The correlation between mandibular buccal shelf thickness and different vertical facial patterns: A CBCT study

Aim: The aim of this study was to evaluate the association between buccal shelf thickness and vertical facial patterns to determine the preferred site for mini-implant placement. Methods: Cone-beam computed tomography (CBCT) scans of 90 Iranian adults, aged 22–40 years, were collected from the digital archive of Islamic Azad University (Tehran city, Iran country) and analysed in this retrospective cross-sectional study in order to determine facial patterns. Participants with an ANB angle of 2° ± 2° were divided into low (<27°), average (27°–37°) and high (>37°) vertical groups based on the SN-GoMe angle. Buccal shelf bone thickness was measured at the first and second molars at 6 mm and 11 mm from the cemento-enamel junction (CEJ). Data were analysed using the Shapiro–Wilk test, independent and paired t -tests, Pearson correlation and Tukey post-hoc test, with significance set at P < 0.05. Results: Among the 90 participants (39 men, 51 women), no significant sex differences in buccal shelf bone thickness were observed. A significant negative correlation existed between SN-GoMe angle and buccal shelf bone thickness. Buccal bone thickness increased in both the apical and posterior directions; the mean (±SD) thinnest values observed at the distal root of the first molar at 6 mm were 1.03 ± 0.79 mm in males and 1.08 ± 0.90 mm in females, while the mean thickest values were observed at the distal root of the second molar at 11 mm, measuring 4.86 ± 1.59 mm in males and 4.74 ± 1.13 mm in females. Conclusions: Individuals with a low vertical angle tend to exhibit greater buccal shelf bone thickness. The distal aspect of the mandibular second molar at 11 mm from the CEJ appears to be the most favourable site for extra-alveolar mini-implant placement.