Periodontal effects and survival rates of different mandibular retainers: comparison of bonding technique and wire thickness
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Objectives: This non-randomized prospective cohort study aimed to compare the periodontal effects and success rates of mandibular canine-to-canine fixed retainers having different bonding techniques and wire thicknesses. Materials and methods: Hundred patients requiring retention after orthodontic treatment were assigned to five study groups (n = 20 in each group, 61 females/39 males, median age range 16.5-18.0 years). Retention was provided by 0.0215"/direct, 0.0215"/indirect, 0.0175"/direct, 0.0175"/indirect bonded multistranded wires and removable Essix appliances. The primary and secondary outcomes were periodontal effects and success rates. The patients were examined in 1 week, 1 month, 3 months and 6 months follow-up appointments. Plaque index, gingival index, probing depth, marginal recession, bleeding on probing, failure rate per retainer wire and survival of retainer wires were analysed by Kruskal-Wallis H, Mann-Whitney U and chi-square tests. Results: Significant differences were observed between the fixed retainer (FR) and Essix (E) groups in gingival index scores at 1 month [mean FR: 1.13 (95% confidence interval (CI): 0.81-1.44), mean E: 0.40 (95% CI: 0.14-0.69), mean difference: 0.73, P < 0.01], 3 months [mean FR: 0.97/1.01 (95% CI: 0.65-1.30/0.72-1.30), mean E: 0.52 (95% CI: 0.25-0.82), mean differences: 0.45/0.49, P < 0.05], 6 months [mean FR: 0.94 (95% CI: 0.62-1.27), mean E: 0.35 (95% CI: 0.15-0.58), mean difference: 0.59, P < 0.05] and in bleeding on probing scores at 1 month [mean FR: 3.05 (95% CI: 2.12-3.98), mean E: 1.15 (95% CI: 0.42-1.88), mean difference: 1.90, P < 0.01]. The survival rates of retainer wires were 85 per cent for the 0.0215" direct/indirect and 90 per cent for the 0.0175" direct/indirect groups for the 6 months follow-up. Limitations: Six months follow-up period, which demonstrates only short-term outcomes. Conclusions: The periodontal outcomes or survival rates of mandibular fixed retainers were not affected by bonding technique or wire thickness, whereas gingival health improved with Essix retainers but not with fixed retainers.