The effect of sodium hypochlorite irrigation on dentin's collagen and shear bond strength of composite resin to dentin

Sodium hypochlorite (NaOCl) as a root canal irrigant during endodontic treatment, may dissolve organic part of the dentin structure, especially collagen. The aim of this study was to analyze the effect of irrigation with 2.5% and 5.25% NaOCl on collagen in dentin and shear bond strength (SBS) values of total-etch adhesive system to dentin with nanofilled composite resin NaOCl. Fifteen human maxillary premolars were halved, which produced 30 specimens that were randomly divided into 3 groups of 10 each for Mallory Azan staining. For the SBS test, 10 different maxillary premolar were sliced into 3 parts each and were divided into 3 groups of 10 each. In each test, 2 of the groups were irrigated with 2.5% and 5.25% NaOCl, and one unirrigated group was used as control. Mallory Azan staining was performed to evaluate the presence of collagen. Evaluation of the specimens irrigated by different concentrations of NaOCl and control group revealed that increasing NaOCl concentration reduced the collagen in the treated dentin (p < 0.05). It was shown that 5.25% NaOCl group had weak collagen staining but had the highest SBS value (15.56 ± 0.43 MPa), compared with 2.5% NaOCl group (9.2 ± 0.65 MPa) and control group (14.41 ± 0.96 MPa) (p < 0.05). Thus, 5.25% NaOCl can be recommended as an irrigation in endodontic treatment because it increased the SBS.