THE EFFECT OF ENVIRONMENTAL-FACTORS ON ELASTOMERIC CHAIN AND NICKEL-TITANIUM COIL SPRINGS

It is well known that elastomers exhibit viscoelasticity and as such h ave their mechanical properties modified by temperature. Nickel titani um archwires are also affected by temperature and have been modified w ith specific temperature related properties for clinical use. What is less well known is the effect that other environmental factors, such a s food, might have on the force delivery properties of both elastomeri c materials and nickel titanium coil springs used for space closure. F or instance gross colour change in elastomeric chain is a common clini cal finding in patients who consume spiced foods. The aim of this work was to determine the effect three common environmental factors namely , water, Coke(R), and turmeric solution have on elastomeric chain and nickel titanium coil springs. In addition, it was decided to re-examin e the effect of temperature at 10, 22, and 37 degrees C on both these space closing materials. Unlike many previous investigations, the test specimens were held at a constant stretch throughout the test period, including during their transfer to the Instron Universal Testing mach ine for force measurement. Six force measurements were made over the f irst hour, then at 24 hours and 7 days. A control group of dry specime ns, maintained at 22 degrees C, had additional measurements made weekl y for a 4-week period. The results indicated that elastomeric chain wa s affected by all the test environments while nickel titanium springs were only affected by temperature.