Effect of bleaching agents containing fluoride or calcium on enamel microhardness, roughness and permeability|
Rauen, Charles Alex; Filho, Júlio Cezar Chidoski; Bittencourt, Bruna Fortes; Gomes, Giovana Mongruel; Gomes, João Carlos & Gomes, Osnara Maria Mongruel
Aim: To evaluate the effect of different in-office bleaching agents on the permeability, roughness
and surface microhardness of human enamel.
Methods: For evaluation of roughness and
microhardness, 40 hemi-faces of 20 premolars were subjected to initial roughness (Ra parameter)
and microhardness (VHN) measurements. Thirty-two premolar’s crowns were used for
permeability test. Then, all specimens were randomly divided into four groups: C - without
bleaching (control), HP35 - bleaching with 35% hydrogen peroxide (HP), HPF38 - 38%
HP+fluoride, HPC35 - 35% HP+calcium. Final roughness (FR) and microhardness (FM)
measurements were evaluated. For permeability, the 32 crowns were immersed in 1% sodium
hypochlorite (20 min) and silver nitrate solutions (2 h) and subjected to developing solution under
fluorescent light (16 h). Three sections from the crowns were analyzed in light microscope (100x)
to evaluate the scores of permeability: Score 0 - no tracer agent penetration; Score 1 - less than
half the thickness of enamel penetration; Score 2 - tracer agent reaching half the enamel thickness;
Score 3 - entire enamel depth penetration, without reaching dentin and Score 4 - tracer agent
reaching dentin. For roughness and microhardness evaluation were used one-way ANOVA and
Dunnet post-test for independent samples, and t test for paired samples. For permeability, the
data were analyzed by Kruskal Wallis and Dunn tests.
Results: A significantly higher permeability
and surface roughness were observed in groups HP35, HPF38 and HPC35 compared to the C
group, as well as decreased microhardness (p<0.05).
Conclusions: All bleaching agents
increased permeability and surface roughness, and decreased microhardness of human enamel;
thus, the addition of fluoride or calcium was not beneficial.
tooth bleaching; dental enamel permeability; hydrogen peroxide; surface properties