The biomechanics of rapid maxillary sutural expansion

Micro-displacements (fringe patterns) in the bones of the craniofacial comp lex as seen through laser holography during midpalatal sutural expansion wi th the Hyrax appliance are used to define the centers of rotation of the ma xillary halves in both the frontal and occlusal views. Biomechanical analys es of the maxillary expansion force system are concomitant with the hologra phic findings and strongly suggest that the stainless steel wires joining t he teeth to any expansion device be of the largest diameter possible. In ad dition, in the case of the Hyrax expansion device, it is recommended that t he manufacturer increase the diameter of the activating screw as well as th ose of the 2 adjacent wire guides. And, importantly, the use of acrylic as a structural member to join the teeth to a sutural expansion device should be avoided if tipping of the maxillary halves is to be minimized, as the ac rylic lacks sufficient rigidity.