Craniofacial growth of Class III subjects six to sixteen years of age.
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OBJECTIVE: To characterize the mixed-longitudinal craniofacial growth of untreated, white, Class III subjects 6 to 16 years of age. MATERIALS AND METHODS: Serial cephalograms of 19 females and 23 males with Class III malocclusion were evaluated at three time points (6-8, 10-12, and 14-16 years of age). A similar number of Class I controls were randomly selected and matched for age and sex. The cephalograms were traced and digitized, and 20 variables were evaluated. Growth patterns were quantified, and class and sex differences were evaluated using multi-level analyses. RESULTS: In comparison with Class I subjects, Class III subjects had significantly (P .05) larger mandibular plane angles, gonial angles, mandibular ramus heights, mandibular corpus lengths, and SNB angles, with differences that were maintained between 6 and 16 years of age. Maxillary lengths and ANB angles were significantly smaller and remained smaller in Class III subjects than in Class I subjects. Lower face height, maxillary-mandibular differential, and mandibular body length were also significantly larger and increased significantly more between 6 and 16 years of age in Class III subjects. The WITS appraisal was significantly smaller in Class III subjects and decreased significantly more over time. Most linear measures showed significant sex differences favoring males; the angular measures and anteroposterior (AP) maxillomandibular relationships showed no sex differences. CONCLUSIONS: The AP maxillomandibular relationship of Class III subjects worsens over time. AP discrepancies are primarily due to excessive mandibular growth, which produces a protrusive, hyperdivergent phenotype. The AP discrepancies of males are larger than those of females, with differences increasing over time.