Influence of a Bleaching Agent on Stained Direct Composite Resin

Despite the phenomenal strides in research of dental resin composites regarding their physical and mechanical properties, discolouration, either intrinsic or extrinsic still remains a major drawback and is one of the main reasons for the replacement of these restorations. Objectives: To determine the effect of a tooth bleaching agent on the colour of a stained direct composite resin. Methods: 60 disc shaped specimens (9 x 2mm) of Filtek Supreme XT were prepared. They were randomly divided into 3 groups (n = 20) and exposed to either one of two experimental staining agents, tea or red wine, or artificial saliva (control) continuously over a 7-day period. The specimens were then bleached with Opalescence Xtra Boost, a chemically activated in-office whitening agent for 3, weekly sessions of 30 minutes each, broken into 2, fifteen minute cycles. Colour measurements were carried out at baseline, after each day of staining, at the end of active bleaching treatment and 1-week post-bleaching using a spectrophotometer. The CIE L*a*b* colour space was used and colour changes were monitored using ΔE. A ΔE ≥ 3.3 represented colour changes that were deemed clinically noticeable. Data were analysed using Wilcoxon Signed Rank Sum Test with a significance level set at p≤ 0.05. Results: Both staining solutions discoloured the composite resin samples, but red wine produced greater colour changes than tea. After bleaching, the specimens in the tea group reverted to baseline colour with a ΔE ≤ 3.3 but those in the red wine group did not revert to baseline values with a ΔE ≥ 3.3. Conclusions: Filtek Supreme XT, a nanocomposite, is susceptible to discolouration by chromogenic beverages. Red wine produced deeper staining than tea. Opalescence Xtra Boost was effective in removing tea stains but not red wine stains.