SECTION

EDITOR

Analysis

of the interchangeability

John W . Unger, DDS,a Ralph M. Hoffmann, and John C. Gunsolley, DDS, MSd Virginia Commonwealth University/Medical Va.

of a dental

DMD,b Randy M. Diener,

articulator DDS,”

College of Virginia, School of Dentistry, Richmond,

A series of Dentatus ARL articulators and gauge blocks were tested for the reliability of the system to reproduce articulator mountings. Points of occlusal contact were measured at several locations on a set of casts. Analysis of the data indicated that the location of the occlusal contacts and the gauge block used were critically related to the results. Further studies to quantify the measurement error and to carefully explore where this system could be used are needed. (J PROSTHET DENT 1991;66:813-5.)

T

he use of articulators is a vital part of prosthodontics. Dentists rely extensively on the accuracy of articulators to aid them in the analysis and development of adequate occlusal function. An ideal articulator should retain accuracy over time and should be manufactured to standards that would allow interchangeability among articulators of the same type.l Several articulators have been produced that claim to be manufactured to standards that would allow interchangeability among articulators or permit calibration, making them interchangeable. 2-4 This study examined the accuracy of the Dentatus ARL articulator system (AB Dentatus, Stockholm, Sweden) that permits calibration of the articulator with a special device called a gauge block (Fig. 1). The gauge block is attached to the upper and lower members of the articulator to secure both members while the universal joint at the rear of the articulator is tightened with a wrench to fix the relationship of the upper and lower members (Fig. 2). A more detailed description of the process is available in the manufacturer’s technical manual.4 The manufacturer suggests that this system will permit close approximation of casts transferred from one ARL articulator to another. The directions emphasize that this technique should only be used in complete denture construction and that the final occlusal adjustment should be made on the original articulator. This suggestion presumably avoids any error related to the transfer of the casts affecting the accuracy of the occlusion in the finished dentures. No description is given of the potential error involved with this procedure.

aAssociate Professor and Chairman, Department of Removable Prosthodontics. bAssistant Professor, Department of Removable Prosthodontics. CCo-Director, UCLA/VA Advanced Prosthodontics Residency, Los Angeles, Calif. dDirector, Office of Applied Research. 10/l/25536

THE

JOURNAL

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DENTISTRY

This study determined (1) whether a number of Dentatus ARL articulators, calibrated with the gauge block system, would accurately reproduce the relationship found in a control articulator and (2) what, if any, effect the use of different gauge blocks would have on the reproducibility of the ARL articulator system. MATERIAL

AND

METHODS

Three Dentatus ARL system gauge blocks, designated as A, B, and C, and nine Dentatus ARL articulators were used in this study. Eight of the articulators (numbered 1 to 8) were used during the trials, with the ninth serving as a control. Casts that simulated complete maxillary and mandibular dentures were mounted in the control articulator that had been previously calibrated with gauge block “A.” The casts were adjusted until the shim stock (Artus Corporation, Englewood, N.J.) testing material could not be pulled between the casts at four divergent locations in the molar and first premolar regions on each side. Lines were placed on the casts in the measurement locations to ensure precise location of the shim stock material for each evaluation (Fig. 3). The occlusal contacts of the casts were then evaluated on the test articulators, with each contact being scored independently by the authors. The following scale was used for evaluating contacts: O-no resistance to the removal of shim stock material; l-some resistance to the removal of shim stock material; 2-total resistance to the removal of shim stock material. To ensure the reliability of scoring, the authors were calibrated to the evaluation method prior to the initiation of the study. The first set of measurements was made on each articulator with the articulators having been calibrated to gauge block “A.” These measurements were made to test the ability of the gauge block system to reproduce the contacts found in the control articulator in each of the test articulators. Following these measurements, each test articulator was recalibrated to gauge block “A” and a new series of measurements was made. This remeasurement was used to

813

1. Dentatus ARL articulator tached.

Fig.

with gauge block at-

3. Contact being tested with shim stock material at predetermined location on casts.

Fig.

Table I. Contact score mean values in relation to articulator used Articulator 1

2 3 4 5 6 7 8

2. Rear view of Dentatus ARL articulator. Note universal joint.

Fig.

assess the repeatability of the calibration technique with the same gauge block. This testing protocol was repeated using gauge blocks “B” and “C” to evaluate the effect of using different gauge blocks on the reliability of the system. The casts were returned to the control articulator after each series of measurements and the contact points were evaluated to determine if the contact had changed because of abrasion of the stone casts. At no time did any changes C)C’CUT in the contacts in the control articulator. To ensure the most consistent results possible during the study, all articulat,or calibrations and attachments of the casts to the articulators were performed by the same investigator. RESULTS The individual responses of each of the three evaluators were recorded by measurement position in relation to the articulator and gauge block used. When analyzing the data ;lnd assessing the significance of the results, it is important :o remember, that the data represent an evaluation of how ivell the relationships were reproduced from the control. what is being-measured is the reproducibility and reliabil:iv of the ARL gauge block system. A score of two indicates

Score

1.000 1.055 1.333 1.250 1.388 1.277 1.388 1.444

Standard

error

0.213 0.196 0.205 0.184 0.122 0.141 0.176 0.189

that the same degree of contact was present in the test articulator and the control. A score of one would mean that some resistance was present to the removal of the shim stock testing material but that the contact was clearly not the same as in the control. The absence of any resistance to the removal of the shim stock material resulted in a score of zero. This scoring system does not claim to quantify the distance that exists between the casts with a score of less than two, but instead measures the quality of contact in the test articulator compared with that found in the control. To test the effect that different articulators, different gauge blocks, and different measurement positions could have on the accuracy of the system, a three-way analysis of variance (ANOVA) was used. Since there were three evaluators, the response used in the ANOVA was the average of the three. No significant difference was found between the articulators in their ability to reproduce the contacts found in the control articulator (p < 0.2258). The mean scores for each articulator can be found in Table I. When the effect of the gauge block itself was analyzed, a statistically significant result was found (p < 0.0016). When one reviews the data in Table II, in particular the mean scores of each gauge block, it is apparent that one of the gauge blocks (B) was not as reliable as the other two in reproducing the occlusal contacts in the control articulator.

INTERCHANGEABILITY

Table

OF ARTICULATORS

Contact score mean values related to gauge

II.

block used Gauge

block

score

A B C

Standard

1.406 0.989 1.312

error

0.099 0.120 0.098

Table III. Contact score mean values related to measurement position Measurement

position

Left anterior Left posterior Right anterior Right posterior

Score

0.819 1.083 1.208 1.833

Standard

error

0.159 0.073 0.081 0.063

The score also varied with respect to the measurement position. On analysis, this variation was determined to be a statistically significant difference (p < 0.0000) (Table III). The mean score of the contact in the left anterior region was less than one, with contact in the right posterior nearly approaching a perfect score of two.

Clinical

implications

Clinically, the ability to reliably and accurately transfer mounted casts from articulator to articulator could be most advantageous. Such a system would permit a practitioner to reduce expenses by decreasing the number of articulators needed and eliminate costs associated with shipping articulators to dental laboratories. In addition, damage to an articulator associated with shipping would also be avoided. Asepsis procedures would also be facilitated, as articulators neither leave the office nor return from the dental laboratory. The use of this system, in addition to complete denture fabrication, may also be considered for construction of provisional and transitional restorations and for diagnostic waxing and tooth arrangement. CONCLUSION

pears to be limited. It is clear that the Dentatus ARL articulators in this study could be calibrated in a reliable fashion, with a single gauge block producing no statistically significant differences in the cast mountings between the test articulators. This does not mean that the test articulators and control articulator were identical in terms of contact of the casts. What it does mean, however, is that the error produced by transferring the mounted casts from the control articulator to each test articulator did not vary statistically according to the articulator used. Equally apparent is the fact that the gauge blocks themselves were not interchangeable in this study. One should either use the same gauge block for all articulator calibrations or ensure that the gauge blocks being used will produce compatible results. In addition to the magnitude of the error inherent in the transfer of casts between articulators, one should also understand the direction of such an error. In this study the greatest change was present in the left anterior region. Such knowledge might be helpful to both dentist and technician when using this system. W ithin the limitations presented by this study, one could conclude that the concerns raised by the manufacturer with respect to accuracy are valid. In addition, this system may be useful in treatment situations other than in complete denture construction. Future studies are needed to more closely examine this possibility and to quantify the magnitude and direction of the errors produced by this system of transferring mounted casts. REFERENCES 1. Lang BR, Kelsey CC. International prosthodontic workshop on complete denture occlusion. Ann Arbor:University of Michigan, 1973:39. 2. Denar Office Tutor Training Program. The two instrument system. Anaheim, CaliE Denar Corporation, 1975. 3. Panadent procedure manual. Grand Terrace, CalifzPanadent Corporation, 19&1:2. 4. Instructions for the use of the Dentatus articulator type ARH. Stockholm:AR Dentatus.1934:32. Reprint requests to: DR. JOHN W. UNGER SCHOOL OF DENTISTRY MEDICAL COLLEGE OF VIRGINIA Box 566 MCV STATION RICHMOND, VA 23298

The ability of the Dentatus ARL gauge block system to accurately reproduce articulator mountings of casts ap-

THE

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DENTISTRY

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Analysis of the interchangeability of a dental articulator.

A series of Dentatus ARL articulators and gauge blocks were tested for the reliability of the system to reproduce articulator mountings. Points of occ...
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