Clinical study of intrusion and retraction of maxillary anterior teeth with different sites of implant anchorage

Objective To compare orthodontic treatment course and effects of different sites of mini-implant anchorage on improving gummy smile of patients with convex profile who need teeth extraction, and explore the clinical applicability of these two methods. Methods From February 2007 to September 2012, 86 patients with convex profile and gummy smile due to vertical maxillary excess who were supposed to undergo teeth extraction in Aerospace Center Hospital were enrolled in this study, and they were randomly allocated into 2 groups with 43 cases in each group. Patients in group A were inserted with one miniscrew into anterior alveolar process and two miniscrews in posterior alveolar process. The maxillary anterior teeth were simultaneously retracted and intruded by means of miniscrew anchorage. At the same time, dentist bent arch wire was used to maintain well smile arcs of patients. Patients in group B were inserted with two mini-implants into anterior alveolar process to intrude maxillary anterior teeth. Then, the miniimplants were taken out, and two miniscrews were inserted into posterior alveolar process to retract anterior teeth. The pre-and posttreatment cephalometric measurements were analyzed. Then the courses of treatment and its satisfaction were compared between two groups. Results There was no statistical difference in gender, age, parameters of intrusion and retraction of anterior teeth and satisfaction between two groups. The treatment duration of group A was (30.3±10.3) months, which was significantly less than that in group B (35.2±11.2) months (P=0.036). Conclusion Both two different sites of mini-implant anchorages inserting into anterior alveolar process combining with posterior alveolar process can intrude and retract maxillary anterior teeth effectively. Patients in both groups achieve satisfactory smile arc, smile line and facial profile. Moreover, one mini-implant being implanted between maxillary roots of central incisors and two miniscrews being inserted into posterior alveolar process can shorten the duration of treatment significantly.