Comparison of skeletal and dental morphology in asymptomatic volunteers and symptomatic patients with unilateral disk displacement without reduction.

The purpose of this study was to evaluate the effect of unilateral disk displacement without reduction (UDDN) on the skeletal and dental pattern of affected individuals. There were 12 symptomatic female patients and 46 asymptomatic normal female volunteers. All study participants had bilateral high-resolution magnetic resonance scans in the sagittal (closed and open) and coronal (closed) planes to evaluate the temporomandibular joints. Linear and angular cephalometric measurements were taken to evaluate the skeletal, denture base, and dental characteristics of the two groups. ANOVA was used to compare the symptomatic subjects with the control subjects. A few skeletal differences were found. There was an overall reduction in length of the anterior (S-Na) and total (S-Ba) cranial base measurements in the UDDN group. The mandibular plane angle was steeper and the posterior ramal height (Ar-Go) was shorter in the symptomatic group. The only dental difference found was a relative infraeruption of the lower first molar. This study suggests that subjects with UDDN may manifest altered craniofacial morphology. Although the cephalometric measurements used did not account for any asymmetry, previous studies have shown that UDD may cause mandibular asymmetry. Presence of asymmetry and altered craniofacial morphology should alert the clinician especially while orthodontically treating children and surgical patients.