In-office Bleaching Effects on Color Changes of Tooth-colored Restoratives

Objectives: The study aim was to determine the effects of in-office bleaching on color changes of tooth-colored restorative materials. Methods: Metal molds were used to fabricate 40 samples (8mmdiameter and 2mm thickness) each of a microfilled composite (A110,3M) and a glass-ionomer (Photac-Fil,3M); light-cured according to manufacturer's instructions. The air-inhibited layer was polished off and the samples stored in distilled water at 100% humidity at 37^oC throughout the study. Samples of each restorative material were randomly divided into four groups of 10 each and treated as follows: Group 1: no bleaching (control), Group 2: 15%H₂O₂ light-activated bleaching (Britesmile); Group 3: 35%H₂O₂ (OpalXtra, Ultradent); Group 4: 38%H₂O₂(OpalXtraBoost, Ultradent). Bleaching was carried out for 1 hour according to manufacturers' instructions after 1 week of storage. Shade measurements, recorded as CIELAB co-ordinates using a Minolta colorimeter, were taken at pre-bleaching(t1), immediately after bleaching(t2), 1-week(t3) and 1-month(t4) post-bleaching. Color change was calculated as ΔE=[(ΔL)² + (Δa)²+(Δb)²]^1/2. Data was analysed using repeated measures ANOVA/Bonferonni correction at significance level 0.05. Results: Color change immediately after bleaching was treatment dependent for both materials. Control groups for both materials showed color changes over time. However, bleaching treatment modified this effect for composite only. For glass-ionomer, significant color change was seen in Groups 2, 3 and 4 only immediately after bleaching. For composite, significant color change was seen at all time intervals for Group 2. Groups 3 and 4 showed significant color change immediately after bleaching and 1-month after. Color change after 1-month post-bleaching was dependent on both material and treatment method. Clinically, color change ΔE≥3.3 is perceptible to human eye (Ruyter etal, 1987). This was seen in composite/Britesmile group immediately after bleaching. Conclusions: Within the study limits, color change was dependent on material type, treatment method and time. Only composite/Britesmile group showed clinically perceptible color change immediately after bleaching.