Class III malocclusion - age changes occurring in the craniofacial skeleton

Abstract

Current concepts in orthodontics emphasise the non-pathological variation in craniofacial morphology in relation to etiology of malocclusion, while less frequently malocclusion is considered to result from pathological and functional anomalies. It would appear, therefore, that a system of orthodontic classification predicated to morphology, should facilitate assessment and treatment planning, and at the same time fulfil the requirements of description and communication.

The distinct categories of the Angle classification have allowed concise description, while the stability of the maxillary first molar as defined by Angle, did suggest the groups as morphological entities. However, subsequent investigations have shown the variability of this molar in relation to the cranial base, and the Angle system is now considered to categorise clinical entities rather than groups with specific morphological features.

Although the Angle classification appears to have definite etiological limitations, studies of skeletal patterns within the groups have made significant contributions to the understanding of these malocclusions. In this investigation Angle Class III malocclusion is further studied by re-examining in 1965, some 40 individuals from the sample of 44 Class III malocclusions previously analysed by Cleall in a cephalometric study in 1960.

Malocclusions in this previous study were grouped as having ‘True’ and ‘Pseudo’ Class III anomalies and were compared with a group having normal occlusion. The ‘True' group contained those malocclusions with an Angle Class III molar relationship and were considered to exhibit abnormality as result of mandibular prognathism. The ‘Pseudo’ group consisted of malocclusions with anterior crossbite but having an Angle Class I molar relationship and therefore were considered to show a normal mandibular pattern. The investigation was necessarily cross sectional and certain linear and angular measurements showed statistically significant differences when the ‘Pseudo’ and ‘True’ groups were compared with each other as well as with the Normal group.

Subsequent examination and headfilms, after a five year period, gave an opportunity to investigate general and individual variations with age changes and growth. Relatively few serial studies of Class III malocclusions have been reported and no similar studies have been cited in the literature. [Introduction]