Mandibular arch length increase during the mixed dentition: postretention evaluation of stability and relapse.

Increasing mandibular arch length to resolve crowding has long been debated as a treatment method. Twenty-six patients with records obtained before treatment, after treatment, and a minimum of 6 years out of retention were assessed. All the patients showed a loss of treatment arch length increase with only 6 of 26 patients showing any gain over pretreatment dimensions. Width constriction was a consistent finding, as was crowding of anterior teeth after retention. In 89% the postretention record demonstrated clinically unsatisfactory alignment. Lateral cephalometric superimposition of mandibles showed variable molar and incisor change after retention. As teeth erupted after treatment, mesial molar movement and lingual tipping of incisors were the most common cephalometric findings.