Assessment of the effectiveness of two different orthodontic retention protocols

Introduction: The main goal of orthodontic retention is to keep the teeth in their corrected positions. Fixed or removable retainers are the most common types of retainers used during the retention phase. For the maxilla, various types of retainers have been described, including the vacuum-formed retainers and Hawley retainers. Fixed retainers are used for the lower jaw. Aim: The aim of the present study was to assess the retention characteristics of Hawley retainers, vacuum-formed retainers, and fixed retainers in preserving dental arch dimensions and tooth alignment. Materials and methods: Seventy subjects were examined and distributed into two retention groups. One of the groups received maxillary Hawley retainers and bonded retainers in the mandible. The other group received maxillary vacuum-formed retainers and bonded retainers in the mandible. The mean retention period was two years. Maxillary and mandibular casts were analyzed at pretreatment, debonding, and two years in retention. The assessed measurements were the arch length, intercanine width, interpremolar width, intermolar width and Little’s irregularity index. Results: Vacuum-formed retainers maintained maxillary anterior teeth alignment more effectively than Hawley retainers did. No differences in transversal dimensions were found between the two retention protocols. Hawley retainers showed superior retention characteristics in maxillary arch length preservation compared to vacuum-formed retainers. Even with bonded retainers, relapse could still happen. All measured variables showed a tendency to relapse to the pretreatment values in the two groups. Conclusions: Vacuum-formed retainer maintained maxillary incisor position more effectively than Hawley retainers did. No differences were observed in the transversal dimensions between the two groups. A greater decrease in the mandibular intermolar width was measured between T1 and T2 in both groups where bonded retainers were used.