Glucose toxicity effect and accumulation of methylglyoxal by the periodontal anaerobe Bacteroides forsythus.

Growth of the periodontal pathogen Bacteroides forsythus in broth cultures showed inhibition in the presence of 10mM glucose added to the medium. Glucose inhibition in a number of rumen bacteria has been attributed to the accumulation of methylglyoxal (MG), a highly reactive electrophile known to exhibit cytotoxic effects. HPLC analysis revealed elevated concentrations of MG in cultures of seven strains of B.

Maintenance of DeltapH by a butanol-tolerant mutant of Clostridium beijerinckii.

The isolation of Clostridium beijerinckii mutants that are more tolerant of butanol than the wild-type offered the opportunity to investigate whether the membrane activities which are required for maintaining the transmembrane DeltapH (the difference in pH between the cellular interior and exterior) are sensitive targets of butanol toxicity. The DeltapH was measured by the accumulation of [14C]benzoate using late-exponential-phase cells which were suspended in citrate/phosphate buffer at pH 5 (to maximize the DeltapH component of the protonmotive force) and supplemented with glucose and Mg2+. The DeltapH of the butanol-tolerant tolerant mutant, strain BR54, of C.

Accumulation of methylglyoxal in the gingival crevicular fluid of chronic periodontitis patients.

Background, Aims: Methylglyoxal (MG), a toxic product of cellular metabolism, is elevated in tissues and fluids in a number of human diseases. A cross-sectional study was undertaken to determine whether MG accumulates in the gingival crevicular fluid (GCF) of chronic periodontitis patients.

Methods: GCF samples were collected for 30 s each from three teeth with pocket depths greater than 3 mm (DD sites), from 14 chronic periodontitis patients.

Evidence for the early onset of gingival inflammation following short-term plaque accumulation.

Aim: A study was undertaken to examine cytokine markers in gingival crevicular fluid (GCF) during the early stages of plaque accumulation.

Methods: A panel of five subjects with good oral hygiene went without brushing for 1 or 3 days, after which GCF samples were taken by placing paper strips into the gingival margins of the maxillary premolars and first molar for 30 s. GCF flow rates were determined with a Periotron instrument (Oraflow, Inc.

Cheese consumption and the development and progression of dental caries.

Whereas research into the causes of dental decay has focused on the harmful relationship between dental plaque bacteria and foods, studies into the protective effects of foods have been infrequent and limited in number. Recent investigations showed that milk and cheese could reduce the effects of metabolic acids, and could help restore the enamel that is lost during eating. Postulated mechanisms involve buffering, salivary stimulation, reduction of bacterial adhesion, reduction of enamel demineralization, and/or promotion of remineralization by casein and ionizable Ca and P.

Clostridium beijerinckii and Clostridium difficile detoxify methylglyoxal by a novel mechanism involving glycerol dehydrogenase.

In contrast to gram-negative bacteria, little is known about the mechanisms by which gram-positive bacteria degrade the toxic metabolic intermediate methylglyoxal (MG). Clostridium beijerinckii BR54, a Tn1545 insertion mutant of the NCIMB 8052 strain, formed cultures that contained significantly more (free) MG than wild-type cultures. Moreover, BR54 was more sensitive to growth inhibition by added MG than the wild type, suggesting that it has a reduced ability to degrade MG.

Food starches and dental caries.

Sucrose and starches are the predominant dietary carbohydrates in modern societies. While the causal relationship between sucrose and dental caries development is indisputable, the relationship between food starch and dental caries continues to be debated and is the topic of this review. The current view of dental caries etiology suggests that in-depth evaluation of the starch-caries relationship requires the consideration of several critical cariogenic determinants: (1) the intensity (i.

IL-8 degradation by Porphyromonas gingivalis proteases.

Gingival epithelial cells are the primary barrier to infection by periodontal pathogens. The production of chemotactic cytokines, including interleukin-8 (IL-8), is one mechanism the host uses in response to infection. In this study it was found that both gingival and oral epithelial cells produced IL-8, but after infection with the periodontal pathogen Porphyromonas gingivalis, accumulation of the cytokine could not be detected.

Inhibition of salivary amylase by black and green teas and their effects on the intraoral hydrolysis of starch.

Tea decoctions prepared from a number of black and green teas inhibited amylase in human saliva. Black teas gave higher levels of inhibition than green teas, and removal of tea tannins with gelatin led to the loss of inhibitory activity from all decoctions. Streptococcal amylase was similarly inhibited by tea decoctions.

Cytotoxic effects of short-chain carboxylic acids on human gingival epithelial cells.

Previous studies showed that foods that are retained on the dentition can accumulate high levels of short-chain carboxylic acids (acetic, formic, lactic and propionic). Since gingival epithelium is the first periodontal tissue to be challenged by oral factors, a study was undertaken to determine whether short-chain carboxylic acids can affect epithelial cells in vitro. Immortalized human oral epithelial cells were grown in supplemented keratinocyte growth medium at 37 degrees C, and the effects of short-chain carboxylic acids were determined with tetrazolium-based and trypan blue exclusion assays.

Gingival inflammation induced by food and short-chain carboxylic acids.

Earlier studies in our laboratories demonstrated that particles of a number of snack foods that are retained on the dentition accumulate fermentable sugars and short-chain carboxylic acids (SCCA; acetic, formic, lactic, and propionic) to different degrees. The present study was undertaken to test the hypothesis that the accumulated SCCA can induce a gingival inflammatory response. Five periodontally and medically healthy subjects were given portions of plain doughnuts (high SCCA levels) or oatmeal cookie (low SCCA), or had the SCCA applied directly to the gingival margins of designated teeth.

Effects of a high-bicarbonate dentifrice on intraoral demineralization.

Dentifrices available on the market today contain sodium bicarbonate in a wide range of concentrations. Anticaries efficacy has been demonstrated for these dentifrices in a variety of tests. New insights were gained in the present study in which the effect of a high-bicarbonate dentifrice on the sucrose-induced demineralization of tooth enamel in situ was examined.

Effectiveness of calcium lactate added to food in reducing intraoral demineralization of enamel.

Following the demonstration that rinses with solutions of soluble calcium salts reduced sucrose-induced demineralization, a study was undertaken to determine whether a similar effect could be obtained by the supplementation of a solid food with calcium lactate (CL). Subjects wore palatal appliances containing blocks of bovine enamel that were coated with Streptococcus mutans IB 1600 and ate 5-gram portions of cookies made with defined levels of CL. Determinations were made of changes in iodide penetrability (delta Ip) of the enamel, as well as the pH, calcium and inorganic phosphate of the streptococcal plaque.

Short-chain carboxylic-acid-stimulated, PMN-mediated gingival inflammation.

This communication reviews the effects of short-chain carboxylic acids on human cells of importance to the periodontium. The central hypothesis is that these acids can alter both cell function and gene expression, and thus contribute to the initiation and prolongation of gingival inflammation. Short-chain carboxylic acids [CH3-(CH2)x-COOH, x < 3] are metabolic intermediates with a broad range of apparently paradoxical biological effects.

Accumulation of fermentable sugars and metabolic acids in food particles that become entrapped on the dentition.

Earlier studies (Kashket et al., 1991) showed that particles of high-starch snack foods remained longer on the teeth than those of high-sucrose, low-starch foods. The question arose whether the prolonged presence of food particles enhances cariogenicity.

Effects of a high-bicarbonate dentifrice on intraoral demineralization.

Dentifrices available on the market today contain sodium bicarbonate in a wide range of concentrations. Anticaries efficacy has been demonstrated for these dentifrices in a variety of tests. New insights were gained in the present study in which the effect of a high-bicarbonate dentifrice on the sucrose-induced demineralization of tooth enamel in situ was examined.

Enamel rehardening with cheese in irradiated patients.

Radiotherapy of head and neck malignancies results in severe xerostomia which induces radiation caries. Hard cheese has potent anti-cariogenic effects, even with minimal salivary gland function. Eight patients irradiated for neck cancer volunteered for this study.

Validation of the intraoral delta Ip system and use of the system to test the efficacy of Mentadent dentifrice.

Ongoing efforts within the oral care industry to improve dentifrices by the addition of anti-tartar compounds, bicarbonate and other agents, have necessitated the continuing evaluation of new products in order to assure their anti-caries effectiveness. However, clinical evaluation of new products is time consuming, prohibitively expensive and ethically questionable. Recently, a number of intraoral models have been developed that appear to be well-suited to evaluate new products.

Delayed effect of wheat starch in foods on the intraoral demineralization of enamel.

There is considerable evidence for an association between dental caries and food starches. However, the intraoral utilization of starch may be quite complex, giving rise to conflicting results. Demineralization induced by unsweetened cookies was examined in an intraoral model system that utilized palatal appliances containing blocks of bovine enamel.

Reduction of intra-oral demineralization of enamel after single exposures to sodium fluoride.

Studies demonstrated the effects of single rinses with low concentrations of NaF on the intra-oral demineralization of enamel. Blocks of bovine enamel were covered with Streptococcus mutans IB1600, mounted in palatal appliances, and worn in the mouths of volunteers for specified times. Subjects rinsed with solutions of NaF, with or without sucrose.

Effect of timing of administered calcium lactate on the sucrose-induced intraoral demineralization of bovine enamel.

A number of soluble calcium salts are known to reduce the demineralization of enamel in the mouth. The present study was undertaken to examine the effects of rinses containing different concentrations of calcium lactate, and the time of giving the rinses with respect to sucrose challenges. Subjects wore palatal appliances containing blocks of bovine enamel whose surfaces were covered with Streptococcus mutans IB 1600, and rinsed with 10% sucrose for 1 min.

Limitations in the intraoral demineralization of bovine enamel.

A model system was used to examine the relation between the duration of plaque pH fall and enamel demineralization following the intake of dietary carbohydrate in humans. Subjects wore palatal appliances containing blocks of bovine enamel covered with Streptococcus mutans IB 1600, and rinsed with 5 or 10% sucrose. Changes in iodide penetrability (delta Ip) of the enamel, and the pH and extracellular calcium and inorganic phosphate (Pi) concentrations of the streptococcal plaque were determined.

Lack of correlation between food retention on the human dentition and consumer perception of food stickiness.

When dental health professionals advise that sticky foods be avoided, it is left to the consumer to choose correctly among different foods. In this study, comparisons were made among consumer ratings of stickiness of 21 commercially available foods and objective measurements of tooth retention of each of the foods. No correlation was found between the two, and neither the rates of clearance of food particles from the teeth nor the rates of clearance of food-derived sugars from the saliva correlated with ratings of food stickiness.

The effect of sucrose and fat in cookies on salivation and oral retention in humans.

Six adults were served accurately weighed portions (about 5 g) of cookies varying in sucrose and fat content. The cookies were chewed and spat out at the time the subjects were ready to swallow. Additional spittings were collected at intervals up to two, three, and four min.

Accumulation of enamel constituents in Streptococcus mutans plaque during intraoral demineralization.

Studies were carried out with an intraoral demineralizing system in order to determine whether calcium and inorganic phosphate (Pi) accumulate in plaque during active demineralization of enamel. Blocks of bovine enamel were coated with Streptococcus mutans and were carried in palatal appliances worn by human volunteers. Demineralization was determined as changes in the iodide penetrability (delta Ip) of the enamel surfaces.