Vacuum-formed retainers and bonded retainers for dental stabilization—a randomized controlled trial. Part II: patients’ perceptions 6 and 18 months after orthodontic treatment

Summary Objective To compare removable vacuum-formed Essix C retainers with bonded cuspid-to-cuspid retainers (CTCs) regarding patients’ perceptions after debonding and 6 and 18 months of retention. Trial design A single-centre two-arm parallel-group randomized controlled trial. Methods This trial included 104 adolescent patients, computer-generated randomized, with sequentially numbered, opaque and sealed envelopes, into two groups and stratified by gender. They were treated with fixed appliances with and without tooth extractions in both jaws and were ready for debond. Patients in the intervention arm received a vacuum-formed retainer (VFR) in the mandible (n = 52), and patients in the active comparator arm received a CTC (n = 52). Both groups had a VFR in the maxilla. Treatment outcome satisfaction, quality of care and attention, side-effects during the retention phase, and retainer acceptance and compliance were assessed with questionnaires at baseline (T1, 2 weeks after debond) and after 6 (T2) and 18 months (T3) of retention. Operator was blinded to group assignment during measurements. Results Ninety-five patients completed the questionnaires at all three time points. Patients were overall satisfied with treatment outcome, quality of care and attention, and how their retainers worked at all three time points, with no differences between groups. At T1 and T3, the VFR group reported significantly more pain and discomfort (T1: P = 0.005, T3: P < 0.0001) and soreness (T1: P = 0.001, T3: P = 0.011) in the mandible compared to the CTC group. The CTC group found it easier to get used to their retainers. After 18 months, 70.5 per cent in the VFR group and 73.9 per cent in the CTC group reported the recommended wear-time of the VFRs. Decreased wear-time was correlated to perceived pain and discomfort (rs = −0.421, P < 0.0001). Limitations The results were limited by our retainer design and recommended wear regimen. Conclusions Both groups reported high treatment outcome satisfaction and low levels of side-effects during the retention phase. Nevertheless, the VFR group reported more pain and discomfort at T1 and at T3. Self-reported compliance was the same in both groups. The VFR group was more concerned about relapse. Trial registration NCT03070444 (https://clinicaltrials.gov).