Horizontal skeletal typing in an ethnic Chinese population with true Class III malocclusions.

Eighty Chinese adults with true Class III malocclusions were analysed cephalometrically to determine the percentage in each horizontal skeletal subtype. The maxillary and mandibular skeletal bases for each subject were analysed using angular (SNA/SNB) as well as linear (point A/B to McNamara's line) criteria. Results indicated that mandibular hyperplasias with normal anteroposterior maxillary position comprised the majority of true Class III malocclusions. While the majority of Class III in males were due to hyperplastic mandibles and normal maxillary antero-posterior relationship, most of the female Class III malocclusions were due to normal mandibles and hypoplastic maxillae. There was no significant difference between the incidence in Class III subtypes when using either angular or linear criteria.