Temporomandibular joint morphology and disc position in skeletal class III patients

Introduction: The purpose of this study was to investigate the relationship between temporomandibular joint (TMJ) morphology, including discal tissue and clinical symptoms in class III dentofacial deformity patients. Material and Methods: Forty-four patients were examined with lateral, frontal and axial cephalograms. They were divided into two groups, consisting of a class III symmetry and a class III asymmetry group. By using magnetic resonance imaging the 88 joints could be classified into four types on the basis of disc position and shape: anteriorly displaced disc, anterior type, fully-covered type and posterior type. Furthermore, TMJ morphology was measured tomographically in the sagittal plane, Results: Anteriorly displaced discs in the asymmetry group (56.8%) occurred significantly more frequently than in the symmetry group (18.2%; p<0,05), TMJ symptoms (clicking, crepitus, closed lock, pain) were seen in 17/44 joints (38.6%) of the symmetry and 24/44 joints (54.5%) of the asymmetry group, for a total of 41/88 joints (46.6%), There were no differences in joint space ratio and condyle ratio. However, the fossa ratio on the deviation side was significantly higher than on the non-deviation side in the asymmetry group (p<0.05), Conclusion: The incidence of internal derangement in asymmetrical class III patients is higher than in symmetrical mandibular prognathism, and this difference is associated with a difference in TMJ morphology of both sides. (C) 2000 European Association for Cranio-Maxillofacial Surgery.