Comparison of Skeletal and Conventional Anchorage Methods in Conjunction with Pre-operative Decompensation of a Skeletal Class III Malocclusion

When treating pronounced dentoalveolar compensation of a skeletal Class III malocclusion, preoperative decompensation frequently requires the extraction of maxillary lateral teeth and retraction of the incisors. In this context, maximum anchorage of the maxillary molars is frequently necessary to attain the significant increase in negative overjet that is desired. The aim of this study was to compare the quality of conventional and skeletal molar anchorage using mini-implants in association with pre-operative decompensation. Pre-operative decompensation involved the symmetric extraction of two lateral teeth from the maxilla as well as retraction of the front teeth in each of 20 patients with a marked skeletal Class III. The molar anchorage half of the patients received was conventional (transpalatal arch) while the other half were treated with skeletal anchorage via mini-implants inserted in the anterior palate. Study models were prepared and analyzed using a 3D scanner before and after space closure (OrthoProof). We analyzed the bilateral degree of mesial molar migration and change in the transversal dimension (DigiModel software). All patients demonstrated mesial migration of the upper molars as a response to the load on the anchorage unit. The 4.21 mm (+/- 1.17 mm) anchorage loss associated with conventional anchorage was greater than that of skeletal anchorage in the anterior palate (2.05 mm [+/- 1.39 mm]). We observed a tendency towards transversal expansion in the molar region according to the design and thickness of the transpalatal arch. Skeletal molar anchorage proved to be more effective than the conventional anchorage. Hence, skeletal anchorage is preferable, especially when patients are in serious need of preoperative decompensation. The anterior palate has proven to be an advantageous region for insertion in conjunction with the correct mechanics.