Effect of Fluoride Treatments on Bleached Enamel Microhardness and Surface Morphology.
OBJECTIVE
To evaluate the effect of three different fluoride treatments on the surface microhardness and morphology of human enamel exposed to two different bleaching agents.


METHODS
Twenty-three extracted human third molars were sectioned to obtain 90 enamel fragments, mounted on acrylic resin supports, polished and randomly divided into 9 groups (n = 10). The specimens were exposed to a combination of two bleaching agents (22% carbamide peroxide [CP] and 38% hydrogen peroxide [HP]) and three fluoride treatments (0.05% NaF daily, 0.2% NaF weekly and 5% NaF final topical fluoridation). The positive control group specimens were not exposed to bleaching agents or fluoride treatments. The negative control group specimens were exposed to the bleaching agents but none of the fluoride treatments. All specimens were stored in artificial saliva during the entire experiment, and enamel microhardness was evaluated. Surface microhardness data were statistically analysed using two-way ANOVA and Tukey's post-hoc test at a significance level of α = 0.05. Additionally, three specimens of each experimental group were examined under SEM.


RESULTS
Two-way ANOVA revealed significant differences between the experimental groups (p < 0.05). The bleached group specimens which did not receive fluoride treatment exhibited significantly lower microhardness than those treated with fluoride (p < 0.05). Varying degrees of surface changes were observed among the experimental groups.


CONCLUSIONS
Both bleaching agents significantly reduced enamel microhardness and the topical fluoride treatments after bleaching significantly enhanced the surface microhardness of the enamel. The surface morphology of the enamel was altered after bleaching and fluoride treatments.
Dimitrios
D
Dionysopoulos
Eugenia
E
Koliniotou-Koumpia
Kosmas
K
Tolidis
Paris
P
Gerasimou
D000704:Analysis of Variance; D003743:Dental Enamel / Q000187:drug effects*; D006244:Hardness / Q000187:drug effects*; D006801:Humans; D011897:Random Allocation; D012969:Sodium Fluoride / Q000008:administration & dosage / Q000494:pharmacology*; D013499:Surface Properties / Q000187:drug effects; D058205:Tooth Bleaching Agents / Q000494:pharmacology*
D058205:Tooth Bleaching Agents; D012969:Sodium Fluoride