Semilongitudinal cephalometric study of craniofacial growth in untreated Class III malocclusion.

INTRODUCTION Class III growth in white subjects is poorly characterized because of the low prevalence of the disharmony and the clinical tendency to treat this condition early. The purpose of this study was to investigate craniofacial growth changes by using longitudinal cephalometric records of white subjects with untreated Class III malocclusions to provide comparison data for studies of Class III treatment outcomes. METHODS Longitudinal records of 103 subjects were analyzed. Annual incremental growth changes in craniofacial variables from early childhood to late adolescence were examined for each sex. Inferential statistics were applied to changes in mandibular length, midfacial length, and lower anterior facial height of each sex (Wilcoxon tests) and between sexes (Mann-Whitney U tests). RESULTS In the girls, the adolescent spurt in mandibular growth occurred between the ages of 10 and 12 years. In the boys, the adolescent mandibular growth spurt was between 12 and 15 years. Statistically significant growth changes in the average increments of growth of these linear measurements occurred in both sexes between 12 and 15 years. Adolescent peaks in midfacial growth were at prepubertal ages in both sexes. During childhood (5-7 years), much craniofacial growth occurred. Moreover, there was considerable mandibular growth relative to the maxilla in Class III subjects after the adolescent growth spurt. CONCLUSIONS White Class III subjects showed definite worsening of the relative mandibular prognathism and sagittal skeletal discrepancy between the jaws with growth. The growth pattern of 3 fundamental cephalometric measurements (lower anterior face height, midfacial length, and mandibular length) exhibited differences between Class III male and female subjects in both the timing and the size of average growth increments in the adolescent growth spurt.