Three-dimensional evaluation of tooth movement in Class II malocclusions treated without extraction by orthodontic mini-implant anchorage

Objective: The aim of this study was to analyze tooth movement and arch width changes in maxillary dentition following nonextraction treatment with orthodontic mini-implant (OMI) anchorage in Class II division 1 malocclusions. Methods: Seventeen adult patients diagnosed with Angle’s Class II division 1 malocclusion were treated by nonextraction with OMIs as anchorage for distalization of whole maxillary dentition. Three-dimensional virtual maxillary models were superimposed with the best-fit method at the pretreatment and post-treatment stages. Linear, angular, and arch width variables were measured using Rapidform 2006 software, and analyzed by the paired t-test. Results: All maxillary teeth showed statistically significant movement posteriorly (<i>p</i> &lt; 0.05). There were no significant changes in the vertical position of the maxillary teeth, except that the second molars were extruded (0.86 mm, <i>p </i>&lt; 0.01). The maxillary first and second molars were rotated distal-in (4.5^o, <i>p</i> &lt; 0.001; 3.0^o, <i>p </i>&lt; 0.05, respectively). The intersecond molar width increased slightly (0.1 mm, <i>p </i>&gt; 0.05) and the intercanine, interfirst premolar, intersecond premolar, and interfirst molar widths increased significantly (2.2 mm, <i>p </i>&lt; 0.01; 2.2 mm,<i> p</i> &lt; 0.05; 1.9 mm, <i>p</i> &lt; 0.01; 2.0 mm, <i>p</i> &lt; 0.01; respectively). Conclusions: Nonextraction treatment with OMI anchorage for Class II division 1 malocclusions could retract the whole maxillary dentition to achieve a Class I canine and molar relationship without a change in the vertical position of the teeth; however, the second molars were significantly extruded. Simultaneously, the maxillary arch was shown to be expanded with distal-in rotation of the molars.[Korean J Orthod 2016;46(5):280-289]