Individual growth in Class III malocclusions and its relationship to the chin cap effects.

Individual growth characteristics of the maxilla and the mandible in Class III malocclusions were investigated in terms of growth amount, growth direction, and timing of growth; chin cap effects were considered in the context of growth characteristics of the jaws. Longitudinal cephalograms of six untreated Japanese Class III subjects were used for the analysis of jaw growth from 8 to 14 years of age. The facial patterns were classified into the five groups with different effects of therapy by discriminant functions derived from our previous chin cap study. The results obtained were as follows: (1) Among the six subjects, inhibition of maxillary forward growth was found in four subjects at ages before the maximum pubertal growth in body height occurred, resulting from occlusal interference of anterior cross bite. The growth potential of the jaws appeared genetically normal, and the facial patterns were classified into groups in which chin caps have been found to be effective to some extent. (2) A subject with growth characteristics of strong mandibular downward growth was classified in a group showing backward growth of the mandible by chin caps. (3) One of the remaining sample showing the strongest mandibular forward growth was classified in a group where chin caps are not effective. (4) It was concluded that effects of chin cap therapy are closely related to growth characteristics of the mandible in Class III treatment.