Safe sites in the mandibular buccal shelf for orthodontic mini-screws: Tomographic study in different facial types

Objectives: The objective of this study was to verify safe sites on the mandibular buccal shelf (MBS) for extra-alveolar mini-screw insertion according to facial type. Material and Methods: In this retrospective study, 84 cone-beam computed tomography scans were equally divided into three groups according to the patient’s facial type: Group 1, hyperdivergent; Group 2, neutral; and Group 3, hypodivergent. The total buccal alveolar bone thickness was measured in five zones between the mesial root of the first molar and the distal root of the second molar, 3, 6, and 9 mm apical to the cementoenamel junction (CEJ). Results: MBS areas with adequate thickness for temporary anchorage device (TAD) insertion were as follows: Group 1, second molar distal root 9 mm from the CEJ; Group 2, second molar distal root 6 and 9 mm from the CEJ; and Group 3, second molar mesial root 9 mm from the CEJ and second molar distal root 6 and 9 mm from the CEJ. Conclusion: The safe zones on the MBS for TAD insertion were located on the distal root of the second molar, 9 mm from the CEJ, for all facial types. For neutral and hypodivergent patients, the site located on the second molar distal root, 6 mm from CEJ, was included; for hypodivergent patients, the site located on the second molar mesial root, 9 mm from the CEJ, was included.