Image analysis on the color stability using CIELAB color processing S Image analysis on the color stability using CIELAB color processing S.M. MASUDI1, B.I. IRAWAN2, S.I. IRAWAN2 and N.S. MASUDI1 1School of Dental Sciences, Universiti Sains Malaysia, Kubang Kerian, Malaysia 2Stanford University, 450 Serra Mall Stanford, CA 94305, USA. 510 ABSTRACT RESULTS Objective: Vital tooth bleaching such as carbamide peroxide were found to have a profound influence on the color of tooth-coloured restorations. This in vitro study is designed to evaluate the effect of  Home and Office bleaching agents, on color stability of dental restorative filling materials. Method:  Ultradent Opalescence PF Home and Ultradent Opalescence Boost Office were used as home and office bleaching agents. As for the restorative materials, nanofilled composite Filtex Z350 XT, the sub-micron composite Estelite Sigma Quick, and nanofilled glass ionomer Ketac N100 nano ionomer were used. Samples were fabricated using plexiglass discs of 6 mm diameter and 2 mm height in three groups: I (Filtex Z350 XT), II (Estelite Σ), and III (Ketac Nano) where n=90. Each group was further divided into three subgroups (n=10): A (home bleaching), B (office bleaching), and C (Distilled water) as control. Samples were bleached and rinsed following the manufacturer’s instructions for a two week period. Discoloration can be evaluated with different instruments and techniques. The Commission Internationale de I’Eclairage (CIE L*,a*,b*) system was chosen for image processing. Photos of samples were taken with a Nikon D200 digital camera and CIELAB color values were analyzed from digital raw images taken from the samples using software Photoshop CS3 Ver 10.0. Result:  All dental restorative materials showed significant color changes (ΔE).  Statistical significance was declared if the P value was ≤ 0.05. The mean color change of Estelite Σ (3.82±1.6) was the highest, followed by Ketac Nano (2.97±1.2). Filtex Z350 XT showed the least color change (2.25±1.0) with all bleaching agents. Conclusion:  Sub-micron resin composite showed the highest color changes followed by Ketac nano-ionomer. The Nano filled composite was found to be highly stable in terms of color. Nano filled composite and glass ionomer showed better color stability compared to microfilled tooth color materials.   Table 1. Comparison of ∆E between 3 different tooth-colored restorative materials after bleaching (between resotrative materials). Group Subgroup Mean±SD P Value Filtex Z350 XT Office Bleaching 2.6 ±1.1 0.039* Home Bleaching 2.2±1.0 Estellite Σ Quick 3.0±1.2 0.002* 3.7±1.5 Ketac N100 2.7±1.2 0.016* 3.1±1.2 Mann-Whitney Test p < 0.05 INTRODUCTION Materials were divided into three groups as follows: Group I (n = 30): Filtex Z350 XT nanofilled composite (3M-ESPE, USA); Group II (n = 30): Estelite S sub-microfilled composite (Tokuyama Dental, Japan), and Group III (n = 30) Ketac N100 (3M-ESPE, USA) nano ionomer cement. Nano GIC were and light-cured for 10”and the two composite materials were placed incrementally into the discs and light-cured for 20” after each increment (Fig. B). All materials (n = 90) were polished with soflex disc (3M -ESPE, USA) up to extra fine discs (Fig. C). Each group was further divided into three subgroups of 10 and were subjected to bleaching agents. Subgroup A were treated with Opalescence home bleaching PF (Ultradent, USA) and bleached for 1 hour per day. Subgroup B were treated with Opalescence office bleaching Chair-side Whitening Boost (Ultradent, USA). Subgroup C were treated with distilled water as control. This process was repeatedly for 2 weeks and kept in distilled water at 37°C. Samples were then put on top of a neutral grey card and photos were taken with Nikon D200 digital camera. CIELAB color values were analyzed using software Photoshop CS3 Ver 10.0. and Mann-Whitney test were used to determine the significant color change (∆E) of the restorative materials between two color positions. Table 2 Table 2. Comparison of ∆E value of the tooth-colored restorative materials after bleaching (between the bleaching agents). Over the past decade, multiple studies have evaluated the effects of bleaching agents on restorative materials. These bleaching agents were found to have a profound influence on the color behaviour of tooth-colored restorations. Thus, as result of bleaching, there could be incorrect color matching and major esthetic failure. Standard Comision Internationale de L, Eclairage (CIELAB) is color system that assesses chromatic differences in Colorimetry. The use of digital cameras to capture accurate color in dentistry is advantageous in the color replication process, and ease to share calibration models.   Group Subgroup Mean±SD P Value Office Bleaching Filtex Z350 XT 2.6 ±1.1 0.001* Estellite Σ Quick 3.0±1.2 Ketac N100 2.7±1.2 Home Bleaching 2.2±1.0 3.7±1.5 3.1±1.2 Mann-Whitney Test p < 0.05 DISCUSSION PURPOSE The three restorative materials showed significant color changes (ΔE) P<0.05. From the results we also determined that the mean color change of all tested restorative materials was greater for in home bleaching than office bleaching. This may be due to the longer application time, in spite of the fact that the concentration of hydrogen peroxide is lower for home bleaching agents. The aims of this experimental in vitro study is to evaluate the effect of bleaching agents on the color stability of tooth colored restorative materials, to compare the color stability between 3 different tooth- colored restorative materials after bleaching, and to compare the effect of home bleaching agent vs. office bleaching agent on 3 tooth-colored restorations. In assessing the chromatic differences, the CIELAB system was chosen for this study. CONCLUSION Sub-micron resin composite showed the highest color changes followed by Ketac nano-ionomer. The Nano filled CR was found to be highly stable in terms of color. Nano filled composite and glass ionomer showed better color stability compared to microfilled tooth color materials. MATERIALS AND METHODS Samples in shade A2 were fabricated using plexiglass discs of 6 mm diam. and 2 mm in height covered by polyethylene sheets and pressed with glass glass slides (Fig. A). Research presented at the 43rd Annual Meeting of the AADR and 38th Annual Meeting of the CADR, March 19-22, 2014