Influence of Whitening on Gloss and Roughness of Resin Composites

Objectives: The aim of the present study was to assess in vitro the influence of whitening therapy associated with induced aging on gloss and roughness of microparticled and nanofilled resin composites.
Methods: Two resin composites, nanofilled (Z350 XT – 3M/ESPE) and microparticled (Durafill – Heraeus Kulzer) were tested. Two whitening materials were used; 38% hydrogen peroxide (Opalescence Boost - Ultradent) and 15% carbamide peroxide (Opalescence PF 15% - Ultradent). Sixty specimens of each resin composite were fabricated per analysis (gloss or roughness). Specimens were divided into three groups: without whitening - NW, 38% hydrogen peroxide - HP (1h weekly, 2 weeks), and 15% carbamide peroxide - CP (8h daily, 2 weeks). Gloss evaluation (GU) was performed with Novo-Curve (TM RHOPOINT, East Sussex, England), and surface roughness (Ra) was determined with Maxsurf XCR profilometer (Mahr - Goettingen, Germany). Repeated measures ANOVA and Tukey’s test analyzed data, both with 5% significance level.
Results: Gloss increased after whitening procedures (p<0.0001) (GU=73.16 and 76.87). There were differences between resin composites (p<0.0001) (GU=68.24 and 81.79, for Durafill and Z350 XT, respectively). No differences were detected for whitening protocols (p=0.4986). Roughness was resin dependent (p=0.0103), with lower roughness for Durafill (Ra=0.1209 and 0.3186 for Durafill and Z350 XT, respectively). The whitening protocol did not influence roughness of both resin composites (p=0.6686) (Ra=0.1742, 0.2290, and 0.2562, for NW, HP, and CP, respectively).
Conclusions: The increase in surface gloss for the two tested resin composites is independent of their roughness. Gloss might be related to other variables, namely: color and translucency.