Assessment of Surface Roughness of Nickel Free Orthodontic Brackets and Archwires (An In Vitro Comparative Study)

Abstract

Objectives: Orthodontic appliances may cause many side effects, one of these is inducing nickel
hypersensitivity as a result of nickel content of these appliances, therefore, it is essential to choose a
bracket and archwire that are nickel free and have a better surface characteristic to be more efficient for the
orthodontic treatment. Hence, the aim of this study is to assess the surface roughness of nickel free metal
brackets and archwires.
Materials and Method: Two types of nickel free brackets were used (Ni free SS brackets and Co-Cr
brackets), a 0.022-inch slot, and three types of nickel free archwires of 0.018 x 0.025 inch were used (Ni
free SS, TMA, and rhodium coated SS archwires). These brackets and wires were examined for their surface
roughness by the atomic force microscope (AFM) using the roughness average parameter (Ra). For the
statistical analysis Mann-Whitney U test was used for the comparison between the brackets, while, KruskalWallis test was used for the comparison among the archwires (non-parametric tests) at level of significant
0.05, by using SPSS software version 23.
Results: Regarding the brackets, there was no statistically significant difference between the surface
roughness of the two brackets types, while, regarding the archwires, there was a statistically significant
difference between the as received archwires; as the nickel free stainless steel wires had the lowest value of
roughness average, while, the TMA wires had the highest value of roughness average.
Conclusions: Ni free SS wires considered the best choice as a working wire for patients with nickel allergy