The antimicrobial effect of various endodontic sealers.

The antimicrobial activity of an endodontic sealer can be helpful in destroying any remaining root canal microbes. Therefore it was decided to test the antimicrobial activity of several commonly used endodontic sealers. The sealers used were Grossman's sealer, Tubliseal, Calciobiotic, Sealapex, Hypocal, eucapercha, Nogenol, and AH26. Also tested were dry calcium hydroxide powder, calcium hydroxide mixed with saline, and a Teflon formulation. The microbes used were Streptococcus mutans (a gram-positive microaerophile). Staphylococcus aureus (a gram-positive facultative anaerobe), and Bacteroides endodontalis (a gram-negative obligate anaerobe). The freshly mixed sealers were placed into the prepared wells of agar plates inoculated with the test microorganisms. After varying periods of incubation, the zones of inhibition of bacterial growth were observed and measured. Grossman's sealer had the greatest overall antibacterial activity. However, AH26 had the greatest activity against B. endodontalis. The zinc oxide-eugenol-based sealers had more antimicrobial activity than either the calcium hydroxide-based sealers or eucapercha.

In vitro effect of tobacco on the growth of oral cariogenic streptococci.

Most pouch and plug chewing tobaccos with high sugar contents are able to support the growth of S mutans and S sanguis in vitro. Snuff and unprocessed tobacco, although not able to stimulate growth of these organisms, do not inhibit growth. Inhibitory agents present in tobacco leaves do not preclude use of tobacco sugars by the organisms tested. Because factors other than bacterial populations play an important role in caries initiation, clinical studies are needed to identify the effects of commercial tobacco on the human dentition.

Improved ELISA conditions for detection of plant viruses.

Clover yellow vein virus (CYVV) and homologous antisera were used to test effects of time and temperature on enzyme-linked immunosorbent assay (ELISA) in polystyrene substrate plates. Replicated lattice square and Youden square experimental designs were used to measure and account for variation in absorption values associated with sample position within polystyrene plates. Adsorption of coating antibody to polystyrene was relatively rapid, reaching optimum assay efficiency in 1 h at 5 degrees C when applied at 2.5 microgram/ml. Binding of antigen and enzyme-linked antibody (conjugate) in their respective steps during ELISA was also rapid. Incubation of antigen and conjugate for 2 h each was adequate to enable detection of 20 ng CYVV in a 100 microliter sample, but longer incubation of either reactant improved results. At this virus concentration, reduction in antigen incubation time by one-half could be compensated by doubling the conjugate incubation time and vice versa. Incubation of conjugates at 5 degrees C rather than 30 degrees C increased final ELISA readings (A400nm) more than two-fold. Substrate hydrolysis followed classic first order kinetics at room temperature. Greater efficiency of late antisera in ELISA was demonstrated by comparison of antisera produced relatively early and late during a rabbit's immune response. Alfalfa mosaic virus and peanut stunt virus with their homologous antisera were used to test the effects of antigen and conjugate incubation times for optimum assay efficiency. The results of these time course experiments with both viruses were similar to those obtained with CYVV. These time and temperature effects on ELISA should be applicable to most rabbit serum-virus combinations.

cis-terpin hydrate metabolism by a Brevibacterium: patterns of enzyme induction, and accumulation of -terpineol in growth.

A brevibacterium, strain TH-4, previously isolated by aerobic enrichment on the monocyclic monoterpenoid cis-terpin hydrate as a sole carbon and energy source, was found to grow on alpha-terpineol and on a number of common sugars and organic acids. Oxidation of these terpenoids was shown to occur via an induced enzyme system, as measured manometrically by oxygen uptake and prevention of protein synthesis with chloramphenicol or puromycin. Oxidation of terpin hydrate by cell suspensions appeared to be coincidentally induced by growth on alpha-terpineol, and oxidation of alpha-terpineol similarly appeared to be induced by growth on terpin hydrate. Culture fluids in which the TH-4 organism was grown at the expense of cis-terpin hydrate were found to contain (-)-alpha-terpineol in combined butanol-ether extracts. The isolated compound was shown to be chromatographically and spectrophotometrically identical to an authentic sample of alpha-terpineol. The stereospecificity of an enzymatic dehydration of terpin hydrate to alpha-terpineol is considered.