Alignment Efficiency of Open-Coil Spring Versus Conventional Technique in Relieving Anterior Crowding: A Single-Center Randomized Clinical Trial

This study compares a new technique for teeth alignment to the conventional method. The teeth were aligned using an open-coil spring, i.e. simultaneous space opening and alignment, on round nickel-titanium (NiTi) archwires. The purpose of this 2-arm parallel trial (1:1 allocation ratio) was to evaluate the alignment efficiency of conventional and open-coil spring techniques in anterior crowding treatment.

In this clinical trial study, sixty-two non-extraction patients (70 dental arches: 24 upper arches and 46 lower arches) with ≥3mm of Little’s Irregularity Index (LII) were recruited in two groups based on the minimization method. Blinding was applicable for outcome assessment only. In one group, the teeth were aligned using an open-coil spring, whereas the alignment in the other group was done conventionally, (space opening on steel wires followed by alignment with an auxiliary NiTi wire). The alignment duration was the primary outcome that was investigated for survival analysis and alignment rate ratios, and levels of crowding were calculated with Cox proportional hazard regression. The pre- and post-treatment intercanine widths were also recorded as the secondary outcome. The chi-square and t-test were used to compare other variables between the groups. The level of statistical significance was set at P<0.05.

There was no significant difference in the alignment duration between the conventional (185.48±74.82 days) and open-coil (179.19±64.15 days) groups (P=0.725). No harm was detected using the mentioned methods.

The use of open-coil spring over brackets on NiTi or steel wires does not seem to affect anterior crowding treatment time.