No abstract

Cariogenic bacteria and periodontopathic bacteria are present in dental plaque as biofilms. In this study, we investigated the antibacterial effects of essential oils on the following oral bacteria: Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, Fusobacterium nucleatum, Streptococcus mutans, and Streptococcus sobrinus. We tested manuka oil, tea tree oil, eucalyptus oil, lavandula oil, and romarinus oil and determined their minimum inhibitory concentration and minimum bactericidal concentration. The essential oils inhibited the growth of the bacteria tested, manuka oil being the most effective. Minimum bactericidal concentration values showed that lavandula oil acts bacteriostatically, and the remaining oils, bactericidally. Periodontopathic bacterial strains tested were killed completely by exposure for 30 s to 0.2% manuka oil, tea tree oil or eucalyptus oil. Tea tree oil and manuka oil showed significant adhesion-inhibiting activity against P. gingivalis. All the essential oils tested inhibited the adhesion of S. mutans. This study showed that, among the essential oils tested, manuka oil and tea tree oil in particular had strong antibacterial activity against periodontopathic and cariogenic bacteria. From the viewpoint of safety, we also examined the effects of these essential oils on cultured human umbilical vein endothelial cells and found that, at a concentration of 0.2%, they had little effect on cultured cells.

Singlet oxygen generation from laser-excited photosensitive dyes was measured directly using a sensitive near-infrared emission spectrometer to monitor the O2(1 delta g)-->O2(3 sigma -g) transition at 1268 nm. The emission intensity was proportional to both the laser power and the concentration of the dyes. The singlet oxygen producing ability of the dyes was compared with that of eosin YS as a standard in methanol. The relative efficiencies of singlet oxygen generation were determined for rose bengal, erythrosine B, phloxine B and eosin YS as 2.39, 1.73, 1.38, 1.00, respectively, while uranine showed no emission in this spectral region. Using rose bengal, erythrosine B, phloxine B and eosin YS, the efficiency of singlet oxygen generation correlated with the photobleaching reaction rate of azo-dyes by these dyes, suggesting singlet oxygen to be a species responsible for causing the photobleaching of azo-dyes. The halogen substituent effect on the efficiency of singlet oxygen generation from laser-excited photosensitive dyes was also examined systematically.

Oral halitosis has been associated with periodontal disease. Hydrogen sulphide, methyl mercaptan and dimethyl sulphide are the major components of halitosis originating in the oral cavity. These compounds are mainly produced by periodontopathic bacteria in the oral cavity. In the absence of the bacteria, the odoriferous compounds are not generated. We have demonstrated the antibacterial effects of essential oils on the periodontopathic bacteria such as Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans and Fusobacterium nucleatum. As essential oils, manuka oil, tea tree oil, eucalyptus oil, lavandula oil, and romarinus oil were used, and their minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined. The essential oils inhibited the growth of the bacteria tested, and manuka oil did so most effectively. MBC values showed that lavandula oil acted bacteriostatically, and the remaining oils bactericidally. Bacterial strains tested were killed completely by exposure for 30 s to 0.2% manuka oil, tea tree oil or eucalyptus oil. This study showed that among the essential oils tested, tea tree oil and manuka oil, particularly the latter, had strong antibacterial activity against periodontal disease associated bacteria. In the present study, we investigated the clinical effects of essential oils in the treatment of oral halitosis. When the degree of halitosis before and after the treatment was evaluated, the essential oils demonstrated efficacy in reducing the level of the three major components of halitosis. From the data of the present study, we consider that essential oils can be used in oral health management. This study was supported by grant from Kanpou Science Foundation.

Aims To provide information on the time‐dependent behaviour of microbe staining by fluorescent dyes in the order of seconds, which is important in terms of the recent rapid and online techniques for microbe measurements and/or environmental microbe analysis. Methods and Results For combinations of yeast (Saccharomyces cerevisiae) and typical dyes, including DAPI (4′,6‐diamidino‐2‐phenylindole) and Auramine‐O, a suspension of yeast cells in ultrapure water was injected into a dye solution in a micro cuvette placed inside a spectrofluorometer and the fluorescence intensity of the resulting solution was measured at 1 s intervals, starting immediately after the mixing and continued until the time for the maximum intensity using various concentrations of yeast and dyes. The relaxation time τ, which corresponds to ~63·2% of the maximum fluorescence intensity, was shown to decrease to below 1 s with increasing DAPI concentration, whereas it remained constant for 2–3 s with increasing Auramine‐O concentration, for example at a yeast concentration of 100 µg ml−1. Conclusions For the conditions of yeast >10 µg ml−1, DAPI >1 µg ml−1 and Auramine‐O >0·1 µg ml−1, τ could be adjusted to below 5 s to achieve a rapid and stable staining. Significance and Impact of the Study Design and operating conditions for rapid and online measurements of microbes can be optimized.