Safe regions of miniscrew implantation for distalization of mandibular dentition with CBCT

BACKGROUND: To assess the anatomy of the mandibular buccal shelf (MBS) with cone-beam computed tomography (CBCT) and to identify the region of miniscrew implantation for the distalization of mandibular dentition. MATERIALS AND METHODS: The MBS was assessed in 80 patients at four regions as follows: (i) between the buccal root of the mandibular second premolar and the mesiobuccal root of the first molar (L5(b)–L6(mb)), (ii) between the mesiodistal root of the first molar (L6(mb)–L6(db)), (iii) between the distobuccal root of the first molar and the mesiobuccal root of the second molar (L6(db)–L7(mb)), and (iv) between the mesiodistal roots of the second molar (L7(mb)–L7(db)). The buccal alveolar bone thickness, the narrowest inter-radicular space at the buccal side of the roots, and the distance between the implantation site and the mandibular neural tube were measured at horizontal planes of 3, 5, 7, and 9 mm from the alveolar crest. RESULTS: The buccal alveolar bone thickness increased from the premolar to the molar and from the crest edge to the mandibular roots. The L7(mb)–L7(db) region had the thickest buccal alveolar bone of 7.61 mm at a plane of 9 mm. The buccal inter-radicular spaces were smallest in the L7(mb)–L7(db) region and greatest in the L6(db)–L7(mb) region. The distances from the implantation site to the mandibular neural tube at planes of 3, 5, 7, and 9 mm were all > 13 mm from the L6 region to the L7 region. CONCLUSIONS: The L6(db)–L7(mb) region should be the first choice for miniscrew implantation in the MBS for the distalization of mandibular dentition.