Heat-activated nickel-titanium versus conventional nickel-titanium archwire sequences for maxillary anterior alignment: A randomised controlled trial

Abstract

Objective: To compare the clinical effectiveness of conventional nickel-titanium (NiTi) and heat-activated nickel-titanium (HANT) archwire sequences in terms of anterior alignment, root length, alveolar bone changes and pain. Methods: This was a two-arm parallel randomised controlled trial. Patients (Little’s Irregularity Index (LII) 7–9 mm) requiring fixed orthodontic treatment with first premolar extractions were enrolled. Participants were randomly allocated (1:1) using a computer-generated random sequence to either the HANT or conventional NiTi group. Digital scans were obtained at baseline (T0) and monthly until 6 months (T6) to calculate alignment using LII. Pain was assessed at 24 h and 3 and 7 days after activation using a visual analogue scale. Cone-beam computed tomography scans were taken before and after alignment to evaluate root length and alveolar bone changes. Statistical analyses included repeated-measures ANOVA and appropriate between-group tests. Results: A total of 46 participants were randomised, and 44 (22 per group) completed the trial. Two participants (one from each group) discontinued during follow-up. Both groups showed significant reductions in irregularity ( P < 0.001). A statistically significant time × group interaction was observed ( P = 0.035). The HANT group showed a slightly higher, but non-significant, 6-month alignment rate (1.35 vs. 1.30 mm/month). Pain scores were lower in the HANT group. No between-group differences were detected in root length or alveolar bone changes. Conclusion: HANT showed greater LII reduction between months 1 and 3, whereas the overall 6-month alignment rate did not differ significantly. The HANT group also showed lower pain without increasing root resorption or bone loss. These differences were small, so they may be of limited clinical significance. Registration: Ethics Committee of Can Tho University of Medicine and Pharmacy (No. 24.384.HV-ĐHYDCT) and registered at ClinicalTrials.gov (NCT07176871).