INTRODUCTION
The aesthetic appearance of anterior teeth has become a major concern for patients. Discolored vital anterior teeth have long been treated with different approaches, including crowns, direct and indirect veneers, composite resin restorations, and, most conservatively, bleaching. Both take-home and in-office bleaching techniques have proven effective in whitening teeth, with the latter having the advantage of producing immediate results.1,2
The typical in-office bleaching regimen involves application of a high-percentage hydrogen peroxide formulation to the teeth surfaces, which is activated either chemically or by a light source. The theoretical advantage of using lights is their ability to heat hydrogen peroxide, thereby enhancing the rate of oxygen decomposition. The increased amount of oxygen-free radicals produced thus enhances the release of stain-containing molecules and, therefore, results in enhanced whitening.3,4
The literature is rich with reports concerning the effects of in-office bleaching on natural teeth, but its effect on tooth-colored restorations is not, as yet, fully known. Resin composites are widely used as restorative materials because of their excellent aesthetic properties. However, their initial color may change over time as a result of surface and marginal staining, as well as internal material deterioration.5,6 Staining of resin composites by beverages such as coffee, tea, and soda or by mouth rinse agents has been reported to varying degrees.7–9 In addition to color, surface characteristics contribute significantly to the aesthetic quality of restorations. Surface roughness has a detrimental effect on light reflection, resulting in a dull appearance that stands out from the rest of the teeth. Moreover, rough surfaces promote bacterial plaque adhesion, with subsequent increased staining.10–13
Anterior composite restorations are typically made with either microfilled or microhybrid formulations, depending on the class of the cavity. In the microfilled formulations, ultrafine inorganic filler particles with mean diameters of .04 microns are used. These render such materials highly polishable, but due to the limited amount of inorganic fillers that can be incorporated into such formulations, their mechanical properties are typically less than those of the microhybrid versions. Therefore, their use is limited to non-stress-bearing restorations. In contrast, modern microhybrid composites have a variety of sizes of fine inorganic fillers with a mean value of less than 1 micron. Because of their high inorganic filler content, such materials are suited for the stress-bearing situations such as Class 4 restorations.
Monaghan et al14 reported that 30% hydrogen peroxide bleaching produced a significant color change in freshly prepared specimens of different composites. On the other hand, Hubbezoglu et al15 found that bleaching with 35% hydrogen peroxide resulted in composite resin color change values of a lesser magnitude. However, the ability of bleaching to remove acquired stains has not, as yet, been fully investigated. With regards to surface properties, some reports indicated that bleaching agents containing 30 to 35% hydrogen peroxide did not affect the surface texture as revealed by profilometric analysis.16,17 Nevertheless, analysis of surface reflectance showed significant changes in microfilled and hybrid composites.16
The purpose of this study was to determine color change and surface roughness of two composites, a microfilled and a microhybrid, when subjected to coffee staining and bleaching using different light- and chemically activated in-office bleaching systems. The null hypothesis was that the two composites will respond similarly to the different bleaching agents.