ABSTRACTPain is a common undesirable side effect of dental bleaching. This symptom is related to the contact the dental pulp with irritating substances leached from the bleaching agents. To circumvent this problem the phototherapy with low intensity lasers could be used because it presents analgesic and antiinflammatory properties. The aim of this in vitro study is to analyze the effect of phototherapy with visible red laser in low intensity on the viability of cells previously stimulated with culture medium conditioned by dental bleaching gel. Human dental pulp fibroblasts (FP5 cell line) will be plated in 96 wells microtitration plates (1x10³ cells/well). The cells will be placed in contact with the culture medium conditioned by the bleaching gel (35% H2O2) during 40 min in order to simulate the time used for the clinicians to perform the dental bleaching. Then, the cultures will be irradiated or not (negative control) with an AlGaInP diode laser (» = 660nm, 40 mW, spot size 0.04 cm2) in punctual and in contact mode. Non irradiated cells grown in fresh culture medium will serve as positive control. Three energy densities will be tested (4, 6 and 10J/cm2, during 4, 6 and 10 s, respectively). All groups will be under the same environmental conditions. The cell viability will be obtained by the measurement of the mitochondrial activity using the MTT reduction test immediately and 24 h after the irradiation. The results will be compared using a statistical test to be determined after the analysis of the homogeneity of the data.
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