Three-dimensional dental arch and palatal form changes after extraction and nonextraction treatment. Part 1. Arch length and area.

The purpose of this study was to investigate changes in arch length, arch area, and irregularity index in patients treated with and without premolar extractions. Records collected at pretreatment, at bracket removal, at the end of retention, and 5 years out of retention were examined. Stone casts were mounted on an articulator with an anatomic face-bow and a central wax record, and measurements were made with a 3-dimensional digitizer. In general, the maxillary arch exhibited less relapse tendency than did the mandibular arch for both patient groups. In general, the extraction group showed the same relapse tendency as the nonextraction group.