In vitro effect of low intensity laser on the cytotoxicity produced by substances released by bleaching gel

Abstract

This in vitro study aimed to analyze the effect of different parameters of phototherapy with low intensity laser on the viability of human dental pulp fibroblasts under the effect of substances released by bleaching gel. Cells were seeded into 96 wells plates (1 x 10 3 cells/well) and placed in contact with culture medium conditioned by a 35% hydrogen peroxide bleaching gel for 40 minutes, simulating the clinical condition of the in-office bleaching treatment. Cells cultured in ideal growth conditions served as positive control group (PC), and the cells grown in conditioned medium and non-irradiated served as negative control group (NC). Cells grown in conditioned medium were submitted to a single irradiation with a diode laser (40 mW, 0.04 cm²) emitting at visible red (660 nm; RL) or near infrared (780 nm; NIR) using punctual technique, in contact mode and energy densities of 4, 6 or 10 J/cm². The cell viability was analyzed through the MTT reduction assay immediately and 24 hours after the irradiation. The data was compared by ANOVA followed by the Tukey's test (p ≤ 0.05). The cell viability increased significantly in 24 hours within each group. The PC presented cell viability significantly higher than NC in both experimental times. Only the NIR/10 J/ cm² group presented cell viability similar to that of PC in 24 hours. The phototherapy with low intensity laser in defined parameters is able to compensate the cytotoxic effects of substances released by 35% hydrogen peroxide bleaching gel.

Effect of low-level laser therapy on odontoblast-like cells exposed to bleaching agent

“…However, the laser protocols tested were not capable of influencing the metabolism of previously damaged odontoblast-like cells. These data were not corroborated by results from in vitro studies in which osteoblasts, odontoblasts, or even fibroblasts exposed to bleaching agents were positively modulated by low-level laser irradiation [26,29,30]. The differences observed when results of these investigations were compared with those from the present study may be at least partly due to the variable parameters of the laser protocols tested (wavelength, potency, energy density).…”

“…Analysis of the data obtained in the present study, and other previous investigation [26] , indicated that low-level laser irradiation may represent an alternative therapy for the modulation of pulp cell responses against the toxic effects caused by bleaching agent components capable of diffusing across dental hard tissues, i.e., enamel and dentin. Nevertheless, other factors, such as the number of laser irradiations and the energy doses used, need to be evaluated in further studies.…”

“…Researchers have worked hard to obtain dental bleaching protocols that provide an effective aesthetic clinical outcome without causing collateral deleterious effects to pulp cells [8,9,26]. In a current study, Lima et al [8,9] demonstrated that the administration of sodium ascorbate before the dental bleaching treatment may reduce the cell damage caused by toxic sub-products released from bleaching agents.…”

Cytotoxicity of non-vital dental bleaching agents in human gingival fibroblasts

“…In this study, the conditioned medium remained in contact with the cells for just 30 min, because pilot studies have shown that after this period, the bleaching agents becomes extremely toxic, making it impossible to realize this type of research. This data is according with the study of Dantas et al [26], that placed the conditioned medium is contact with the cells for 40 min. Moreover, Soares et al [27], evaluated the cytotoxicity of 35% Hydrogen peroxide and different periods of contact of the gel with odontoblast-like cells (MDPC-23) and conclude that cytotoxic effects were proportional to the contact time of the bleaching gel.…”

Hypoplastic Enamel Treatment in Permanent Anterior Teeth of a Child

“…The AAPD does not indicate the total arch treatment for patients with mixed dentition. 15 Taking into account that a young patient's pulp is wider than that of an adult patient, and that the diffusion of hydrogen peroxide at high concentrations into dental tissues is extensive, [16][17][18] a safer treatment was selected for the current patient: 10% carbamide peroxide, reducing the possibility of sensitivity. [19][20][21] This treatment was performed in an individualized way for this patient: using direct applications on the more pigmented areas followed by application with personal trays for 14 days, and only with the affected teeth.…”