Rapid palatal expansion for spontaneous Class II correction

Palatal expanders have been advocated for spontaneous correction of some Class II malocclusions. Hypothesis. The patient's centric occlusion is close to their maximum intercuspation before palatal expansion, and expansion causes a mandibular functional shift forward in order for the teeth to come together into maximum intercuspation. Objectives. To determine if maxillary expansion causes a "spontaneous" correction of a Class II malocclusion. Methods. This is a retrospective study taken from an orthodontic office where models are mounted in centric occlusion and maximum intercuspation before and after treatment. The target sample is Class II patients who were treated by expansion alone in the previous two years. Their study models were measured before and after expansion to compare the centric occlusion to the maximum intercuspation position. Results. The only measurements with statistically significant changes from pre-treatment to post-expansion were upper intermolar widths. Conclusions. Rapid maxillary expansion does not correct Class II malocclusions.