Is the postretention relapse of maxillary and mandibular incisor alignmentrelated?

Previous studies suggest a poor association between initial and postretenti on pattern of incisor irregularity. One explanation may be that the incisor movements are limited by the boundaries provided by the incisors in the op posite arch. If so, postretention malalignment of the maxillary and mandibu lar incisors may be related. To test this hypothesis, long-term postretenti on study models of 96 patients with acceptable occlusion at the time of app liance removal were examined. The occlusal surfaces of the postretention st udy models were photocopied, and tooth anatomical contact points were digit ized. An algorithm was used to fit the dental arch to the digitized points. The amount of incisor rotation and anatomical contact point displacement o f maxillary and mandibular anterior teeth, relative to their respective den tal arches, were computer generated. Overbite, the number of occlusal conta ct points in the anterior segment, and concavity of the lingual surfaces of the maxillary incisors were recorded manually. Statistical analyses demons trated a significant association (P < .05) between the overall irregularity of the maxillary and mandibular incisors. The association did not differ a mong subgroups that were stratified according to overbite or number of occl usal contacts. No associations were found for the overall amount of incisor rotation in the 2 arches (P > .05). The amount and direction of displaceme nt of antagonistic pairs of maxillary and mandibular central incisors were also associated (P < .05), but not the amount and direction of rotation (P > .05). The lingual configuration of the maxillary incisors did not affect the pattern of mandibular incisor malalignment.