34 Archives of Orofacial Sciences The Journal of the School of Dental Sciences Universiti Sains Malaysia Arch Orofac Sci (2013), 8(1): 34-40. Original Article Effect of home bleaching agents on the hardness and surface roughness of resin composites Farahiyah Mohamad Taib, Zuryati Ab Ghani*, Dasmawati Mohamad School of Dental Sciences, Health Campus, Universiti Sains Malaysia, 16150, Kubang Kerian, Kelantan, Malaysia. * Corresponding author: zuryati@kb.usm.my Submitted: 05/11/2012. Accepted: 04/04/2013. Published online: 04/04/2013. Abstract Ten percent carbamide peroxide is an effective, safe home bleaching agent. Higher concentrations are more effective, but there are mixed reports on their hardness and surface roughness effects on resin composites. To evaluate the effect of home bleaching agents; Opalescence Now 10% carbamide peroxide (Ultradent Products, USA) and Perfect Bleach 17% carbamide peroxide (Voco, Germany) on the surface hardness of microhybrid resin composites; Filtek Z250 (3M ESPE, USA) and Point 4 (Kerr, USA) and their surface roughness of selected treatment. Thirty specimens were prepared using acrylic moulds (4mm diameter x 2mm thick). N=5 controls placed in distilled water for 14 days. N=5 treated with Opalescence, and n=5 treated with Perfect Bleach for 2 hours every day for 14 days. Surface hardness was tested using Vickers hardness tester FV-7 (Future Tech Corp, Japan). Data analyzed with Mann-Whitney test with (P<0.05) considered significant. One specimen from 10% carbamide peroxide group was randomly selected for surface roughness, (Ra) evaluation using Atomic Force Microscopy (Ambios Technology, California, USA). All tested materials showed no significant changes in surface hardness after 14 days bleaching with 10% and 17% carbamide peroxide. However, AFM evaluation revealed an increase in Ra in both composites with 10% carbamide peroxide. Fourteen days bleaching using 10% and 17% carbamide peroxide did not have different effect on the surface hardness of Point 4 and Filtek Z250. The Ra increased after bleaching in both composites. The AFM surface roughness evaluation observed in 3D images shows to be a promising technique. Keywords: Bleaching, composite, hardness, surface roughness. Introduction Bleaching is one of the options to improve aesthetics in a dental restorative treatment. The use of bleaching has widened after the introduction of home bleaching treatment systems in the 1990s (Haywood and Heymann, 1989), almost a century after the first use of bleach to whiten teeth in the late 1870s (Fasanaro, 1992). Bleaching agent works by the decomposition of peroxides from hydrogen peroxide or its compounds such as carbamide peroxide (CP) into unstable free radicals. These radicals further breakdown into large pigmented molecules either through oxidation or reduction reaction. The oxidation or reduction process changes the chemical structure of interacting organic substances of tooth, which result in colour change (Greenwall, 2001). The types of bleaching methods include non vital bleaching, in-office professional bleaching and home bleaching. Night guard home bleaching uses a relatively low level of whitening agent, usually 10% CP and applied to the teeth via a custom fabricated mouth guard and is worn at night for at least 2 weeks duration. This relatively low concentration was proven to have minimal effects on the soft tissues of the mouth (Kelleher and Roe, 1999) and also accepted by the American Dental Association as the standard bleaching concentration (American Dental Association, 2006). Studies had confirmed that higher concentration of bleaching agents will whiten the tooth faster (Kihn et al. 2000; Braun et al. 2007). It is then imperative to study the impact of higher