Effect of gastric acids on surface topography and bending properties of esthetic coated nickel-titanium orthodontic archwires

Abstract

Objective: The purpose of this study was to evaluate the effect of simulated gastric acid solution on surface topography and bending properties of esthetic coated nickel-titanium (NiTi) archwires. Materials and methods: Three brands of as-received white-coated superelastic NiTi upper archwires were used in this study: Dany, Perfect, and Nitanium. Uncoated metallic areas for each white-coated NiTi archwire were used for comparison with the coated areas. The specimens for each archwire were divided into two groups according to coating as follows: Group A, uncoated, and group B, coated. Then, each group was further subdivided into two subgroups according to the immersion medium as follows: Subgroup 1, immersed in artificial saliva, and subgroup 2, immersed in simulated gastric acid. Surface roughness, surface morphology, and three-point bending test were performed. The data were analyzed statistically using ANOVA and Tukey test. Results: The archwires immersed in simulated gastric acid solution showed significantly higher surface roughness and lower forces on loading and unloading than the archwires immersed in artificial saliva (P < 0.001). Perfect archwire showed significantly the highest surface roughness compared with Dany and Nitanium archwires (P < 0.001). The uncoated archwires showed higher loading and unloading forces compared with coated archwires for all groups (P < 0.001). Nitanium archwire showed the lowest loading and unloading forces at different deflections (P < 0.001). Conclusions: The simulated gastric acid solution decreased considerably the amount of force applied at a given deflection. The loading-deflection and surface roughness properties of coated archwires were affected by the type of coating material. Clinical relevance: The impact of gastric acids on surface and mechanical properties of orthodontic archwires depend on type of coating materials.