Objective This study aimed to measure the distance between a tooth and a soft tissue. This study also aimed to determine the safe region of micro-implant for orthodontic anchorage positioning in the posterior maxillary alveolar bone. Methods Twenty-one cone beam computed tomography reconstruction images of the craniofacial bone of preorthodontic patients were used in this research. Both sides of the mesiodistal distance of the two adjacent teeth in the posterior maxillary alveolar bone were measured at 6, 8, 10, 12, 14, and 16 mm from the horizontal plane. A vernier caliper was used to measure the clinical crown height of the posterior maxillary teeth in the plaster maxillary dentition model. A periodontal probe along the long axis of a tooth was used to determine the width of the free gingiva and the width from the gingival margin to the mucogingival junction. Results In the posterior area of the maxilla, the widest mesiodistal distance of tooth roots was between the second premolar and the first molar. Among the teeth, the maxillary first premolar yielded the highest crown height. The maxillary second molar region showed the widest attached gingiva. Conclusion The safe region of the micro-implant is located in the second premolar and the first molar; the vertical distance from the horizontal plane is 10-11 mm.
