Posterior transpalatal distraction with pterygoid disjunction: A short-term model study

The transpalatal distractor (TPD) allows for maxillary expansion according to the concepts of distraction osteogenesis. Unlike tooth-borne, surgically assisted rapid palatal expansion devices, the bone-borne TPD is designed t o avoid periodontal ligament compression, buccal root resorption, fenestrat ion, tooth tipping, and orthodontic relapse during and after the expansion. When the distractor is placed on the palate at the level of the second pre molar and pterygomaxillary disjunction is not performed, more expansion occ urs in the anterior part of the maxilla than it does in the posterior. The aim of this investigation was to test the hypothesis that pterygomaxillary disjunction and placement of the TPD on the palate at the level of the firs t molars result in more parallel expansion of the maxillary segments. Twent y consecutive patients were included in a prospective way, and their predis traction and postdistraction models were electronically analyzed. The chang e in resistance and force application resulted, on average, in parallel seg ment expansion. The results showed that pterygomaxillary disjunction and po sterior placement of the TPD are indicated for patients having transverse m axillary deficiency with lateroposterior crossbite.