Relation of cranial base flexure to cranial form and mandibular position.

From the annually examined sample of the Burlington Growth Centre, the 10% of the boys and girls with the largest, most open cranial base angles were contrasted with the 10% with the smallest, most closed cranial base angles at ages 4, 8, 12, and 16 years with respect to cranial length, width and height, cranial base length, mandibular condyle position, and Angle Class of occlusion. Both groups had crania of similar length, width, and cephalic index, and similar anterior cranial base length. The children with the flattest cranial bases had significantly larger upper cranial height, but much smaller lower cranial height, and as a result had smaller total cranial height than the children with the most closed cranial base angles. Children with the flattest cranial bases had a slightly shorter posterior cranial base region, and the mandibular condyles were located further backward and upward. These children showed a strong tendency to Class II molar relationships. The condyles of the closed cranial base angle groups were more forward and downward, but none of the children had Class III occlusions, and most were normal or Class I. These results do not support the views of Weidenreich (1943, 1945, 1946, 1947), Enlow with others (1973, 1975, 1980) and Lavelle with others (1977, 1979), but agree with the findings of Björk (1955) in 20-year-old males.