Introduction
CPD, maxillary incisors, incisors
The stability of aligned teeth after orthodontic treatment is challenging, and relapse and natural changes may jeopardize the treatment results. Maintaining the position of the anterior maxillary teeth is of particular concern since this anatomical site, commonly defined as the aesthetic zone, is essential for patients when evaluating the outcomes after orthodontic treatment. In addition, relapse in this region is often why patients ask for re-treatment (Several retention strategies for the maxilla are available. Usually, one of these three strategies is used: 1. a retainer bonded to the incisors and the canines, 2. a retainer bonded to the four incisors, or 3. a removable vacuum-formed retainer (VFR) covering the occlusal surfaces of all teeth (Based on Reitan and co-workers’ histological findings (Most previous clinical follow-ups on stability during and after the retention period have mainly focussed on the mandibular anterior teeth. At the same time, only a few studies regarding the stability of maxillary anterior teeth seem to be available (This study examined the retention capacity and 1-year post-retention changes of the six maxillary anterior teeth when the retainers were removed. Both the increase in irregularity and single tooth contact point discrepancy (CPD) were evaluated for the three maxillary retention strategies: 1. bonded retainer to the six maxillary anterior teeth, 2. bonded retainer to the four maxillary incisors, and 3. a VFR covering all maxillary teeth. We hypothesized that post-retention changes would occur. However, even if significant, the overall post-retention changes would be clinically acceptable and equivalent between the retention groups and the changes seen during the retention period.