The effect of autoclave cycles on the mechanical properties and surface roughness of NiTi archwires: ex-vivo study

Objectives To evaluate the effect of the universal and rapid autoclave cycles on the mechanical properties and surface roughness of nickel-titanium archwires following clinical use. Material and methods Thirty-six NiTi archwires (0.016 x 0.022 inch) were equally divided into a control group (Group A) and 2 experimental groups (Group B & C). Wires in group A were tested in the "as-received" form. Wires in the two other groups were installed in patients mouth for 4 weeks, and then autoclaved using the rapid- cycle (Group B) or the universal- cycle (Group C). All wires were subjected to 3-point bending test to calculate the elastic limit, modulus of elasticity, spring-back, yield strength, resilience and toughness. Atomic force microscopy (AFM) was used for surface roughness qualitative and quantitative analysis. Results Group B showed significantly higher values of elastic limit, modulus of elasticity, resilience, yield strength and toughness than the other two groups. No significant differences were detected between groups A and C (P > 0.05). Group B showed significantly lower average surface roughness than the other two groups, but no significant differences were detected between groups A and C (P > 0.05). Conclusions The mechanical properties and surface roughness of clinically used NiTi wires were less affected by the universal-cycle than the rapid- cycle autoclaving. However, the difference between the effect of both autoclave cycles was diminutive. Clinical relevance The mechanical properties and surface roughness of the tested NiTi wires were not notably altered by clinical use and autoclaving.