AIMSTo determine whether patients with temporomandibular joint disease or masticatory muscle pain can be usefully differentiated from asymptomatic controls using multifactorial classification tree models of attrition severity and/or rates.METHODSMeasures of attrition severity and rates in patients diagnosed with disc displacement (n = 52), osteoarthrosis (n = 74), or masticatory muscle pain only (n = 43) were compared against those in asymptomatic controls (n = 132). Cross-validated classification tree models were tested for fit with sensitivity, specificity, accuracy and log likelihood accountability.RESULTSThe model for identifying asymptomatic controls only required the three measures of attrition severity (anterior, mediotrusive and laterotrusive posterior) to be differentiated from the patients with a 74.2 +/- 3.8% cross-validation accuracy. This compared with cross-validation accuracies of 69.7 +/- 3.7% for differentiating disc displacement using anterior and laterotrusive attrition severity, 68.7 +/- 3.9% for differentiating disc displacement using anterior and laterotrusive attrition rates, 70.9 +/- 3.3% for differentiating osteoarthrosis using anterior attrition severity and rates, 94.6 +/- 2.1% for differentiating myofascial pain using mediotrusive and laterotrusive attrition severity, and 92.0 +/- 2.1% for differentiating myofascial pain using mediotrusive and anterior attrition rates. The myofascial pain models exceeded the > or =75% sensitivity and > or =90% specificity thresholds recommended for diagnostic tests, and the asymptomatic control model approached these thresholds.CONCLUSIONMultifactorial models using attrition severity and rates may differentiate masticatory muscle pain patients from asymptomatic controls, and have some predictive value for differentiating intracapsular temporomandibular disorder patients as well.

AIMS:To consider temporomandibular joint (TMJ) anatomic interactions in order to refine hard tissue models differentiating (1) joints diagnosed with disc displacement with reduction (DDwR) or without reduction (DDw/oR) from asymptomatic joints (Normals), and (2) DDwR joints from DDw/oR joints.METHODS:TMJ tomograms of 84 women with unilateral DDwR and 78 with unilateral DDw/oR were compared against each other and against those of 42 female Normal joints through the use of 14 linear and angular measurements, 8 ratios, and 34 interactions. A classification tree model for each comparison was tested for fit with sensitivity, specificity, accuracy, and log likelihood and compared to logistic regression models.RESULTS:In the classification tree model comparison, the DDwR model versus the Normal model realized 35.9% log likelihood (88.0% sensitivity, 66.7% specificity); the DDw/oR model versus the Normal model realized 38.8% log likelihood (69.6% sensitivity, 85.7% specificity). The DDwR model versus the DDw/oR model realized 33.3% log likelihood (76.0% sensitivity, 73.1% specificity). In the logistic regression model comparison, the DDwR model versus the Normal model realized 40.8% log likelihood (82.1% sensitivity, 78.6% specificity) and the DDw/oR model versus the Normal model realized 61.1% log likelihood (85.9% sensitivity, 90.5% specificity). The DDwR model versus the DDw/oR model realized 21.5% log likelihood (60.3% sensitivity, 79.8% specificity). The addition of interactions to the logistic regression models improved the previously published log likelihood from 99% to 149%.CONCLUSION:The interactions improved logistic regression models and the data suggest that anatomic characteristics influence joint functional status. Because the models incorporated nearly all considered anatomic measurements, no anatomic factor is redundant in the closed TMJ biological system.

STATEMENT OF PROBLEM:There is disagreement about the predictive value of temporomandibular joint tomographic anatomy in the diagnosis of internal derangements.PURPOSE:This study aimed to identify multifactorial temporomandibular hard tissue relationships that differentiate disk displacement with reduction and disk displacement without reduction from normals.MATERIAL AND METHODS:Temporomandibular joint tomograms from females diagnosed with unilateral disk displacement with (n=84) or without (n=78) reduction were compared to 42 asymptomatic normal joints with the use of 14 linear and angular measurements and 8 ratios. A validated classification tree model was tested for accuracy with sensitivity, specificity, goodness of fit, and the amount of log likelihood accounted for. The tree model was compared with a multiple logistic regression model and univariate testing.RESULTS:The disk displacement with reduction tree model consisted of 3 disease and 2 normal pathways with interactions between fossa width to depth ratio, condyle position, and linear posterior joint space. This class was characterized by either a much wider- and shallower-than-average fossa shape and/or by a moderately posterior condyle position when the fossa shape was average to deeper and/or narrower. The logistic regression and univariate models also suggested wider and/or shallower fossae, as well as longer eminence length. The disk displacement without reduction tree model consisted of 2 disease pathways and 1 normal pathway. Interactions characterized this class by either a posterior to very posterior condyle position or by a much deeper than average fossa depth when the condyle position was concentric to anterior. The logistic regression model emphasized greater fossa depth and width versus normals. The tree models conservatively predicted the disease classes: Rescaled Cox and Snell R(2) 37.0%, sensitivity 70.2%, and specificity 90.5% for disk displacement with reduction; R(2) 28.8%, sensitivity 66.7%, and specificity 85.7% for disk displacement without reduction.CONCLUSION:Within the limitations of this study, hard tissue relationships revealed by central tomogram sections were able to model notable differences between disk displacement with reduction and disk displacement without reduction versus asymptomatic normals when temporomandibular joints were examined as a multifactorial system typified by interactions of fossa width to depth proportions and condyle position. While substantial, the hard tissue predicted only part of the biology. The model could be broadened by additional factors and interactions.

Statement of Problem. There is persistent dispute about the diagnostic value of hard tissue anatomic relationships in predicting temporomandibular joint disorders and normals. Purpose. The goal of this study was identification of multifactorial temporomandibular hard tissue relationships that differentiate asymptomatic normal joints. Material and Methods. Central section lateral tomograms of 162 female temporomandibular joints with pooled diagnoses of unilateral disk displacement with and without reduction were compared to 42 female asymptomatic normal joints using 14 linear and angular measurements and 8 ratios. A validated classification tree model was tested for accuracy with sensitivity, specificity, goodness of fit, and the amount of the log likelihood accounted for. The tree model was compared with a multiple logistic regression model and univariate testing. Results. The classification tree model consisted of 3 asymptomatic and 4 disk displacement terminal nodes consisting of interactions of condyle position with measures of fossa size and shape, of which mainly average nonextreme measurements and more frequent concentric ranges typified the asymptomatic joints. The logistic regression and univariate models also incorporated condyle position and size, but the logistic regression accounted for less of the log likelihood than the tree (23.3% vs. 32.6% Rescaled Cox and Snell R2). The tree and the logistic regression models were moderately good predictors for distinguishing normals from disk displacement joints (sensitivity 67.9% and 72.2%, specificity 85.7% and 76.2%, respectively). Although the univariate analysis showed that the asymptomatic joints had smaller mean fossa width to fossa depth ratios (P<.0005), shorter mean eminence length (P<.007), and more concentric to anterior mean condyle position (P<.049), overlap in most of the ranges limited the predictive value. Conclusion. Within the limitations of this study, multifactorial analysis revealed that several subsets of asymptomatic temporomandibular joints could be distinguished from joints with disk displacement according to hard tissue measurements taken from central section tomograms. In general, asymptomatic normal joints were typified by interactions of less extreme ranges of fossa size, shape, and condyle position. (J Prosthet Dent 2002;87:289-97.)

Statement of problem. Without multifactorial models, it is difficult to resolve whether hard tissue tomographic relationships can distinguish differences between temporomandibular joint (TMJ) internal derangement diagnoses. Purpose. The purpose of this study was to use multifactorial models to examine whether there are hard tissue anatomic and orthopedic characteristics that distinguish temporomandibular joints with disk displacement with reduction from disk displacement without reduction. Material and methods. TMJ tomograms from female patients who had unilateral disk displacement diagnosed with (n = 84) or without (n = 78) reduction were compared with the use of 14 linear and angular measurements and 8 ratios. A representative classification tree model was tested for fit with sensitivity, specificity, accuracy, and likelihood accountability, and the results were compared with a multiple stepwise logistic regression model and univariate analysis. Results. Disk displacement without reduction joints had longer mean postglenoid fossa heights (P<.0005), greater mean fossa depth (P<.017), and narrower mean absolute superior joint spaces (P<.041) than disk displacement with reduction joints (univariate t test). The classification tree had 4 terminal nodes; to differentiate the joints, it used the eminence radius and the absolute superior joint space to anterior joint space ratio subordinate to the postglenoid process height. The tree model accounted for 31.4% of the likelihood (Rescaled Cox and Snell R2) with 73.5% accuracy (sensitivity 82.6% and specificity 65.4%). Disk displacement without reduction joints had either deeper posterior fossa walls or posterior walls of average length combined with a superior-to-anterior joint space ratio of less than 0.83; this suggests a more open-wedge-shaped anterior joint space combined with a less-rounded articular eminence. In contrast, most disk displacement with reduction joints had shorter posterior fossa wall height combined with more equal or larger superior-to-anterior joint spaces. The logistic regression model was less accurate than the classification tree model (sensitivity 60.9%, specificity 66.7%) and accounted for only 9.9% of the likelihood (Rescaled Cox and Snell R2) and 63.6% accuracy. The postglenoid process height was the strongest differentiating factor in all models. Conclusion. Hard tissue relationships revealed by central tomogram sections were able to model notable differences between disk displacement with and without reduction joints when examined as contingency-based multifactorial systems. (J Prosthet Dent 2001;86:407-19.)

Statement Of Problem. A consensus is lacking on the association between occlusal variables and temporomandibular disorders (TMDs). Purpose. This study estimated the maximum potential power of occlusal variables to differentiate patients with TMD from asymptomatic normal adult subjects. Material And Methods. The occlusal characteristics in 2 sets of female patients with intracapsular TMD (1993, n = 257, and 1998, n = 124) differentiated into disk displacement and osteoarthrosis subdiagnoses were compared with asymptomatic female controls (n = 51 and 47) with multiple logistic regression analysis. Significant variables and total contribution to the log likelihood were compared with the predictive value of univariate analysis, including sensitivity and specificity. Results. Occlusal factors in the females (1993, 1998) explained no more than 4.8% to 27.1% of the log likelihood. In comparison to the logistic regression analysis, univariate analysis was less predictive of patients with TMD, due to notably lower sensitivity. Patients with disk displacement were mainly characterized by unilateral posterior crossbite and longer RCP-ICP slides. Patients with osteoarthrosis were most consistently characterized by longer RCP-ICP slides and larger overjet, and in part to reduced overbite. Significant relative risk for disease (odds ratio > 2:1) was mainly associated with infrequent, more extreme ranges of occlusion measurements. Conclusion. Occlusal factors may be cofactors in the identification of patients with TMD, but their role should not be overstated. Some occlusal variation may be a consequence of rather than a cause for TMD. Single variables have more limited value and it takes sets of adverse variables to model TMD. Combinations of variables appear to be disease specific. Some extreme ranges of occlusion were the domain of patients with TMD, but most patients were within the normal ranges. (J Prosthet Dent 2000;83:66-75.)

Statement Of Problem. Confusion about the relationship of occlusion to temporomandibular disorders (TMD) persists. Purpose. This study attempted to identify occlusal and attrition factors plus age that would characterize asymptomatic normal female subjects. Methods And Material. A total of 124 female patients with intracapsular TMD were compared with 47 asymptomatic female controls for associations to 9 occlusal factors, 3 attrition severity measures, and age using classification tree, multiple stepwise logistic regression, and univariate analyses. Models were tested for accuracy (sensitivity and specificity) and total contribution to the variance. Results. The classification tree model had 4 terminal nodes that used only anterior attrition and age. "Normals" were mainly characterized by low attrition levels, whereas patients had higher attrition and tended to be younger. The tree model was only moderately useful (sensitivity 63%, specificity 94%) in predicting normals. The logistic regression model incorporated unilateral posterior crossbite and mediotrusive attrition severity in addition to the 2 factors in the tree, but was slightly less accurate than the tree (sensitivity 51%, specificity 90%). When only occlusal factors were considered in the analysis, normals were additionally characterized by a lack of anterior open bite, smaller overjet, and smaller RCP-ICP slides. The log likelihood accounted for was similar for both the tree (pseudo R2 = 29.38%; mean deviance=0.95) and the multiple logistic regression (Cox Snell R2 = 30.3%, mean deviance=0.84) models. Conclusion. The occlusal and attrition factors studied were only moderately useful in differentiating normals from TMD patients. (J Prosthet Dent 2000;83:76-82.)

The simultaneous contribution of 11 occlusal factors, dental attrition severity, orthodontic history, trauma (motor vehicle accident [MVA] and non-MVA), and age in defining two independent large populations of females diagnosed with five mutually exclusive temporomandibular disorders was tested through multiple stepwise logistic regression analysis. Non-MVA trauma was significant in both groups in defining disc displacement (DD) with and without reduction, and osteoarthrosis (OA) (both primary and following DD). Anterior open bite was also a significant factor in defining OA in both groups. Much smaller contributions were also made by missing teeth in one of the populations with OA following DD, and by retruded contact position-intercuspal position slide lengths and overjet in one of the primary OA populations. Motor vehicle accident trauma was significant in defining myofascial pain (MP) in both populations, and laterotrusive attrition mildly defined MP in one population. Only a minority of total variance was explained: 6% to 8% of DD with reduction; 10% to 14% of DD without reduction; 11% to 20% of OA following DD; 17% to 38% of primary OA; and 4% to 10% of MP. Non-MVA trauma was the major defining feature of the temporomandibular joint intracapsular disorders, and MVA trauma explained a very small percentage of the MP patients. Implications are discussed and recommendations are made for future research.

The purpose of this study was to assess jaw function status and disability in an elderly population. The sample consisted of 429 Medicare recipients dwelling in the community (mean age = 74.4 +/- 5 yr; 58% female and 42% male) who were enrolled in an HCFA-sponsored prevention demonstration project. An evaluation of TMJ and jaw muscle status was conducted at the completion of a general dental examination. This included assessment of joint sounds (clicking or crepitus), joint and jaw muscle tenderness to palpation, and measurement of maximum opening. Pain or disability during jaw use and history of TMD problems were assessed by self-report. The prevalence of TMJ clicking was 16%, crepitus 19%, TMJ tenderness 8%, jaw muscle tenderness 13%, and opening < 40 mm 22%. Pain on jaw use was reported by 6.5%, and 12% reported a history of TMD problems. There was no significant relationship between TMD signs and symptoms and dental status. The lack of consistent relationship between TMD signs and symptoms and health status measures suggests that TMD is a localized disease process and not an extension of a general condition such as arthritis or depression, nor does it have major impact on activities of daily living. Examiner referral for treatment was low (1%) indicating that TMD was not a significant treatment concern in this sample of the elderly.

Dental attrition ranked according to a validated severity scale correlated with age as a proxy for functional wear in 148 asymptomatic subjects. Anterior, posterior, mediotrusive, laterotrusive, and total attrition severity was analyzed. The geometric contribution of canine attrition to the variance of posterior attrition was also tested through correlations, and the time span required to record a statistically significant difference in attrition using the scale was determined. Age explained 12.6% of the differences the total attrition scores (P < .001, Spearman's rho), 6.4% of the anterior scores (P < .01), and 20.9% of the laterotrusive scores (P < .0001). Canine wear in subjects aged 20 to 49 years explained between 20% to 34% of the posterior attrition (P < .05 to P < .001), 6% to 36% of the mediotrusive attrition (P < .05 to P < .01), and 20% to 29% of the laterotrusive attrition (P < .05 to P < .001). At least 20 to 30 years was necessary to show significant clinical differences, except that laterotrusive attrition changes could be discriminated in only 10 years for the 20- to 29-year-old group. Notable attrition was already evident in the 20- to 29-year-olds, and accelerated wear rates prior to age 20 years were not maintained in most areas of the dentition. A nonlinear progression with age was observed, thereby inhibiting prediction of subsequent attrition from prior levels. Attrition was concluded to have multifactorial etiology, with age and the geometry of canine guidance having a significant influence, in addition to commonly accepted parafunction.

This study used low-power light microscopy to examine the histologic organization of the lateral pterygoid muscle interface with the temporomandibular joint. The sample included parasagittal sections of 20 intact temporomandibular joints from young adults (mean age 26.2 years) at autopsy. The lateral pterygoid muscle showed no consistent divisions into separate anatomic muscle heads at the insertion. The muscle fibers attached to the pterygoid fovea of the condyle immediately inferior to the articular surface in all cases. Some additional fibers inserted superiorly into the more anterior part of the articular disc in a minority of cases (31%). Fibers inserting into the disc represented only 2.4% to 6% of the total superior-inferior length of the muscle insertion. It is hypothesized that the muscular force exerted by these few fibers inserting into the disc would not be sufficient to displace the disc anteriorly to the condyle. There were two histologic types of insertion of the lateral pterygoid muscle to the condyle. The superior part of the insertion was characterized by an identifiable tendon inserting through fibrocartilage. In the inferior part of the insertion, the muscle attached to periosteum without an obvious tendon. The presence of this tendon must be recognized in interpretation of soft tissue temporomandibular joint imaging.

Histological variation was studied in serial sections, in contrast to previous studies which have generalized from representative sections. The sample consisted of consecutive serial sagittal sections from the central third of nine condyles, plus an accompanying stone cast showing the intact articular surface before sectioning. The thickness of the articular soft tissue and its fibrous connective tissue and cartilage components was measured, and the presence of undifferentiated mesenchymal (UM) cells was assessed by low-power light microscopy. Components of variance analysis showed that section-to-section variation in thickness was of the same order as differences between joints, each explaining approx. 50% of the variance in both connective tissue and cartilage thickness. The fibrous connective tissue contributed as much to the overall variation in soft tissue thickness as did the cartilage component (SD 0.0946 versus 0.0909 mm for the superior sector). Serial UM cell variability was common, and the UM cells were often distributed in islands rather than uniformly across the articular tissue. Condyles with the greatest surface irregularity were characterized by greater serial variability in fibrous connective tissue thickness, more frequent absence of cartilage, and more areas of UM cell depletion. These results suggest that serial variation in histological character may be more important than mean values in the description of surface contours and articular tissue relations in the temporomandibular joint. This should influence the design of future investigations.

This study examined whether the overall shape of the articular soft tissue overlying the posterior slope and articular eminence of the temporal bone could be predicted by the underlying osseous contour in a histologic model of 51 central sagittal sections of young adult temporomandibular joints. Articular soft tissue and bone contours were traced, and osseous landmarks identified on the basis of joint geometry. Soft tissue thickness measurements were made under low power light microscopy. Seven categories of articular soft tissue pattern were identified. The soft tissue uniformly followed the osseous contour in only one (14%). A progressive increase in soft tissue thickness from the middle of the posterior slope to the articular crest was the most common pattern (35%) but did not describe most of the sample that was more asymmetric. Pattern was poorly perdicted by the shape and slope of the temporal bone outline or by dental factors that describe anterior guidance and did not relate to disk displacement. The articular soft tissue compensated for flatter eminence slopes and osseous irregularities and maintained an intact surface. This study has clinical implications for radiographic interpretation of disk space, condyle translation pathways, and the integrity of the functional articular surface.

A multiple logistic regression analysis was used to compute the odds ratios for 11 common occlusal features for asymptomatic controls (n = 147) vs. five temporomandibular disorder groups: Disc Displacement with Reduction (n = 81), Disc Displacement without Reduction (n = 48), Osteoarthrosis with Disc Displacement History (n = 75), Primary Osteoarthrosis (n = 85), and Myalgia Only (n = 124). Features that did not contribute included: retruded contact position (RCP) to intercuspal position (ICP) occlusal slides < or = 2 mm, slide asymmetry, unilateral RCP contacts, deep overbite, minimal overjet, dental midline discrepancies, < or = 4 missing teeth, and maxillo-mandibular first molar relationship or cross-arch asymmetry. Groupings of a minimum of two to at most five occlusal variables contributed to the TMD patient groups. Significant increases in risk occurred selectively with anterior open bite (p < 0.01), unilateral maxillary lingual crossbite (p < 0.05 to p < 0.01), overjets > 6-7 mm (p < 0.05 to p < 0.01), > or > 5-6 missing posterior teeth (p < 0.05 to p < 0.01), and RCP-ICP slides > 2 mm (p < 0.05 to p < 0.01). While the contribution of occlusion to the disease groups was not zero, most of the variation in each disease population was not explained by occlusal parameters. Thus, occlusion cannot be considered the unique or dominant factor in defining TMD populations. Certain features such as anterior open bite in osteoarthrosis patients were considered to be a consequence of rather than etiological factors for the disorder.

The osseous architecture of central sagittal histologic sections of the temporal component of 51 temporomandibular joints of young adults at autopsy was studied to determine if this predicted the thickness of the overlying articular soft tissue and disk displacement. Geometric groupings of fossa-eminence shapes were generated using a hierachical cluster analysis of the osseous fossa-eminence sigmoid curve, size, and slope. Six cluster groups were evolved and tested for relationship to soft tissue thickness measured at the eminence crest, mid-point of the eminence slope, closed pack location of the condyle, the inflection point, and the depth of the fossa. Soft tissue thickness at the inflection point and depth of the fossa was remarkably constant between cluster groups. Increased soft tissue thickness at the eminence crest and lower part of the posterior slope was weakly correlated to a flatter eminence slope and curve, explaining 10% to 20% of the variance (r2). There were no relationships between the parameters studied to the fossa curvature. An ANOVA showed no statistical difference in the posterior slope angle between the categories of disk position (p = 0.715) or to the six cluster groupings. The results suggest that the osseous contours seen on radiographs may not accurately predict the actual articular surface of the temporal component.

Dental attrition severity as the cumulative record of parafunctional and functional wear was graded from study cast analysis using established methodology. Attrition severity was compared in anterior, posterior mediotrusive, and posterior laterotrusive segments. Attrition scores in 48 female and 100 male totally asymptomatic controls were compared to 239 female and 31 male patients differentiated into five patient groups of temporomandibular disorders: (1) disc displacement with reduction, (2) disc displacement without reduction, (3) osteoarthrosis with a history of prior derangement, (4) osteoarthrosis without a history of prior derangement, and (5) myalgia only. All the male patients were in the myalgia-only group. Age was controlled in the analysis to control for functional wear. Comparisons between patients and controls were made according to 10-year age intervals. Analysis included ANCOVA confirmed by a Games-Howell post-hoc test, with P < .01 interpreted as a significant difference in the attrition score. Only 1 of 112 ANCOVAs showed a significant difference, with younger men from 20 to 29 years of age in the myalgia-only group having lower mediotrusive attrition than the male controls. It would therefore be difficult if not impossible to differentiate patients from nonpatients based on the severity of dental attrition. Consequently, a major peripheral occlusal etiologic role for attrition in TMD is questioned. Some clinical implications are elaborated.

The histologic character of the articular surfaces and synovial tissues in the temporomandibular joints of 20 young adults was described. Each joint compartment had a continuous connective-tissue lining that was fibrous on the articular surfaces, went through a transition, and was continuous with the lining tissue in the recesses. Areolar synovial tissue was found only in the upper posterior recess of the temporomandibular joint, fibrous synovial tissue was predominantly found in the upper anterior and lower posterior recesses, and an intermediate type of synovial tissue was found in the lower anterior recess. There was no distinct boundary between articular and synovial tissue. The structure and continuity of these lining tissues suggest that they constitute a continuous tissue system, here termed the "articular-synovial lining tissue system," that has a histologic character which depends on location and functional demands. It is hypothesized that all of the lining tissues should be considered synovial, based on a functional definition of nonadherence.

Undifferentiated mesenchymal (UM) cells, the progenitor cells of the cartilage layer, have been assigned a significant role in TMJ articular tissue maintenance. This was based on reports of UM cell reduction with increased soft-tissue thickness for the condyle and temporal component. However, the strength of this inverse relationship was not presented and remained unclear. The purpose of the present study was to assess the strength of the correlation between UM cell presence and soft-tissue thickness in young adult TMJs at autopsy. Sagittal histological sections from the central thirds of 50 joints were evaluated with respect to articular soft-tissue thickness, histological character, and UM cell presence in the condyle and temporal component. The superior sector of the condyle and the articular eminence showed the greatest variability in soft-tissue thickness and were the only areas to show localized UM cell absence. The eminence was the only location to show an inverse relationship between soft-tissue thickness and UM cell presence, and this was consistent in both an ANOVA (p = 0.0016) and a Spearman correlation analysis. However, the strength of this correlation was only moderate (rho = -0.52), and no such relationship was observed in any other location. This study suggests that the relationship between UM cell presence and soft-tissue thickness is more complex than previously hypothesized and that the contribution of UM cells to articular tissue maintenance has been overstated, while other biological processes were overlooked.

This review highlights the consensus existing in past research on the role of functional occlusal factors in the pathophysiology of temporomandibular disorders (TMD). The functional occlusal relationships considered are balancing and working occlusal contacts, length and symmetry of retruded contact position-intercuspal position (RCP-ICP) slides, occlusal guidance patterns, parafunction, and dental attrition. Controlled studies fail to demonstrate any association between occlusal interferences and TMD signs or symptoms. Temporomandibular joint condylar autorepositioning secondary to intracapsular arthrosis is associated with larger and asymmetric RCP-ICP slides. Other TMD conditions are not associated with any slide length or asymmetries. Occlusal guidance patterns are not associated with TMD symptom provocation or, conversely, health. Parafunction appears to be universal and is not associated with TMD development or symptomatology in healthy individuals. Furthermore, parafunction is not provoked by longstanding, naturally occurring occlusal variations. Dental attrition is not associated with TMD, and any observed increased attrition in osteoarthrosis patients is likely the result of age effects and occlusal alterations secondary to condylar positional changes.

Overbite and overjet were studied as continuous variables to examine for any relationship to diagnostic groups of temporomandibular disorders (TMD) compared with symptom-free controls. This avoided the bias of arbitrary definitions of normal and abnormal for these occlusal variables and also avoided the masking effect of studying symptoms rather than diagnostic entities. Incisal overbite in primary osteoarthrosis (OA) was shifted toward the minimal and open bite ranges as compared with the controls (p less than 0.02). Open bite occurred in only the two OA classes studied and in a few cases with myalgia only but was absent in the symptom-free controls. Overbite in myalgia was slightly skewed to the lower range. Deep bite was not more common in the myalgia, disk displacement (with or without reduction), or the OA groups. Increased overjet characterized OA groups, especially when there was a history of derangement (p less than 0.004), but did not characterize the other diagnostic groups. Except for open bite, overbite and overjet characteristics as isolated variables did not distinguish TMD patient groups. It is hypothesized that open bite in OA can be the result of joint changes rather than a predisposing occlusal cause.