AbstractBackground: Chlorhexidine could have effect on shear bond strength of composite resin-dentin.Objective: The purpose of this study is to compare two methods of chlorhexidine application ofshear bond strength degradation between composite resin and dentin. Methods: Thirty samples ofdentin were taken from the crown of premolars and then divided into three groups (n = 10). Group1 were applied bonding without chlorhexidine, group 2 were applied with liquid chlorhexidine andfollowed by bonding, group 3 were applied bonding which contains chlorhexidine. Each group wasdivided into two sub-groups (n = 5): the group with and without 10% NaOCl immersion for onehour. Then, 4 samples in each sub-group were used to measure shear bond strength using Universal Testing Machine, and 1 sample was examined with Scanning Electron Microscope (SEM). Datawere analyzed using SPSS 17 by Mann-Whitney and Kruskal Wallis test. Results: The highest meanshear bond strength without 10% NaOCl immersion was in group 1, while the highest mean with10% NaOCl immersion was in group 3. Significant differences occurred between the groups 1 and2, groups 2 and 3. Conclusion: Method of using bonding contains chlorhexidine can increase andinhibit degradation shear bond strength between composite resin and dentin.KeywordsChlorhexidine, Composite Resin, Dentin, Shear Bond Strength