No abstract

The adsorption of strains of prominent oral bacteria to hydroxyapatite (HA) surfaces was studied by use of an adsorption model based on the Langmuir adsorption isotherm; this permitted comparative estimates of the number of adsorption sites and the strength of the adsorption bonds on untreated and salivatreated HA surfaces for strain of Streptococcus mutans, S. salivarius, S. sanguis, S. mitis, Actinomyces viscosus , and A. naeslundii . The experimental data closely followed the adsorption model as judged by the high correlation coefficients obtained for all strains studied. Adsorption to untreated HA was similar for strains of the six species studied, suggesting that a common adsorption mechanism, possibly Ca 2+ bridging, may exist for attachment to HA. More complex interactions appeared to be involved in bacterial adsorption to saliva-treated HA since adsorption of the strains tested at unsaturating cell concentrations varied more than 30-fold. This indicates that adsorbed salivary components on HA surfaces impart a higher order of specificity for subsequent bacterial adsorption. Fewer cells of strains of S. mutans, S. salivarius , and A. naeslundii adsorbed to saliva-treated HA than to untreated HA because adsorbed salivary components presented fewer adsorption sites. Substantially higher numbers of cells of strains of S. sanguis, S. mitis , and A. viscosus adsorbed to saliva-treated HA because the film of adsorbed salivary components increased the number of adsorption sites for these strains. The affinity constants for all but one strain studied were lower on saliva-treated HA than on untreated HA. The number of bacterial cells which adsorbed to saliva-treated HA more closely related to the number of available binding sites than to the strength of their adsorption bonds when tested at an initial concentration of 2 × 10 7 organisms/ml. Although some differences were observed in the adsorption of strains of S. mutans representative of five serological groups, the numbers which attached to saliva-treated HA did not vary widely; this suggests that factors other than their ability to attach to a pellicle-covered HA surface may be responsible for their varying geographic distribution in human populations.

No abstract

Under the conditions of this study, the various vehicles associated with calcium hydroxide pastes did not influence the time required for microbial inactivation.

The aim of this study was to determine the minimum inhibitory concentration (MIC) and antimicrobial effectiveness by the direct exposure test of 4 endodontic irrigants [1% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), 1% calcium hydroxide (Ca(OH) 2; prepared with 1 g of Ca(OH) 2 and 100 mL of sterile distilled water), a solution of Ca(OH) 2 + detergent (HCT20)] for S. aureus, E. faecalis, P. aeruginosa, B. subtilis, C. albicans and a mixed culture. Microbial growth was analyzed by two methods: turbidity of the culture medium that was confirmed by Gram stain and subculture in a specific nutrient broth. In the dilution test, NaOCl solution showed MIC equal to 0.1% for S. aureus, E. faecalis, P. aeruginosa and C. albicans and equal to 1% for B. subtilis and the mixed culture. CHX (2%) presented MIC equal to 0.000002% for S. aureus, 0.02% for E. faecalis, B. subtilis, C. albicans and the mixed culture and 0.002% for P. aeruginosa. Ca(OH) 2 solution (1%) showed MIC greater than 1% for all the microorganisms except P. aeruginosa for which it was equal to 1%. Calcium hydroxide solution + detergent showed MIC equal to 4.5 mL for S. aureus, P. aeruginosa, B. subtilis, C. albicans and the mixed culture and greater than 4.5 mL for E. faecalis. In the direct exposure test, NaOCl had better antimicrobial effectiveness for all microorganisms at all times. CHX (2%) was effective for S. aureus, E. faecalis and C. albicans at all times, and ineffective for P. aeruginosa, B. subtilis and the mixed culture. The other solutions showed the worst results.