Anti-bacterial efficacy of montmorillonite modified with cetylpyridinium chloride

Objective: Cetylpyridinium chloride (CPC) is as a cationic quaternary ammonium compound with antiseptic properties, typically used in mouthrinses and tooth pastes. While CPC could theoretically provide antibacterial properties to dental materials such as adhesives, cements, and composites, a main difficulty is its limited release in particular after curing. In this study, we examined the anti-bacterial efficacy of montmorillonite modified with CPC (CPC-Mont). Method: CPC-Mont powder was synthesized and characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). In addition, experimental adhesives based on Clearfil S³ Bond (Kuraray Noritake) that contain either no (control), 1wt% or 3wt% CPC-Mont were polymerized in a 10x1mm silicon mold plate. The anti-bacterial effects against Streptococcus mutans (S. mutans) were determined by optical density (OD). Adhesion of S. mutans on HAp treated with the experimental adhesives was observed by SEM. Respective adhesive-dentin interfaces were imaged by transmission electron microscopy (TEM). Result: XRD revealed an increase in interlayer distance of montmorionite from 1.26 to 4.16 nm after modification with CPC. The growth of S. mutans was significantly inhibited not only at, but also around the surface, as was revealed by OD and SEM and as opposed to the control without CPC-Mont. No difference was found between the 1 and 3wt% CPC-Mont samples. The adhesive-dentin interfaces appeared tight for all experimental adhesives.  Conclusion: Montmollironite could be loaded with CPC. CPC-Mont significantly inhibited growth of S. Mutans. CPC-Mont did not alter the adhesive potential of the experimental adhesives to dentin.