In vitro investigation of the effects of different tooth whitening products on enamel

The purpose of this in vitro study was to evaluate the effects of different over-the-counter whitening products on the microhardness, surface roughness, color, shear bond strenght and surface charecteristics of enamel comparing with an at-home bleaching agent containing 10% carbamid peroxide.Seventy eight extracted human maxillary central teeth were used in the study. After the crowns were seperated from the roots and mounted into acrilic blocks the enamel surfaces were flattened with a series of sandpapers. and the specimens were then divided into 6 groups (n=13). Group 1: Opalescence PF %10, Group 2: Opalescence Go, Group 3: Opalescence Whitening toothpaste, Group 4: Listerine Healthy White, Group 5: Cavex Bite&White.The specimens in Group 6. recieved no treatments. All specimens were subjected to microhardness, surface roughness. and color tests except Group 6 before application of bleaching products. OTC products were applied according to the instructions of the manufacturers and the tests were repeated. The specimens were immersed in artificial saliva for 14 days. At the end of 14 days the measurements were again repeated. During the test period, all specimens were kept in artificial saliva at 37⁰C. One specimen from each group was examined by SEM. The specimens including the Group 6 underwent to shear bond strenght test. Data were analysed statistically by ANOVA, Fisher's LSD and Welch tests.Opalescence PF %10, Opalescence Go, Listerine Healthy White and Cavex Bite&White decrased the microhardness (p<0.05); no significant change was observed in microhardness of enamel treated with Opalescence whitening toothpaste (p>0.05). Opalescence PF %10, Opalescence Go ve Opalescence whitening toothpaste increased the surface roughness(p<0.05); where as Listerine Healthy White and Cavex Bite&White did not make any change (p>0.05). Opalescence PF %10 showed the highest color change(p<0.05), however no significant change was observed with the Opalescence whitening toothpaste(p>0.05).Among the tested OTC products, only Opalescence PF %10 significantly decreased the shear bond strenght of the enamel(p<0.05).No significant change was observed in SEM evaluations. Bleaching products affected enamel surfaces differently after bleaching or 14 days after bleaching. All the tested OTC products affected the microhardness, surface roughness, color and shear bond strenght of enamel differently. Keywords: bleaching, microhardness, surface roughness, shear bond strenght