Alveolar bone changes in the mandibular incisors after genioplasty, a three-dimensional study

Functional genioplasty aims to achieve lip competence at rest and reduces lip pressure against the mandibular incisors. The purpose of this study was to describe the radiographic changes in alveolar bone of the mandibular incisors after functional genioplasty.

Cone beam CT images from 36 patients were compared between immediate (T0) and delayed postoperative period (T1). The mean time to complete the second imaging was 10.9 ± 4.7 months. Dental and bone parameters were assessed: the vestibular bone height (BH), the bone thickness (BT) with regard to the apex of the central incisor (BT2) and at equidistance between the cementoenamel junction and the dental apex (BT1). The existence of fenestrations, the apical-root resorption and the incisor-mandibular plane angle (IMPA) were also collected.

No significant change occurred in the BH. BT was improved of a mean 47.9% and 53.6% at the BT1 level on #31 and #41, respectively (p₁=0.01 and p₂=0.02, respectively); and of 53.0% at the level of the apex of both mandibular central incisors (p₁=0.003 on #31 and p₂=0.009 on #41). No difference in the number of fenestrations was observed between T0 and T1. A significant decrease in the root length on both mandibular incisors was observed on the delayed CBCT (from 21.96 ± 1.35 to 21.68 ± 1.32 mm for #31, p=0.0007; from 22.26 ± 1.66 to 21.96 ± 1.48 mm for #41, p=0.002). Finally, the IMPA remained stable between the two examinations with a mean 106.1 ± 7.38° vs 105.8 ± 6.51° (p=0.38).

Functional genioplasty favours the alveolar bone formation of the mandibular central incisors, probably by direct bone grafting, but also by the relaxation of the perioral and chin musculature.