Nickel titanium springs versus stainless steel springs: A randomized clinical trial of two methods of space closure

Abstract

Objective: To compare the clinical performance of nickel titanium (NiTi) versus stainless steel (SS) springs during orthodontic space closure. Design: Two-centre parallel group randomized clinical trial. Setting: Orthodontic Department University of Manchester Dental Hospital and Orthodontic Department Countess of Chester Hospital, United Kingdom. Subjects and methods: Forty orthodontic patients requiring fixed appliance treatment were enrolled, each being randomly allocated into either NiTi (n = 19) or SS groups (n = 21). Study models were constructed at the start of the space closure phase (T₀) and following the completion of space closure (T₁). The rate of space closure achieved for each patient was calculated by taking an average measurement from the tip of the canine to the mesiobuccal groove on the first permanent molar of each quadrant. Results: The study was terminated early due to time constraints. Only 30 patients completed, 15 in each study group. There was no statistically significant difference between the amounts of space closed (mean difference 0.17 mm (95%CI −0.99 to 1.34; P = 0.76)). The mean rate of space closure for NiTi coil springs was 0.58 mm/4 weeks (SD 0.24) and 0.85 mm/4 weeks (SD 0.36) for the stainless steel springs. There was a statistically significant difference between the two groups (P = 0.024), in favour of the stainless steel springs, when the mean values per patient were compared. Conclusions: Our study shows that stainless steel springs are clinically effective; these springs produce as much space closure as their more expensive rivals, the NiTi springs.

Key words:

• Nickel titanium spring
• orthodontic space closure
• rate
• stainless steel spring

Acknowledgements

Colleagues for enrolling patients in the trial. Dr Sarah Haniza Abdul Ghani, Consultant Orthodontist, for her kind assistance on this paper.

Disclaimer Statements

Contributors SMC was responsible for study design, logistic, patient recruitment and management, administrative support and data interpretation; critical revision and final approval of article. NHN was responsible for study design, obtaining ethical approval, recruitment of participants and patient management, data collection, analysis and drafting. HW was responsible for statistical analysis and critical revision. SMC is the guarantor.

Funding None.

Conflict of interest None.

Ethics approval This study has been granted ethical approval from the NHS/HSC Research and Development North West 3 (Liverpool East) Research Ethics Committee (Reference: 10/H1002/71) for both sites of this study.