Evaluation of human enamel permeability exposed to bleaching agents|
Horning, Diego; Mongruel Gomes, Giovana; Fortes Bittencourt, Bruna; Ruiz, Lucas Manuel; Reis, Alessandra & Mongruel Gomes, Osnara Maria
Aim: To evaluate the human enamel permeability after different external bleaching techniques.
Methods: The coronal portions of 20 maxillary human incisors were covered with an acid
resistant varnish, except the labial surface, to prevent dye penetration of silver nitrate. The
specimens were divided randomly into four groups (n=5) according to the bleaching treatments:
Group 1 (G1) - without bleaching agent (control group), Group 2 (G2) - 35% hydrogen peroxide
(HP) – one session of three 10-min applications, Group 3 (G3) - 35% HP – 2 sessions of three
10-min applications, and Group 4 (G4) - 6% HP – 14 days (1h/day). G1 was exposed to artificial
saliva only and in the other groups the bleaching agents were applied following the manufacturers’
recommendations. After bleaching, teeth were immersed in a 50% silver nitrate solution for 2 h
and photodeveloped for 16 h. Then, three longitudinal slices of each tooth were photographed
by an optical microscope (100x). The degree of dye penetration was analyzed in the middle third
of the dental crowns using a 0 to 4 score system (0= no dye penetration, 1= less than half the
enamel thickness, 2= half of the enamel thickness, 3= full extent of enamel without reaching the
dentin, and 4= tracer agent reaching dentin). The data were analyzed statistically by the Kruskal-
Wallis and Dunn tests (α=0.05).
Results: The median (1st/3rd interquartiles) ranges were: G1:
0(0/0), G2: 2(2/3), G3: 3(3/3) and G4: 3(3/3). G2, G3 and G4 showed significantly higher dye
penetration compared with G1 (p=0.0017).
Conclusions: The use of bleaching agents increased
dental enamel permeability, regardless of the bleaching technique.
dental enamel, bleaching agents, permeability