Influence of a bleaching agent on stained direct composite resins
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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. Toothbrushing and polishing procedures have been attempted to eliminate extrinsic staining without optimal results. Vital tooth bleaching has over 90% success rates in whitening discoloured teeth and this may be an alternative treatment modality for discoloured composite resins. Aim: The aim of this study was to determine whether tooth bleaching agents alter the colour of stained direct composite resins. Material and Method: 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. They were all then bleached with Opalescence Xtra Boost, a chemically activated in-office whitening agent for 3, weekly sessions of a half hour each, broken into 2, fifteen minute cycles. Colour determinations were made using a reflectance spectrophotometer, from baseline, after each day of staining, after the bleaching treatments and after a 1 week rehydration period. The CIE Lab colour space was used and colour changes were monitored using ΔE, that was calculated during intervals between the experimental episodes using L, a and b values. A ΔE ≥ 3.3 represented colour changes that were deemed clinically noticeable. Data analysis was carried out using Microsoft excel and a non-parametric test (Wilcoxon Signed Sum Rank Test) with a significance level set at ≤ 0.05 for colour differences that are statistically significant. 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. Conclusion: 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.