Comparative study on mineralization-related intraoral parameters in periodontitis-affected and periodontitis-free adults.

The parameters related to an intraoral mineralization tendency in periodontitis-affected (P+) and periodontitis-free (P-) study subjects (16 adults, 46-74 yr, matched for sex and age) were compared. For this purpose the calcium (Ca) and phosphate (P) concentration of both plaque and saliva, resting pH and the acidogenic response of interdental plaque, plaque wet weight, salivary flow rate, buffering capacity and sucrase activity, interdental plaque, plaque S. mutans levels as well as salivary lactobacilli and yeast levels were estimated. Plaque Ca (micrograms/mg protein, P less than 0.025) and P (micrograms/mg protein, P less than 0.05), saliva Ca (micrograms/ml, P less than 0.005) and the saliva Ca:P ratio (P less than 0.005) were higher in the P+ than in the P- group. The resting pH values were higher (P less than 0.025) and the acidogenic response of the interdental plaque was lower (P less than 0.025) in the P+ group than in the P- group. The P+ group had lower S. mutans levels in saliva and interdental plaque. No differences were found in the wet weight of plaque and in the flow rate, buffering capacity or sucrase activity of saliva between the groups. The findings of the mineralization-related parameters in the two "extreme" groups of periodontal status suggest a higher intraoral mineralization tendency in periodontitis-affected persons than in periodontitis-free subjects. Ca and P accumulation of supragingival plaque seem to be connected with low acidogenicity of plaque and high salivary Ca concentration.

Plaque fluid as a bacterial milieu.

Studies of the extracellular, free concentrations of substrates, growth factors, inhibitors, and end-products of metabolism to which the intact plaque microflora is exposed in situ can assist in the understanding of factors controlling plaque pathogenicity. Information is becoming increasingly available from analysis of fluid separated by centrifugation of plaques collected at various intervals after an intra-oral pulse of dietary or experimental substrate, or different procedures or treatments having cariostatic potential. Such analytical results give more information than those obtained by analysis of aqueous or other extracts, because they yield values of substrate concentration representing those occurring at the bacterial cell surface. The largest body of information concerns extracellular levels of acid end-products of sugar catabolism in relation to food quality or sequence, and of amino acids and other products of nitrogen metabolism, in relation to studies of the detailed metabolic events of the Stephan curve, and of the demineralizing effect of the plaque environment. Areas where little information is available and which merit further study include plaque clearance of salivary and other components with anti-caries activity (e.g., antibodies, enzymes, fluorides, cations, other antimicrobials, etc.), and substrate concentrations to determine gradients for diffusion into and out of plaque.

Facts and artefacts in research on human dental plaque fluid.

In 1966, Jenkins suggested that the plaque fluid environment was likely to have higher concentrations of extracellular solutes than was apparent from analyses of total plaque concentrations. Early work on plaque fluid confirmed this contention, but some artefact was also generated by the prolonged centrifugation used for separation. The solute concentrations in plaque fluid mostly exceed those in saliva or crevicular fluid. Thus, the environmental conditions are distinctly different from those based on the assumption that saliva readily permeates films of dental plaque. In contrast, the presence of serum proteins suggests a crevicular input to plaque fluid. These data suggest that exchange between dental plaque and its environment is apparently restricted. Diffusion rates measured in dental plaque by different methods do not agree on how restricted it is. However, measuring diffusion in plaque introduces artefacts in packing density, a major determinant of the diffusion rate. The conditions used for collection and analysis have been reported to produce artefactual changes in plaque fluid potassium, a predominantly intracellular ion. Measurements of predominantly extracellular ions, such as calcium, are no less prone to artefact, whether based on ion-selective electrodes or on total calcium. We have much to learn about the fluid environment of the teeth and about dynamic changes in plaque fluid composition and properties during perturbations. Such information can give insights into pathological processes such as tooth demineralization and dental caries, calculus formation, and gingival inflammation.

An assessment of recent advances in the study of the chemistry and biochemistry of dental plaque fluid.

This paper discusses key points made during the symposium in the light of work carried out in other laboratories. It is emphasized that the unique importance of plaque fluid is that the net result of chemical changes induced by microbial activity is reflected in this medium, which is in intimate contact with the enamel surface, and that this medium is accessible to chemical and biochemical analyses. However, in order to assess the cariogenic potential of plaque, we must consider the properties of both whole plaque and plaque fluid together. Although it is apparent that results of plaque fluid composition are sensitive to both isolation and the storage procedures utilized, plaque fluid appears to be a distinct entity within the oral cavity. Technical advances have been made which allow for the determination of the activity of selected ions (hydrogen, calcium, phosphate, potassium, fluoride) in plaque fluid obtained from a single site within the mouth. It appears, however, that such data alone may be insufficient to define the cariogenic potential of plaque appropriately. Evidence is presented from which it can be concluded that, with use of pooled samples of plaque obtained from individuals with clear differences in caries experience, results on plaque and plaque fluid composition can be obtained which are consistent with noted differences in caries susceptibility. The importance of base production is also discussed, and it is noted that few studies have been carried out to elucidate the role of proteins found in plaque fluid. In conclusion, recent advances in the study of plaque fluid have provided new insights into the mechanism of caries formation which are also germane to the formation of dental calculi.

Micro-analysis of plaque fluid from single-site fasted plaque.

Despite the site-specific nature of caries, nearly all data on the concentration of ions relevant to the level of saturation of plaque fluid with respect to calcium phosphate minerals or enamel are from studies that used pooled samples. A procedure is described for the collection and analysis of inorganic ions relevant to these saturation levels in plaque fluid samples collected from a single surface on a single tooth. Various methods for examining data obtained by this procedure are described, and a mathematical procedure employing potential plots is recommended.

Computer simulation of oral fluoride clearance.

The presence of fluoride in saliva and dental plaque is important for prevention of dental caries. The elimination of fluoride from the oral cavity after introduction of a fluoride containing agent is a complicated physiological process. This process was simulated with a Pascal program running under MS-DOS on IBM-compatible microcomputers. The program calculated the fluoride concentration in saliva as a function of time from several input parameters, the most important being the amount of fluoride, salivary stimulation due to the fluoride vehicle, resting salivary flow rate and volume factors. Furthermore, factors such as excretion of fluoride in the saliva following fluoride absorption in the intestinal tract were modeled. The fluoride concentration in dental plaque due to diffusion was also calculated. Output was directed to files which could be processed by a graphics interface. The results of the computations were very similar to findings in vivo.

Fluoride analysis in nanoliter- and microliter-size fluid samples.

A variety of techniques is described for measuring fluoride in volumes of from 0.005 to 5 microL, including: (1) micropipette procedures for transference and dilution of samples, (2) construction of miniature and micro fluoride-selective electrodes, and (3) methods for adapting standard electrodes for micro- and semi-micro volumes. These described techniques have a number of advantages, including speed of analysis, high accuracy, and adaptability to many types of fluid samples. Recent studies involving use of these procedures include the analysis of fluoride in: (1) plaque fluid samples from single sites before and after topical fluoride administration, (2) tooth mineral samples recovered by acid-etch or microdrill biopsy of enamel, and (3) fluid recovered from the interior of the tooth during simulation of the caries process.

Pharmacokinetics of fluoride in man and its clinical relevance.

A large number of parameters will influence and mediate the activity and the pharmacological response of dental fluoride products after systemic or topical treatment. This report reviews some aspects of the pharmacokinetics of fluoride in man, fluoride bio-availability, plasma kinetics, and kinetics of fluoride in saliva and plaque fluid. Pharmacokinetic studies in growing dogs show that 90% of a single injected fluoride dose is retained shortly after birth, but at maturity it decreases to about 50%. The degree of fluoride accumulating in calcifying tissues seems to be strongly related to age. The bio-availability of fluoride from swallowed fluoride toothpaste is shown to be decreased if the toothpaste is ingested close to a meal. Several studies show that fluoride exerts its cariostatic effects through the liquid phase surrounding the enamel. The importance of fluoride in the fluid environment of the teeth and the kinetics of fluoride in saliva are discussed. Clinical studies using different slow-release fluoride systems indicate that they are promising cariostatic agents--in particular intra-oral slow-release devices and lozenges. A new micro-analytical method to study the kinetics of fluoride in plaque fluid collected from single tooth sites has been developed. Preliminary studies show that the clearance of fluoride from plaque fluid is slowest in the upper incisor region, followed by the molar region, and faster in the lower incisor region. A site-by-site study of the concentration of fluoride in plaque fluid after topical fluoride administration could be extremely beneficial in optimization of the methods and recommended safety regimens for fluoride therapy.

Fluoride in dental plaque and its effects.

Total plaque fluoride is in the range 5-10 mg/kg (ppm) on a wet-weight basis. The variability of literature data on plaque fluoride is partly ascribed to analytical problems, many assays being close to or below the concentration detection limit of the fluoride electrode. A change in classification of plaque fluoride compartments is necessary, since recent work indicates that there are two pools of plaque F: less than 5% of the total F is in plaque fluid as the free ion, and the large remaining portion of total plaque F is designated as bound F, with the total F being greater than 95% extractable by cold 0.5 mol/L perchloric acid. Sources of plaque fluoride include the diet, saliva, and crevicular fluid; enamel is unlikely to be a regular source for plaque F unless it is either coated daily with labile fluoride compounds, such as calcium fluoride, or released by demineralization. The location and nature of plaque bound F are not established, but the present evidence is consistent with an intracellular location. Bound F may be released by acids produced in plaque during sugar fermentation, but it is unlikely to reach ion concentrations high enough for sufficient time periods to exert significant inhibition of plaque acidogenesis. Epidemiological evidence showing correlations between pooled plaque F concentrations and caries prevalence in the plaque donors does not exclude the possibility of coincidental effects of water F on both caries and plaque F concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Biochemical effects of fluoride on oral bacteria.

Fluoride inhibition of carbohydrate metabolism by the acidogenic plaque microflora is well-established, although it has not always been appreciated that oral bacteria vary considerably in their susceptibility to fluoride. Early studies demonstrated that the F-induced reduction in acid production was due, in part, to the inhibition of the glycolytic enzyme, enolase, which converts 2-P-glycerate to P-enolpyruvate. The decreased output of PEP in the presence of F, in turn, results in the inhibition of sugar transport via the PEP phosphotransferase system (PTS). Bacterial accumulation of fluoride involves the transport of HF, a process requiring a transmembrane pH difference or pH gradient, which is generated only by metabolically active cells. The uptake of HF into the more alkaline cytoplasm results in the dissociation of HF to H+ and F- and, if allowed to continue, the accumulation of protons acidifies the cytoplasm, causing a reduction in both the proton gradient and enzyme activity. Current information indicates that in addition to enolase, F- also inhibits the membrane-bound, proton-pumping H+/ATPase, which is involved in the generation of proton gradients through the efflux of protons from the cell at the expense of ATP. Thus, fluoride has the dual action of dissipating proton gradients and preventing their generation through its action on H+/ATPase. The collapse of transmembrane proton gradient, in turn, reduces the ability of cells to transport solutes via mechanisms involving proton motive force. In spite of these known effects on the bacterial cell, there is no general agreement that the anti-microbial effects of F contribute to the anti-caries effect of fluoride.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationships between the biochemical composition of both free smooth surface and approximal plaque and salivary composition and a 24-hour retrospective dietary history of sugar intake in adolescents.

The relationships between the composition of both free smooth surface and approximal plaque and salivary composition and sugar intake assessed from a retrospective 24-hour dietary history were investigated. The inorganic phosphorus concentrations of both types of plaque collected from the permanent dentition were directly related to concentrations in stimulated whole saliva of 45 males aged 12-13 years. The calcium, inorganic phosphorus, water-soluble carbohydrate and protein concentrations of free smooth surface plaque were related to both the time since the last reported sugar intake and the amount of sugar and number of sugar intakes consumed in the previous 24 h as assessed from the retrospective diet histories of 75 females aged 14-15 years. A similar relationship with the reported time since sugar was observed for the calcium and carbohydrate concentrations in approximal plaque, but an association with the reported 24-hour sugar intake was not observed. Fewer statistically significant correlation coefficients were observed between the composition of both types of plaque and the reported sugar intake in the male subjects. The results indicate that the composition of both types of plaque are related to the composition of saliva and the time elapsed since the last sugar intake, but the relationship between the composition of plaque and sugar intake may differ between free smooth surface and approximal plaque.

A mineral-related feature of young plaque characteristic to periodontitis-affected adults.

The calcium concentration of 3-day-old total supragingival plaque in periodontitis-affected adults (n = 12) and their age and sex-matched periodontitis-free pairs was compared. The young plaque of the periodontitis-affected adults contained more calcium per protein (P less than 0.025, sign test) than that of the periodontitis-free pairs. The findings of the present study may suggest that high Ca-content of supragingival plaque is connected to the development of adult periodontitis.

Identificación de enzimas glucosiltransferasas en muestras de placa dental provenientes de pacientes con caries / Identification of glucosiltransferases in dental plaque sampling coming from patients with caries

Demostración del origen extracelular de las enzimas glucosiltransferasas, mediante un estudio de microscopía electrónica del homogenato de placa y por medición de la actividad de Lactato Deshidrogenasa como marcador citoplasmático, comprobandose finalmente, la presencia de GTF extracelular en placa dental, contribuyendo así, en la síntesis de polisacáridos extracelulares in vivo en la placa dental

Composición quimica (carbohidratos) de la placa dental de diferentes áreas de la boca. I. Resultados preliminares / Chemical composition (carbohydrates) of dental plaque of several oral area. Preliminar results I

En general se han reportado diferencias en cuanto a la composición de la placa obtenida de dientes posteriores y anteriores. La placa colectada de los dientes entero-superiores o inferiores es diferente en cuanto a composición microbiológica y pH. Los resultados logrados en este estudio demuestran que la placa obtenida de los dientes antero-inferiores contiene una menor concentración, por unidad de peso, de polisacáridos extracelulares alcali-soluble que los dientes antero-superiores. Por otra parte, no se encontraron diferencias en cuanto a la concentración de polisacáridos acuo-solubles y acuo-insolubles en esta misma área de la boca. En la placa obtenida de los dientes postero-superiores e inferiores no se observaron diferencias significativas en ninguno de los parámetros estudiados

Effect of fluoride-containing chewing gum on remineralization of carious lesions and on fluoride uptake in man.

The remineralization effect of chewing gum containing fluoride (F) was studied on natural carious lesions. Maxillary acrylic appliances carrying the carious enamel sections were worn by three subjects. After 3 days of chewing 15 sticks of fluoride gum (Fluogum, containing 0.113 mg F/stick sweetened with xylitol/sorbitol), there was a significant reduction in both lesion depth and in the size of the body of the lesion (p less than 0.001). Exposure of carious lesions to 3 days in an oral environment without fluoride supplement reduced the size of the body of the lesions by an average of 5% (p less than 0.05). Chewing one or two sticks of the gum for 15 minutes raised the salivary-fluoride concentration to a peak of 1.13 ppm 5 minutes after chewing one stick, and raised the concentration to 2.73 ppm 10 minutes after chewing two sticks. The area under the curve of salivary-fluoride concentration versus time obtained following chewing one and two sticks were 0.78 h.microgram/ml and 1.89 h.micrograms/ml, respectively. There was a high positive correlation (r = 0.78) between the saliva flow and elimination of fluoride. Plaque fluoride level increased 1.7 fold following chewing two sticks of gum (p less than 0.05). The effect of chewing two sticks (a dose of 0.226 mg F) on plasma fluoride level was negligible, an indication of the safety of chewing gum regimen. More work is needed to document the cariostatic efficacy of a fluoride-containing chewing gum.

The interpretation of CO2 equilibration data to obtain plaque fluid buffer capacities, and comparison with results obtained by titration.

Titration measurements of pooled plaque fluid buffering capacity (Shellis and Dibdin, 1988), which showed a broadly defined minimum at pH 7, were compared with recent curves published by Carey et al. (1988a), which they obtained by an ultra-micro CO2-equilibration technique and which suggested a quite different profile, peaking sharply at pH 7.1. When analyzed in a different, more conventional way, the raw measurements in the latter study become more consistent with our own results and with earlier findings of Tatevossian (1977). In particular, we conclude that the peak at pH 7.1 is an artifact, and that Carey et al. underestimated buffer capacities below pH 6.4 and above pH 7.4. Rationales for the two modes of analysis are compared, and possible reasons for the remaining differences between the re-analyzed CO2-equilibration results and the titration results are discussed. Suggestions for the improvement of the accuracy of the CO2-equilibration technique are put forward.

An evaluation of 6 dentifrice formulations for supragingival anticalculus and antiplaque activity.

A 4 week, double blind clinical trial was conducted to assess the antiplaque/anticalculus activity of test dentifrices containing varying levels of zinc citrate. Subjects were divided into 6 groups, 4 experimental, 1 positive control and a placebo group. All subjects only brushed at home using the placebo control during study weeks 1 and 3. Plaque and calculus were collected at the end of study weeks 2 and 4 on mylar strips worn on lower incisor teeth. Dentifrice efficacy was assessed by comparing group dry and ash weight decrements. While there were no significant differences between the test and control groups, there was a demonstrable trend toward greater inhibition with higher zinc citrate levels, especially among subjects with high levels of plaque and calculus at baseline.

[Clinical study of the correlation between bad breath and subgingival microflora].

A dark field microscopic examination of subgingival microorganisms and gas chromatographic analysis of volatile sulphur compounds were employed to investigate the role of subgingival microflora in the production of bad breath. Subjects (11 female, 13 male; aged 24 to 61) were divided into the following 2 groups on the basis of apparent bad breath by the olfactory judgement; bad breath group (group B, n = 13), and no bad breath group (group N, n = 11). A gas tight syringe was employed to withdraw 5 ml mouth air samples, which were injected directly into the gas chromatograph. Volatile sulphur compounds produced in mouth air were analyzed by gas chromatograph to determine volumes of CH3SH. Subgingival plaque samples were taken with sterilized paper points from the deepest site of probing depth in each subjects. The samples were examined by means of dark field microscopy and 100 bacteria in randomly selected fields were classified on a percentage basis into one of the following morphological categories: (1) spirochetes, (2) motile rods, (3) filaments, (4) fusiforms, (5) straight rods, and (6) coccoid cells. Total cell counts per 1 ml were calculated from bacterial counts of each categories. Comparison of 2 independent means from each groups were carried out by Wilcoxon's rank sum test for nonparametric values. Correlations of bacterial data with CH3SH values in mouth air were determined by means of Spearman rank correlation cofficient. Results were as follows; 1. Significant differences existed in the microbial flora between the 2 groups: percentage of spirochetes and motile rods in group B were significantly higher than those in group N (p less than 0.01). Total cell counts of group B were significantly greater than group N, and there were statistically significant differences (p less than 0.01). 2. CH3SH values in mouth air had positive correlations with the percentage of spirochetes, the percentage of motile rods, and total cell counts. These results are consistent with the view that subgingival microorganisms play a certain role in the production of bad breath. Moreover, it was suggested that spirochetes and motile rods are related to the mechanism of bad breath production.