Monomer 12-methacryloyloxydodecylpyridinium Bromide Research Articles

Water sorption and colour stability of composites containing the antibacterial monomer MDPB

Objectives: Previously, we have reported that composites incorporating the newly developed antibacterial monomer methacryloyloxydodecylpyridinium bromide (MDPB) inhibited bacterial growth and plaque accumulation on their surfaces without releasing antibacterial components, and that the antibacterial effect was not lost even after ageing in a wet environment for a long period. The purpose of this study was to investigate the influence of the incorporation of MDPB on the water sorption characteristic and colour stability of Bis-GMA based composites.Methods: Cured disc-shaped specimens of composites containing 0.4% or 0.5% MDPB were fabricated, and water uptake, the diffusion coefficient and the surface contact angle for water were determined. Discoloration of MDPB-containing composites was evaluated after immersion in water at 37°C and 60°C for 4weeks and compared with that of the control composite without MDPB.Results: There were no significant differences in water uptake, diffusion coefficient and contact angle between the control and MDPB-containing composites. Although composites incorporating MDPB showed greater discoloration than the control when maintained at 37°C, no difference was found after 4weeks of immersion in water at 60°C.Conclusions: Incorporation of small amounts of the antibacterial monomer MDPB showed no influence on the water sorption characteristic and affected a little the colour stability of the Bis-GMA based composite, causing rapid discoloration.

Antibacterial activity of cured dental resin incorporating the antibacterial monomer MDPB and an adhesion-promoting monomer.

In this study, the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) and an adhesion-promoting phosphoric monomer were incorporated into Bis-GMA-based dental resin and its antibacterial activity after curing was investigated. The experimental resin containing MDPB and 10-methacryloyloxydecyl dihydrogen phosphate (MDP) was polymerized and washed with methanol, and the bacteriostatic and bactericidal effects against Streptococcus mutans were determined. Growth of S. mutans was strongly inhibited by contact with the surface of cured MDPB/MDP-containing resin, although the bactericidal effect was small. Cured MDPB/MDP-containing resin also showed an inhibitory effect against in vitro plaque formation on its surface by S. mutans. The bactericide immobilized in Bis-GMA-based resin demonstrated bacteriostatic activity as a contact antimicrobial even when adhesion-promoting phosphoric monomer was incorporated into the materials.

Antibacterial activity of dentine primer containing MDPB after curing

Objectives: A monomer methacryloyloxydodecylpyridinium bromide (MDPB) has antibacterial activity before polymerization. Furthermore, the antibacterial agent is immobilized by the polymerization of MDPB and the resin-based material incorporating MDPB is able to show an antibacterial effect even after being cured. The purpose of this study was to investigate the antibacterial effect of a dentine primer containing MDPB after curing. Methods: The inhibitory effect of a cured MDPB-containing primer on the growth of Streptococcus mutans, Actinomyces viscosus and Lactobacillus casei was determined by the agar-disc method. The bactericidal activity of cured primer during a 1-h contact period was assessed using S. mutans, and the elution of unpolymerized MDPB was measured with high performance liquid chromatography. Results: Cured MDPB-containing primer showed an inhibitory effect on the growth of all species which were in contact with the specimen surface, and displayed a little bactericidal effect on S. mutans without releasing any unpolymerized antibacterial components. Conclusion: Incorporation of antibacterial monomer MDPB into dentine primer is beneficial for providing antibacterial activity after curing.

Incorporation of antibacterial monomer MDPB into dentin primer.

The polymerizable monomer methacryloyloxydodecylpyridinium bromide (MDPB) shows antibacterial activity when immobilized in a resin-based material. In this study, the antibacterial effect of a dentin primer incorporating MDPB was investigated. The influence of incorporation of MDPB on bond strength to dentin and on the curing performance of the adhesive system was also evaluated. Experimental primers were prepared by addition of MDPB into a proprietary primer at 1, 2, or 5%. Antibacterial effects of experimental primers were compared with those of control primer and two other proprietary primers by an agar disc-diffusion method and bactericidal activity test. Experimental primers produced greater inhibition zones against Streptococcus mutans, Actinomyces viscosus, and Lactobacillus casei than any of three proprietary primers, and inhibition increased as the concentration of MDPB was increased. Bactericidal activity of MDPB-containing primers against Streptococcus mutans was greater than those of the other three primers, with incorporation of MDPB at 5% showing complete killing of bacteria after 30 s contact. No decrease in tensile bond strength was observed for materials containing MDPB. On the contrary, the primer incorporating 1 and 2% MDPB showed higher bond strength than all the others, including the control (p < 0.05). When the degree of conversion of the complex of primer and adhesive resin was determined with Fourier Transform Infrared Spectroscopy, there were no significant differences between any of the experimental primers and the control (p > 0.05). These results indicate that incorporation of the antibacterial monomer MDPB enhanced the antibacterial effect of a proprietary dentin primer before curing, and had no adverse influence on bond strength to dentin and curing of the adhesive system.

Antibacterial activity of MDPB polymer incorporated in dental resin

Objectives: Previously, we have reported that dental composite incorporating the new monomer methacryloy-loxydodecylpyridinium bromide (MDPB) showed no release of antibacterial components after being cured but still exhibited antibacterial activity against Streptococcus mutans on its surface. In this study, in order to elucidate the mechanism of the antibacterial effect of immobilized MDPB, the bactericidal activity of MDPB polymer in water-soluble and -insoluble form was investigated, and the effect of MDPB polymer on bacterial attachment was estimated. Methods: Solutions of homo-polymer of MDPB and co-polymer of MDPB with acrylamide were prepared and the viability of seven major oral streptococci was determined after incubation with each polymer solution. For the estimation of bactericidal activity of insolubilized MDPB polymer, bacteria were kept in contact with cured unfilled Bis-GMA-based resin discs with or without MDPB, and the recovery of viable cells was measured. Attachment of streptococci to cured resin discs with or without MDPB was also compared using radiolabelled bacteria. Results: Water-soluble homo-polymer of MDPB and co-polymer with acrylamide showed bactericidal activity against oral streptococci. However, cured resin incorporating MDPB, which is in water-insoluble form, had little bactericidal activity. Attachment of streptococci, including species which are early colonizers in dental plaque formation, to the cured resin containing MDPB was significantly less than to the control without MDPB. Conclusions: These results indicate that the bactericidal activity of MDPB polymer is reduced after immobilization, but MDPB on the surface of a resin-based material still shows a bacteriostatic effect and antiadhesion property against oral streptococci.