Silver nanoparticles added to a commercial adhesive primer: Colour change and resin colour stability with ageing

Abstract

This study evaluated the influence of silver nanoparticles (NAg) incorporated into the primer of a three-step adhesive system (Scotch-Bond Multi-purpose) over the composite-resin colour (CIELab and CIEDE 2000) as a function of the concentration and ageing methods. Ninety specimens were prepared and distributed into 6 groups (n = 15), according to the NAg concentration: NAg 0 (0 wt%); NAg 50 (0.005 wt%); NAg 100 (0.010 wt%); NAg 150 (0.015 wt%); NAg 200 (0.020 wt%); NAg 250 (0.025 wt%). Initial colour readings were performed to evaluate colour change (CC) after NAg addition to primers. Readings after 30 days of storage in water (30D), thermocycling (TC), and accelerated artificial ageing (AAA) were performed to verify the influence of each method over CC. Data was calculated according to CIELab and CIEDE 2000 systems and analysed with one-way and two-way ANOVA (p ≤ 0.05), complemented with post-hoc Tukey test. Data presented normality, homoscedasticity, and statistical difference. ΔEs gradually increased according to the percentage of added NAg into the primer. Thermocycling and UV light exposure induced a higher colour change when compared to water ageing (D30). Significant statistical difference was found for all ageing methods. CIEDE 2000 and CIELab are similar methods of colour evaluation. Besides, primers with up to 0.025 wt% applied in cavities deeper than 1 mm were colour-safe and did not jeopardise the aesthetic perception of the simulated restoration.