Inhibition of methionine gamma lyase deaminase and the growth of Porphyromonas gingivalis: A therapeutic target for halitosis/periodontitis.

BACKGROUND AND OBJECTIVES: Pathogenic infections caused by Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia can result in the production of volatile sulfur compounds (VSC's) and other toxic compounds from methionine catabolism that can lead to halitosis and periodontitis. Our aim is to block the activity of methionine gammalyase-deaminase (Mgld) of methionine catabolism to prevent halitosis/periodontitis. DESIGNS: Cloned, expressed, Mgld protein was tested for purity by SDS-PAGE and western blotting. Mgld activity was tested by UV-vis spectroscopy and DTNB assay. Effects of Mgld inhibitor propargylglycine (PGLY) was tested on P. gingivalis growth by turbidity measurements. The effects of PGLY on oral epithelial and periodontal ligament cells in culture at different concentrations and time were tested for cell viability by MTT and Live-Dead assays. Amino acid comparisons of Mgld from different oral pathogens were done using standard bioinformatics program. RESULTS: Propargylglycine (PGLY) inhibited purified Mgld activity completely. In vivo, PGLY is a potent inhibitor on the growth of the P. gingivalis over 24 h, grown at 25 °C and 37 °C. Correspondingly in vivo Mgld activity was also affected by PGLY. Amino acid comparisons of oral pathogens showed 100% identity on the key residues of Mgld catalysis. Mammalian oral cell lines with PGLY, showed no difference in cell death over untreated controls assessed by MTT and Live-Dead assays. CONCLUSIONS: PGLY arrest's VSC's production by P. gingivalis. Since initial Mgld activity is inhibited subsequent enzymatic and nonenzymatic products formed will be prevented. PGLY showed no toxicity towards cultured mammalian oral cells. Thus, PGLY can serve as a mouthwash ingredient to prevent halitosis/periodontitis.

Novel bone adhesives: a comparison of bond strengths in vitro.

Fracture fixation using adhesive is a promising alternative in craniofacial surgeries, replacing the plates and screws system. The advantages include the ease of application and avoidance of drilling holes that may weaken the bone and cause fractures. In this study the bond strengths of selected adhesives were evaluated and compared with resorbable plates and screws. Four adhesives, octyl-cyanoacrylate, N-butyl-cyanoacrylate, a novel methyl-methacrylate, and a novel cyanoacrylate derivative, were tested for their microtensile and shear bond strengths. The bone samples were cut into rectangular bars and bonded with selected adhesives for microtensile testing. For the shear bond test, paired bars were bonded at the overlap, while two other sets of bars were attached by a Lactosorb plate using either adhesive or screws. Data were analysed by analysis of variance (ANOVA). The microtensile bond strengths of N-butyl-cyanoacrylate, novel cyanoacrylate derivative, and novel methyl-methacrylate derivative were significantly greater than octyl-cyanoacrylate. When bone sections were fixed with resorbable plates and adhesives, shear bond strength was significantly greater for N-butyl-cyanoacrylate than plate and screws, while the bond strengths of other adhesives were comparable with the plate and screws. N-Butyl cyanoacrylate was shown to have the greatest potential for fixation of fractured bone in craniofacial surgical applications.