Comparison of survival time between two types of orthodontic fixed retainer: a prospective randomized clinical trial

BACKGROUND The aim of this prospective clinical study was to compare the mean durability and the failure rates of two types of orthodontic retainers. METHODS Orthodontic patients (142) aged between 14 and 28 years were recruited in this study. The polyethylene woven ribbon (Ribbond, Seattle, WA, USA) retainer was compared with a 0.0175-in flexible spiral wire (Respond, Ormco, Glendora, CA, USA) retainer. When treatment was completed, the retainers were bonded from canine to canine in the maxillary and the mandibular arches of the participants. In the follow-up visits, the patients were re-evaluated every 3 months over a period of 18 months. The time taken for the retainers to remain without any fracture was appraised. Kaplan-Meier analysis and the logrank test were employed to identify significant differences in the survival functions between the groups. The rates of the retainers' failure between the groups were analyzed using Chi-square test. RESULTS It was revealed that the mean survival of the flexible spiral wire retainer was 15.34±0.47 and 15.60±0.42 months in the maxillary and mandibular arches, respectively. The mean survival of the ribbon retainer was 13.95±0.55 and 14.26±0.57 months in the maxillary and mandibular arches, respectively. Ribbon retainers showed a failure rate of 50% in the maxillary and 42.6% in the mandibular arches. Flexible spiral retainers showed a failure rate of 36.5% in the maxillary and 37.8% in the mandibular arches. The differences were not statistically significant. Regarding the evaluation period, the differences had limited clinical significance. CONCLUSION The mean survival time and the failure rates of the polyethylene woven ribbon retainer were comparable to the flexible spiral wire retainer during the 18 months after orthodontic treatment.