Three-dimensional evaluation of surgically assisted implant bone-borne rapid maxillary expansion: a pilot study.

Introduction: The purpose of this study was to evaluate 3-dimensional changes in dental, alveolar, and skeletal structures caused by a bone-borne implant-supported rapid maxillary expansion device (Dresden distractor).

Methods: Axial computed tomography scans of 10 patients (mean age, 25.3 years) treated with the Dresden distractor were examined. Scans were taken immediately before and 9 months after expansion. Distances in all 3 dimensions were calculated for 38 skeletal, alveolar, and dental landmarks with respect to the reference point ELSA (point equidistant to both foramina spinosa).

Results: In the transverse dimension, a V-shaped opening of the suture was shown; the greatest amount of opening was anteriorly directed, with convergence of the suture opening in the posterior aspect of the palate. The expansion of the maxillary dental arch showed a V pattern similar to the opening of the suture. In the frontal view, expansion caused a wedge-shaped opening with its base at the central incisors and the estimated center of rotation next to the frontonasal suture. The alveolar processes tipped buccally (9.9 degrees to 13.3 degrees) as did the molars (2.5 degrees to 3.5 degrees) and the premolars (3.0 degrees to 3.9 degrees). Less tipping of teeth compared with skeletal tipping (about 6 degrees to 9 degrees less) is related to the torque effect of the fixed appliance.

Conclusions: The Dresden distractor is a minimally invasive bone-borne expansion appliance that protects teeth by inducing more skeletal than dental changes. This might be a precondition for stable postsurgical occlusion.