Variation in surface topography of different NiTi orthodontic archwires in various commercial fluoride-containing environments

Abstract

Objectives: The surface topography can affect the friction behavior between an orthodontic wire and brackets during clinical applications. The purpose of this study was to investigate the influence of a fluoride-containing environment on the surface topography variations of different nickel-titanium (NiTi) orthodontic archwires.

Methods: Four different NiTi commercial orthodontic archwires were immersed in fluoride mouthwashes and in artificial saliva with the addition of commercial fluoride toothpastes or prophylactic gels for a 28-day period. Atomic force microscopy (AFM) was used to measure the three-dimensional surface topography of NiTi archwires before and after the immersion tests. Two-way analysis of variance (ANOVA) was used to analyze the surface roughness variance (including DeltaR(a), DeltaR(ms), and DeltaR(z)) with the archwire manufacturer and immersion test environment as the factors.

Results: Both the archwire manufacturer and immersion environment had a significant influence on DeltaR(a), DeltaR(ms), and DeltaR(z) (manufacturer: P<0.05; environment: P<0.0001). Regardless of the archwire manufacturer, no statistically significant difference in DeltaR(a) (<70 nm), DeltaR(ms) (<90 nm), and DeltaR(z) (<450 nm) was observed on the tested NiTi archwires in lower fluoride-containing (<2500 ppm) environments, including the various fluoride mouthwashes and the artificial saliva added with fluoride toothpastes. In artificial saliva added with high fluoride prophylactic gel (around 17,000 ppm), a significant increase in DeltaR(a) (around 120-250 nm), DeltaR(ms) (around 140-320 nm), and DeltaR(z) (around 770-1410 nm), i.e. increasing the surface roughness, was observed on the tested NiTi archwires.

Significance: The variation in the surface topography of the NiTi orthodontic archwires in the commercial fluoride-containing environments should be taken into consideration when the friction between the archwire and bracket is a clinical concern.