Relationship of degenerative changes of the temporomandibular joint (TMJ) with the angle of eminentia

The purposes of this study were threefold: (i) to assess the degenerative changes of the temporomandibular joint [TMJ (condyles and articular eminence of the glenoid fossa)], (ii) to determine whether the TMJ degeneration levels differ by ethnic group and gender and (iii) to assess the association between the angles of eminentia and TMJ degeneration, while controlling for gender, ethnicity, age and number of teeth. The sample included 245 20th century dry skulls: 130 African-American (82 male and 48 female) and 115 European-American (75 male and 40 female), with a mean age of 46.4 +/- 19.9 years. The angles of eminentia were measured in a sagittal plane. The medial, central and lateral portions of the articular slope and anterior portion of the condyle were assessed for degenerative changes. Degeneration scores were calculated for the eminentia and condyles. Statistical analyses included two-way ANOVAS, Pearson's correlation coefficients and linear regression models. There were differences in the degree of TMJ degeneration of the African-American and European-American males and females. European-American females retained fewer teeth, had the highest TMJ degeneration scores and exhibited significant relationships between the eminentia angles and degeneration. When the independent variables were entered into the regression model, only the degeneration of the eminentia was significantly associated with the angles of eminentia. Although the degeneration of the eminentia explained some of the variation of the eminentia angles, it is clear that the inclusion of multiple factors is essential to study the remodelling of the glenoid fossa.