Azambuja, N. Evaluation of the Interaction between Sodium Hypochlorite and Chlorhexidine Gluconate and its Effect on Cytotoxicity and Genotoxicity of cell cultures [thesis]. São Paulo: Universidade de São Paulo, Faculdade de Odontologia; 2012. Versão Original. New antimicrobial therapies have been introduced in Endodontics for periapical lesions and treatment-resistant infections. Alternating irrigating solutions such as 1% sodium hypochlorite (NaOCl) solution and 2% chlorhexidine (CHX) solution has shown promising results. However, inside the root canal system the NaOCl and CHX interact producing byproducts (Bps) represented by a liquid (Liq) and a solid precipitated (Sol) that remain on the canal walls. Objectives: To study the cytotoxicity of such Bps and CHX using cultured fibroblasts (FMM1) and stem cells(PDH3). Two cell lines were chosen to test if different differentiated cell types would present different survival results. Methods: Equal parts of 1% NaOCL and 2% CHX solutions were mixed and the Bps were obtained. Three drug solutions were tested: cell culture medium dilution of CHX, cell culture medium dilution of Liq and cell culture medium conditioned by the Sol byproduct. They were prepared in fresh medium in 4 different concentrations (100%, 1%, 0,5%, 0,25%) and applied to the cells for 15 minutes. In the control wells the cells grew on fresh medium. Cytotoxicity was measured by using the MTT reduction assay in 24 replicates per concentration per solution. Twenty-four hours later cell viability was analyzed. Micronucleus counting was used to check genotoxicity (number of micronucleus/ 1000 cell, 2 counting). Data was evaluated through ANOVA test with post hoc Tukey(p<0,05) for MTT assay and qui-square for genotoxicity. Lethal dose concentration 50%(LD50) was obtained in concentrations less than 0,5% with CHX and around 1% for Liq and Sol. there were obtained same number of micronucleous for all the substances tested. PDH3 cells presented higher survival rate to higher concentrations, so they were more resistant than FMM1. There was no statistical difference between control and tested groups for genotoxicity. 2% CHX solution when applied to cell cultures was not biocompatible in concentrations above 0,5%; there is no increase in micronucleous number with tested substances.
