A 3D finite element analysis of maxillary molar distalization using unilateral zygoma gear and asymmetric headgear.

Abstract

The aims of this study were (a) to evaluate the displacement and stress distribution in the maxillary dentition associated with the use of two different unilateral distalization appliances-unilateral zygoma gear (UZG) appliance and asymmetric headgear (AHG)-in non-growing patients; and (b) to assess the effects of fully erupted maxillary third molars on the distalization of the first molar with both appliances by using three-dimensional finite element analysis. Two 3D models of the maxilla were created: one with third molars and one without. Next, two distalizing appliances (UZG and AHG) were added to each model to create four models. Distalization forces were applied, and the resultant displacements were recorded at the mesiobuccal and distolingual cusps and palatal root apex of each molar and the incisal edge root apex of the central incisors. The resulting von Mises stress distributions were evaluated. With the UZG, the first molar showed greater root distalization than the crown in the model with the third molar, whereas the model without the third molar showed distalization and distal tipping of the first molar. With the AHG, the first molar showed a large amount of distal tipping in the model without a third molar. However, this tipping was less than that in the model with third molars. The presence of completely erupted third molars decreased the amount of uncontrolled distal tipping in both appliances. UZG can be considered as an effective option for maxillary molar distalization.