Stability, survival and costs of vacuum-formed retainers versus bonded lingual braided rectangular and multistranded round wire retainers in the mandible of orthodontic patients over a two-year period

BACKGROUND: To assess the efficacy in relation to costs of three retention techniques: vacuum-formed retainers (VFR) with lingual-bonded braided and multistranded wire retainers in the mandible. METHODS: A total of 93 participants, aged 12–21 years at the start of the retention phase (median age: 16 years; 66% females) were assessed. Analysis included retainer survival rate, costs associated with retention procedures, degree of mandibular incisor irregularity, and patient satisfaction. The cost-minimization analysis accounted for direct costs (material and production expenses, utility costs, and chair time based on personnel wages). RESULTS: The survival rate of retainers was 74% for VFR, 71% for rectangular wire retainers, and 62% for round wire retainers, with no significant differences among groups. Incisor alignment relapse was minimal overall but was highest in the VFR group compared to both wire types (p < 0.001). No differences in satisfaction were observed between groups. However, total retention costs varied significantly (p = 0.001), with the VFR group showing the lowest median cost (34.39 €) and rectangular wire group the highest (44.61 €). CONCLUSION: The retainers demonstrated similar survival rates, provided equal patient satisfaction, and maintained alignment effectively, with differences in stability remaining below evidence-based thresholds. However, VFR incurred 21–23% lower costs than fixed retainers, a finding with practical relevance for public or resource-limited settings. TRIAL REGISTRATION: ClinicalTrials.gov, NCT05121220. Registered 02 October 2021.