Transdentinal cytotoxicity and effect of carbodiimide (EDC) on resin-dentin bond degradation: in vitro and in vivo studies

Abstract

The overall aim of this study, divided into 3 experiments, is to evaluate the transdentinal citotoxicity of carbodiimide (EDC) in distinct concentrations, as well as the influence of the application of this agent on the immediate and long term stability of resin-dentin bonds in vivo. Experiment #1: To evaluate the transdentinal cytotoxicity of EDC solutions in 3 concentrations on MDPC-23 cells. Third human molars (n=60) will be cut to obtain 0.4 mm-thick dentin discs. The permeability of each disc will be measured and then assigned into 6 groups. After fitting the discs in artificial pulp chambers, MDPC-23 cells will be seeded on the pulpal side of the discs. On the occlusal side, after phosphoric acid conditioning, the following solutions will be applied: distilled water (negative control), cacodilate buffer 0.05M, EDC at 0.1M, 0.3M or 0.5M, or 29% hydrogen peroxide (negative control). Each solution will be kept in place for 60 s, followed by abundant rinsing. Cell metabolism (MTT assay), morphology (MEV), type of cellular death (flow cytometry) and EROs production will be analyzed. Experiment #2: To investigate the effect of EDC application on immediate and long term bond strength of a two-step etch-and-rinse adhesive system on dentin. Flat dentin surfaces will be produced from sound molars (n=72). The dentin will be phosphoric acid conditioned and treated for 30 or 60 s with EDC (concentration to be selected from the first experiment) or deionized water. After the treatment, Single Bond Plus will be applied and resin blocks built-up. Beam specimens (0.81 mm2) will be produced and microtensile tested after 24 h or after aging in artificial saliva (6 and 12 months). Experiment #3: To evaluate the effect of EDC on the stability of resin-dentin bonds produced in vivo in deciduous molars. At least 10 subjects between 7 and 11 years of age with at least two deciduous molars with occlusal caries will be invited to participate of the study. After randomization, one tooth per pair will receive EDC (concentration and time of application determined in the previous experiments). The teeth will be kept in function until exfoliation and then prepared for TEM analysis. Statistical analyses of data: The statistical tests for all experiments will be selected after analyzing the respective data sets as to normal distribution and homoscedasticity at 5% level of significance. Additionally, the tests will also be chosen based on the number of factors of each study. (AU)