pH Of Human Dental Plaque Research Articles

Cariogenic Potential of Lactosylfructoside as Determined by Acidogenicity of Oral Streptococci in vitro and Human Dental Plaque in situ

The cariogenic potential of lactosylfructoside [O–β–D–galactopyranosyl–(1→4)–O–α–D–glucopyranosyl–(1↔2)–β–D–fructofuranoside] was estimated by experiments on oral streptococci in vitro and human dental plaque in situ. Lactosylfructoside was unable to support growth of the strains of Streptococcus mutans and S. sobrinus used in this study. However, it was able to support growth of strains of S. sanguis, S. mitis and S. oralis. Acid was produced rapidly by cell suspensions of S. oralis ATCC 10557 incubated with lactosylfructoside. Application of 5% w/v solution decreased the pH of human dental plaque. The minimum pH value was below 5.3. The results suggest that lactosylfructoside is as acidogenic as lactose and could be cariogenic if it is consumed frequently and retained for a long period in the mouth.

Effects of lactate dehydrogenase and nicotinamide adenine dinucleotide on human dental plaque pH and acid anion concentrations

The effect of sucrose rinses supplemented with L-LDH and NAD was investigated. When LDH or NAD were added to the sucrose rinse, the pH fall was less marked than with rinsing with sucrose alone. Significant differences ( p < 0.05) in mean minimum pH and cH areas were observed when sucrose rinses were supplemented with LDH, NAD or with a combination of LDH and NAD, when compared with sucrose alone. Plaque fluid concentrations of lactate and acetate significantly decreased with all rinses when compared with sucrose alone. Phosphate levels also decreased, although not significantly, when NAD was the sole supplement. No significant decreases were observed in succinate, formate or propionate concentrations. The results confirm the beneficial effect of LDH in reducing the accumulation of lactate in plaque following a sucrose rinse. The inclusion of NAD in the rinse demonstrated the role of extracelluar hydrogen acceptors in the reaction. Further work is required to identify endogenous hydrogen receptors and to clarify the fate of pyruvate resulting from the oxidation of lactate before the potential role of LDH as a cariostatic agent can be fully understood.

Diet patterns and caries.

Few dietary studies have been designed to investigate the effects of intake patterns of food items upon the environment of the teeth. This brief review considers evidence about the effects of choice, combination, and sequence of ingested food and drink upon the pH of human dental plaque in vivo. A series of three studies, which were designed to investigate some of the intra-oral biological events associated with cariogenicity during various eating patterns, are discussed. The principal findings show that if a "meal" includes an item which contains carbohydrate such as sucrose, glucose, or fructose which is rapidly fermented by the acidogenic microorganisms in dental plaque, there will be rapid acid production and the plaque pH will fall. However, other items eaten immediately before, during, or after the consumption of the sugary item can influence the plaque pH. If the non-sugary item stimulates saliva, it will have a pH-raising effect. The remineralizing potential may be enhanced if, for instance, calcium or fluoride is released from the food. However, if one sugary item is followed by another, the demineralizing potential may be enhanced. The results of these experiments are discussed in the context of our current understanding of the dynamics of the carious process. Recent preliminary experiments suggest that other factors, such as the individual subject's speed of consumption, may also affect the cariogenic potential of the oral environment.

Effects of chemically modified starches in suspensions and lozenges on pH of human dental plaque

The aim was to evaluate chemically modified starches (CMS) from a cariologic point of view as alternatives to gum arabic in sugar-free lozenges. Two commercial CMS, Purity Gum 40 and Capsul, were selected due to their comparatively low availability to alpha-amylase in vitro. Both gelatinized CMS suspensions and lozenges were tested in vivo by measuring plaque pH. The results showed that suspensions of Purity Gum 40 or Capsul were less available to alpha-amylase in vitro than the soluble starch reference. However, the initial phase of amylolysis was comparatively rapid also with CMS. In spite of the slower rate of hydrolysis, suspensions of the two CMS reduced pH of dental plaque in vivo to the same extent as soluble starch, but somewhat less compared with glucose. Lozenges with Purity Gum 40 also lowered plaque pH, although less than when administered as a precooked suspension. The most prominent pH drop was found with a lozenge containing Purity Gum 40-sucrose-glucose, while tablets with gum arabic-maltitol and pectin-gelatine-Lycasin somewhat increased the pH values. To conclude, it is not recommended to exchange gum arabic for CMS in sugar-free lozenges, since the cariogenic properties of the products are negatively affected.

Effects of variously processed starch on pH of human dental plaque.

The aim of this investigation was to study the effect of starch in various cereal products on pH of human dental plaque in vivo as compared to availability to the alpha-amylase of starch in vitro. Three separate experimental series were performed including: 1) rye and wheat products, 2) wheat products processed under both mild and severe conditions, and 3) wheat products with and without added sucrose. The pH drop in dental plaque was studied after a mouthrinse in groups of 10 subjects. Solutions of glucose or sucrose were used as references. No differences were found between boiled rye and boiled wheat, nor between rye bread and wheat bread. Severely popped wheat resulted in the greatest pH drop, followed, in order, by drum-dried and extrusion-cooked products. Mildly steam-flaked and mildly dry-autoclaved products induced comparable small pH falls. Sucrose-sweetened wheat products resulted in lower plaque pH values compared to unsweetened products. This effect was most pronounced with a mildly processed sample. In all three series, the glucose and sucrose reference solutions showed the greatest pH drop. In conclusion, all processing methods increased the fermentability of starch in human dental plaque in vivo. Thus, the more severe the processing conditions the more prominent the pH falls. The pH drop in plaque in vivo correlated (r = 0.96 in Series 1 and r = 0.92 in Series 2) with the rate of starch hydrolysis with alpha-amylase in vitro.

Effects of Parafilm and cheese chewing on human dental plaque pH and metabolism.

The effects of chewing Parafilm and cheese following sucrose rinsing on human dental plaque pH and plaque fluid organic and amino acid concentrations were investigated. Immediate increases in plaque pH were observed following chewing with concomitant decreases in lactate and acetate concentrations and increases in the concentration of formate and many amino acids. Chewing with cheese when compared with Parafilm resulted in significantly higher (p less than 0.05) plaque fluid concentrations of most amino acids, although significant decreases (p less than 0.05) in phosphate, succinate, and acetate concentrations were observed. However, no significant difference in the levels of formate, lactate, and propionate were found between the two chewing treatments.

Human dental plaque pH, and the organic acid and free amino acid profiles in plaque fluid, after sucrose rinsing

The relationship between these factors was studied in plaque and plaque fluid samples taken at intervals during the Stephan pH curve following a sucrose mouth rinse. Levels of lactate rose after the rinse, then fell during the pH recovery phase. Levels of acetate, propionate and phosphate fell after rinsing, then rose again. Amino acid concentrations also changed, with many showing a fall followed by a rise; others rising then falling; and some showing a more variable or complex pattern. In resting plaque fluid, only alanine, proline, glutamic acid, glycine and ammonia were present at concentrations above 1 mmol/l. Delta-aminovaleric acid was detected at levels below those that have been found in monkeys. Hydroxyproline and hydroxylysine were consistently detected, levels of arginine were generally low, and those of cystine consistently very low. The results may provide a basis for understanding the complex metabolic interrelations that occur in the course of the Stephan curve and which may reflect or produce the observed pH changes. They suggest that besides the amount of acid produced, the type of acid, buffering power and base production should be considered as determinants of plaque pH.

Comparison of in vivo Human Dental Plaque pH Changes within Artificial Fissures and at Interproximal Sites

Ion-sensitive field-effect transistor (ISFET) pH electrodes were used to monitor changes in plaque pH at the base of artificial occlusal surface fissures and at interproximal sites. Bovine enamel was used to construct fissures (1.5 x 0.1 x 1.0 mm) containing a small ISFET electrode. The fissures were fixed to carrier appliances and worn by 4 human volunteers. After plaque accumulation for 4 days changes in pH were monitored by wire telemetry following 1-min rinses with 10% solutions of either sorbitol or sucrose. Results were compared to data obtained from interproximal sites in the same subjects. Responses to sorbitol in the fissure and on the proximal surfaces were minimal and showed no significant difference in minimum pH (5.9 +/- 0.4 and 6.1 +/- 0.3, respectively) and area under pH 7.0. The response to sucrose at the two sites was very different revealing unique pH profiles which were statistically significantly different with regard to minimum pH (5.0 +/- 0.3, fissure and 4.3 +/- 0.2, proximal) and area under pH 5.7. Thus, the acidogenic potential of fermentable carbohydrate at two caries-prone sites in the human dentition is significantly different and conclusions based on interproximal telemetry measurements may not be applicable to occlusal surface fissures.

Site-specific differences in human dental plaque pH after sucrose rinsing

The object was to find out whether site-specific variations of pH might correlate with those of oral clearance as indicated by past studies using fluoride, sucrose and glucose as markers. Eleven subjects with 24 h growth of dental plaque rinsed the mouth with a 10% solution of sucrose. The pH of plaque, harvested from the labial or buccal cervical and approximal regions of certain teeth or groups of teeth, was then measured. The results confirmed previous reports that plaque pH varies from site to site in the mouth; the pattern observed was similar in each of the subjects. In the anterior part of the mouth, concentrations of hydrogen ion were invariably higher in plaque from the upper than from the lower surfaces of the teeth. The reverse pattern was found in the posterior part. This site-specific pattern was similar to that of oral clearance, as indicated by comparison with known values for glucose concentrations, a finding consistent with the view that site-specific pattern of plaque pH may reflect or at least be influenced by such differential clearance patterns.

Measurement of Human Plaque Acidity: Comparison of Interdental Touch and Indwelling Electrodes

The pH of human dental plaque following ingestion of five reference foods was monitored for 120 min in 4 subjects using an interdental metal-metal oxide touch microelectrode concurrently with a glass indwelling interproximal electrode mounted in a removable acrylic partial denture. Time that pH remained under given values, and time-pH unit area under these lines provided more separation among foods than did minimum pH or pH drop. Data obtained after 60 and 120 min gave similar results in terms of significant ordering of reference foods for the touch, but not the indwelling electrode system. The indwelling system detected a significantly greater magnitude and duration of pH fall after ingestion of all foods. However, ordering of and discrimination between pH falls induced by the foods was similar in both electrode systems.

Plaque sampling and telemetry for monitoring acid production on human buccal tooth surfaces

The plaque sampling method and wire telemetry using miniature, glass pH electrodes on the buccal surface of mandibular first permanent molars, compared human dental plaque pH responses to a 10 per cent solution of sucrose. Nine subjects abstained from oral hygiene and were tested in morning sessions on 5 consecutive days. The mean resting plaque pH value for all sessions by plaque sampling was 6.60 ± 0.18 (mean ± SD) and by telemetry was 6.56 ± 0.19. After a 1 min sucrose rinse, 1-day-old plaque showed a decrease in pH to approx. 5.5 by both methods. The 2-, 3-, 4- and 5-day-old plaque showed a consistent and more marked response to the carbohydrate. With 5-day-old plaque, the mean minimum pH achieved was 4.69 ± 0.28 as measured by sampling and 3.94 ± 0.49 as determined by telemetry. The times taken to reach minimum pH as determined by the two methods were almost identical. The electrode calibration data showed that all the telemetry electrodes responded consistently for all 5 days of study. Scanning electron microscopy and microbiological analysis of electrode tips and enamel replicas revealed that plaque accumulated on glass at the same rate and with a similar bacterial composition to plaque formed on clean enamel. It is proposed that glass microelectrodes and wire telemetry are a reasonable means for continuously monitoring plaque pH in situ. Comparison with plaque sampling suggested that telemetric responses reflect the type of plaque which accumulates at particular sites on the dentition.

Influence of sugar content in soft bread on pH of human dental plaque.

Quantitative determination of monosaccharides, disaccharides and sorbitol by use of gas-liquid chromatography (GLC) was performed on thirty-three samples of different commercial soft bread. Maltose was found in all the bread samples. Fructose and glucose were found only in samples of sweetened bread. Sucrose was detected in 5 samples, lactose in 2, and sorbitol in 2. Up to 20 per cent of the fresh bread weight was found to be low-molecular weight carbohydrates. Plaque pH-changes were studied in 18 persons following a 30-second month rinse with each of 3 solutions: (1) 50% sucrose, (2) water extract of sweetened bread, and (3) water extract of unsweetened bread. Mouth rinsing with the extract of sweetened wheat bread (sucrose 7.7 per cent of the dough weight) caused pH-decreases in plaque which were significantly more pronounced than those induced by the water extract of unsweetened wheat bread.