Anti-bacterial Efficacy of Probiotics used in Provisional Polymethyl Methacrylate Crowns against Porphyromonos gingivalis – an In vitro Study

Aim: To evaluate the effect of Probiotic used in PMMA Temporary restorations on gingival inflammatory response by its action on the marginal gingival epithelial cells. Materials and Methods: This is an in vitro Interventional pilot study using discs of PMMA ( Group A ) and PMMA incorporated with Probiotics (Group B . The effect of probiotics incorporated PMMA on strains of Porphyromonos gingivalis grown on culture plates will be assessed using zone of inhibition test and minimum inhibitory concentration was assessed . Data was recorded, tabulated and statistically evaluated using SPSS software. Results: The zone of Inhibition in the Group B was (Mean = 16.30mm) is comparatively higher than that of Group A with mean value 12.92mm. Results states that among the various concentration of Probiotic Lozenges (2.5, 5, 10, 15 and 20 µg/ml) used to determine the antibacterial activity , Highest mean zone of inhibition was observed with 20 µg/ml with 16 mm, followed by 15 µg/ml with 14mm , 10 µg/ml with 9mm, 5 µg/ml with 11 mm & with the lowest inhibition observed in 2.5 µg/ml with 8mm. There is significant correlation between concentration of probiotics and its antibacterial efficacy. The increase in concentration of probiotics in the PMMA discs is directly proportional to its antibacterial efficacy against P. gingivalis. Conclusion: Thus the study proved a significant correlation between Probiotic used in PMMA Temporary crowns and reduction in gingival Inflammation at the margins of the restoration which will be beneficial when used in crowns used in patients undergoing Orthodontic treatment or Immediate Implant Loading with acrylic crowns.

In Vitro Investigation of the Cytotoxic Effects of Different Detergent-Containing Children's Toothpastes on Human Gingival Epithelial Cells

Background: This study aimed to evaluate possible cytotoxic effects to gingival epithelial cells exposed to children toothpastes containing different detergent. Methods: Tissues required fort he isolation of human gingival epithelial cells were obtained by biopsy during the extraction of the impacted third molar tooth. Toothpaste solutions of different concentrations were prepared from five different children’s toothpastes with different detergent contents. Isolated gingival epithelial cells were stimulated with experimental groups consisting of toothpaste solutions (Colgate, Sensodyne, Splat, Nenedent, Perlodent) at different concentrations and a control group consissting of complete Dulbocco’s modified eagle medium. After the experiments, cell viability was evaluated using flow cytometry. Data analysis were done using One Way ANOVA test and Tukey post-hoc test. Results: In all experimental groups, there was a decrease in live cell rates and an increase in dead cell rates due to increased concentration. The statistically highest live cell ratios were detected in Splat’s toothpaste solutions after the control group and the group with the lowest viability values was determined in Colgate group (p<0.05). Conclusions: According to the results of the study, it was observed that toothpastes containing SLS affected the viability of cells more negatively than toothpastes with other detergent contents.

Bitter Taste Receptor T2R14 Modulates Gram-Positive Bacterial Internalization and Survival in Gingival Epithelial Cells

Bitter-taste receptors (T2Rs) have emerged as key players in host–pathogen interactions and important modulators of oral innate immunity. Previously, we reported that T2R14 is expressed in gingival epithelial cells (GECs) and interacts with competence stimulating peptides (CSPs) secreted by the cariogenic Streptococcus mutans. The underlying mechanisms of the innate immune responses and physiological effects of T2R14 on Gram-positive bacteria are not well characterized. In this study, we examined the role of T2R14 in internalization and growth inhibitory effects on Gram-positive bacteria, namely Staphylococcus aureus and S. mutans. We utilized CRISPR-Cas9 T2R14 knockdown (KD) GECs as the study model to address these key physiological mechanisms. Our data reveal that the internalization of S. aureus is significantly decreased, while the internalization of S. mutans remains unaffected upon knockdown of T2R14 in GECs. Surprisingly, GECs primed with S. mutans CSP-1 resulted in an inhibition of growth for S. aureus, but not for S. mutans. The GECs infected with S. aureus induced T2R14-dependent human β-defensin-2 (hBD-2) secretion; however, S. mutans–infected GECs did not induce hBD-2 secretion, but induced T2R14 dependent IL-8 secretion. Interestingly, our results show that T2R14 KD affects the cytoskeletal reorganization in GECs, thereby inhibiting S. aureus internalization. Our study highlights the distinct mechanisms and a direct role of T2R14 in influencing physiological responses to Gram-positive bacteria in the oral cavity.

Uptake of Nanotitania by Gingival Epithelial Cells Promotes Inflammatory Response and Is Accelerated by Porphyromonas gingivalis Lipopolysaccharide: An In Vitro Study

Titanium is often used in the medical field and in dental implants due to its biocompatibility, but it has a high rate of leading to peri-implantitis, which progresses faster than periodontitis. Therefore, in the present study, the expression of cytokines from gingival epithelial cells by nanotitania was investigated, which is derived from titanium in the oral cavity, and the additional effect of Porphyromonas gingivalis (periodontopathic bacteria) lipopolysaccharide (PgLPS) was investigated. Ca9-22 cells were used as a gingival epithelial cell model and were cultured with nanotitania alone or with PgLPS. Cytokine expression was examined by reverse transcription-quantitative polymerase chain reaction and enzyme-linked immunosorbent assay. In addition, cellular uptake of nanotitania was observed in scanning electron microscopy images. The expression of interleukin (IL)-6 and IL-8 significantly increased in Ca9-22 cells by nanotitania treatment alone, and the expression was further increased by the presence of PgLPS. Nanotitania was observed to phagocytose Ca9-22 cells in a dose- and time-dependent manner. Furthermore, when the expression of IL-11, related to bone resorption, was investigated, a significant increase was confirmed by stimulation with nanotitania alone. Therefore, nanotitania could be associated with the onset and exacerbation of peri-implantitis, and the presence of periodontal pathogens may worsen the condition. Further clinical reports are needed to confirm these preliminary results.

Cigarette Smoke Stimulates SARS-CoV-2 Internalization by Activating AhR and Increasing ACE2 Expression in Human Gingival Epithelial Cells

A large body of evidence shows the harmful effects of cigarette smoke to oral and systemic health. More recently, a link between smoking and susceptibility to coronavirus disease 2019 (COVID-19) was proposed. COVID-19 is due to infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which uses the receptor ACE2 and the protease TMPRSS2 for entry into host cells, thereby infecting cells of the respiratory tract and the oral cavity. Here, we examined the effects of cigarette smoke on the expression of SARS-CoV-2 receptors and infection in human gingival epithelial cells (GECs). We found that cigarette smoke condensates (CSC) upregulated ACE2 and TMPRSS2 expression in GECs, and that CSC activated aryl hydrocarbon receptor (AhR) signaling in the oral cells. ACE2 was known to mediate SARS-CoV-2 internalization, and we demonstrate that CSC treatment potentiated the internalization of SARS-CoV-2 pseudovirus in GECs in an AhR-dependent manner. AhR depletion using small interference RNA decreased SARS-CoV-2 pseudovirus internalization in CSC-treated GECs compared with control GECs. Our study reveals that cigarette smoke upregulates SARS-CoV-2 receptor expression and infection in oral cells. Understanding the mechanisms involved in SARS-CoV-2 infection in cells of the oral cavity may suggest therapeutic interventions for preventing viral infection and transmission.

Elucidation of the mechanism of prolonged inflammation and delayed wound healing during malnutrition: possible HMGB1 dysfunction

Japan is a country with a long average life expectancy. With this comes challenges in the form of a growing number of elderly people that require long-term support and care. Among the conditions that can affect the elderly are prolonged inflammation and delayed wound healing. Professor Keisuke Yamashiro, Department of Oral Health, Kobe Tokiwa Junior College, Japan, is working to understand more about the mechanisms behind these conditions. A key hypothesis for Yamashiro and his team is that inflammation may be prolonged by malnutrition. In addition to an insufficient or unbalanced diet, malnutrition can also be caused by the inability to swallow or ingest certain foodstuffs due to problems with the teeth or gums. A key focus for the researchers is on HMGB1, which is a molecule that plays important roles in inflammation and regeneration. The team is working to improve understanding of HMGB1 in order to improve patient outcomes. Yamashiro's current project builds on previous research on HMGB1 and the researchers recently succeeded in administering an anti-HMGB1 antibody that inhibits its action to periodontitis model mice and confirming the effect of bone resorption by periodontitis. This enabled the team to inhibit the translocation of HMGB1 to the nucleus in gingival epithelial cells and suppress the inflammation caused by periodontitis. Ultimately, the researchers believe that the development of an anti-HMG1 treatment will be useful for various diseases such as sepsis, traumatic brain injury and brain ischemia, as well as chronic and immunologic inflammation such as rheumatoid arthritis and arteriosclerosis.