Abstract: PURPOSE: To provide some references of using micro-implant anchorage in clinical orthodontic treatment, the thickness of buccal bone of mandible of different vertical facial type in adults with cone-beam CT(CBCT) were measured. METHODS: Initial 3-dimensional images of 45 adult patients (15 men, 30 women)were reoriented by using a standardized protocol, and divided into 3 groups by angle of mandibular plane (G1: high angle,15 patients; G2: average angle, 15 patients; G3: low angle, 15 patients). After signing the informed consent form, three measurement points were defined at 4, 6, and 8mm from the alveolar crest in each measurement area. Statistical analysis was performed with SPSS11.0 software package. RESULTS: The thickness of buccal bone in mandible was thinner in G1 than in G2, and was thinnest in G3. The cortical bone thickness was thickest at the 8 mm level and thinnest at the 4mm level. CONCLUSIONS: The study suggested that the cortical bone thickness at 4mm level from the alveolar crest was safe for implantation. It is more stable when the distance of implants was more away from the alveolar crest. Patients with low mandibular plane angle should use self-tapping micro-implant anchorage.

Key words: Vertical facial type, Thickness of buccal bone, Cone-beam CT