SCIENTIFIC ARTICLE Australian Dental Journal 2010; 55: 390–398 doi: 10.1111/j.1834-7819.2010.01259.x Effect of bleaching versus repolishing on colour and surface topography of stained resin composite M Abd Elhamid,* R Mosallam  *El Seka El Haded Hospital, Cairo, Egypt.  Department of Operative Dentistry, Faculty of Oral and Dental Medicine, Cairo University, Egypt. ABSTRACT Background: The aim of this study was to examine the effect of ozonated gel, carbamide peroxide bleaching agent and polishing paste on the colour and surface topography of stained resin composite. Methods: Ninety disc-shaped resin composite specimens were used in this study. They were randomly divided into three groups of 30 specimens each according to the immersion solutions used, i.e., tea, cola or artificial saliva. Each group was further subdivided into three equal subgroups (n = 10) according to the type of whitening treatment applied; 30% carbamide peroxide, ozonated KY gel or polishing paste. Colour and surface roughness was measured at baseline, after immersion, also following whitening procedures by using a stereomicroscope. The results were recorded, tabulated and statistically analysed. Results: The colour values of artificial saliva displayed the highest statistically significant mean colour difference compared to cola and tea. However, there was no statistically significant difference in surface roughness. Also, a superior whitening effect was demonstrated with ozonated gel. Ozonated gel showed statistically significant lowest roughness compared to both carbamide peroxide and polishing paste. Conclusions: Immersion solutions have a positive influence on the colour of resin composite. Also, ozonated gel is an efficient bleaching agent with the least adverse effect on surface roughness. Keywords: Laboratory research, ozonated gel, carbamide peroxide bleaching, polishing paste, tooth bleaching. Abbreviation: CIE = Commission Internationale de l’Eclairage. (Accepted for publication 2 March 2010.) INTRODUCTION Resin composites were introduced into the field of dentistry in the 1940s to solve an aesthetic rather than a functional problem. Resin composites are widely used because of their good aesthetics, adequate strength, moderate cost compared with that of ceramics, and their ability to bond to the tooth structure. Colour matching of resin composite restorations with the tooth colour is good due to the increase in the number of available colour shades. In addition, the development of microfilled and nanofilled types of resin composites provide restorations with a good surface finish and a smooth texture to give a more natural appearance. 1,2 The success of dental resin composite restorations depends mainly on their surface properties and colour stability. However, discolouration after prolonged exposure to the oral environment is still a major problem, leading to an unacceptable colour match of the restoration, patient dissatisfaction and the addi- tional expense for replacement. 3 The degree of colour change can be affected by a number of factors, including the structure of resin composite, the characteristics of the filler particles, the degree of polymerization and water sorption. Coloured food materials and drinks, smoking habits and oral hygiene are also important factors affecting the colour of resin composites. Finishing and polishing procedures may also influence resin composite surface quality. In addition, roughening of the surface caused by wear may affect the gloss and, consequently, increase extrinsic staining. 4 There are many ways to remove superficial stains from resin composite restorations. For example, tooth- brushing, polishing techniques or bleaching procedures using either the commercially available bleaching agents or ozone which has been recently used in bleaching because of its strong oxidizing capacity. 5 The removal of stains with toothbrushing is a slower process. Therefore, it is preferred to use more rapid methods, such as polishing or bleaching techniques. 6 However, polishing procedures sometimes cannot restore resin composite restorations to their original 390 ª 2010 Australian Dental Association Australian Dental Journal The official journal of the Australian Dental Association