Effective approach for improving a gummy smile : Upward movement of the maxillary occlusal plane using midpalatal miniscrews and a modified transpalatal arch.

Purpose: Correction of a gummy smile by orthodontic treatment alone has recently become feasible with the use of miniscrews. However, the optimal treatment mechanics remain unclear. Here we cephalometrically evaluated jaw and tooth displacement in cases where a gummy smile was improved using a level anchorage system (LAS).

Methods: Sixteen patients underwent orthodontic treatment using an LAS consisting of a modified transpalatal arch and midpalatal miniscrews. Cephalometric pretreatment and posttreatment measurements were compared using the paired t‑test to determine significant skeletal and dental changes. The Mann-Whitney U test was used for nonparametric data. Spearman's rank correlation coefficient was used to evaluate correlations between different variables and the vertical change in prosthion position which was used to indicate the amount of gingival exposure.

Results: The changes noted after treatment were intrusion of the maxillary first molars (P < 0.001) combined with only minor extrusion of the mandibular first molars. Suppressed extrusion of the mandibular first molars was significantly correlated with greater upward movement of the prosthion (r = 0.676, P < 0.01). Upward movement of the prosthion was also significantly correlated with intrusion of the maxillary and mandibular incisors, anterior upward movement of the maxillary occlusal plane, and an increase of the SNP angle.

Conclusions: Treatment involving the combined use of miniscrews and a modified transpalatal arch resulted in intrusion of the maxillary first molars and maxillary incisors and consequently elevated the maxillary occlusal plane. The results of this study suggest that intruding the maxillary occlusal plane and minimizing mandibular molar extrusion were effective to induce autorotation of the mandible and to improve a gummy smile.