The aetiological factors in Class III malocclusion.

This retrospective, cephalometric study was undertaken in an attempt to identify the aetiological features which may be associated with a Class III malocclusion in the growing child. Four-hundred-and-ninety-five lateral cephalometric radiographs (210 control and 285 Class III films) formed the basis of the study. All subjects were Caucasian: the material was divided into four age groups, and males and females were examined separately. Comparisons were made between control and Class III children in each of these eight subgroups. Class III children showed differences in facial morphology in all facial areas examined, when compared with their control peers. The cranial base angle was more acute, the maxilla shorter and more retrusive, whilst the mandible was longer and more prominent. This was due in part to a more ventral position of the mandibular articulation. The proclined upper incisors were as far forward within the face in the Class III group as in the controls, but the retroclined lower teeth were even more labially placed. The range of individual variation was wide and few Class III children exhibited all characteristic features. Both control and Class III male faces showed their greatest increments of growth between 14 and 17 years of age: in control females, facial growth had ceased by this time, but in the Class III group, development remained active. The Class III female face seemed to have a tendency towards horizontal development, whereas the males exhibited a more vertical growth pattern.