Evaluation of human enamel permeability exposed to bleaching agents

Abstract

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 (1 st /3 rd 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.

Effect of bleaching agents containing fluoride or calcium on enamel microhardness, roughness and permeability

“…The methodology of permeability analysis was based on previous studies 5,7,22 . After bleaching, all specimens, including the control group (n=32), were stored in a dark environment in artificial saliva for 48 h at 37 o C. The lingual and proximal surfaces and the CEJ were sealed with cyanoacrylate resin (Super Bonder Loctite, Henkel Ltda, São Paulo, SP, Brazil) and a nail varnish to prevent dye penetration of silver nitrate (tracer agent) through this area.…”

“…There is concern that bleaching agents (hydrogen peroxide and carbamide peroxide) bring some damage to enamel surface, like increased roughness [3][4] and permeability [5][6] . This effect was demonstrated in a previous study 7 where silver nitrate penetration in tooth structure after bleaching was performed and it was found that these agents might diffuse into dentin by opening channels in tooth structure.…”

The effect of in-office bleaching materials with different pH on the surface topography of bovine enamel

“…The enamel is composed of inorganic material contains 97% of its total weight and essentially constituted of hydroxyapatite, 1% of organic material; primarily proteins such as amelogenin and enamelin, and 2% of water 15) . The organic layer is a semipermeable membrane that allows hydrogen peroxide to penetrate the tooth structure and react chemically with tooth discoloration and the tooth structure 16) . Enamel hardness is related to the mineral and protein content.…”

Perbandingan kekerasan mikro dentin mahkota setelah aplikasi berbagai bahan bleaching intrakoronal

“…17 Perbedaan nilai rata-rata kekerasan mikro dentin dalam penelitian ini dapat juga dikarenakan berat molekul bahan bleaching yang rendah. 18 Hidrogen peroksida memiliki berat molekul lebih rendah (34,0147 g/mol) dibandingkan sodium perborat (153,86 g/mol). Berat molekul rendah dapat menyebabkan hidrogen peroksida berpenetrasi ke dalam struktur gigi dan melepaskan oksigen yang akan merusak ikatan ganda dari kandungan organik dan anorganik di dalam tubulus dentin.…”