Upper Molars Distalization With Clear Aligners and Vertical Dimension Control

Objectives: A common strategy applied in the non-extraction treatment of Class II molar relationship is maxillary molar distalization but there are many side-effects including increase in lower face height, undesirable tipping of the maxillary molars and loss of anterior anchorage. The aim of this study was to analyze the influence of the upper distalization movement on the vertical dimension and molar tipping.
Methods: A restrospective analysis of lateral radiographs was performed on a sample of 10 subjects. Skeletal class I or II and bilateral class II molar relationships were the inclusion criteria and the subjects were treated with upper molar distalization with clear aligners (Invisalign®, Align Technology, San Josè, CA, USA). Lateral cephalograms were performed on radiographs obtained before the beginning of the treatment (T0) and at the end of the orthodontic treatment (T1). Among the analyzed cephalometric parameters, the primary outcomes were the variables SN^PP, SN^OP and SN^GoGn, related with the vertical dimensions of the subjects.
A Student’s t test was applied in order to analyze the statistical differences in the considered parameters.

Results: After having achieved the first molar class, among the primary outcomes, there were no significant increases in the SN^GoGn and SN^PP angles with a significant low increase of the SN^OP angle (3°; p=0.011). Furthermore, there were absence of significant molar tipping and a significant reduction of the upper incisor inclination (-12.4°; p=0.012).
Conclusions: The use of clear aligners for upper molar distalization seems to ensure an ideal control of the vertical dimension thank to the absence of molar tipping. Furthermore, an ideal control of the upper incisal torque without loss of anchorage was achieved.