Feb 21, 2007 - Beard CC, Donaldson K, Clayton JA. ... Utz KH, Muller F, Luckerath W, Fuss E, Koeck B. Accuracy of check-bite registration and centric condylar ...
The horizontal condylar inclination: Clinical comparison of different recording methods By Paul J. Boulos, DDS Salim M. Adib, MD, DrPH Levon J. Naltchayan, DDS Featured in General Dentistry, March/April 2007 Pg. 112-116
Contact Us Send to a Friend Send to Printer Close Window
Posted on Wednesday, February 21, 2007 Paul J. Boulos, DDS Salim M. Adib, MD, DrPH Levon J. Naltchayan, DDS Various types of semi-adjustable articulators (arcon and nonarcon), in combination with different interocclusal recording materials (wax and polyether), have been proposed as an easier alternative to extraoral tracing devices or axiographs. There is no consensus as to which combination is the nearest to the recognized standard extraoral tracing devices. This trial measured differences in performance among four combinations of interocclusal recordings in calculating the horizontal condylar inclination (HCI). The mean HCI measurement obtained by axiograph was 50.3 degrees (SD = 10.2) for the right condyle and 52.5 degrees (SD = 9.3) for the left. Of the four tested combinations, the arcon Whip Mix with wax was most likely to reproduce HCI values obtained using the axiograph. Received: July 10, 2006 Final revisions: October 11, 2006 Accepted: October 23, 2006 A dental prosthesis must work with the movements of the mandible to prevent any undesirable effects on either the periodontal tissues or the temporomandibular joint (TMJ) elements. This harmony is crucial for the success of the prosthesis, the fulfillment of the goals of function and preservation, and the reduction of intraoral adjustments. The construction of the dental prosthesis requires an articulator that can mimic the mandibular movements closely. The articulator is programmed according to the patient¡¯s condylar pathways: the horizontal condylar inclination (HCI) and the lateral inclination (also known as the Bennett angle). These inclinations can be calculated by using an extraoral tracing device (that is, an axiograph) or by using eccentric (that is, protrusive and lateral) interocclusal records. Some studies have highlighted the advantages of extraoral tracing devices over eccentric interocclusal records, while others have mentioned the fact that these devices may be more operatorsensitive, time-consuming, and costly than eccentric records.1,2 The precision and reliability of extraoral tracing devices (mechanical and electronic) in measuring condylar settings have been investigated extensively in recent years. According to the literature, these devices, while cumbersome, can provide an accurate measure of those angles.3-8 Background Extraoral tracing devices have been compared to eccentric interocclusal records that are easier to use, although less accurate.9 Price and Bannerman compared articulator settings obtained from wax lateral interocclusal and electronic pantographic records and found that the wax records demonstrated more variance and produced more potential occlusal errors.10 In a 1991 bench study, Pelletier and Campbell compared three groups of methods for recording condylar settings and found that a pantograph (electronic or mechanical) and simplified jaw tracking devices (that is, axiographs) produced more accurate and reproducible condylar settings than interocclusal records.1 Ecker et al compared mandibular movements from 16 subjects by using two simplified jaw tracking devices and interocclusal wax records. The authors found that the interocclusal wax technique produced wider ranges and higher standard deviations for condylar settings than either of the jaw tracking devices.11 Among the instruments available for extraoral tracing, simplified jaw tracking devices such as the Panadent Quick Analyzer (Panadent Corporation, Grand Terrace, CA; 800.368.9777), the Quick Set Recorder (Whip Mix, Louisville, KY; 800.626.5651), and the Quick-Axis axiograph (Sintec, East Wakefield, NH; 800.233.2162) are more practical than the pantograph. The recordings of jaw movements on the pantograph are tridimensional; by comparison, simplified jaw tracking devices record movements in only the sagittal plane.
However, these jaw tracking instruments are expensive and their success depends on the skill and experience of the operator.2 As a result, eccentric interocclusal records are used widely and recommended routinely in dental textbooks, although some, like Craddock, consider them unreliable and invalid.12,13 The axiograph is a simplified jaw tracking device that is based on analyzing the condylar path translation during the opening and closing movements of the jaw instead of the protrusion movement that other simplified jaw tracking devices use for analysis. The HCI is determined by directly reading on special graph paper the value of the angle formed by the horizontal plane of reference and a line connecting the origin of the axes to the intersection of the condylar tracing with a partial circle within a radius of 5.0 mm. There is no need for drawing a tangent to the tracing for the use of protractors; as a result, potential measurement errors are avoided when calculating condylar settings.2,4 The axiograph has been investigated fairly and the mechanical axiograph¡¯s ability to determine the transverse hinge axis has been compared favorably to that of the electronic version.14 According to Ozawa and Tanne, the axiograph showed acceptable results in diagnostic procedures when compared to MRI.15 Dos Santos suggested that arcon articulators simulated the jaw movements more closely than nonarcon ones.16 Arcon semi-adjustable articulators such as the Whip Mix 8500 (Whip Mix) display the anatomy of the TMJ joint with an upper maxillary element mimicking the glenoid fossa and a lower one mimicking the mandibular condyle. By contrast, nonarcon semi-adjustable articulators such as Dentatus AHR (Dentatus USA, New York, NY; 800.323.3136) position the condylar head on the maxillary member of the articulator, while the glenoid fossa is carried on the mandibular one. In 1990, Gross et al questioned the reproducibility of arcon semi-adjustable articulators compared to electronic pantographs.17 Lundeen and Wirth used extraoral means to evaluate the mandibular movement patterns in plastic blocks.18 According to the literature, elastomeric materials (such as polyether or polyvinyl siloxanes) are superior to wax and other materials, yielding condylar values closer to pantographic recordings.19-21 Millstein et al tested two types of waxes and concluded that these interocclusal materials were unreliable and unpredictable, even under a careful technique.22 More recent studies found wax to be superior to other interocclusal recording materials.23,24 This study involved a clinical trial that investigated four different combinations of interocclusal materials and semi-adjustable articulators (arcon and nonarcon) to determine the ability of each to measure HCI. The performances were compared to an axiograph that was used as a reference. This study sought to determine which combination provided the best valid alternative to the axiograph in clinical practice. Materials and methods Thirty pre-and post-doctorate dental students (aged 18¨C33) agreed to participate in this clinical study and signed an informed consent form. Eligible participants had to have a complete dentition and a Class I jaw relation without extractions, artificial crowns, or extensive restorations. All participants had to be free from signs and symptoms of temporomandibular disorders or bruxism. To ensure unbiased measurements, participants could not have any centric slide between the centric relation position and the maximum intercuspation position. All participants were subjected to the same set of combined measurements. Procedures An axiograph Quick-Axis (Sintec) was mounted on each participant¡¯s head and mandible according to manufacturer¡¯s instructions. The clutch was affixed on the mandibular anterior teeth using a quick-setting plaster (Xanthano, Heraeus-Kulzer, Inc., Armonk, NY; 800.431.1785). The stem of the clutch was centered in relation to the sagittal plane. The incisal edges of the teeth were covered with utility wax (Wax Utility Strips, Henry Schein Co., Melville, NY; 800.472.4346) to facilitate removal of the clutch. Participants were asked to hold the clutch in the centered position until the plaster had set. The axiograph facebow was secured tightly to the head using the nasal piece, the earpieces, and the headband. Special graph papers were fixed to the flags on both sides of the face. The transverse bar was affixed to the stem of the clutch and the lateral arm holding a stylus in the direction of the graph papers mounted on the flags was attached to the transverse bar. Participants remained in centric relation position while the stylus was adjusted to the origin of the axes that represented the arbitrary hinge axis (Fig. 1); at that point, the participants were asked to open and close the mouth to test the stylus¡¯s return to the origin of the axes position. An articulating paper (Accufilm, Parkell Inc., Farmingdale, NY; 800.243.7446) was interposed between the stylus and the graph paper. Participants were asked to open the mouth slowly to the maximum. At the end of movement, the articulating paper was removed and the tracing was checked for validity (Fig. 2). HCI was calculated using the method described above (Fig. 3). This procedure was repeated for the right and left sides.
Using an improved dental stone (Silky-Rock, Whip Mix, Louisville, KY; 800. 626.5651) and an irreversible hydrocolloid impression material (Jeltrate, Dentsply Caulk, Milford, DE; 800.532.2855) with perforated metallic trays (Coe Stainless Steel Trays No. 264008, GC America Inc., Alsip, IL; 800.323.7063), diagnostic casts were obtained for each participant. Maxillary casts were mounted (according to the manufacturer¡¯s instructions) on two different articulators, respectively, with corresponding facebow transfers: Whip Mix No. 8500 with Whip Mix Quick Mount No. 8600 (Whip Mix) or Dentatus AHR with Dentatus earbow (Dentatus USA). Mandibular casts were mounted using centric interocclusal wax records (Beauty Pink Wax; Moyco Union Broach-Thompson, Montgomeryville, PA; 800.221.1344) Two sets of eccentric interocclusal records were made, as required. An arithmetical mean was computed from the two sets for each condylar setting. Wax (Aluwax Bite and Impression Wax and waxed cloth sheets, Aluwax Dental Products Co., Grand Rapids, MI; 616.895.4385) and polyether (Ramitec, 3M ESPE, St. Paul, MN; 800.364.3577) were used for the recordings. The interocclusal records were used within two hours to avoid possible wax distortions. The Whip Mix and Dentatus articulators were programmed to calculate the condylar inclinations by using the different eccentric interocclusal records. At that point, angle measurements were recorded on the worksheet for each participant. Plan of analysis The HCIs on each side of the jaw were measured with four different articulator/material combinations and tabulated. The mean values with their corresponding 95% confidence intervals (CI) were computed for each combination alone. Every single mean value derived from each combination was compared separately to the mean reference value obtained by the axiograph. Differences were tested using the paired t-test; those with a P value ¡Ü 0.05 were considered to be statistically significant. The analysis sought to identify the combination most similar to the axiograph with the least significant mean difference (that is, the largest possible P-value) from the mean measured by the axiograph. These judgment criteria were applied to all one-to-one comparisons presented in this article. All computations were conducted with SPSS 11 software (SPSS Inc., Chicago, IL; 800.543.2185). Results Of the 30 volunteers who participated in this trial, 12 (40%) were women. The average age of the participants was 22.5 years (¡À 2.7 years). Axiographic recording revealed that 23% of participants showed a difference of more than 10 degrees between the left and right condyle. With the axiograph, the mean HCI obtained for the right condyle was 50.3 degrees (95% CI: 30.7¨C69.9). By contrast, the four alternative methods reported HCIs ranging from 46.2 degrees (for Dentatus articulator with polyether) to 50.7 degrees (for Whip Mix articulator with wax) (see the table). Compared to the axiograph, there were no significant differences in mean values for Whip Mix and wax, Whip Mix and polyether, and Dentatus and wax; Whip Mix and wax produced the smallest difference (P = 0.83). Only one combination (Dentatus and polyether) presented a significantly different mean value (P = 0.07) than the axiograph. The same data were computed on the left condyle, where the axiograph revealed an average setting of 52.5 degrees (95% CI: 34.2¨C70.8). Concerning the four tested combinations, Dentatus and polyether was significantly different from the axiograph (P = 0.02). Details are available in the table.
Discussion This study was conducted to evaluate various combination techniques for measuring condylar inclinations that might be easier to use in everyday practice than the standard yet cumbersome axiographs. Results obtained from 30 volunteers showed that HCI settings obtained from the Whip Mix articulator with wax were nearly identical to those obtained with the reference axiograph. Measurements with all other combinations were smaller on average than the reference ones, although not significantly so. The combined Dentatus articulator with polyether was the least reliable method, resulting in significantly lower estimations of the HCI. The mean HCI values presented in this study using the axiographic method were significantly lower than those found in a 1998 study by Stamm et al, who used an electronic axiograph and recorded a mean HCI of 62.5 degrees in a normal occlusion group.5 The values in the present study were similar to those found by Ecker et al (48.7 degrees) using the Quick Set recorder from Whip Mix.11 A 2005 study by Kucukkeles et al compared mechanical and computerized axiographs to check their compatibility and reported a similar value (52.4 degrees).8 The findings in the present study were higher than those in studies that used extraoral tracing drills or a Denar Pantronic (Denar Corp., Anaheim, CA; 800.525.2020) to calculate the HCI angle.3,18 This also was true for measurements made by Dos Santos et al (38.5 degrees), who used the Quick Set recorder but utilized a different plane of reference.2 The Quick Set recorders are simplified jaw tracking devices that use the protrusive movement of the mandible to record the condylar path. The calculation method of the HCI and the horizontal plane of reference are possible causes of disparities between certain simplified jaw tracking devices and the axiograph. Differences of more than 10 degrees between the left and right sides were found in 23% of subjects in this study; this finding is similar to those found in previous studies and highlights the clinical importance of graphic registration that can treat the right and left sides independently.4,6,7 In the present study, HCIs generated by interocclusal records were lower on average than those found with the axiograph, regardless of the combination of articulator and recording material. These results compare favorably to studies that reported higher HCI values from extraoral tracing devices than from interocclusal records.10 Based on the present study, Whip Mix with wax (followed by Whip Mix with polyether) is the combination most likely to yield an HCI nearest to that produced by the axiograph, a finding that contradicts a 1988 study by Assif et al suggesting that polyether was more effective than wax for simulating condylar values.20 Polyethers may reproduce the incisal and the occlusal forms of the teeth more accurately than the plaster casts; however, they also remain nonrigid after setting. Balthazar et al suggested that both of these factors can interfere with the placement of the plaster casts into the recording medium during mounting procedures.24 Differences may exist between reference planes for measurements of the different instruments (Whip Mix, Dentatus, Axiograph). In a study involving three arcon semi-adjustable articulators, Gross et al reported that the angle between the reference plane of the Whip Mix articulator and the maxillary occlusal plane was 1.5 degrees less on average than the angle formed between the maxillary occlusal plane and the axis-orbital plane usually adopted by Dentatus articulators.17 Although the Frankfort Plane is the point of reference for the axiograph (as well as for the Whip Mix and Dentatus articulators), there may be minor variations regarding the anterior reference point.
The axiograph and the Whip Mix articulator use the nasion as an anterior reference point, while the Dentatus articulator adopts the orbitale point. All three instruments use the porion as the posterior reference point. Lower reference planes notwithstanding, values with Whip Mix remained higher on average than those with Dentatus and closer to mean values with the axiographic tracing. This suggests that the results were not biased by differences in the planes of reference. The clinical significance of these results may not be as practically meaningful as their statistical significance would suggest. Errors in evaluating the HCI may affect the cusp height and, to a lesser extent, groove and ridge positions. Price et al reported HCI measurement errors of 0.24 mm for every five degrees on the first molar cusp height on the nonworking side when the lateral displacement of the mandible was 3.0 mm from the maximal intercuspal teeth position.25 Clinically, since the HCI estimations produced by the interocclusal records technique are lower on average than the values produced by the axiograph, it follows that restorations constructed on articulators programmed with eccentric interocclusal records (especially on the nonworking side) generally will have lower cusp height. This situation is beneficial with fixed restorations, since shorter cusps may reduce the risk of undesirable tooth contact on the balancing side of the mandible. On the contrary, it would be considered a disadvantage for removable restorations (that is, a complete denture), where shorter cusps would reduce the chance of balancing teeth contacts on the nonworking side, an important factor in the stability of complete dentures. Nevertheless, fixed restorations constructed on a Dentatus articulator programmed with polyether might encounter undesirable occlusal prematurities on the nonworking side, due mostly to repercussions of errors in HCI on groove and ridge positions. It is important to note that random errors were minimized by obtaining two sets of records for each measurement, standardizing the displacements of the mandible during the recording of the eccentric movements, and respecting the properties of the recording materials. These precautions were designed for better reproducibility of the results. Conclusion Within the limitations of this study, the axiographic tracings produced higher values for HCIs than eccentric interocclusal records on arcon (Whip Mix) and nonarcon articulators (such as Dentatus). Most combinations of eccentric interocclusal record techniques were statistically similar to the axiographic technique, a finding that contradicts past studies that labeled eccentric interocclusal records techniques as unreliable. The results showed that as an interocclusal recording material, wax was as reliable and valid as elastomeric recording materials. Acknowledgements This research was funded by a research grant from Saint Joseph University in Beirut-Lebanon. This work is in memory of our late professor, Dr. Victor O. Lucia, whose remarks to the first author prompted this study. Authors information Dr. Boulos is Maitre-Assistant, Department of Removable Prosthodontics, Faculty of Dental Medicine, Saint Joseph University, Beirut, Lebanon, where Dr. Naltchayan is a professor and Head of the Department of Removable Prothodontics and Dr. Adib is an associate professor, Department of Epidemiology and Community Health, Faculty of Medicine. References 1. Pelletier LB, Campbell SD. Comparison of condylar settings using three methods: A bench study. J Prosthet Dent 1991;66:193-200. 2. Dos Santos J Jr, Nelson S, Nowlin T. Comparison of condylar guidance setting obtained from a wax record versus an extraoral tracing. A pilot study. J Prosthet Dent 2003;89:54-59. 3. Beard CC, Donaldson K, Clayton JA. A comparison of articulator settings to age and sex. J Prosthet Dent 1986;56:551-554. 4. El-Gheriani AS, Winstanley RB. Graphic tracings of condylar paths and measurements of condylar angles. J Prosthet Dent 1989;61:77-87. 5. Stamm T, Vehring A, Ehmer U, Bollmann F. Computer-aided axiography of asympto-matic individuals with Class II/2. J Orofac Orthop 1998;59:237-245. 6. Zamacona JM, Otaduy E, Aranda E. Study of the sagittal condylar path in edentulous patients. J Prosthet Dent 1992;68:314-317. 7. Preti G, Scotti R, Bruscagin C, Carossa S. A clinical study of graphic registration of the condylar path inclination. J Prosthet Dent 1982;48:461-466.
8. Kucukkeles N, Ozkan H, Ari-Demirkaya A, Cilingirturk AM. Compatibility of mechanical and computerized axiographs: A pilot study. J Prosthet Dent 2005;94:190-194. 9. Gross M, Nemcovsky C, Tabibian Y, Gazit E. The effect of three different recording materials on the reproducibility of condylar guidance registrations in three semi-adjustable articulators. J Oral Rehabil 1998;25:204-208. 10. Price RB, Bannerman RA. A comparison of articulator settings obtained by using an electronic pantograph and lateral interocclusal recordings. J Prosthet Dent 1988;60:159-164. 11. Ecker GA, Goodacre CJ, Dykema RW. A comparison of condylar control settings obtained from wax interocclusal records and simplified mandibular motion analyzers. J Prosthet Dent 1984;51:404-406. 12. Shillingburg HT, Hobo S, Whitsett LD, Jacobi R, Brackett SE, eds. Fundamentals of fixed prosthodontics, ed. 3. Chicago: Quintessence Publishing Co.;1997:44-45. 13. Craddock FW. The accuracy and practical value of records of condylar path inclination. J Am Dent Assoc 1949;38:679-710. 14. Nagy WW, Smithy TJ, Wirth CG. Accuracy of a predetermined transverse horizontal mandibular axis point. J Prosthet Dent 2002;87:387-394. 15. Ozawa S, Tanne K. Diagnostic accuracy of sagittal condylar movement patterns for identifying internal derangement of the temporomandibular joint. J Orofac Pain 1997;11:222-231. 16. Dos Santos Jr J, Ash MM. A comparison of the equivalence of jaw and articulator movements. J Prosthet Dent 1988;59:36-41. 17. Gross M, Nemcovsky C, Freidlander LD. Comparative study of three semi adjustable articulators. Int J Prosthodont 1990;3:135-141. 18. Lundeen HC, Wirth CG. Condylar movement patterns engraved in plastic blocks. J Prosthet Dent 1973;30:866-875. 19. Michalakis KX, Pissiotis A, Anastasiadou V, Kapari D. An experimental study on particular physical properties of several interocclusals recording media. Part II: Linear dimensional change and accompanying weight change. J Prosthodont 2004;13:150-159. 20. Assif D, Himel R, Grajower Y. A new electromechanical device to measure the accuracy of interocclusal records. J Prosthet Dent 1988;59:672-676. 21. Curtis DA. A comparison of protrusive interocclusal records to pantographic tracings. J Prosthet Dent 1989;62:154-156. 22. Millstein PL, Clark RE, Kronman JH. Determination of the accuracy of wax interocclusal registrations. II. J Prosthet Dent 1973;29:40-45. 23. Utz KH, Muller F, Luckerath W, Fuss E, Koeck B. Accuracy of check-bite registration and centric condylar position. J Oral Rehabil 2002;29:458-466. 24. Balthazar Y, Fattore LD, Hart TO, Malone WFP. Interocclusal records. In: Malone WFP, Koth DL, eds. Tylman¡¯s theory and practice of fixed prosthodontics, ed. 8. St. Louis: Ishiyaku EuroAmerica, Inc.; 1989:275. 25. Price RB, Kolling JN, Clayton JA. Effects of changes in articulator settings on generated occlusal tracings. Part I: Condylar inclination and progressive side shift settings. J Prosthet Dent 1991;65:237-243.
General Dentistry, March/April 2007 , Volume 55 , Issue 2
Contact Us Send to a Friend
Rate it! Current Rating 12345Rate & Comment | Rate
Average (0 votes) Current Rating
Send to Printer Close Window
2 3 4 5
