Effects of whitening toothpastes on the optical and surface properties of single-, group-, and multi-shade universal...

The aim of this study was to evaluate the effects of whitening toothpastes containing blue covarine or activated charcoal on the color change, surface roughness, microhardness, and gloss of single-, group-, and multi-shade universal composites.

Each of three composite resin groups (Omnichroma-supra-nanospherical single-shade; Neo Spectra ST HV-nanoceramic group-shade; and Filtek Z550-nanohybrid multi-shade) were divided into three subgroups (n = 15) based on the whitening toothpastes used: Distilled water (brushing without paste), Curaprox White is Black, and Signal White Now. Baseline measurements for color, surface roughness, microhardness, and gloss were made on each of the specimens. Subsequently, all specimens were immersed in coffee for 6 days to simulate 6 months of coffee consumption, after which the measurements were repeated. The stained specimens were subsequently brushed with an electric toothbrush for 24 min to simulate the effect of brushing teeth for 6 months. Again, measurements were made following this toothbrushing process. Additionally, one specimen from each subgroup was prepared for scanning electron microscopy (SEM) analysis. To evaluate if data had normal distributions, the Shapiro-Wilk test was used. Normally distributed data were analyzed using a generalized linear model followed by Tukey's post-hoc test. Non-normally distributed data were evaluated using robust ANOVA and Holm-corrected robust t-tests through the use of Walrus package. Quantitative data were reported as mean ± standard deviation or trimmed mean ± standard error. The statistical significance threshold was set at p < 0.05.

Omnichroma showed the greatest color change, whereas Filtek Z550 showed the smallest. The Neo Spectra ST HV subgroup brushed with Signal White Now showed the highest efficacy in stain removal. The highest surface roughness after brushing was observed in the specimens brushed with Curaprox White is Black, with no statistically significant difference compared to those brushed with Signal White Now. Microhardness was ranked independently of toothpaste and time as Filtek Z550 > Neo Spectra ST HV > Omnichroma. There were statistically significant differences in gloss values depending upon the type of composite resin being tested, the type of toothpaste being tested and the time of testing (p < 0.001).

Whitening toothpastes with blue covarine and activated charcoal partially reduced coffee-induced staining on universal composite resins but caused an increase in surface roughness of composite resins as well as a decrease in gloss. On the other hand, the toothpastes had no significant effect on the microhardness values of the composite resins.

Whitening toothpastes may contribute to the reduction of extrinsic stains on composite restorations. However, since these toothpastes contain abrasives, they may increase the roughness of surface and decrease the gloss of restorative materials. As such, clinicians should be aware of the possible effects of whitening toothpaste on the surface characteristics of composite restorations prior to making recommendations to patients.