The association between anterior crossbite, deep bite and temporomandibular joint morphology validated by magnetic resonance imaging in an adult non-patient group.

The aim of this study was to determine whether associations exist between anterior edge-to-edge bite, anterior crossbite, deep bite and morphology of the temporomandibular joint (TMJ) in the vertical dimension, evaluated by magnetic resonance imaging (MRI) in adults. A total of 148 subjects (90 females, 58 males) were selected from the cross-sectional epidemiological population-based study "Study of Health in Pomerania" (SHIP) for this evaluation. In each person a clinical orthodontical examination was performed. Four linear measurements and one ratio from MRI scans of the TMJs were evaluated. To estimate the effects of anterior edge-to-edge bite, anterior crossbite and deep bite on TMJ variables, linear regression was applied. (Analyses were adjusted for sex, age, school education, and orthodontic treatment.) Anterior edge-to-edge-bite/crossbite had shorter mean eminence heights (eh) on both joint sides (p<0.01). In deep bite without gingival contact the postglenoid process height (pgph) decreased significantly in left joints (p=0.018) and there was a tendency to a decrease in right joints (p=0.059). The ratio between eminence height and postglenoid process height (eh/pgph) was increased on both left (p<0.001) and right (p=0.002) joints. In conclusion, anterior edge-to-edge-bite/crossbite is connected to a reduced eminence height and deep bite without gingival contact with an increased ratio between eminence height and postglenoid process height. Therefore the condylar path in the anterior edge-to-edge bite and crossbite cases can be interpreted to be reduced and in the deep bite cases without gingival contact to be steepened.