A comparison of survival rates using 3 methods of mandibular fixed retainer fabrication: A randomized clinical trial

The objective of this prospective trial was to compare the 2-year survival of bonded mandibular lingual retainers, using 3 different fabrication methods, as well as comparing a range of clinical and patient-centered outcomes.

This was a single-center, prospective, randomized clinical trial based in a specialist orthodontic practice setting between November 2017 and December 2021. A total of 300 participants, aged 14 and 18 years, who had completed a course of comprehensive fixed appliance treatment, were randomly allocated to 1 of 3 mandibular fixed retainer fabrication intervention groups: chairside-fabricated and directly bonded Ortho FlexTech; laboratory-fabricated and indirectly bonded multistranded gold-plated wire; and laboratory-fabricated and directly bonded Blu-Elgiloy wire. The primary outcome measure was the 2-year survival of retainers, and secondary outcomes included the clinical efficiency and effectiveness of the 3 methods, along with patient-reported outcomes. An electronic block randomization program was used along with opaque envelopes to conceal allocation. All data were anonymized and assessed blind, using descriptive statistics, and analyzed to detect between-group differences.

There was a significant difference in bonded wire survival between the 3 groups. Survival at 2 years was estimated to be 68% in the multistrand group, and >90% in the other 2 groups. As there was an overall difference in survival between the 3 groups, additional comparisons were made between each pair of groups. The results suggested statistically significant differences between both the Direct Ortho Flex and BlueElgiloy groups with the multistrand group (Bonferroni-adjusted P <0.001). Highly significant (P <0.001) differences were detected in the mean (standard deviation) combined fabrication and clinical time (seconds) between the direct Ortho FlexTech (733 [SD, 122]) and the other 2 indirect methods of multistranded retainer (2948 [SD, 409]) and the Blu-Elgiloy group (2522 [SD, 436]). No significant differences were detected in the alignment of the mandibular anterior teeth, periodontal parameters, or patient-reported outcomes.

At 24 months, significant differences were observed in bonded wire survival between the 3 groups. The direct Ortho FlexTech means that combined fabrication and clinical time was 3 times faster than the other 2 indirect methods. No significant differences were detected in the alignment of the mandibular anterior teeth, periodontal parameters, or patient-reported outcomes.