Longitudinal Skeletal and Dental Changes in Untreated Children with Angle Class I and III Malocclusions: A Retrospective Cephalometric Cohort Study.

Background: Class III malocclusion presents complex craniofacial growth patterns, yet longitudinal evidence remains limited compared with Class I malocclusion. This study compared skeletal and dental changes in children with untreated Angle Class I and Class III malocclusions. Methods: Forty-eight untreated children (24 Angle Class I and 24 Angle Class III) from the AAOF Craniofacial Growth Legacy Collections were included. Lateral cephalograms were taken at ages 4-5 (T0), 7-8 (T1), 10-11 (T2), and 13-14 (T3). Because the radiographs originated from heterogeneous mid-20th-century X-ray equipment with unknown magnification factors, only angular measurements were used. Cephalometric tracing was conducted using WebCeph™ software with good-to-excellent intra-examiner reliability (κ = 0.71-0.98). Growth changes were assessed using three-way repeated-measures ANOVA, with effect sizes (ηp2), mean differences (MDs), and 95% confidence intervals (95% CI) calculated. Results: Significant differences in growth patterns were observed between the groups. Class III children showed greater FMA (MD = 6.0°, 95% CI [2.3, 9.7], p < 0.05) and gonial angles (MD = 8.1°, 95% CI [3.4, 12.8], p < 0.01) at T3, alongside a progressive decrease in ANB (MD = -2.6°, 95% CI [-5.5, -0.3], p < 0.01) and A-B mandibular angles (MD = -9.5°, 95% CI [-13.1, -5.9], p < 0.05). Class III children also exhibited significant upper incisor proclination and lower incisor retroclination (p < 0.001) compared to Class I children. No sex-related differences were observed, except for an SNA angle increase among Class I males (p < 0.05). Conclusions: Distinct craniofacial growth trajectories were observed between malocclusion classes, with Class III children showing progressive sagittal and vertical divergence from normal growth. The results highlight the need for early detection and monitoring of those at risk for pronounced Class III patterns.