 1955;5:162-8. 16. Tucker KM. Accurate record bases for jaw relation procedures. J Prosthet Dent 1966;16:224-6. 17. Elahi JM, Abdullah M. Effect of polymerization techniques on dimensional stability of record bases. J Prosthet Dent 1994;71:150-3. 18. Loney RW. Stabilized record bases for implant-retained overdentures. J Prosthet Dent 1994;72:16-8. 19. Myers ML. Centric relation records historical review. J Prosthet Dent 1982;47:141-5. 20. Swenson MG. Complete dentures. 6th ed. St Louis: CV Mosby; 1970. 21. Hanau RL. Why is centric relation once established not retained subsequently? Chicago: Northwestern University Dental School Library; 1929. 22. Wright WH. Use of intraoral jaw relation wax records in complete denture prosthesis. J Am Dent Assoc 1939;26:542-5. 23. Block LS. Common factors in complete denture prosthetics. J Prosthet Dent 1953;3:736-46. 24. Schuyler C. Intraoral method of establishing maxillomandibular relation. J Am Dent Assoc 1932;19:1012-9. 25. Payne SH. Selective occlusion. J Prosthet Dent 1955;5:301-4. 26. Trapozzano VR. Occlusal records. J Prosthet Dent 1955;5:325-32. 27. Greene JW. Greene brothers' clinical course in dental prosthesis, 1910. 28. Akerly WB. A tripodal method of recording centric relation. J Prosthet Dent 1979;42:461-5. 29. Shanahan TE. Physiologic jaw relations and occlusion of complete dentures. J Prosthet Dent 1955;5:319-24. 30. Balkwi]l FH. The best form and arrangement of artificial teeth for mastication. Odont 5oc Gt Brit Tr (1st Ser) 1866;5:133-58. 31. Sears VH. Centric jaw relation. Dent Dig 1952;58:302-6. 32. Gysi A. The problem of articulation. Dent Cosmos 1910;52:1-19. 33. Sears VH. Jaw relations and a means of recording the most important articulator adiustment. Dent Cosmos 1926;68:1047-54. 34. Stansbery CJ. Functional position checkbite technique. J Am Dent Assoc 1929;16:421-40. 35. Hall RE. Full denture construction. J Am Dent Assoc 1929;16:1157-8. 36. Phillips GB. Fundamentals in the reproduction of mandibular movements in edentulous mouths. J Am Dent Assoc 1927;14:409-15. 37. Hanau RL. Dental engineering. Vol. l, Part II. Buffalo: Hanau Engineering Co; 1927. 38. Yurkstas AA, Kapur KK. Factors influencing centric relation records in edentulous mouths. J Prosthet Dent 1964;14:1054-65. 39. Hardy IR. Technique for use of nonanatomic acrylic posterior teeth. Dent Digest 1942;48:562-6. 40. Pleasure MA. Occlusion of cuspless teeth for balance and comfort. J Prosthet Dent 1955;5:305-12. 41. Porter CG. The cuspless centralized occ[usal pattern. J Prosthet Dent 1955;5:313-8.

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42. Silverman MM. Centric occlusion and jaw relations and fallacies of current concepts. J Prosthet Dent 1957;7:750-69. 43. Boos RH. Intermaxillary relation established by biting power. J Am Dent Assoc 1940;27:1192-9. 44. Walker RC. A comparison of jaw relation recording methods. J Prosthet Dent 1962;12:685-94. 45. Niswonger ME. The rest position of the mandible and the centric relation. J Am Dent Assoc 1934;21:1572-82. 46. Granger ER. Centric relation. J Prosthet Dent 1952;2:160-71. 47. Lauritzen AG. Function, prime object of restorative dentistry; a definite procedure to obtain it. J District of Columbia Dent Soc 1957;32:19-28. 48. Hunt GC, Yoxsimer JN. Edentulous gnathologic recordings utilizing "vacustatics." J Prosthet Dent 1976;35:588-94. 49. Shoen PE, Stewart JL. The effect of temporary bases on the accuracy of centric jaw-relationship records. J Prosthet Dent 1967;18:211-6. 50. Obrez A, Stohler CS. Jaw muscle pain and its effect on gothic arch tracings. J Prosthet Dent 1996;75:393-8. 51. Obrez A, Tfirp JC. The effect of muscoskeletal facial pain on registration of maxillomandibu[ar relationships and treatment planning: a synthesis of the literature. J Prosthet Dent 1998;79:439-45. 52. Needles JW. Practical use of the curve of Spee. J Am Dent Assoc 1923;

10:918-27. 53. Patterson AH. Construction of artificial dentures. Dent Cosmos 1923; 65:683-4. 54. Meyer FS. A new, simple and accurate technique for obtaining balanced and functional occlusion. J Am Dent Assoc 1934;21:195-203. 55. House MM. Full denture technique. Whittier: Whittier Publishing Co; 1937. 56. House MM. Studies in prosthesis (mandibular movements, articulators). J Am Dent Assoc 1931 ;18:827-52. 57. Swanson KH. Complete dentures using theTMJ articulator. J Prosthet Dent 1979;41:497-506. 58. Hemphill CD, Parker ML, Regli CP. Effects of uneven occlusal contact when registering maxillomandibular relations. J Prosthet Dent 1972;28: 357-9. 59. Boos RH. Occlusion from rest position. J Prosthet Dent 1952;2:575-88. 60. Boos RH. Basic anatomic factors of jaw position. J Prosthet Dent 1954; 4:200-3. 61. Boos RH. Centric relation and functional areas. J Prosthet Dent 1959;9: 191-6. 62. Pyott JE, Schaeffer A. Simultaneous recording of centric occlusion and vertical dimension. J Am Dent Assoc 1952;44:430-6. 63. Boos RH. Physiologic denture technique. J Prosthet Dent 1956;6:726-40. 64. Nasr MF, Griffiths NH. Exercise therapy for accurate recording of centric relation. J Prosthet Dent 1973;29:5-9. 65. Shafgah I, Yoder JL, Thayer KE. Diurnal variance of centric relation position. J Prosthet Dent 1975;34:574-82. 66. Latta GH Jr. Influence of circadian periodicity on reproducibility of centric relation records for edentulous patients. J Prosthet Dent 1992;68:780-3. 67. Stewart KL, Rudd KD, Kuebker WA. Clinical removable partial prosthodontics. 2nd ed. St Louis: Ishiyaku EuroAmerica; 1992. 68. Beckett LS. Accurate occ[usal relations in partial denture construction. J Prosthet Dent 1954;4:487-95. 69. Akerly WB. A combination impression and occlusal registration technique for extension-base removable partial dentures. J Prosthet Dent 1978;39:226-9. 70. Freilich MA, Altieri JV, Wahle JJ. Principles for selecting interocclusa] records for articulation of dentate and partially dentate casts. J Prosthet Dent 1992;68:361-7. 71. Schnader YE. The stone core intaglio in restorative dentistry. Dent Clin North Am 1981;25:493-510. 72. Ziebert GJ, Balthazar-Hart Y. Stabilized baseplate technique for interocclusal records. J Prosthet Dent 1984;52:606-8. 73. Pameijer JH. Periodontal and occ[usal factors in crown and bridge procedures. Amsterdam: Dental Center for Postgraduate Courses; 1985. p. 283345. 74. Warren K, Capp N. A review of principles and techniques for making interocclusal records for mounting working casts. Int J Prosthodont 1990;3:341-8. 75. Lundquist DO, Fiebiger GE. Registrations for relating the mandibular cast to the maxillary cast based on Kennedy's classification system. J Prosthet Dent 1976;35:371-5. 76. Curtis TA, Taylor RC, Rositano SA. Physical problems in obtaining records of the maxillofacial patient. J Prosthet Dent 1975;34:539-54.

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77. Gysi A. Practical application of research results in denture construction. J Am Dent Assoc 1929; 16:199-223. 78. Craddock FW. The accuracy and practical value of records of condyle path inclination. J Am Dent Assoc 1949;38:6974710. 79. Frazier QZ, Wesley RC, Lutes MR, Henderson D, Rayson JH, Ellinger CW, et al. The relative repeatability of plaster interocclusal eccentric records for articulator adjustment in construction of complete dentures. J Prosthet Dent 1971 ;26:456-67. 80. Berman MH. Accurate interocclusal records. J Prosthet Dent 1960;10: 620-30. 81. Lassila V. Comparison of five interocclusal recording materials. J Prosthet Dent 1986;55:215-8. 82. Bell JW, Davies EH, yon Fraunhofer JA. The dimensional changes of elastomeric impression materials under various conditions of humidity. J Dent 1976;4:73-82. 83. Breeding LC, Dixon DL. Compression resistance of four interocclusal recording materials. J Prosthet Dent 1992;68:876-8. 84. Millstein PL, Hsu CC. Differential accuracy of elastomeric recording materials and associated weight change. J Prosthet Dent 1994;71:400-3. 85. Chai J, Tan E, Pang IC. A study of the surface hardness and dimensional stability of several intermaxillary registration materials. Int J Prosthodont 1994;7:538-42. 86. Mullick SC, Stackhouse JA Jr, Vincent GR. A study of interocclusal record materials. J Prosthet Dent 1981;46:304-7. 87. MiJller J, G6tz G, Bruckner G, Kraft E. An experimental study of vertical deviations induced by different interocclusal recording materials. J Prosthet Dent 1991 ;65:43-50. 88. Breeding LC, Dixon DL, Kinderknecht KE. Accuracy of three interocclusal recording materials used to mount a working cast. J Prosthet Dent 1994;71:265-70.

89. Weinberg LA. An evaluation of basic articulators and their concepts. Part II. Arbitrary, Positional, Semiadjustable Articulators. J Prosthet Dent 1963;13:645-63. 90. Celenza FV. An analysis of articulators. Dent Clin North Am 1979;23:30526. 91. Hobo S, Shillingburg HT, Whitsett LD. Articulator selection for restorative dentistry. J Prosthet Dent 1976;36;35-43. 92. Weinberg LA. An evaluation of basic articulators and their concepts. Part IV. Fully adjustable articulators. J Prosthet Dent 1963;13:1038-54. 93. Stuart CE. Use of the Stuart articulator in obtaining optimal occlusion. Dent Clin North Am 1979;23:259-70. 94. Guichet NE The Denar system and its application in everyday dentistry. Dent Clin North Am 1979;23:243-57. 95. Lundeen HC. Mandibular movement recordings and articulator adjustments simplified. Dent Clin North Am 1979;23:231-41. 96. Bellanti ND. The significance of articulator capabilities. Part I. Adjustable vs. semiadjustable articulators. J Prosthet Dent 1973;29:269-75.

Reprint requests to: DR DONNA L. DIXON 1 760 TWIN BRIDGEDR BIRMINGHAM,AL 35243 E-MAIL: [email protected] Copyright © 2000 by The Editorial Council of The Journal of Prosthetic Dentistry. 0022-3913/2000/$12.00 + 0. 10/1/104279

N e w p r o d u c t news

The January and July issues o f the Journal carry information regarding new products o f interest to prosthodontists. Product information should be sent 1 month prior to ad closing date to: Dr. Glen P. McGivney, Editor, SUNY at Buffalo, School o f Dental Medicine, 345 Squire Hall, Buffalo, NY 14214. Product information may be accepted in whole or in part at the discretion of the Editor and is subject to editing. A black-and-white glossy photo may be submitted to accompany product information, Information and products reported are based on information provided by the manufacturer. N o endorsement is intended or implied by the Editorial Council o f The Journal of Prosthetic Dentistry, the editor, or the publisher.

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