Cranial base features in skeletal class III patients

Objective: To investigate the cranial base configuration in skeletal Class III patients to clarify the conflicting findings from literature. Materials and Methods: Initial lateral radiographs of 54 skeletal Class III patients and 54 matched controls (Class I, II/1, II/2) aged 14 to 24 years were analyzed retrospectively for 21 cephalometric basicranial variables and jaw lengths relative to anterior cranial base length. Results: In contrast to overall cranial base length, the anterior (N-S) and posterior (S-Ba, S-Ar) sections failed to show a significant reduction in Class III patients. The significantly more acute angles Ca-S-Ba and Se-S-Ba reflected increased cranial base flexure. Resulting anterior condylar displacement was shown by significant reduction of Se-S-Cd and Ar-Ca. Relative mandibular length was significantly increased. Conclusions: Decreased basicranial angulation associated with Class III mandibular protrusion was clearly confirmed for skeletal Class III patients. Overall shortening of the cranial base apparently resulted from various minor alterations. The results are compatible with the deficient orthocephalization hypothesis of Class III morphogenesis. The basicranial-maxillary,relationship in skeletal Class III remains unclear.