Abstract
The purpose of the present study was to investigate craniofacial morphological deviations in cases with mandibular arch crowding and their relationship to discrepancies in the permanent dentition, and to establish treatment objectives for crowding in the mixed dentition. The subjects comprised 20 females with mandibular arch crowding at Hellman's dental age IVA (the crowding group), who all had Angle class I occlusion and existing mandibular third molars. The mean age of the crowding group was 17 years and 8 months. The materials consisted of posteroanterior, lateral and forty-five degree oblique cephalograms, and mandibular models of the crowding group. The measurements for craniofacial morphological deviations, and anterior, posterior and total discrepancies were made in the crowding group. Statistical analyses were made for these deviations compared with the previous reported Japaneses norms, and their correlation to discrepancies investigated.
The characteristic features in the crowding group were the smaller cranial base and gonial angles, the shorter ramus height, the anteriorly and upward rotationed mandibule, the mesial inclination of the canines, first and second premolars and first molars, and the infraversion of the canines, and first and second premolars. The anterior discrepancy showed a significant correlation with the mesial inclination and infraversion of canines, and the distal inclination of second molars. The posterior discrepancy showed a significant correlation with the distal inclination of second premolars and first molars. The interception of these morphogical deviations was the objective of the treatment for mandibular arch crowding in the mixed dentition.
