A Co-Association of Streptococcus mutans and Veillonella parvula/dispar in Root Caries Patients and In Vitro Biofilms.

Root caries in geriatric patients is a growing problem as more people are maintaining their natural teeth into advanced age. We determined the levels of various bacterial species previously implicated in root caries disease or health using quantitative real-time PCR in a pilot study of 7 patients with 1 to 4 root caries lesions per person. Levels of 12 different species on diseased roots compared to healthy (contralateral control) roots were measured. Four species were found at significantly higher levels on diseased roots (Streptococcus mutans, Veillonella parvula/dispar, Actinomyces naeslundii/viscosus, and Capnocytophaga granulosa) compared across all plaque samples. The level of colonization by these species varied dramatically (up to 1,000-fold) between patients, indicating different patients have different bacteria contributing to root caries disease. Neither of the two species previously reported to correlate with healthy roots (C. granulosa and Delftia acidovorans) showed statistically significant protective roles in our population, although D. acidovorans showed a trend toward higher levels on healthy teeth (P = 0.08). There was a significant positive correlation between higher levels of S. mutans and V. parvula/dispar on the same diseased teeth. In vitro mixed biofilm studies demonstrated that co-culturing S. mutans and V. parvula leads to a 50 to 150% increase in sucrose-dependent biofilm mass compared to S. mutans alone, depending on the growth conditions, while V. parvula alone did not form in vitro biofilms. The presence of V. parvula also decreased the acidification of S. mutans biofilms when grown in artificial saliva and enhanced the health of mixed biofilms.

In vitro Streptococcus mutans adhesion and biofilm formation on different esthetic orthodontic archwires.

OBJECTIVES: To evaluate the ability of different esthetic archwires to retain oral biofilms in vitro. MATERIALS AND METHODS: Seven different brands of coated orthodontic archwires were tested: two epoxy coated, two polytetrafluoroethylene coated, two rhodium coated, and one silver plus polymer coated. Conventional uncoated metallic archwires were used as controls. Streptococus mutans adherence to archwires was quantified by colony count following 24 hours of biolfilm growth, and total wire-associated biofilm was measured using a crystal violet staining assay. For both tests, two conditions were used: 0% sucrose and 3% sucrose. For statistical analysis, P < .05 was considered as statistically significant. RESULTS: For S. mutans colony forming units per biofilm, there were no statistically significant differences among the various archwires (P = .795 for 0% sucrose; P = .905 for 3% sucrose). Regarding total biofilm formed on archwires in the 3% sucrose condition, there were statistically significant differences in crystal violet staining only for the comparison between Niti Micro Dental White and Copper Ni-Ti wires (P < .05). CONCLUSIONS: The clinical use of esthetic-coated orthodontic wires may be considered to have similar risks as uncoated archwires for biofilm retention.

Activation of cannabinoid receptors promote periodontal cell adhesion and migration.

OBJECTIVE: Medical and recreational cannabis use is increasing significantly, but its impacts on oral health remain unclear. The aim of this study is to investigate the effects of tetrahydrocannabinol (THC), the major active component in cannabis, on periodontal fibroblast cell adhesion and migration to explore its role in periodontal regeneration and wound healing. MATERIAL AND METHODS: The different distribution of cannabinoid receptors 1 (CB1) and 2 (CB2) was characterized in the mouse periodontium. Human periodontal fibroblast cell (HPLF) adhesion and migration was analysed by in vitro wound healing assay with and without THC. The focal adhesion kinase (FAK) signalling pathway was investigated to uncover the underlying cellular mechanism. The receptor dependency of cannabinoid effects was examined by using selective antagonists to block THC. RESULTS: Both CB1 and CB2 were expressed in periodontal tissues but with different expression patterns. Tetrahydrocannabinol promoted periodontal cell wound healing by inducing HPLF cell adhesion and migration. This was mediated by focal adhesion kinase (FAK) activation and its modulation of MAPK activities. The effect of cannabinoids on periodontal fibroblast cell adhesion and migration was mainly dependent on the CB2. CONCLUSION: These results suggested that cannabinoids may contribute to developing new therapeutics for periodontal regeneration and wound healing.

Cytotoxicity and Genotoxicity of a New Intracanal Medicament, 2-hydroxyisocaproic Acid-An In Vitro Study.

INTRODUCTION: A successful outcome of root canal therapy relies on effective disinfection of the root canal system, including the use of intracanal medicaments, which vary in their bactericidal and cytotoxic properties. Assessing the benefits and risks associated with the use of these medicaments is of extreme importance, especially in regenerative endodontic procedures, because residual stem cells may be harmed. In this study, we tested the cytotoxicity and genotoxicity of a novel agent, 2-hydroxyisocaproic acid (HICA), and compared its properties with those of a well-established medicament, calcium hydroxide. METHODS: Human periodontal ligament fibroblasts were exposed to varying concentrations of HICA (1, 2.5, 5, 10, 20, and 40 mg/mL) for 24 hours, and a dose-response curve was generated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Immunofluorescence for 2 markers of DNA double-strand breaks, phosphorylated γH2AX and 53BP1, was used to establish the genotoxicity of HICA at various half maximal effective concentration (EC50) fractions. Cytotoxicity and genotoxicity of HICA and calcium hydroxide at 1 mg/mL were compared at 24 and 48 hours using the same methods. RESULTS: At 10 mg/mL and higher, HICA was significantly more cytotoxic and genotoxic than the control (P < .05 and P < .0001, respectively). Calcium hydroxide at 1 mg/mL was more cytotoxic than HICA at 1 mg/mL at 24 and 48 hours (P < .05 for both), whereas no difference in the accumulated DNA damage was observed. CONCLUSIONS: HICA is not cytotoxic and genotoxic at concentrations <10 mg/mL. At the concentration of 1 mg/mL, HICA is significantly less cytotoxic than calcium hydroxide.

Defining the Ail Ligand-Binding Surface: Hydrophobic Residues in Two Extracellular Loops Mediate Cell and Extracellular Matrix Binding To Facilitate Yop Delivery.

Yersinia pestis, the causative agent of plague, binds host cells to deliver cytotoxic Yop proteins into the cytoplasm that prevent phagocytosis and generation of proinflammatory cytokines. Ail is an eight-stranded ß-barrel outer membrane protein with four extracellular loops that mediates cell binding and resistance to human serum. Following the deletion of each of the four extracellular loops that potentially interact with host cells, the Ail-Δloop 2 and Ail-Δloop 3 mutant proteins had no cell-binding activity while Ail-Δloop 4 maintained cell binding (the Ail-Δloop 1 protein was unstable). Using the codon mutagenesis scheme SWIM (selection without isolation of mutants), we identified individual residues in loops 1, 2, and 3 that contribute to host cell binding. While several residues contributed to the binding of host cells and purified fibronectin and laminin, as well as Yop delivery, three mutations, F80A (loop 2), S128A (loop 3), and F130A (loop 3), produced particularly severe defects in cell binding. Combining these mutations led to an even greater reduction in cell binding and severely impaired Yop delivery with only a slight defect in serum resistance. These findings demonstrate that Y. pestis Ail uses multiple extracellular loops to interact with substrates important for adhesion via polyvalent hydrophobic interactions.