Effect of various tooth-whitening products on enamel microhardness

Abstract

Objectives: The purpose was to evaluate the effect of various tooth-whitening products on the South African market, containing carbamide peroxide (CP) or hydrogen peroxide (HP), on enamel microhardness. Methods: Enamel blocks were exposed to: Nite White® ACP 10% CP (group 2, n=10); Yotuel® Patient 10% CP (group 3, n=10); Opalescence® PF 10% CP (group 4, n=10); Opalescence® PF 20% CP (group 5, n=10); Opalescence® Treswhite Supreme 10% HP (group 6, n=10); Yotuel® 10 Minutes 30% CP (group 7, n=10); Opalescence® Quick 45% CP (group 8, n=10), Yotuel® Special 35% HP (group 9, n=10), Opalescence® Boost 38% HP (group 10, n=10) according to the instructions of the manufacturers. The control group (1) was enamel blocks (n=10) kept in artificial saliva at 37˚C without any treatment. The microhardness values were obtained before exposure and after a 14-day treatment period. Specimens were kept in artificial saliva at 37˚C between treatments. Data were analysed using Kruskal-Wallis one-way ANOVA and Tukey-Kramer Multiple Comparison Test. Indent marks on the enamel blocks were also examined under the scanning electron microscope. Results: All whitening products decreased enamel microhardness except group 10. Only Groups 2,3,4,5 and 7 showed significant decrease in enamel microhardness as compared to the control group (p<0.05). Groups 2, 3 and 7 differed significantly from all the other groups (p<0.05). The highest damage was recorded for group 2 (Nite White® ACP 10% CP), which differed significantly from groups 3 and 7. SEM images also showed damage to enamel. Conclusions: All products damaged enamel except Opalescence® Boost 38% HP. In general, the products containing carbamide peroxide were more damaging while longer treatment periods influenced the microhardness values negatively. Nite White® ACP without fluoride showed relatively more damage than all the other products containing fluoride.