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.

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.