Influence of benzalkonium chloride on dentin μTbs and MMPs activity

Purpose/aim: Benzalkonium chloride (BAC) is a nitrogenous cationic surface-acting agent containing a quaternary ammonium group claimed to inhibit dentin matrix metalloproteinases (MMPs) in addition to its disinfectant ability. The aim of the studywas to investigate the adhesive bond strength and the dentin enzymatic activity of a multi-mode universal adhesive system (All-Bond Universal; Bisco Inc., ABU) and an experimental adhesive with BAC blended within its formulation (SBAC, Bisco Inc.,) employed in etch-and rinse (E&R) or self-etch (SE) mode. Materials and methods: A standardized smear layer was created using a 180-grit silicon-carbide paper on 32 middle/ deep human dentin surfaces. Specimens were assigned to the following groups (n = 8) according to the adhesive procedure: G1: SBAC employed in E&R mode after dentin etching with 35% phosphoric acid for 15 s. G2: SBAC employed in SE mode on untreated dentin. G3: ABU employed in E&R mode after dentin etching with 35% phosphoric acid for 15 s. G4: application of ABU in SE mode on untreated dentin. All adhesives were applied according to manufacturer’s instructions and cured for 20 s. Composite buildups were created on the bonded surfaces, then specimens were cut for microtensile bond strength test (TBS) and stressed to failure at a crosshead speed of 1mm/min after 24-h storage in artificial saliva at 37 ◦C. TBS data were analyzed using two-way ANOVA and Tukey’s multiple comparison tests. Additionally, enzymatic activity was evaluated using a zymographic assay on protein extracts obtained from adhesive-treated dentin powder of each tested group. Results: Results of TBS showed no significant differences after 24h storage in artificial saliva within the four groups. Furthermore, zymographic analysis revealed increased expression of dentin endogenous MMP-2 and -9 after application of All Bond Universal in SE mode, while in the E&R mode the expression of the MMP-2 decreased and MMP-9 was inhibited. SBAC employed in SE mode increased the expression of MMP-2, while inactivating the MMP-9. The application of SBAC in the E&R mode also inactivated MMP-9, while MMP-2 activity was significantly decreased. Conclusions: Further studies and longer aging are needed to clarify the influence of BAC blended within the adhesive formulation in improving bond longevity and dentin MMPs inhibition.