Bleaching effectiveness, hydrogen peroxide diffusion, and cytotoxicity of a chemically activated bleaching gel

Abstract

Although the chemical activation of H2O2 by adding FeSO4 to the bleaching agent improved the bleaching effectiveness, this metal ion has no significant protective effect against pulp cell cytotoxicity.

Immediate and late analysis of dental pulp stem cells viability after indirect exposition to alternative in-office bleaching strategies

“…In a histological analysis of human mandibular incisors submitted to this therapy, the occurrence of areas of partial coronal pulp necrosis associated with an inflammatory reaction in the subjacent tissue was demonstrated [7]. These clinical data corroborate laboratory studies, in which researchers demonstrated the occurrence of intense trans-enamel and trans-dentinal cytotoxicity to pulp cells when bleaching gels with elevated concentrations of H 2 O 2 were applied to tooth enamel [4,8].…”

“…For each period, the cells were incubated with MTT solution (5 mg/mL) diluted in DMEM (1:10), and were incubated at 37°C and 5 % CO 2 for 4 h. Next, the formazan crystals formed in the viable cells were dissolved in acidified isopropanol, and the absorbance was measured in an Elisa reader at 570 nm (Tp Reader, Thermoplate, Nanshan District, Shenzhen, China) [8,9]. The mean absorbance value of the negative control group in time interval T1 was considered 100 % cell viability, with the percentage cell viability for each experimental group at T1 and T2 being calculated from this parameter.…”

“…Obtaining the specimens Enamel/dentin disks, from bovine incisors, measuring 5.6 mm in diameter and 3.5 mm thick were used in this study, as previously described [4,8,11]. The enamel surface of the disks was cleaned with solution of pumice stone and water using a low-speed hand piece.…”

“…Up to the present time, at-home bleaching using 10 % carbamide peroxide (CP) has been considered the safest bleaching therapy for the pulp-dentin complex [8][9][10][11]. However, this technique has several limitations, such as the fact that the professional does not directly supervise the entire treatment and the long bleaching time needed to achieve significant color improvement as well as the risk of gel application over exposed dentin and soft tissue [10].…”

“…However, this technique has several limitations, such as the fact that the professional does not directly supervise the entire treatment and the long bleaching time needed to achieve significant color improvement as well as the risk of gel application over exposed dentin and soft tissue [10]. Therefore, alternative professional bleaching therapies, with the goal of minimizing the toxic effect on pulp cells, have been the target of diverse contemporary researches [4,8]. Recently, it was demonstrated that a reduction from 35 to 17.5 % in the concentration of H 2 O 2 in a bleaching gel, and a reduction in the time of the product in contact with enamel, resulted in effective bleaching associated with a reduction of around 60 to 95 % in H 2 O 2 diffusion through the tooth structure, when compared with the traditional therapy [14].…”