The evaluation of cytotoxicity of dentin desensitizing agents and the effects of these desensitizing agents on the shear bond strength of adhesive resin to dentin

The first objective of this thesis is to evaluate the cytotoxic effects of the desensitizing agents used in the treatment of dentin hypersensitivity on human gingival and pulpal fibroblast cell cultures. To that end, different concentrations (50%, 20%, 10%, 1%) of 12 different agents (Smart Protect, Systemp Desensitizer, Seal&Protect, Aqua-Prep F, Isodan, Gluma, BisBlock, D/Sense Crystal, UltraEZ, Colgate Sensitive Pro-Relief, Topex and Clinpro White Varnish) were directly applied on human gingival fibroblast cells. The cells that were still alive were dyed with MTT dyes and the level of optical density was measured. So that cytotoxic effects of different concentrations on gingival fibroblasts were assessed for each group.Pulpal cells were cultured from an immatured mandibular 3rd molar tooth in order to determine the indirect cytotoxic effects of desensitizing agents on pulpal fibroblast cells. Dentin discs with different thicknesses (0.5 and 1 mm) were placed between the pulpal cells and the agents. Indirect cytotoxic effects of the agents on the pulpal cells was determined by applying the agents on the dentin discs with different thicknesses. Then, direct cytotoxic effect of the wells taken from the plates in which dentin discs with different thicknesses were used on pulpal filoblasts in 96-well plates was evaluated.According to the cytotoxicity evaluations on gingival fibroblast cells; Colgate Sensitive Pro-Relief, Topex and Clinpro White Varnish groups showed less cytotoxic effects by in all concentrations (p<0.0125). According to the cytotoxicity evaluations on pulpal fibrablasts, less cytotoxic effects were seen in BisBlock, UltraEZ, Colgate Sensitive Pro-Relief, Topex and Clinpro White Varnish groups (p<0.025).As a result of evaluating the direct effect of cytotoxic effects of wells taken from the plates in which dentin discs with different thicknesses were used on pulpal filoblasts in 96 well-plates, the groups of Seal&Protect, BisBlock, UltraEZ, Colgate Sensitive Pro-Relief, Topex and Clinpro White Varnish were found less cytotoxic than other groups in all concentrations (p<0.00625).The second objective of this thesis is to analyze the shear bond strength of a self-etch adhesive resin (Clearfil Tri-S Bond) on the dentin samples from taken cervical regions of the teeth which were treated with the agents. The highest level of shear bond strength of all groups was seen in the group on which Gluma was used (p<0.05). Statistically, the levels of shear bond strength of the groups on which D/Sense Crystal, Topex and Clinpro White Varnish were applied were remarkably lower than the control group (p<0.05). More comprehensive in vitro and clinical studies are needed to analyse the effect of the dentin desensitizing agents on resin-dentin bond strength.