| Summary: | 碩士 === 國立臺灣大學 === 臨床牙醫學研究所 === 94 === INTRODUCTION: Among the factors affecting the treatment outcome of orthodontics, “anchorage control” is the one that plays a very important role. Recent application of the mini-implants provides good and stable orthodontic anchorage for patients requiring maximum anchorage without patient’s compliance. This is a retrospective clinical study to compare the orthodontic treatment outcome between the patients with traditional extra-oral appliance and the ones receiving the mini-implant for maximum anchorage. MATERIAL & METHOD: We compare the treatment outcome of two groups of patients, receiving different anchorage systems during their orthodontic treatment for maximum retraction of the maxillary dentoalveolar process. They were diagnosed either as Angles Class l bimaxillary dentoalveolar protrusion or Angle Class II malocclusion with maxillary dentoalveolar protrusion, with the treatment plan including extraction of bilateral maxillary first premolars. Group 1 (n=28) received traditional anchorage with the transpalatal arch and headgear; group 2 (n=30) received mini-implants (miniscrews or miniplates) for anchorage control. Superimpositions of pre- and post-treatment lateral cephalograms ,and 3-D images obtained via using 3-D digitizer recording on pre- and post-treatment dental models were used to compare (1) the amount of retraction (2) torque of maxillary central incisor (3) change of transverse width of maxillary dentition (4) change of mandibular plane angle between 2 groups. RESULTS: The results showed that the mini-implant anchorage group had more anterior teeth retraction than the headgear group (1.19 mm) with a shorter treatment duration (3.4 months ). Analysis the types of incisor movement (controlled tipping, translation, or uncontrolled tipping) showed mini-implant anchorage group had more translation movement than the headgear group. The intercanine width was wider after orthodontic treatment in both groups. When the cases receiving either miniscrews or miniplates were compared, the cases receiving miniplate had more intrusion of maxillary first molar (0.77 mm ) than that receiving miniscrews, with a counterclockwise rotation of the mandibular plane (1.25 o ). When cases with high mandibular plane angle were analyzed, the subjects receiving mini-implant anchorage had more intrusion on the maxillary first molar (0.59 mm) than that receiving headgear, with a counterclockwise rotation of the mandibular plane (1.44o) to improve the profile of Class II malocclusion. We also observed some remodeling in A point in cephalometric analysis. A point was retracted in the headgear group and protracted in the mini-implant group, though the latter with a larger individual variation. CONCLUSION: The treatment time of the mini-implant anchorage was reduced. The mini-implant anchorage performed better both in sagittal and vertical directions for retraction and eliminating the opening of the mandibular plane angle without patient compliance. Especially in the cases with high mandibular plane angle, the maxillary posterior teeth were successfully intruded to obtain for more satisfactory profile in addition to improving the Class II relationship.
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