Kazuyoshi Higashi’s research while affiliated with Kanagawa Dental University and other places

To investigate the in vitro antimicrobial effects of carbamide peroxide (CP) and CP-based home bleaching agents against polymicrobial (PM) biofilms. Using a high-throughput active attachment model, PM biofilms were cultured on glass coverslips by diluting the stimulated saliva of one healthy adult. All experiments were performed anaerobically in McBain medium, which was refreshed twice daily. After biofilm formation for 24 or 72 hours, the biofilms were treated with 0.5%, 2.5%, 5%, or 10% CP, 20-fold dilutions of HiLite Shade Up (HS) or Opalescence Regular (OR), 0.2% chlorhexidine digluconate (CHX), 0.2% NaF, or deionized water (n = 10 each). Biofilms were dispersed and the number of colony forming units (CFU) was measured on tryptic soy agar blood plates. Coverslips containing 72-hour biofilms treated with 0.5% and 10% CP and deionized water were stained and scanned by confocal laser scanning microscopy (CLSM). Treatment of 24- and 72-hour biofilms with HS, OR and CH yielded significantly fewer colonies than treatment with water or 0.2% NaF. No growing colonies were observed after treatment with 10% CP. CLSM showed that the percentage of dead bacteria increased as the concentration of CP increased.

Objective: PancilPS-M (Rilis Co., Ltd, Osaka, Japan) is a food addictive containing condensed tannin extracted from astringent persimmon. The purpose of this study was to examine the antibacterial action of Pancil PS-M on the formation of polymicrobial biofilms. Methods: PancilPS-M was dissolved in distilled water, sterilized and serially diluted for the experiments. Polymicrobial biofilm specimens were cultured on glass plates (diameter: 12 mm, thickness: 0.15 mm) using dilution (x 50) of stimulated saliva of one healthy adult in a high-throughput active attachment model. Experiments were performed anaerobically in Mcbain medium, which was refreshed twice daily on a schedule of 10 h and 14 h of growth. After biofilm formation for 72 h, single treatment was conducted as follows: The specimens (9 per group) were immersed for 5 min in: 0.2% chlorhexidine digluconate (CHX) (Corsodyl, GlaxoSmithKline) (group 0.2C); 0.05% CHX (group 0.05C); 0.5%, 0.7%, 1.0%, 2.0%, 3.0% and 4.0% PancilPS-M (groups 0.5P, 0.7P, 1P, 2P, 3P, and 4P); and deionized water (control group). After these treatments, specimens were harvested by ultrasonic wave and plated on tryptic soy agar blood plates for CFU counts which were analyzed statistically (One-way ANOVA, Tukey’s, p< 0.05). Morphological analysis of the biofilms was performed by scanning electron microscopy (SEM). Results: All treatment groups showed significantly lower CFU than that of control group. Pancil PS-M showed concentration-dependent inhibition of CFU. Group 4P (1.53 × 107 CFU/ml) and 0.2C (2.03 × 107 CFU/ml) showed significantly lower CFU levels than other groups. SEM observation of groups 4P and 0.2C revealed that aggregation of bacteria was suppressed. Conclusion: PancilPS-M has a potential to suppress polymicrobial biofilms.

In recent years, it has become well known that the production of reactive oxygen species (ROS) induced by blue-light irradiation causes adverse effects of photo-aging, such as age-related macular degeneration of the retina. Thus, orange-tinted glasses are used to protect the retina during dental treatment involving blue-light irradiation (e.g., dental resin restorations or tooth bleaching treatments). However, there are few studies examining the effects of blue-light irradiation on oral tissue. For the first time, we report that blue-light irradiation by quartz tungsten halogen lamp (QTH) or light-emitting diode (LED) decreased cell proliferation activity of human gingival fibroblasts (HGFs) in a time-dependent manner (<5min). Additionally, in a morphological study, the cytotoxic effect was observed in the cell organelles, especially the mitochondria. Furthermore, ROS generation induced by the blue-light irradiation was detected in mitochondria of HGFs using fluorimetry. In all analyses, the cytotoxicity was significantly higher after LED irradiation compared with cytotoxicity after QTH irradiation. These results suggest that blue light irradiation, especially by LED light sources used in dental aesthetic treatment, might have adverse effects on human gingival tissue. Hence, this necessitates the development of new dental aesthetic treatment methods and/or techniques to protect HGFs from blue light irradiation during dental therapy.

Although several morphological studies of main excretory duct of the submandibular gland have been performed, few reports present immunohistochemical data. Some epithelial cells or basal cells contain dense granules of an array shape by electron microscopic observation. However, the details of granulated cells have not been clarified immunohistochemically. In this study, both protein gene product 9.5 (PGP 9.5) and chromogranin or serotonin immunoreactive cells in the main excretory duct (MED) of the rat submandibular gland were observed. Some nerve endings were also observed among the epithelium of the MED. Therefore, the modifying mechanism of primary saliva in the MED may be regulated by both serotonergic nerve and endocrine cells with serotonin.