ROLE OF POSTERIOR TRANSVERSE INTERARCH DISCREPANCY IN CLASS-II, DIVISION-1 MALOCCLUSION DURING THE MIXED DENTITION PHASE

Posterior transverse interarch discrepancy (PTID), measured as the dif ference between the maxillary and mandibular intermolar widths, was in vestigated in a sample of 60 Class ii, Division 1 subjects during the mixed dentition phase. Two main groups were detected: Class II group 1 (30 subjects) with PTID and Class II group 2 (30 subjects) without PT ID. A sample of 30 Class I subjects in the mixed dentition phase was u sed as a control group. In Class II group 1, PTID was found to be due to a significantly narrower maxillary arch. The craniofacial skeletal features of both Class II groups and of the Class I group were assesse d. The Class II group with PTID showed mandibular retrusion associated with a posteriorly displaced mandible of normal size (functional mand ibular retrusion). The Class II group without PTID had mandibular retr usion due to a micrognathic mandible (anatomic mandibular retrusion). The relevance of these findings for treatment planning in Class II, Di vision 1 malocclusion in the mixed dentition was stressed.