A clinical investigation of force delivery systems for orthodontic space closure: C. Nightingale and S. P. Jones Journal of Orthodontics 2003;30:229-36

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Elastomeric chains and nickel titanium (Ni-Ti) coil springs are often used to close spaces during orthodontic treatment. Elastomeric chains tend to lose energy during unloading, whereas Ni-Ti coil springs are thought to retain more force during closure over a given time and also provide a more constant force. The aim of the study was to investigate the retentive properties of elastomeric chains and Ni-Ti coil springs in the clinical environment and to compare the rates of closure with the 2 materials. The sample comprised 15 patients wearing preadjusted edgewise appliances undergoing space closure in opposing quadrants. Ni-Ti coil springs and elastomeric chains were used to slide the teeth along an archwire in 40 test quadrants (not all patients required space closure in both arches). A total of 26 springs were tested, because 6 quadrants required more than 1 spring. A further 7 patients had only elastomeric chains applied in 16 quadrants. A total of 36 test quadrants gave data on 53 pieces of elastomeric chain. Patients were asked to return for routine adjustment every 4 to 6 weeks to have the residual force measured.Fifty-nine percent (31 of 53) of the elastomeric sample maintained at least 50% of the initial force over 1 to 15 weeks. No sample lost all its force, and the mean loss was 47% (range, 0%-76%). Ni-Ti coil springs lost force rapidly over 6 weeks; after that, force levels plateaued. Forty-six percent (12 of 26) maintained at least 50% of their initial force over 1 to 22 weeks, and mean force loss was 48% (range, 12%-68%). The rates of mean weekly space closure were 0.21 mm for elastomeric chain and 0.26 mm for Ni-Ti coil springs. There was no relationship between the initial force applied and the rate of space closure. No sample failed during the study period, giving a 100% response rate. The authors concluded that, in clinical use, the force retention of elastomeric chain was better than previously thought. High initial forces resulted in high force decay. Ni-Ti coil springs and elastomeric chain closed spaces at a similar rate. Elastomeric chains and nickel titanium (Ni-Ti) coil springs are often used to close spaces during orthodontic treatment. Elastomeric chains tend to lose energy during unloading, whereas Ni-Ti coil springs are thought to retain more force during closure over a given time and also provide a more constant force. The aim of the study was to investigate the retentive properties of elastomeric chains and Ni-Ti coil springs in the clinical environment and to compare the rates of closure with the 2 materials. The sample comprised 15 patients wearing preadjusted edgewise appliances undergoing space closure in opposing quadrants. Ni-Ti coil springs and elastomeric chains were used to slide the teeth along an archwire in 40 test quadrants (not all patients required space closure in both arches). A total of 26 springs were tested, because 6 quadrants required more than 1 spring. A further 7 patients had only elastomeric chains applied in 16 quadrants. A total of 36 test quadrants gave data on 53 pieces of elastomeric chain. Patients were asked to return for routine adjustment every 4 to 6 weeks to have the residual force measured. Fifty-nine percent (31 of 53) of the elastomeric sample maintained at least 50% of the initial force over 1 to 15 weeks. No sample lost all its force, and the mean loss was 47% (range, 0%-76%). Ni-Ti coil springs lost force rapidly over 6 weeks; after that, force levels plateaued. Forty-six percent (12 of 26) maintained at least 50% of their initial force over 1 to 22 weeks, and mean force loss was 48% (range, 12%-68%). The rates of mean weekly space closure were 0.21 mm for elastomeric chain and 0.26 mm for Ni-Ti coil springs. There was no relationship between the initial force applied and the rate of space closure. No sample failed during the study period, giving a 100% response rate. The authors concluded that, in clinical use, the force retention of elastomeric chain was better than previously thought. High initial forces resulted in high force decay. Ni-Ti coil springs and elastomeric chain closed spaces at a similar rate.