Comparison study between three tooth positioners.

Maintenance of arch dimensions during treatment and retention is essential for the stability of orthodontic results. This study compared ten essential measurements between posttreatment models and three different tooth positioners. Two custom-made positioners and one prefabricated positioner were evaluated. The material for this study consisted of models of twelve patients who were treated orthodontically to a Class I occlusion. Three sets of models were made at the debanding appointment. One set was kept as the original control model. The other two sets were sent to two different laboratories for construction of custom-made positioners. Identical instructions were included. A fourth set of models was made from the prefinisher positioner that was selected for each patient. The original control model, the returned individualized setups, and the prefinisher models were compared. Changes in maxillary and mandibular intercanine and intermolar widths were recorded, along with arch length, molar classification, rotations, spaces, curve of Spee, overjet, overbite, midline discrepancies, and teeth positioned out of arch symmetry. This study showed that there was a significant difference in the mandibular intercanine and maxillary intermolar width between the control model and the prefinisher model. No significant difference in arch length, maxillary intercanine width, and mandibular intermolar width was found between the control model and the other three models. All studied models had a Class I molar relationship. Open contact points and a slight curve of Spee were found in a high percentage of cases. Rotations, midline discrepancies, overjet, and overbite were within normal limits. Arch symmetry was acceptable in all but one case. Positioners, although they appear in most cases to respect individual arch dimensions, should be checked carefully before delivery to the patient.