Several studies have demonstrated that phototherapy may increase dentin matrix synthesis and deposition by odontoblasts as well as decrease the local inflammatory reaction. The light source generated by light emitting diodes (LED) has been widely studied, and several positive effects in tissue repair have been reported. Therefore, the objective of this study will be to evaluate the effect of LED 850 nm on stem cells from dental pulp and dentin-pulp complex. For the laboratory experiments, stem cells from dental pulp will be seeded on acrylic plates and /or on 0.2-mm-thick dentin disks obtained from sound human molars (n = 102). The LED will be applied directly on cells and/or on the occlusal surface of the dentin discs. Cell metabolism (MTT), alkaline phosphatase expression (ALP), total protein synthesis, mineralized nodule formation (Alizarin Red), cell proliferation (Trypan Blue) and cell morphology (MEV) will be evaluated. The expression of genes that encode for collagen type-1 (Col-1), dentin sialoprotein (DSPP), dentin matrix protein (DMP-1), alkaline phosphatase (ALP) and octamer-binding transcription factor 4 (OCT-4) will be analyzed by RT-PCR. For in vivo study, Class I cavities (n = 150) will be prepared on the proximal surface of first molars of rats (n = 60), with the presence or absence of pulp exposure. The cavities will be irradiated with the best parameter of LED, determined by the laboratory experiments, and submitted to direct pulp capping with calcium hydroxide (for the group with pulp exposure) and /or restored with glass ionomer cement. After 7, 15 or 30 days, the animals will be sacrificed and teeth will be processed for histological and immunohistochemical analysis. Statistical tests will be selected depending on the type of variable and data set.
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