Morphology of the temporomandibular joint in subjects with Class II Division 2 malocclusions

Temporomandibular joint (TMJ) morphology has not been studied adequately in subjects with various types of malocclusion, and it is not known if TMJ morphology and facial morphology are related. Such knowledge might assist in the establishment of biological treatment strategies, especially when the TMJ is the target of the treatment plan. The aim of this study was to explore the morphological characteristics of the TMJ in subjects with skeletal Class II Division 2 malocclusions.

The material consisted of corrected lateral tomograms of 94 joints in 47 subjects with Class II Division 2 malocclusions (age range, 8.3-42.8 years). The subjects were divided into 5 groups according to age.

Intragroup comparisons showed statistically significant differences for condylar angle, condylar position, eminence height, eminence inclination, ramus height, and condylar-neck height. These differences were found mainly between the youngest and oldest groups. The Pearson correlation coefficient was greater than 0.60 for eminence height and eminence inclination, eminence height and ramus inclination, eminence inclination and ramus inclination, fossa posterior-eminence midpoint and fossa posterior-eminence top, and fossa posterior-eminence midpoint and fossa posterior-fossa roof. Condylar shape was most often round, followed by oval, flattened, and triangular; fossa shape was most often oval, followed by triangular, trapezoidal, and round.

The results suggest that (1) fossa morphology and condylar length attain their final sizes early; (2) articular eminence and ramus morphology (height, inclination) have great variability; (3) some joint components such as eminence height with eminence inclination, eminence height with ramus inclination, eminence inclination with ramus inclination, and fossa anteroposterior dimensions are highly correlated with each other; and (4) the most prevalent condylar and fossa anteroposterior shape is oval.