For an extraoral maxillary orthopedic protraction device such as facemask or reverse headgear, the direction of protraction has been proven to be 30-degree downward and forward biomechanically in order for a bodily protraction of the maxilla. However, by utilizing vertical biting force during mouth closiing, it is extremely difficult biomechanically for an intraoral non-compliant device to deliver a 30-degree downward protraction force through the center of resistance of maxilla. The technique of effective maxillary orthopedic protraction is developed for the maxillary protraction in growing Class III patients in the early permanent dentition. This technique includes alternate rapid maxillary expansions and constrictions (Alt-RAMEC) for an effective loosening of the circumaxillary sutures, and a pair of B-TI intraoral protraction springs for the non-compliant maxillary orthopedic protraction. The center of resistance of maxilla varies with the extension of loosening of the circumaxillary sutures by the Alt-RAMEC, and therefore, the protraction result by using the B-Ti intraoral protraction springs varies accordingly. Through 2 and 3 dimensional cephalometric and computer tomographic analyses of the maxillary positional changes before and after portraction, this presentation will present the design and the orthopedic biomechanics of the B-Ti intraoral protraction springs and the clinical tips and results on the application of Alt-RAMEC and B-Ti intraoral protraction springs.
For the orthopedic biomechanics in maxillary protraction, the center of resistance of maxilla varies with the extension of loosening of the circumaxillary sutures, and therefore, the protraction result by using intraoral non-compliant retraction springs varies accordingly