1 - 3D assessment of the mandibular buccal shelf for the most favorable placement of orthodontic micro-implant

Abstract

Currently, there is no consensus regarding the favourable micro-implant (MI) insertion site in the Mandibular Buccal Shelf (MBS). This study aimed at 3D assessment of the width, cortical thickness, and transversal steepness along the mesiodistal MBS length to determine the most favourable MI insertion site. This retrospective observational investigation assessed the Cone Beam Computed Tomography of 94 patients (60 females and 34 males). The paired MBS sites adjacent to the mesiobuccal cusp, buccal groove, distobuccal cusp and the tangent to the distal surface of the mandibular second molar were determined. A total of 24 measurements were extracted, presenting the width, steepness and cortical bone thickness of each MBS. Descriptive statistics and Spearman correlation coefficient were performed at P<0.05. The MBS width significantly increased from the mesial to the distal direction, while both the steepness and cortical bone thickness significantly decreased from mesial to distal (p<0.05). Furthermore, a significant negative correlation was observed between age and the cortical bone thickness adjacent to the distal cusp and distal tangent of the left mandibular second molar. Regarding the symmetry, there were significant differences between the right and left MBS steepness at all sites and the paired cortical thickness at the mesiobuccal cusps, buccal groove and distobuccal cusps of the mandibular second molar (p<0.05). There is sufficient width and cortical bone thickness along the MD length of the MBS, vestibular to the mandibular second molar, for MI insertion. However, considering the MBS steepness, the MI insertion is safer towards the distal direction.