Adaptive changes in the face of the Macaca mulatta monkey following orthopedic opening of the midpalatal suture.

The classical effects of lateral orthopedic stress on the midpalatal suture were confirmed in this study conducted on ten female Macaca mulatta monkeys in the mixed dentitional period. The suture was opened with consequent expansion of the maxillary arch, of the intranasal space, and of the palatal vault. There was marked buccal displacement of the upper posterior teeth together with a definite broadening of the entire midface. Modest relapse of maxillary expansion and of palatal depth occurred when retention was terminated after four months. Normal angulation of the upper first molars at the end of the experimental period is indicative of a predominantly translatory expansion of the arch or of a rapid restoration of normal tooth alignment and inclination. Subsidiary expansion of the mandibular arch and reclosure of the midpalatal suture also occurred. Of particular importance to this study was confirmation of changes in the bony configuration of the midface manifested by prominence of the canine eminence and the general pug-nosed appearance of treated animals althrough this could not be attributed to retrusion of the premaxilla.