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Attempts to produce resin composite with antibacterial properties by incorporation of an antibacterial agent such as chlorhexidine have been reported, but problems can arise due to release of the inhibitory agent from the composite. Such problems may include toxic effects, influence on mechanical properties, and loss of effectiveness. A new monomer, methacryloyloxydodecylpyridinium bromide (MDPB), was synthesized by combining an antibacterial agent and methacryloyl group. The monomer was incorporated into resin composite to develop a non-releasing antibacterial composite. The ability of composite incorporating MDPB to inhibit growth and plaque accumulation by Streptococcus mutans in vitro was assayed, elution of antibacterial components from the material was investigated, and the influence of incorporation of MDPB on the mechanical properties of composite was studied. Uncured MDPB revealed antibacterial activity against S. mutans and six other species of oral streptococci, with the minimum inhibitory concentration for S. mutans being comparable with that of triclosan. After composite incorporating MDPB was cured, no elution of the antibacterial components was observed from the material, even after 90 days' immersion in water or other solvents. Growth of S. mutans on agar under specimens of MDPB-containing composite was inhibited compared with controls. In a bacterial accumulation study, S. mutans accumulated to a lesser degree on the surface of composite incorporating MDPB (p < 0.05) than on control. Incorporation of MDPB had no significant influence on the mechanical properties of the composite.

109When heat-killed whole organisms of Streptococcus mutans strain Ingbritt (serotype c ) were injected into rabbits, antibodies to at least 12 antigens were detectable by crossed immunoelectrophoresis. In contrast, when rabbits were immunized with organisms which had been subjected to extraction with the detergent sodium dodecyl sulphate (SDS), antibodies to only two protein antigens were found. These two proteins (A and B), while existing in a form apparently closely associated with peptidoglycan, could also be recovered from homogenates of whole organisms after sonication and from culture filtrates. Antigenic material was excreted throughout growth. SDS-polyacrylamide gradient gel electrophoresis showed A to have a molecular weight of 29000, while B had a molecular weight of 190000. Antigen B was purified to apparent homogeneity as judged by SDS-polyacrylamide gel electrophoresis and isoelectric focusing. All of six strains of serotype c examined produced antigen B. Strains of serotypes e and f also produce antigenically identical proteins and strains of serotypes d and g produce proteins which cross-reacted with antigen B. Antigen B was specifically precipitated by rabbit antiserum to human heart tissue. I N T R O D U C T I O NExperiments from a number of laboratories have clearly shown that immunization of animals with Streptococcus mutans or its subcellular fractions can confer protection against dental caries induced by this organism (Bowen et al., 1976), but the mechanism of this protection and the bacterial antigens involved remain unknown. For the development of an effective vaccine it is desirable to identify the antigen(s) involved in eliciting protective antibody, and the means by which protection is conferred. Identification and purification of such an antigen would aid in the understanding of the mechanism of protection, allow monitoring of vaccine preparations for efficacy, and facilitate study of its relationship with any toxic components of a crude vaccine. Of particular concern in the case of S. mutans is the demonstration of an antigenic relationship between S. mutans and human heart tissue (van de Rijn et al., 1976).An earlier report from this laboratory described successful protection of monkeys immunized with walls of S. mutans (Bowen et al., 1975). Walls treated with trypsin, on the other hand, fail to confer protection suggesting that the protective antigen might be protein in nature (Colman & Cohen, 1979). The present paper describes studies of proteins associated with S. mutans walls and the purification of one wall-associated antigen. The purified antigen is also demonstrated to be antigenically related to human heart tissue. M E T H O D R. R. B. R U S S E L Lyeast extract, 3 g; NaCI, 2 g; K2HP04, 2 g; NaHCO,, 1 g; glucose, 5 g; water, 1 1) and the chemically defined (CD) medium of Janda & Kuramitsu (1976) supplemented with 0.2% (w/v) Na,CO, (Terleckyj & Shockman, 1975). Antisera. New Zealand white rabbits (each 2 to 3 kg) were used for the preparation of antisera. Injection schedule...

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.