There is no reliable evidence from the trials included in this review that any specific initial arch wire material is better or worse than another with regard to speed of alignment or pain. There is no evidence at all about the effect of initial arch wire materials on the important adverse effect of root resorption. Further well-designed and conducted, adequately-powered, RCTs are required to determine whether the performance of initial arch wire materials as demonstrated in the laboratory, makes a clinically important difference to the alignment of teeth in the initial stage of orthodontic treatment in patients.
Alignment efficiency of superelastic coaxial nickel-titanium vs superelastic single-stranded nickel-titanium in relieving mandibular anterior crowding: a randomized controlled prospective study.
To clinically evaluate the alignment efficiency of 0.016-inch coaxial superelastic nickel-titanium (NiTi) and 0.016-inch superelastic NiTi in the lower anterior region over a period of 12 weeks. Materials and
                A sample of 24 patients requiring lower anterior alignment were included in this single-center, single-operator, double-blind clinical trial and were randomly allocated into two groups of 12 patients. The type of wire selected for each patient was not disclosed to the provider or to the patient. Comparison of pretreatment characteristics of the archwire groups revealed no discrimination between two samples, thus verifying the random allocation of the intervention. An initial alginate impression of the lower arch was followed by impressions at 4-, 8-, and 12-week intervals. Casts were measured using the coordinate measuring machine to denote the degree of alignment. Duplicate readings of the cast series were taken to assess measurement variation.
                A statistically significant difference (P < .05) in the mean values of tooth movement demonstrated the superior aligning efficiency of coaxial superelastic NiTi over single-stranded superelastic NiTi in relieving lower anterior crowding. The measurement error recorded was within acceptable limits, with range values within 95% limits of agreement.
                Coaxial superelastic NiTi wire proved superior to single-stranded NiTi in its efficiency in relieving lower anterior crowding over a 12-week period.