Three-dimensional evaluation of upper anterior alveolar bone dehiscence after incisor retraction and intrusion in adult patients with bimaxillary protrusion malocclusion

Objective： The purpose of this study was to evaluate three-dimensional （3D） dehiscence of upper anterior alveolar bone during incisor retraction and intrusion in adult patients with maximum anchorage. Methods： Twenty adult patients with bimaxillary dentoalveolar protrusion had the four first premolars ex- tracted. Miniscrews were placed to provide maximum anchorage for upper incisor retraction and intrusion. A computed tomography （CT） scan was performed after placement of the miniscrews and treatment. The 3D reconstructions of pre- and post-CT data were used to assess the dehiscence of upper anterior alveolar bone. Results： The amounts of upper incisor retraction at the edge and apex were （7.64±1.68） and （3.91±2.10） mm, respectively, and （1.34±0.74） mm of upper central incisor intrusion. Upper alveolar bone height losses at labial alveolar ridge crest （LAC） and palatal alveolar ridge crest （PAC） were 0.543 and 2.612 mm, respectively, and the percentages were （6.49±3.54）% and （27.42±9.77）%, respectively. The shape deformations of LAC-labial cortex bending point （LBP） and PAC-palatal cortex bending point （PBP） were （15.37±5.20）° and （6.43±3.27）°, respectively. Conclusions： Thus, for adult patients with bimaxillary protrusion, mechanobiological response of anterior alveolus should be taken into account during incisor retraction and intrusion. Pursuit of maximum anchorage might lead to upper anterior alveolar bone loss.