The role of matrix metalloproteinase (MMP-2 and MMP-9) on the bond strenght of dentine at different levels of the root following different endodontic irrigation protocols

Abstract

Aim: To identify matrix metalloproteinases (MMP) in root dentine, evaluate the effects of different root canal irrigating solutions on the activity of MMP, push-out bond strength (PBS) and nanoleakage expression (NL) in the root dentin. Methods: Seventy-two teeth were randomly distributed into 4 groups (n=6 for in-situ zymography, n=10 for PBS and n=2 for NL) according to the irrigating solutions used during instrumentation: I) Saline (S); II) 5.25% sodium hypochlorite (NaOCl); III) 5.25% NaOCl + 10% citric acid (CA); IV) 5.25% NaOCl + 10% CA + 0.2% chlorhexidine (CHX). After root canal obturation, post space was prepared with specific drills to receive glass fiber post. Dual-cure resin was used for luting and light-polymerization was performed. The root/fiber post assemblies were sectioned horizontally and subjected to the in-situ zymography, PBS and NL expression analysis tests. The enzymatic activity was quantified and expressed as a percentage of the green fluorescence while fractographic evaluation was performed after PBS with a stereomicroscope and data were statistically analysed at p<0.05. Results and conclusions: The in-situ zymography analysis showed high expression of MMPs in the middle third of the radicular dentine in all groups while the most activity of MMPs following the irrigating solutions was observed in groups I and III. Inversely, group IV recorded the highest PBS, and the statistical analysis of the groups were ranked as follows: IV > II > III > I (p<0.05). The combination of NaOCl, CA and CHX resulted in lower expression of MMP activities and higher push-out bond strength of fiber posts to root dentin, with no difference seen in the nanoleakage expression.