Comparison between round multi-strand wire and rectangular wire bonded retainers: a randomized clinical trial

The primary objective was to compare round multi-strand wire and Ortho-Flex-Tech™ rectangular wire retainers in terms of gingival health. The secondary objectives were to assess plaque/calculus accumulation, and to determine the effectiveness of these retainers in maintaining tooth alignment and their failure rate.

This single-center study was a two-arm parallel randomized clinical trial and was conducted at the Orthodontic clinics in Dental Teaching Center/Jordan University of Science and Technology. Sixty patients, with bonded retention for the mandibular anterior segment after fixed orthodontic treatment, were randomly selected. The sample comprised Caucasian patients with mild to moderate pretreatment crowding in the mandibular anterior region, Class I relationship, treated without extraction of mandibular anterior tooth. In addition, only patients presenting normal overjet and overbite after treatment were included.

One group received round multi-strand wire retainer (30 patients, average age: 19.7 ± 3.8 years), while the other group received Ortho-Flex-Tech™ retainer (30 patients; average age: 19.3 ± 3.2 years). In both groups, the retainers were bonded to all mandibular anterior teeth from canine to canine. All patients were recalled one year after bracket debonding. Randomization sequence was created using Excel 2010, with a 1:1 allocation, using random block size 4. The allocation sequence was concealed in sequentially numbered, opaque and sealed envelopes. Only participants were blinded to the type of bonded retainer used. The primary outcome was to compare the gingival condition between the two groups. The secondary outcomes were to assess plaque/calculus indices, irregularity index of the mandibular anterior teeth and retainers' failure rate. Comparisons were conducted using Mann-Whitney U test or chi-square test. Statistical significance was predetermined at the p≤ 0.05 level for all tests.

Complete data were collected for 46 patients (round multi-strand wire retainer group, n=24 patients; rectangular Ortho-Flex-Tech™ retainer group, n=22 patients). No significant differences were found in the gingival health parameters between the two groups (p>0.05). Ortho-Flex-Tech™ retainers maintained the alignment of mandibular anterior teeth more than multi-strand retainer (p<0.05). No significant difference was found in the failure rate between the two groups (p>0.05).

Gingival health parameters and failure rate were not different in both groups. However, Ortho-Flex-Tech™ retainers were more efficient to retain the mandibular incisors than the multi-strand retainers; nevertheless, the difference was not clinically significant.