Alignment efficiency of coaxial tubular superelastic nickel‐titanium vs single‐stranded superelastic nickel‐titanium in relieving mandibular anterior crowding in extraction cases: A single‐centre randomized controlled clinical trial

Structured Objectives To compare the alignment efficiency of coaxial tubular and single‐stranded 0.016” superelastic NiTi archwires in relieving mandibular anterior crowding in extraction cases and to evaluate whether alignment efficiency differed as the initial irregularity increased. Setting and Sample Population Forty female patients aged between twelve and twenty years from the postgraduate orthodontic clinic at the authors’ centre. Materials and Methods All patients in this single‐centre, 2‐arm parallel trial were randomly allocated in a 1:1 ratio and the mandibular anterior irregularity was measured from the mandibular cast at 0‐, 4‐, 8‐ and 12‐week intervals using a digital calliper. Results All forty patients (mean age, 15.08 ± 2.11) completed the study with either coaxial tubular superelastic NiTi (mean age, 15.30 ± 2.36) or single‐stranded superelastic NiTi (mean age, 14.85 ± 1.84). The largest mean irregularity index reduction of −4.88 ± 2.74 and −6.17 ± 2.38 in the single‐stranded superelastic NiTi and the coaxial tubular superelastic NiTi groups, respectively (P = 0.122) was at 4 weeks. Student's t test and repeated measures ANOVA indicated that none of the mean comparisons were statistically significant at a 5% level. Pearson's correlation value (r) indicated no statistically significant influence of initial crowding on alignment efficiency. Conclusions There was no statistically significant difference between the alignment efficiency of coaxial tubular superelastic NiTi and single‐stranded superelastic NiTi in extraction cases, and the degree of initial crowding had no influence on the alignment efficiency.