Comparison of chairside rectangular chain retainers and multi-stranded conventional retainers: a randomized controlled trial.

Background: While retention appliances are widely used in orthodontics, there is still no evidence-based consensus regarding the optimal type of appliance or time of retention.

Objectives: To compare chairside rectangular chain retainers, which can be placed in one sitting, with conventional multi-stranded bonded retainers regarding their levels of stability, biological side effects, complications, and patient experiences.

Trial design: A single-centre, two-arm, parallel-group randomized controlled trial.

Methods: In total, 48 patients were included in this single-centre, randomized controlled trial conducted in Varberg, Region Halland, Sweden. The patients were randomized to two groups: the chairside rectangular chain retainer group, using the Ortho FlexTech retainer (OFT); and the conventional retainer group, using the 0.0195 Penta One multi-stranded spiral wire (PeO). The primary outcome was Little´s irregularity index (LII) evaluated at debond (T0) and at 3 months (T3) and 12 months (T12). The secondary outcomes were inter-canine distance (ICD), plaque index (PI), calculus index (CI), bleeding on probing (BoP), and caries, evaluated at T0, T3, and T12, as well as patients' perceptions, evaluated at T3 and T12, and technical complications that were registered throughout the study period. The Mann-Whitney U-test was used for continuous variables for inter-group comparisons, and the Wilcoxon Signed Rank test was used for intra-group comparisons.

Results: There were no statistically significant differences between the groups regarding LII, biological side effects, technical complications, or patients' experiences. However, there was a small but statistically significant difference between the groups regarding the maintenance of the ICD. Within the OFT group, there was a significant increase in CI, and within the PeO group, there was a significant increase in BoP.

Conclusions: In terms of clinical relevance, the chairside rectangular chain retainer and the conventional multi-stranded spiral wire provide similar outcomes with respect to the stability of alignment, biological side-effects, technical complications, and patients' experiences short-term.

Trial registration: VGFOUreg-929962. Keywords: Orthodontic retainers; fixed retainers; retention; stability.