Cephalometric comparison of mandibular growth in Brazilian children with Class II malocclusion and normal occlusion during the growth stages determined by the cervical vertebrae maturation.

Objective: This study compared mandibular growth in children, aged 7 to 12 years, with Class II malocclusion and normal occlusion, between the following stages of cervical vertebrae maturation: initiation (I), acceleration (A), transition (T).

Material and methods: A total of 148 lateral cephalograms (78 males, 70 females) of Class II malocclusion patients, and 60 lateral cephalograms (30 males, 30 females) of normal occlusion patients were included. The following linear cephalometric measurements were performed: Co-Gn (effective mandibular length), Co-Go (ramus height), and Go-Gn (length of mandibular body). Mean values of increments between stages (I-A, A-T, I-T) were obtained for each group and gender. Results were compared using the Student t-test, and a significance level of 0.05% was adopted.

Results: Females group: A-T interval presented a greater increment in Co-Go in the Class II group, which was not significant for the I-T interval, with numerically smaller increments in Co-Gn and Go-Gn, without statistical significance. Males group: intervals I-A, A-T and I-T showed numerically smaller growth increments in the Class II group, with statistical significance for Co-Gn in I-A (p=0.001) and I-T (p=0.003). Comparing genders of the Class II group, Co-Go was higher in males (p=0.002) and I-T interval (p=0.031). In the Normal Occlusion group, the male gender had the greatest Co-Gn (p=0.038) for the I-A interval. In A-T and I-T, Co-Go in males was higher, with statistical significance (p=0.000 and p=0.002, respectively).

Conclusion: Growth phenomenon affects the mandibular dimensions regardless of the character of the malocclusion, with a tendency to be smaller in the presence of Class II malocclusion.