The relationship between partial disc displacement and mandibular dysplasia in female adolescents.

Background: The objective of the present study was to investigate the possible relationship between partial disc displacement of the temporomandibular joint (TMJ) and mandibular dysplasia.

Material/methods: The TMJ disc position of 46 female adolescents, with Class II, Division 1 malocclusion, aged 10.1 approximately 12.8 years, was quantitatively measured with magnetic resonance imaging (MRI) examinations. Meanwhile, mandibular size and form were determined from cephalometric radiographs. The possible correlation between disc status and mandibular morphology was assessed by means of the Pearson Correlation. In addition, the differences in mandibular size and form between the partial disc displacement group (displaced group) and the disc normal group were also assessed.

Results: The results of Pearson Correlation showed that the displaced group had shorter mandibular body length and total mandibular length (Go-Po/Ca-Dm, r=-0.500; Go-Po/ Dp-Cc/Cs-Cc, r=-0.500; Ar-Me/ Ca-Dm, r=-0.459). The patients with horizontal growing style presented more anterior displaced disc (N-S-Gn/ Ca-Dm, r=-0.492). Furthermore, a significantly shorter mandibular body length (Go-Po), a steeper mandibular plane (MP/FH) and a more obtuse mandibular angle (Ar-Go-Me) were found in the displaced group. However, no relationship between the size of the vertical mandible and the disc status was noticed.

Conclusions: Partial disc displacement in Class II, Division 1 cases may be associated with the mandible with horizontal deficits instead of the mandible with vertical deficits.