No description available.

No description available.

No description available.

No description available.

No description available.

The emergence of antibiotic-resistant bacteria has become a major threat to public health. The increased use of antibiotics has selected for the dissemination of antibiotic resistance genes between organisms from different species and different genera. There is a large body of evidence that the indigenous microbiota can act as a reservoir of antibiotic-resistant bacteria. However little is known about the molecular basis for this in bacteria from the oral cavity. Therefore the aim of this work was to determine the prevalence of antibiotic-resistant bacteria and antibiotic resistance genes in the cultivable oral microbiota. Saliva and plaque samples were taken from each of 60 healthy adults who had not taken any antibiotics during the previous three months. Each sample was plated onto antibiotic-containing media to quantitate and identify antibiotic-resistant strains. All of the individuals harboured bacteria resistant to erythromycin, gentamicin, vancomycin and tetracycline. Only 4 individuals (7%) did not have any cultivable bacteria resistant to amoxycillin. Oral bacteria resistant to gentamicin were the most commonly isolated (constituting 23% of total cultivable oral bacteria) followed by erythromycin (18% of the total viable count), vancomycin (16% of the total viable count), tetracycline (10% of the total viable count) and amoxycillin (4% of the total viable count). Multiply-resistant bacteria were found with 55% of tetracycline-resistant isolates being resistant also to erythromycin and 6% resistant also to both amoxycillin and erythromycin. The most prevalent genes encoding tetracycline and erythromycin resistance were tet(M), tet(W), tet(0), and mef and erm(B) respectively. In some cases, tet(M) and ermB were contained within a Tn/5 5-like conjugative transposon and could be co-tranferred to Enterococcus faecalis. Finally the nature of the genetic support for one of the tet(W) genes, was determined and found to be flanked by two transposases belonging to two different families of insertion sequences (IS30 and IS256). This element was highly unstable in E. coli. This study showed that antibiotic-resistant bacteria and antibiotic resistance genes are present in the oral microbiota and that oral bacteria are likely to play an important role in the evolution and dissemination of antibiotic resistance genes.

Dental plaque can build up to levels which predispose the oral cavity to dental caries or periodontal disease. Therefore many dental products contain antimicrobial compounds to help control plaque formation. Triclosan (TeN) has been used as an antimicrobial in oral care for over 30 years. It has a broad spectrum of antimicrobial activity with high activity against Gram-negative bacteria (those associated with oral disease states). Strategies to increase the delivery efficiency of antibacterials using formulation aids such as polyamidoamine (P AMAM) dendrimers are of interest. P AMAM dendrimers can potentially act as a mucoadhesive delivery system due to electrostatic interactions between the cationic dendrimer and an ionic mulch in oral buccal mucus. Solubilisation studies demonstrated an increase in the level of triclosan solubilised with increasing dendrimer concentration over the range 1mM-5mM. However, solubilisation studies over the pH range 5-12 showed that the dendrimer was unable to enhance triclosan solubility at lower pH values. The solubilising effect observed was attributed to the ionization of triclosan (pKa 7.9) resulting from dendrimer induced pH changes. T\ IH NMR telaxation studies on a solution of 3 mM G3 PAMAM dendrimer and triclosan in pH 12 aqueous solution showed a reduction in T\ for proton resonances corresponding to triclosan, compared to triclosan without dendrimer. However, no significant chemical shift or line broadening effects were observed inferring the interaction between dendrimer and triclosan is relatively weak.

Aim of the research: This in vitro study aimed to investigate tooth surface loss with immediate or delayed brushing after exposure to acids associated with either erosive tooth surface loss (citric acid) or that associated with a cariogenic challenge (acetic acid). Study design: A randomised longitudinal in vitro study. Materials and method: In this in vitro study, 60 enamel slabs were allocated randomly to 4 groups; citric acid with immediate brushing (CIB), citric acid with 30 minutes delayed brushing (COB), acetic acid with immediate brushing (AlB) and acetic acid with 30 minutes delayed brushing (ADB). During the 28-days slabs in all groups were subjected to an abrasive challenge 4 times per cycle day with brushing machine using brushing load of 200g. They were immersed in acid 5 times per day cycle. Measurements of enamel surface loss were done using surtace profilometry on 3 different intervals during the cycle 7, 14 and 28 days. In addition, in the acetic acid group surface microhardness was also used for the final assessment at day 28. Results: Using repeated measures ANOVA no significant difference between both immediate and 30 minutes delayed brushing was detected. Result also indicated that the effect of time was found to achieve statistical significance (p<0 .05) within the multivariate tests conducted, with tooth surtace loss increasing progressively from 7-28 day test period. Also there was significantly (p<0.05) more tooth surface loss evident with citric acid both with immediate and delayed brushing compared with acetic acid. Conclusion: It was shown that 30 minutes remineralisation period had no effect when compared to immediate brushing. This was true for both acids (citric and acetic). It was also concluded there was significantly more tooth surface loss with citric acid compared with that acetic acid.

Although bleaching is considered a conservative technique, controversy surrounds whether bleaching demineralises or modifies tooth surfaces. Little is known about how bleaching may predispose enamel to subsequent acid challenges or how it affects the adsorption of protective salivary pellicles. Aim: To investigate the effects of bleaching on: susceptibility of hydroxyapatite to subsequent acid attack; on adsorption of salivary proteins and their protective properties and to carry out an in situ study to investigate the impact of a commercial bleaching product on mineral density of human enamel. Methods: Hydroxyapatite powder bleached in vitro was used to examine the effect of bleaching on: acid solubility; salivary protein adsorption and the protective properties of adsorbed salivary proteins using SDS-PAGE and for protein identification using mass spectrometry. An in situ study, employing extra-oral bleaching, examined the effect of bleaching ' on enamel mineral density as measured by X-ray NanoCT scanning technique. Results: The results indicated that bleaching had no effect on hydroxyapatite acid susceptibility. However, bleaching did affect the adsorption of salivary proteins such as a-salivary amylase. A novel finding was that the precise effect observed was donor specific i.e. salivary protein heterogeneity between individuals dictated how bleaching effected the nature of the adsorbed salivary pellicle. Bleaching appeared to significantly increase the ability of the salivary pellicle to protect hydroxyapatite from acid attack. Increasing the pH of the bleaching agent enhanced subsequent adsorption of the model protein bovine serum albumin. The in situ study indicated that the bleaching regime used here had no significant effect on the inner enamel but Significantly increased mean mineral density at the enamel surface by 6.8%. It is suggested that peroxide incorporates in the hydroxyapatite lattice and modifies mineral properties. Conclusions: Overall, data indicates that the specific bleaching regimes employed here do not have a detrimental effect on mineral density and may actually increase mineral density.

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