Specific parameters of infrared LED irradiation promote the inhibition of oxidative stress in dental pulp cells

Abstract

ObjectivesThe present study aimed to assess the oxidative stress and the viability of dental pulp cells stimulated by lipopolysaccharide (LPS) and submitted to photobiomodulation (PBM) with infrared light-emitting diode (LED, 850 nm). DesignThree healthy primary teeth (n = 3) were collected and seeded in 24-well plates with 10 µg/mL of LPS to induce inflammatory mediator formation. The cells were irradiated (850 nm, 40 mW/cm2 and 80 mW/cm2) at the proposed radiant exposures of 0 (control), 4, 15, and 30 J/cm2 shortly after LPS supplementation. The tests were performed 24 h after irradiation to assess mitochondrial activity (MTT assay), the number of viable cells (Trypan Blue), cell morphology (Scanning Electron Microscopy - SEM), and the quantification of Nitric Oxide (NO) and Reactive Oxygen Species (ROS). The data were analyzed using Kruskal–Wallis and Dunn’s tests (p < 0.05). ResultsThe irradiated groups showed larger viable cells number than the non-irradiated group with LPS (p < 0.0001). All irradiation parameters decreased ROS concentrations after LPS application compared to the non-irradiated group (p < 0.05). All irradiation parameters enhanced the NO values compared to those of the control group (p < 0.05). The SEM images showed cells with regular morphology that adhered to the substrate. ConclusionsAccording to the parameters used in this study, the radiant exposure of 15 J/cm2 and irradiance of 40 mW/cm2 were the most effective irradiation parameters to stimulate and modulate oxidative stress in the primary teeth-derived dental pulp cells.