Comparison of the effect of three different approaches of retention on reopening of extraction space of fixed orthodontic patients in three different retention phases

Abstract

After completion of orthodontic treatment, the retention phase is necessary for teeth to preserve them in an ideal esthetic and functional relationship and to counteract the inherent tendency of teeth to return to their previous positions. Different fixed and removable retainers are used to prevent relapse in the anterior segment of the dental arch. Retainers that are bonded to 6 anterior teeth, i.e. flexible spiral wires (FSW), are more commonly used. In addition, extended bonded retainers are used to keep the extraction space closed, which are bonded to premolars in addition to anterior teeth. In orthodontic treatments involving tooth extraction, the inability of retainers to prevent the re-opening of the extraction space will result in some periodontal and occlusion problems and patient dissatisfaction. Therefore, the present study evaluated the ability of extended fixed retainers in comparison to FSW retainers, along with overnight use of removable retainers, to prevent re-opening of the extraction space. Materials and method: Thirty-one patients (60 quadrants) were included in this study after obtaining informed consent. Convenient sampling technique was used to assign patients to two group with 13 and 27 quadrants. In group 1, an extended fixed retainer (from the second premolar on one side to the second premolar on the other side) and in group 2 FSW retainer (from the canine tooth on one side to the canine tooth on the other side) in association with overnight use of Hawley retainer were administered. Opening of the interdental space was evaluated by measuring the distance between the mandibular second premolar and first molar on each side in both groups using a leaf gauge at baseline and 2 and 6 months after placing the retainers in the oral cavity. Wilcoxon’s test was used to compare the spaces between the mandibular second premolar and first molar in each group at each time interval. Mann-Whitney U test was used to compare changes in interdental spaces between the two retainer types. Results: The interdental spaces decreased from the time of debonding up to two months after debonding, which was statistically significant in the FSW + Hawley group (P=0.21). During the next 4 months, the space remained unchanged in the extended FSW group and slightly increased in the FSW + Hawley group, which was not significant. In general, the interdental space decreased from the debonding session up to six months later, which was not statistically significant (P=0.91). Conclusion: Both extended fixed retainer and fixed retainer in association with the overnight use of Hawley retainer were successful in keeping the extraction space closed in fixed orthodontic patients during the first 6 months.