Cortical bone thickness in the buccal posterior region for orthodontic mini-implants

The aim of this study was to investigate cortical bone thickness in the buccal posterior region mesial and distal to the first molar, where mini-implants are often placed, and determine any differences according to location, age and sex. The subjects were 43 patients who had mini-implants placed in the posterior buccal alveolar bone as anchors for orthodontic treatment. Computed tomography was used for diagnostic imaging of the area surrounding the site of implant placement. Cortical bone thickness was measured from 1 to 15 mm below the alveolar crest at 1-mm intervals. The average cortical bone thicknesses ranged from 1.09 to 2.12 mm in the maxilla and 1.59 to 3.03 mm in the mandible. The greater the height, the thicker the cortical bone tended to be, and the mandibular cortical bone was significantly thicker than that of the maxilla. The cortical bone was thinner in females than in males in the region of attached gingiva in the maxilla mesial to the first molar. The mandible suffices as a preparation site for mini-implants, while the maxilla might be insufficient at shallow locations. Regardless of age, the initial stability of mini-implants in shallow locations in the maxilla of women should be considered.