Comparison of clinical characteristics of conventional and nickel free metal brackets before and after recycling

Objective: To compare the clinical characteristics of conventional and Nickel-free metal brackets before and after recycling. Materials and Method: Total of 25 Nickel-free (Co-Cr alloy) premolar brackets MBT 0.022? slot and equal number of 17-4 Stainless Steel premolar brackets MBT 0.022? slot were used in the study. For evaluation of slot dimension, brackets were viewed at 40X magnification under Stereomicroscope. Acrylic jig was made by stabilising 0.019X0.025? Stainless Steel on which test bracket was placed and evaluated for frictional resistance by Universal Testing Machine (UTM). An occluso-gingival load via UTM was applied on bracket-adhesive interface for testing shear bond strength. Results: Paired t- test values for slot dimension showed significant differences between the groups before recycling on both Face and Base. When comparison was made within the groups, there was significant difference in 17-4 Stainless Steel brackets before and after recycling on both Face and Base. For frictional resistance, paired t test showed significant difference within Nickel-free brackets before and after recycling. For shear bond strength, paired t- test showed significant difference within the 17-4 Stainless Steel brackets before and after recycling. Conclusion: Shear bond strength of recycled brackets was greater than as-received brackets for both 17-4 Stainless Steel and Nickel-free brackets. The slot dimensions of as-received brackets exhibited a wider dimension at face than at the base. On recycling, Nickel-free brackets showed a significant increase in frictional values.