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A randomized clinical trial to compare three methods of orthodontic space closure

University Dental Hospital of Manchester, UK

Address for correspondence:
Dr N. A. Mandall, Orthodontic Department, University Dental Hospital of Manchester, Higher Cambridge Street, Manchester M15 6FH, UK. E-mail:
Nicky{at}fsi.den.man.ac.uk

Abstract

Aim To compare the rates of orthodontic space closure for: Active ligatures, polyurethane powerchain (Rocky Mountain Orthodontics, RMO Europe, Parc d'Innovation, Rue Geiler de Kaysersberg, 67400 Illkirch-Graffenstaden, Strasbourg, France) and nickel titanium springs.

Sample Patients entering the space closure phase of fixed orthodontic treatment attending six orthodontic providers. Twelve patients received active ligatures (48 quadrants), 10 patients received powerchain (40 quadrants) and 11 patients, nickel-titanium springs (44 quadrants).

Method Patients were randomly allocated for treatment with active ligatures, powerchain or nickel titanium springs. Upper and lower study models were collected at the start of space closure (T_o) and 4 months later (T₁). We recorded whether the patient wore Class II or Class III elastics. Space present in all four quadrants was measured, by a calibrated examiner, using Vernier callipers at T_o and T_1. The rate of space closure, in millimetres per month (4 weeks) and a 4-monthly rate, was then calculated. Examiner reliability was assessed at least 2 weeks later.

Results Mean rates of space closure were 0.35 mm/month for active ligatures, 0.58 mm/month for powerchain, and 0.81 mm/month for NiTi springs. No statistically significant differences were found between any methods with the exception of NiTi springs showing more rapid space closure than active ligatures (P < 0.05). There was no effect of inter-arch elastics on rate of space closure.

Conclusions NiTi springs gave the most rapid rate of space closure and may be considered the treatment of choice. However, powerchain provides a cheaper treatment option that is as effective. The use of inter-arch elastics does not appear to influence rate of space closure.

Key words: Active ligatures, orthodontic space closure, nickel titanium springs, powerchain, rate of tooth movement, randomized clinical trial

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