Temporomandibular joint morphology and disc position in skeletal class IIIpatients

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 a xial 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 d isc position and shape: anteriorly displaced disc, anterior type, fully-cov ered type and posterior type. Furthermore, TMJ morphology was measured tomo graphically in the sagittal plane, Results: Anteriorly displaced discs in t he asymmetry group (56.8%) occurred significantly more frequently than in t he 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 jo ints (54.5%) of the asymmetry group, for a total of 41/88 joints (46.6%), T here were no differences in joint space ratio and condyle ratio. However, t he fossa ratio on the deviation side was significantly higher than on the n on-deviation side in the asymmetry group (p<0.05), Conclusion: The incidenc e of internal derangement in asymmetrical class III patients is higher than in symmetrical mandibular prognathism, and this difference is associated w ith a difference in TMJ morphology of both sides. (C) 2000 European Associa tion for Cranio-Maxillofacial Surgery.