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.

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.

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.

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.

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.

Trauma history was studied for association with disease among six diagnostic subgroups of 230 patients with temporomandibular disorder (TMD) from a private practice setting with (1) disk displacement (DD) with reduction, (2) DD without reduction, (3) osteoarthrosis (OA) with prior derangement history, (4) primary OA, (5) myalgia only, and (6) subluxation only. Except for subluxation (29%), trauma history typified TMD patient groups 1 to 5 (63%, 79%, 44%, 53%, 54%) (p < 0.001) compared with 13% and 18% of asymptomatic (n = 61) and symptomatic (n = 161) student control subjects, and 11% of general dental patients (n = 150). TMD groups 2 and 3 differed significantly (p < 0.05). The high prevalence of trauma in the myalgia-only group complicates the concept of myofascial pain-dysfunction syndrome as solely a stress or centrally mediated disorder. DD without reduction (43%) and with reduction (38%) had the highest prevalences of motor vehicle accident trauma, myalgia and OA groups had less, and subluxation-only cases had none. On the other hand, patients with DD without reduction were also the only group to report multiple trauma (29%), suggesting that although specific traumatic events may seem to precipitate clinical symptoms, they may not always have initiated the problem. Trauma may be both an important cumulative and precipitating event in TMDs.

These guidelines propose performance criteria for the history and examination of patients with temporomandibular (TM) disorders. Pertinent diagnostic subcategories are identified, and the comprehensive history and review of systems are described. The examination procedures include documentation of temporomandibular and craniocervical range of motion, TM joint sounds, and the recording of muscle and joint tenderness. The TM disorders addressed include muscle problems such as myalgia, protective splinting or trismus, spasm, myositis, dyskinesia, muscle contracture, hypertrophy, and bruxism. Temporomandibular joint disorders addressed include disk-condyle incoordination, restricted condyle translation, open condyle dislocation, arthralgia, osteoarthritis, polyarthritis, and traumatic joint injury. Disorders of mandibular mobility such as ankylosis, adhesions, fibrosis, skeletal obstruction, and hypermobility are also described. Finally, disorders of maxillomandibular growth, including masticatory muscle hypertrophy, atrophy, neoplasia, maxillomandibular hypoplasia, condylar agenesis, maxillomandibular hyperplasia, and condyle hypertrophy are described.

One hundred ninety-six TMJ patients differentiated into five diagnostic groups (disk displacement with reduction [n = 40], disk displacement without reduction [n = 14], TMJ osteoarthrosis with a history of past locking [n = 32], TMJ osteoarthrosis without a history of past locking [n = 30], myalgia only [n = 80]) were compared with 222 nonpatient controls for specific occlusal variables. The patient groups could not be differentiated according to the absence of RCP-ICP slide per se, crossbite, or symmetry of RCP contacts. Among males with reducing disk displacement, Class I was less common and Class II division 1 was more common than in controls. Asymmetric RCP-ICP slides and a combination of unilateral RCP contact and no clinically visible RCP-ICP slide were more prevalent in women with reducing disk displacement. Large RCP-ICP slides, asymmetric slides, and anterior open bite were associated with osteoarthrosis, but this study could not state if these associations were etiologic or secondary. Totally asymptomatic controls were characterized by a lack of anterior open bite, small symmetric RCP-ICP slides (greater than 0 less than 1 mm), and bilateral occlusal contact in RCP. By comparing a control group to well-defined patient diagnostic groups rather than according to symptoms, selective occlusal variables appear more closely associated with some TMJ disorders than indicated in past studies with less specific populations.

Dental attrition severity in 222 young adults was assessed from dental casts as the sum of the most severe facet in each arch segment. The attrition scores were compared by age, gender, bruxism awareness, prior bite adjustment, orthodontic class, maxillomandibular relationship, and temporomandibular dysfunction symptoms. Awareness of bruxism was not associated with the wear scores and should not be used to define bruxist groups. Attrition scores did not differ significantly between age groups, indicating that notable attrition, when present, often occurs early. Men had higher attrition scores than women (p<0.01), despite fewer signs and symptoms. Dental attrition was not associated with the presence or absence of TMJ clicking, TMJ tenderness, or masticatory muscle tenderness. Class II division 2 males had laterotrusive attrition scores lower than those of Class III (p<0.05). Class III females had lower incisor attrition scores than did other Angle Classes (p<0.05). Discernible dental attrition in a non-patient population was not associated with signs and symptoms of temporomandibular disorders, nor with the occlusal factors studied. These results are compatible with the findings in other studies that point to bruxism as a centrally induced phenomenon common to all people and unrelated to local factors.

Two complete classes of freshman dental and dental hygiene students, 120 men and 102 women (mean age 23.9 years) were assessed for the presence of masticatory pain or dysfunction by questionnaire, clinical examination, and evaluation of dental casts according to strict criteria. The purpose was to identify the degree of association between observable signs of TMJ disorders and selected combinations of occlusal variables. TMJ tenderness was more frequent in class II, division 2 than in class I (p less than .05), but overall was not associated with occlusal factors such as deep overbites, length of a symmetric RCP-ICP slide, and unilateral contact in RCP. Overall, clicking was not associated with Angle class, deep overbite, length of symmetric RCP-ICP slide, or unilateral RCP contact. Among subjects with unilateral RCP contact, those with no clinically obvious RCP-ICP slide (p less than .005) and those with asymmetric slides (p less than .05) had more TMJ clicking than subjects with symmetric slides. Luxation clicking of the condyle over the articular eminence on wide opening was absent in class II, division 2 subjects, but was most frequent in subjects with some teeth in unilateral posterior crossbite, particularly when this was a unilateral condition (p less than .001). Certain occlusomorphologic conditions may require less adaptation in the TMJs. This article indicates that an ICP anterior to the RCP in association with bilateral occlusal stability may be protective.

Angle classification of occlusion. In this study 68% of subjects were class I; 15% class II, division 1; 4% class II, division 2; and 13% class III. These figures generally Freshman dental and dental hygiene students, 120 men and 102 women (mean age 23.9 years), were assessed for the presence of masticatory pain or dysfunction by questionnaire, clinical examination, and evaluation of dental casts according to strict criteria. The purpose was to identify and analyze the level of signs and symptoms in a nonpatient population and describe occlusal variation.