Naoya Higuchi

Background/Objectives: This study aimed to evaluate the bacterial invasion inhibitory ability of MetaSEAL Soft Paste, which is a root canal sealer that has good sealing properties in dye penetration tests, compared with conventional sealers, using a novel bacterial leakage test model. Methods: We compared MetaSEAL Soft Paste (methacrylate-based resin sealer) with Canals (zinc oxide-eugenol-based sealer), AH Plus Jet (epoxy-based resin sealer), and Dentalis NX (calcium hydroxide-based sealer). In the bacterial leakage tests, the center of the root of a bovine incisor was sliced horizontally. The area of the root canal prepared using a diamond point was filled with a sealer, and the specimen was placed on a brain heart infusion agar medium. Specimens with a filter paper disc containing Enterococcus faecalis were maintained until colonization was observed. The antibacterial properties of the sealers were evaluated using the agar diffusion test and the direct contact test. Results: AH Plus Jet tended to take the longest time to show colonies in the bacterial leakage test; however, this result was not significant compared with MetaSEAL Soft Paste. In the direct contact test, significantly fewer bacteria were detected in MetaSEAL Soft Paste and Canals than in AH Plus Jet or positive controls (p < 0.01). Conclusions: This study suggests that the novel bacterial leakage test model is effective for accurately evaluating the ability of sealers to prevent bacterial leakage, and further suggests that the sealing ability of MetaSEAL Soft Paste may not be superior to that of AH Plus Jet.

Streptococcus pneumoniae is an important causative organism of respiratory tract infections. Although periodontal bacteria have been shown to influence respiratory infections such as aspiration pneumonia, the synergistic effect of S. pneumoniae and Porphyromonas gingivalis, a periodontopathic bacterium, on pneumococcal infections is unclear. To investigate whether P. gingivalis accelerates pneumococcal infections, we tested the effects of inoculating P. gingivalis culture supernatant (PgSup) into S. pneumoniae-infected mice. Mice were intratracheally injected with S. pneumoniae and PgSup to induce pneumonia, and lung histopathological sections and the absolute number and frequency of neutrophils and macrophages in the lung were analyzed. Proinflammatory cytokine/chemokine expression was examined by qPCR and ELISA. Inflammatory cell infiltration was observed in S. pneumoniae-infected mice and S. pnemoniae and PgSup mixed-infected mice, and mixed-infected mice showed more pronounced inflammation in lung. The ratios of monocytes/macrophages and neutrophils were not significantly different between the lungs of S. pneumoniae-infected mice and those of mixed-infected mice. PgSup synergistically increased TNF-α expression/production and IL-17 production compared with S. pneumoniae infection alone. We demonstrated that PgSup enhanced inflammation in pneumonia caused by S. pneumoniae, suggesting that virulence factors produced by P. gingivalis are involved in the exacerbation of respiratory tract infections such as aspiration pneumonia.

Apical periodontitis, an inflammatory lesion causing bone resorption around the apex of teeth, is treated by eradicating infectious bacteria from the root canal. However, it has a high recurrence rate and often requires retreatment. We investigated the bactericidal effect of antimicrobial photodynamic therapy (aPDT)/photodynamic antimicrobial chemotherapy (PACT) using indocyanine green (ICG)-loaded nanospheres coated with chitosan and a diode laser on a biofilm of Enterococcus faecalis, a pathogen of refractory apical periodontitis. Biofilm of E. faecalis was cultured in a porcine infected root canal model. ICG solution was injected into the root canal, which was then irradiated with a laser (810 nm wavelength) from outside the root canal. The bactericidal effect was evaluated by colony counts and scanning electron microscopy. The result of the colony counts showed a maximum 1.89 log reduction after irradiation at 2.1 W for 5 min. The temperature rise during aPDT/PACT was confirmed to be within a safe range. Furthermore, the light energy transmittance through the root was at a peak approximately 1 min after the start of irradiation, indicating that most of the ICG in the root canal was consumed. This study shows that aPDT/PACT can suppress E. faecalis in infected root canals with high efficiency.

Aim: To observe hemichrome formation in human haemoglobin A under various buffer conditions. Method: Hemichrome formation of human oxyhaemoglobin A (HbO2) was studied spectrophotometrically in 0.1 m ...

Bacteroides forsythus, which has been recognized as a pathogen associated with periodontitis, produces a hemagglutinin. The hemagglutinin was localized in the envelope of B. forsythus. The hemagglutinating activity was inhibited by lactose at concentrations as low as 1 mM, and by l‐arginine and l‐lysine at concentrations of 100 mM. N‐Acetylneuraminyllactose (NeuAc‐lactose) was at least 100 times more potent an inhibitor than lactose, as it completely inhibited the hemagglutination at concentrations below 10 µM. This is similar to the Helicobacter pylorl hemagglutinin. The hemagglutinin was heat‐labile, and resistant to treatment with proteases such as trypsin. A specific antibody raised against one of the S‐layer proteins that are major species‐specific proteins had no inhibitory effect on the hemmaglutination. These results suggest that the NeuAc‐lactose‐sensitive adhesin of B. forsythus may play an important role in colonization in the oral cavity.

Bacteroides forsythus produces species‐specific major proteins with high molecular weights of 270 and 230‐kDa (270K and 230K). A specific antibody raised against 270K was used for Western blot analysis and immunoelectron microscopy. Western blot analysis showed that the 270K and 230K proteins were immunologically similar. Immunogold labeling of ultrathin‐sectioned bacterial cells and biochemical fractionation revealed that these proteins were localized at the outermost cell surface, not in the cytoplasm. These results suggest that major proteins ubiquitous to this species may form the S‐layer.