Relationship between the development of skeletal mesio-occlusion and posterior tooth-to-denture base discrepancy--its significance in the orthodontic reconstruction of skeletal Class III malocclusion.

The purpose of this paper is to explain the relationship between the development of Skeletal Class III malocclusion and the posterior discrepancy. Four cases which had severe Skeletal Class III malocclusion and had experienced unsuccessful orthodontic correction are presented to evaluate the causative factors of Skeletal Class III malocclusion. The forward displacement of the mandible was associated with inferiorely positioned maxillary molars and/or superiorly positioned mandibular molars caused by the "squeezing out" effect of posterior discrepancy, which provides a less steep maxillary occlusal plane in the denture frame. Perhaps continuous forward displacement of the mandible induces vertical condylar elongation which establishes the characteristics of Skeletal Class III malocclusion. A new approach to the orthodontic treatment of skeletal Class III malocclusion was achieved by the control of the occlusal plane with four second molars extraction in order to eliminate the posterior discrepancy.