Effect of different PH level of drinks on the surface topography of orthodontic wires

The aim of this study was to evaluate and compare the changes in surface roughness of three different orthodontic wire types after their immersion in different soft drinks with dissimilar pH levels. A total of 90 samples, 30 stainless steel (SS), 30 nickel titanium (NiTi) and 30 titanium molibdenium alloy (TMA) wire sections were immersed in Coca Cola (pH:2.2), iced tea (pH:3.1), kefir (pH:4.3), coffee (pH:6.8) and artificial saliva (pH:7.1) as the control group. The duration of immersion was 60 minutes in each liquid. Then the samples were rinsed with deionized water and preserved in artificial saliva for 28 days at 37 °C. Surface roughness parameters before and after immersion were measured using atomic force microscopy (AFM) and data was statistically analyzed using one-way ANOVA and post-hoc testing at a confidence level of p < 0.05. There were significant differences in the changes of Ra, Rq and Rz of SS, NiTi and TMA wires among soft drink groups (p<0.05). △Ra and △Rq of the SS wire immersed in Coca Cola were significantly higher than that of the SS wires immersed in other soft drinks and the artificial saliva (p<0.001). △Ra of the NiTi wires immersed in Coca Cola were significantly higher than that of the NiTi wires immersed in other soft drinks and the artificial saliva (p<0.001). △Ra of the TMA wires immersed in Coca Cola were significantly higher than that of the TMA wires immersed in other soft drinks and the artificial saliva (p<0.01). Surface roughness changes of SS wires were significantly smaller than that of NiTi and TMA wires in all soft drinks (p<0.05). More acidic soft drinks caused more surface roughness changes on the archwires. In general, NiTi and TMA wires exhibited more increase in surface roughness compared to SS wires when immersed in soft drinks with different pH levels. Keywords: archwires; SS; NiTi, TMA; surface roughness; soft drinks