An in vitro study of bacterial inhibition by VLC calcium hydroxide pulp cap compounds.

The antimicrobial activity of visible light cure (VLC) calcium hydroxide pulp capping products was compared to self-cure products by an in vitro microbial assay. Individual microbial samples were collected from six deep carious lesions, sonicated, and plated onto duplicate T-soy blood agar. Uniform discs of each capping compound were pressed slightly below the surface of the agar and allowed to incubate at 37° C for 24 hr. The diameter of zones of inhibited bacterial growth were measured to the nearest 0.1 mm and tested for significant differences with ANOVA test. All products tested resulted in similar size zones of inhibition (P < .10). Bacteria play a significant role in the overall status of the dental pulp, not only in causing disease, but also in stimulating the formation of reparative dentin. Although the precise mechanism by which reparative dentin is stimulated to form is not completely understood, it is known that as bacteria multiply and approximate the pulp chamber, odontoblasts produce new dentin effectively walling off the vital pulp tissues from the encroaching bacteria. This response is the underlying principle justifying the indirect pulp cap. Success with this procedure is enhanced when performed in young patients whose teeth have large pulp chambers and a good blood supply. When bacteria are allowed to proliferate to sufficient numbers, decay will advance faster than the formation of reparative dentin and eventually infect the pulp. In spite of the operator’s conscious effort to remove infected dentin during cavity preparation, bacteria are frequently, unintentionally left behind in the dentinal tubules overlying the pulp chamber. Bacteria have been cultured from dentin more than a year after having been sealed under restorations.’ Fisher (1966) found bacterial activity to be minimal under restorations, so long as the filling "seals" the bacteria in the dentinal tubules and prevents nutrients from reaching them. Should excessive marginal leakage occur, the bacteria can proliferate and eventually infect the pulp. ~ Besic 1943; Fisher 1966; Schouboe and MacDonald 1962. Kakehashi (1965) demonstrated bacterial contamination to be the major adverse factor influencing the healing of exposed pulps. Attempts by Patterson (1974), Schmidt et al. (1960), and Stark et al. (1976) to disinfect dentin prior to placing the final restoration, have included the use of antibiotics and caustic chemicals. Going (1964) showed copal varnish to effectively inhibit bacterial growth by reducing marginal leakage. Pulp investigators generally agree that decontaminating and sealing the axial walls and pulpal floor of a preparation is the most important factor promoting the health of the pulp. The indirect pulp cap relies mainly on the antimicrobial activity of the pulp capping agent to effectively "hold down" the number of bacteria. Limiting the growth of bacteria allows sufficient time for the pulp tissue to form reparative dentin and to wall itself off from the encroaching bacteria. The antimicrobial activity of several pulp capping products has been studied in vivo and in vitro. Leung et al. (1980) found a reduction in the number of bacterial colony-forming units (CFU)/mg in 85% of their experimental teeth in which Dycab was placed over remaining carious dentin for a period of four weeks. Sixty per cent of these experimental teeth were found to be "operationally sterile." Fairborn et al. (1980) found similar findings with IRM0 and Improved Dycal. Lado et al. (1986) studied the in vitro bacterial inhibition of six selfcure pulp capping products on microorganisms cultured from infected dentin. All but one (PulpdenV M) were found to be significantly more effective than reagent calcium hydroxide (P = .05). Visible light cure (VLC) pulp-capping products recently have come into use that are much harder than the self-cure materials. A concern has been that the vehicle of these new products may prevent or significantly reduce any antimicrobial effects associated with the self-cure products. The issues addressed in this study are whether or not the VLC pulp cap products tested inhibit bacterial growth of microorganisms commonly found in dentin, ’ LD Caulk Co; Milford, DE. 292 VLC CALCIUM HYDROXIDE PULP CAP COMPOUNDS: LADO AND STANLEY and if they do, how effective they are when compared to commercially available self-cure products. Materials and Methods