Anatomic assessment of the mandibular buccal shelf for miniscrew insertion in white patients.

Abstract

Cortical bone thickness, bone width, insertion depth, and proximity to nerves are important factors when planning and placing orthodontic miniscrews. The objective of this study was to anatomically assess the mandibular buccal shelf in a white patient population as the insertion site for orthodontic miniscrews by investigating these 4 variables. Measurements were made on cone-beam computed tomography scans of 30 white patients (18 girls, 12 boys; mean age, 14.5±2years). All measurements were taken adjacent to the distobuccal cusp of the first molar, and the mesiobuccal and distobuccal cusps of the secondmolar. Additionally, bone depth was measured at 2 height levels, 4 and 8mm from the cementoenamel junction. Stereolithographic models of patients were superimposed on the cone-beam computed tomography volumes to virtually create an outline of the soft tissue on the cone-beam computed tomography image to allow identification of the purchase point height (mucogingival junction). The inferior alveolar nerve was digitally traced. Miniscrews (1.6×10mm) were virtually placed at the buccal shelf, and their insertion depths and relationships to the nerve were assessed. Analysis of variance with post hoc analysis was used for data analysis. Insertion sites and measurement levels had significant impacts on both cortical bone thickness and bone width. Cortical bone thickness was typically greatest at the distobuccal cusp of the secondmolar. Bone width was also greatest at the distobuccal cusp of the secondmolar 8mm from the cementoenamel junction. The greatest insertion depth was found again at the distobuccal cusp to the secondmolar, whereas the miniscrews had the greatest proximity to the nerve at this site also. The distobuccal cusp level of the mandibular secondmolar is the most appropriate site for miniscrew insertion at the buccal shelf in white patients.