Distribution of fluoride in saliva and plaque fluid after a 0.048 mol/L NaF rinse

Fluoride in Saliva and Oral Mucosa after Brushing with 1,450 or 5,000 ppm Fluoride Toothpaste

The aim was to measure and compare fluoride concentrations in oral mucosa and saliva following a single brushing with either 1,450 or 5,000 ppm fluoride toothpaste. Fourteen healthy participants provided saliva and oral mucosa samples in the morning before tooth brushing. Then participants brushed their teeth with 1,450 ppm fluoride toothpaste, and saliva and mucosa samples were collected after 1, 2, 4, and 6 h. The experiment was repeated 3-7 days later with 5,000 ppm fluoride toothpaste. All samples were analyzed for fluoride using an ion-selective electrode adapted for microanalysis. Pre-brushing fluoride concentrations were higher in mucosa (mean1,450 0.26 ppm and mean5,000 0.20 ppm) than in saliva (mean1,450 0.08 ppm and mean5,000 0.07 ppm). The mean fluoride concentrations increased in both mucosa and saliva following a single brushing with both 1,450 ppm (meanmuc1,450 (1 h) 1.15 ppm, meansal1,450 (1 h) 0.33 ppm) and 5,000 ppm fluoride toothpaste (meanmuc5,000 (1 h) 3.21 ppm and meansal5,000 (1 h) 0.90 ppm). At 6 h, the fluoride concentrations had returned to pre-brushing levels. Across the 6-h sampling period the fluoride concentration in saliva was statistically significantly 1.4 times higher following brushing with 5,000 ppm compared with 1,450 ppm fluoride toothpaste. For mucosa, this ratio was only 1.1 and not statistically significant. In conclusion, the fluoride level in oral buccal mucosa is higher than in saliva and follows the same fluoride clearance pattern as in saliva. Over the initial 6-h period following a single tooth brushing, the ratio of the fluoride concentration in mucosa to that in saliva is independent of the fluoride concentrations in the toothpastes used.

Effect of Remineralizing Gels on Microhardness, Color and Wear Susceptibility of Bleached Enamel

Objectives:

To evaluate the effect of a remineralizing gel combining fluoride and calcium silicate/phosphate or a sodium fluoride gel on bleached enamel microhardness, color, and wear susceptibility.

Methods and Materials:

Two hundred forty bovine enamel-dentin samples were prepared. Baseline analysis of Knoop microhardness, color coordinates (L*a*b*), and surface profile were performed. According to the baseline microhardness values, specimens were stratified into six groups (n=40): NC (negative control)—no treatment; BL (positive control)—bleaching with 40% hydrogen peroxide gel (Opalescence Boost, Ultradent); BL/Rs—bleaching + application of calcium silicate/phosphate gel (Regenerate Serum, Unilever - Rs); Rs/BL—Rs + bleaching; Rs/BL/Rs—Rs + bleaching + Rs; and BL/F—bleaching + 2% sodium fluoride gel. After the treatment described for each group, color change (ΔE) and microhardness were evaluated again. To evaluate abrasion susceptibility, samples were randomly divided into two subgroups, according to the toothpaste used (Cp—Close Up or Rt—Regenerate), and underwent 100,000 brushing strokes. The profile of each sample was evaluated and the mean wear calculated. The data were analyzed by ANOVA and Tukey tests.

Results:

All bleached groups showed a significant reduction of microhardness in relation to the negative control. The groups treated with remineralizing gels showed a significantly higher microhardness and less wear than the positive control, although nonsignificant differences were observed among them. Nonsignificant differences in ΔE were found among bleached groups. The groups brushed with Regenerate toothpaste showed significantly less wear than those brushed with Close Up toothpaste.

Conclusions:

The remineralizing gels did not interfere with bleaching efficacy. However, all the treatments minimized the surface hardness reduction caused by the bleaching procedure and enamel loss after abrasion. Regenerate toothpaste resulted in less enamel abrasion.

Fluoride Increase in Saliva and Dental Biofilm due to a Meal Prepared with Fluoridated Water or Salt: A Crossover Clinical Study

Knowledge about fluoride delivery to oral fluids from foods cooked with fluoridated water and salt is scarce, and no study has evaluated fluoride concentrations in saliva or biofilm during meal consumption. In this randomized double-blind crossover study, 12 volunteers ingested meals (rice, beans, meat, and legumes) prepared with nonfluoridated water and salt (control group), fluoridated water (0.70 mg F/L; water group), and fluoridated salt (183.7 mg F/kg; salt group). Whole saliva was collected before meal ingestion, during mastication, and up to 2 h after meal ingestion. Dental biofilm was collected before and immediately after meal ingestion. Fluoride concentrations in saliva and dental biofilm were determined by an ion-specific electrode. The mean (±standard deviation; n = 4) fluoride concentrations in meals prepared for the control, water, and salt groups were 0.039 ± 0.01, 0.43 ± 0.04, and 1.71 ± 0.32 μg F/g, respectively. The three groups had significantly different fluoride concentrations in saliva collected during mastication (p < 0.0001) and after meal ingestion (p < 0.04; salt > water > control). The fluoride concentration in saliva returned to baseline 30 min after meal ingestion in the water group but remained high for up to 2 h in the salt group (p = 0.002). The fluoride concentration in biofilm fluid differed only between the salt and control groups (p = 0.008). The mastication of foods cooked with fluoridated water and salt increases fluoride concentrations in oral fluids and may contribute to the local effect of these community-based fluoride interventions on caries control.

Fluoride in Dental Biofilm Varies across Intra-Oral Regions

Information on differences in biofilm fluoride concentration across intra-oral regions may help explain the distribution of caries within the dentition. The aim of this cross-sectional study was to describe the fluoride concentration in saliva and in biofilm fluid and biofilm solids across 6 intra-oral regions. Unstimulated whole saliva was collected from 42 participants and biofilm harvested from the buccal sites in the 4 molar and 2 anterior regions. Samples were collected at least 1 h after use of fluoride dentifrice. No attempt was made to control the participants' food consumption or use of other topical agents. Centrifuged saliva, biofilm fluid, and biofilm solids were analysed for fluoride using a fluoride ion-selective electrode, adapted for microanalysis. Fluoride in biofilm varied across intra-oral regions. The mean biofilm fluid fluoride concentrations across the oral cavity ranged from 11.6 to 16.8 µM, being statistically significantly higher in the upper anterior region than in any other region. In all regions the fluoride concentration in biofilm fluid was higher than in saliva. For biofilm solids the fluoride concentration was highest in the lower anterior region (2,461 μmol/kg) and lowest in the lower molar regions (388 and 406 μmol/kg, respectively). Within biofilm, the solids contained most of the fluoride (81 to >99%). The biofilm fluid fluoride concentration was significantly positively associated with salivary fluoride and only marginally associated with that of biofilm solids. In conclusion, this study has shown pronounced differences in fluoride distribution across intra-oral regions and compartments. This shows that the sampling site is a crucial factor for studies of biofilm fluoride.

Comparative evaluation of the efficacy of fluoride varnish and casein phosphopeptide - Amorphous calcium phosphate in reducing Streptococcus mutans counts in dental plaque of children: An in vivo study

AIM

To assess the comparative efficacy of fluoride varnish and casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) complex visa viz. Streptococcus mutans in plaque, and thereby the role that these two agents could play in the prevention of dental caries.

MATERIALS AND METHODS

A cluster sample of 120 caries inactive individuals belonging to moderate and high caries risk group were selected from 3-5-year-old age group based on the criteria given by Krassee and were randomized to four groups, namely, fluoride varnish - Group I, CPP-ACP complex - Group II, mixture of CPP-ACP complex -Gourp III, and fluoride and routine oral hygiene procedures as control - Group IV. The results thus obtained were analyzed using Statistical Package for the Social Sciences (SPSS) version 16.

RESULTS

A statistically significant difference in the pre and post-application scores of S. mutans (P < 0.01) count was observed in all the groups with CPP-ACP plus fluoride group being the most proficient.

CONCLUSION

Materials such as fluoride varnish, CPP-ACP, and CPP-ACP plus fluoride protects the tooth structure, preserving the integrity of primary dentition, with the most encouraging results being with CPP-ACP plus fluoride.

Calcium Prerinse before Fluoride Rinse Reduces Enamel Demineralization: An in situ Caries Study

A calcium (Ca) prerinse before a fluoride (F) rinse has been shown to increase oral F levels. We tested the anticaries effect of this combination in a dose-response in situ caries model. In a double-blind, crossover experiment, 10 volunteers carried enamel slabs in palatal appliances for 14 days, during which they rinsed twice/day with one of four rinse combinations: (1) a placebo prerinse (150 mM sodium lactate) followed by a distilled water rinse (negative control); (2) a placebo prerinse followed by a 250 ppm F rinse; (3) a placebo prerinse followed by a 1,000 ppm F rinse, or (4) a Ca prerinse (150 mM Ca, as calcium lactate) followed by a 250 ppm F rinse. Sucrose solution was dripped onto the slabs 8×/day to simulate a high cariogenic challenge. The percent surface hardness loss (%SHL) was significantly lower in the Ca prerinse used with the 250 ppm F rinse group (%SHL = 38.0 ± 21.0) when compared with the F rinse alone (%SHL = 59.5 ± 24.1) and similar to the 1,000 ppm F rinse group (%SHL = 42.0 ± 18.3). Compared with the 250 ppm F rinse, the Ca prerinse increased biofilm fluid F only twice (nonsignificant). However, it greatly increased F in biofilm solids (∼22×). The Ca prerinse had little effect on loosely or firmly bound enamel F. The results showed an increased level of protection against demineralization by the use of a Ca prerinse, which seems to be caused by the enhancement of F concentration in the biofilm.

Hair as biomarker of fluoride exposure in a fluoride endemic area and a low fluoridated area

AIM

The aim of the present study was to determine whether hair could be used as biomarker of fluoride exposure.

MATERIALS AND METHODS

The study was carried out on 30 people living in an endemically fluoridated area and a low fluoridated area. Samples of hair from the occipital were taken and subjected to fluoride analysis by a fluoride ion electrode.

RESULTS

Lower fluoride levels in water supplies correlated with lower levels of fluoride in hair and more over higher fluoride levels in water correlated with higher levels of fluoride in hair. A direct relationship was evident between fluoride levels in water supplies and concentration of fluoride in hair (P < 0.01).

CONCLUSIONS

The results of the present study indicate hair can be used as an indicator of fluoride exposure.

Diet and the microbial aetiology of dental caries: new paradigms

The microbial and dietary factors that drive caries have been studied scientifically for 120 years. Frequent and/or excessive sugar (especially sucrose) consumption has been ascribed a central role in caries causation, while Streptococcus mutans appeared to play the key role in metabolising sucrose to produce lactic acid, which can demineralise enamel. Many authors described caries as a transmissible infectious disease. However, more recent data have shifted these paradigms. Streptococcus mutans does not fulfil Koch's postulates - presence of the organism leading to disease, and absence of the organism precluding disease. Furthermore, molecular microbiological methods have shown that, even with a sugar-rich diet, a much broader spectrum of acidogenic microbes is found in dental plaque. While simple sugars can be cariogenic, cooked starches are also now recognised to be a caries threat, especially because such starches, while not 'sticky in the hand', can be highly retentive in the mouth. Metabolism of starch particles can yield a prolonged acidic challenge, especially at retentive, caries-prone sites. These changes in the paradigms of caries aetiology have important implications for caries control strategies. Preventing the transmission of S. mutans will likely be inadequate to prevent caries if a sufficiently carbohydrate-rich diet continues. Similarly, restriction of sucrose intake, although welcome, would be unlikely to be a panacea for caries, especially if frequent starch intake persisted. Instead, approaches to optimise fluoride delivery, to target plaque acidogenicity or acidogenic microbes, to promote plaque alkali generation, to increase salivary flow or replace fermentable carbohydrates with non-fermentable alternatives may be more promising.

Fluoride content in plaque solids and fluid after ingestion of fluoridated milk

This study explored differences in dental biofilm solids and fluid fluoride after ingestion of NaF or Na2FPO3 in milk or non-fluoridated milk. Eighteen volunteers ingested 1 mg fluoride in 200 mL of milk or 200 mL of non-fluoridated milk. Biofilm samples were collected at baseline, 30, 60, and 240 min and biofilm solids and fluid were micro-analyzed for fluoride. Analysis of variance was performed and the total delivery, retention, and clearance of fluoride to biofilm solids and fluid were estimated as the area under the curve between 0 and 240 min. No statistically significant differences were found for baseline values. Biofilm fluid fluoride values ranged from 0.11 ± 0.05 to 0.21 ± 0.08 µg F/mL while biofilm solid values ranged from 0.62 ± 0.39 to 1.75 ± 1.16 µg F/g. Biofilm fluid values were significantly lower at 60 min for Na2FPO3 in milk. Clearance profiles for biofilm fluid diverged after the initial 60 min. Na2FPO3 had a smaller area under the curve from 60 to 240 min than NaF. Results of this study indicate that the release and clearance of fluoride in biofilm vary among fluoridation compounds and that the concentrations in biofilm solids and fluid also vary and are not correlated to each other in many cases.

Deposition of fluoride on enamel surfaces released from varnishes is limited to vicinity of fluoridation site

The aim of the in-situ study was to determine fluoride uptake in non-fluoridated, demineralized enamel after application of fluoride varnishes on enamel samples located at various distances from the non-fluoridated samples. All enamel samples used were demineralized with acidic hydroxyethylcellulose before the experiment. Intra-oral appliances were worn by ten volunteers in three series: (1, Mirafluorid, 0.15% F; 2, Duraphat, 2.3% F and 3, unfluoridated controls) of 6 days each. Each two enamel samples were prepared from 30 bovine incisors. One sample was used for the determination of baseline fluoride content (BFC); the other was treated according to the respective series and fixed in the intra-oral appliance for 6 days. Additionally, from 120 incisors, each four enamel samples were prepared (one for BFC). Three samples (a–c) were placed into each appliance at different sites: (a) directly neighboured to the fluoridated specimen (=next), (b) at 1-cm distance (=1 cm) and (c) in the opposite buccal aspect of the appliance (=opposite). At these sites, new unfluoridated samples were placed at days 1, 3 and 5, which were left in place for 1 day. The volunteers brushed their teeth and the samples with fluoridated toothpaste twice per day. Both the KOH-soluble and structurally bound fluoride were determined in all samples to determine fluoride uptake and were statistically analyzed. One day, after fluoridation with Duraphat, KOH-soluble fluoride uptake in specimen a (=next) was significantly higher compared to the corresponding samples of both the control and Mirafluorid series, which in turn were not significantly different from each other. At all other sites and time points, fluoride uptake in the enamel samples were not different from controls for both fluoride varnishes. Within the first day after application, intra-oral-fluoride release from the tested fluoride varnish Duraphat leads to KOH-soluble fluoride uptake only in enamel samples located in close vicinity to the fluoridation site.

Effect of fluoride on artificial caries lesion progression and repair in human enamel: regulation of mineral deposition and dissolution under in vivo-like conditions

OBJECTIVE

This study was carried out to determine in vitro the effect of fluoride on (1) the demineralization of sound human enamel and (2) the progression of artificial caries-like lesions, under relevant oral conditions.

METHODS

Thin sections of sound human enamel were exposed to solutions undersaturated with respect to tooth enamel to a degree similar to that found in dental plaque fluid following sucrose exposure in vivo, containing fluoride concentrations (0-0.38ppm) found in plaque fluid. Mineral changes were monitored for 98 days, using quantitative microradiography. The effect of fluoride (1.0-25.0ppm) on the progression of artificial caries-like lesions was similarly studied.

RESULTS

Fluoride concentrations of 0.19ppm and greater were found to prevent the demineralization of sound enamel in vitro. However, significantly higher concentrations of fluoride (25.0ppm) were required to prevent further demineralization of artificial caries-like lesions. Demineralizing solutions with intermediate fluoride concentrations (2.1-10.1ppm) induced simultaneously remineralization in the outer portion of the lesion and demineralization in the inner portion. Simultaneous remineralization and demineralization were also observed in hydroxyapatite pellets.

CONCLUSIONS

Our results show that the observed effect of fluoride on enamel demineralization is not solely a function of bulk solution properties, but also depends on the caries-status of the enamel surface. A mechanistic model presented indicates that, in comparison to sound enamel surfaces, higher concentrations of fluoride are required to prevent the progression of artificial caries-like lesions under in vivo-like conditions since the diffusion of mineral ions that promote remineralization is rate-limiting.

Effect in vitro acidification on plaque fluid composition with and without a NaF or a controlled-release fluoride rinse

Plaque fluid ion concentration changes, especially fluoride, in response to the pH decrease associated with a cariogenic episode are important components of the caries process. A "controlled-release" (CR) fluoride rinse, based on the controlled release of fluoride in the presence of calcium, has been shown to form large fluoride reservoirs in resting plaque. In this study, the in vitro acid-induced release of fluoride, and other ions, was examined in 48-hour-fasted plaque fluid from subjects (n = 11) who received no rinse, or who used a 228-ppm CR or NaF fluoride rinse 1 hr before being sampled. After collection, the plaque was centrifuged to yield plaque fluid, acidified (0.1 microL of 0.5 mol/L HCl per milligram plaque), and then re-centrifuged before a second sample was obtained. Although previous studies indicated a higher plaque fluid fluoride after the new rinse relative to NaF, no statistically significant difference was observed here. Average fluoride release after acidification (average pH, 5.2) was statistically greater following the use of the CR rinse (153 micromol/L) compared with the NaF rinse (17 micromol/L). No fluoride release was seen in the no-rinse samples. The pH, free calcium, phosphate, acetate, propionate, and buffer capacity were not affected by the different amounts of fluoride deposited in the plaque. However, following acid addition, an increase in free calcium and phosphate was observed, which was also independent of the rinse. The large release of fluoride following acidification suggests that the new rinse may provide an improved cariostatic effect.

Release of mineral ions in dental plaque following acid production

The release of appreciable amounts of calcium, phosphate and fluoride found in whole plaque into the plaque-fluid phase, following bacterial acid production, can potentially reduce the driving force for tooth demineralization. However, limited information is available on this topic, particularly on the release of fluoride. This study sought to determine the change in calcium, phosphate and fluoride concentrations in plaque fluid after sucrose exposure. 48 h overnight-fasted supragingival plaque samples were collected from all tooth surfaces (with the exception of the lower lingual anterior teeth) of one half of an individual mouth, following a 1 min water rinse. Plaque samples were then collected from the other half of the same mouth, following a 292 mM sucrose rinse. Plaque fluid was isolated by centrifugation and analysed for total calcium and phosphate (ion chromatography) and for free fluoride (ion-specific electrode). Samples were collected from seven individuals. Following sucrose exposure, plaque-fluid pH decreased significantly from 6.5+/- 0.3 to 5.4+/-0.2; calcium concentrations (mmol/l) also increased significantly (p < 0.01) from 1.9+/-0.5 to 5.0+/-2.1. Fluoride and phosphate concentrations in plaque fluid, however, did not increase significantly after sucrose exposure: mean concentrations (mmol/l) of fluoride after the water and sucrose rinses were 0.006+/-0.003 and 0.005+/-0.002, respectively, and mean phosphate concentrations (mmol/l) were 11.0+/-2.0 and 12.0+/-3.0, respectively. When results were expressed per wet plaque weight, phosphate concentrations were also found to increase significantly. The same trends were observed when additional plaque samples were treated in vitro with sucrose: fluoride-ion activity did not increase in plaque under in vivo-like conditions.

Current status in oral fluoride pharmacokinetics and implications for the prophylaxis against dental caries

Fluoride plays a central role in the prevention of dental caries. There is evidence that its effect is mainly topical and that continuous presence of fluoride ions in low concentration at the plaque/enamel interface is essential. The present paper reviews the most important aspects of fluoride kinetics in the oral cavity and discusses their implications on preventive approaches to dental caries. As a continuous presence of fluoride ions in saliva is important for an optimum prophylactic effect, new formulations capable of delivering low levels of fluoride over prolonged periods of time have been developed. These systems consist either of intra-oral devices, or of restorative materials into which fluoride has been incorporated. Among all the preparations investigated, bioadhesive tablets and membrane-controlled reservoirs are the most promising.

Fluoride in plaque fluid and saliva after NaF or MFP rinses

A micro-analytic method, capable of measuring the fluoride concentration in 5 nl of plaque fluid, was used to follow changes in fluoride concentration in saliva and plaque fluid at 6 single tooth-sites in 6 subjects for 180 min after a 0.048 M fluoride rinse as a NaF or MFP (sodium monofluorophosphate) solution. The maximum fluoride concentrations in saliva after NaF was 13x higher than with MFP. About 5% of the total amount of fluoride following the 20 ml NaF rinse was retained in the oral cavity. The corresponding figure followig MFP was <1%. The saliva/plaque fluid fluoride ratios for upper molars and lower incisors were significantly higher than for the upper incisors and lower molars. There was a tendency for a decline in the ratios with respect to time for all sites. To characterize the plaque fluid fluoride intra-oral single-site distribution and clearance, fluoride concentration versus time (AUC) was calculated from 10 to 60 min after a rinse. The NaF AUC followed the order: upper incisor, lower molar, upper molar and lower incisors reflecting a different exposure and clearance pattern due to the different access of the plaque to saliva. The MFP AUC values varied more, but were all significantly lower than the NaF AUC values. Analysis of plaque fluid fluoride curves at various sites revealed an exponential decline in most cases. With NaF, the baseline plaque fluid fluoride levels were not reached within 3 h. It is concluded that NaF solutions result in a significantly higher intra-oral fluoride exposure than MFP solutions. The fluoride distribution and clearance of fluoride from different sites in the oral cavity are linked to salivary access to these sites. These site-specific differences may have clinical consequences with regard to the dynamics of fluoride in the de- and remineralization processes.

A method for determining the distribution of fluoride, calcium and phosphorus in human dental plaque and the effect of a single in vivo fluoride rinse

A new sampling method, capable of sampling plaque from its surface to its interior for quantitative studies, was modified to meet some of the requirements for the determination of the fluoride and mineral (Ca and P) profiles within dental plaque formed in vivo. Plaque samples were repeatedly collected from the same individual, using special devices, before a single fluoride rinse (900 parts/10(6) fluoride) and 10 min and 24 hr after rinse. The method allowed examination of fluoride, calcium and phosphorus distribution along the entire thickness of plaque. Fluoride content significantly increased throughout the sample 10 min after rinsing, indicating the fluoride had rapidly penetrated into the plaque. Although the elevated fluoride concentrations diminished almost to baseline with 24 hr, a high correlation was found between fluoride and minerals in each plaque fraction. It is concluded that this technique will be useful for evaluating the fluoride and mineral behaviour in the saliva/plaque and plaque/enamel interfaces, and the anti caries efficacy of fluoride applications.

Models for Evaluating New Fluoride-Containing Systems: Reaction Paper

The type and number of control formulations to be used in model studies to evaluate new fluoride systems require careful consideration. While many controls may be justified on the grounds of scientific interest, some models can handle only small numbers of treatments without the statistical power of studies being compromised. In those cases, the results of more than one study may need to be combined.

Current models for evaluating fluoride products have most often been developed with systems containing ionic fluoride in mind. To test new types of delivery vehicles or formulations which contain new fluoride agents, model protocols may need to be revised in order to account properly for differences in modes of action-for example, in rates of reaction with enamel or site specificity of active ingredient delivery in the mouth.

Influence of fluoride on titanium in an acidic environment measured by polarization resistance technique

The effect of sodium fluoride on the polarization resistance of titanium was investigated. Titanium plates were exposed to sodium chloride solutions with increasing fluoride concentrations. This was done at pH 7 and 4 at 37 degrees C. The polarization resistance technique was chosen because it is the only electrochemical corrosion test procedure that allows sequential measurements of the same specimen and provides a quantitative basis to estimate corrosion currents unlike measurements of the potential. The results showed a large decrease in polarization resistance with increasing fluoride concentration at pH 4. The polarization resistance at pH 7 remained constant after a slight decrease at a very high value, even with a high fluoride concentration. The results clearly confirm that titanium is attacked by fluoride in an acidic environment. The clinical implications are that fluoride rinses or fluoride gels must have a neutral pH if there is a titanium containing device in the oral environment despite the less prophylactic effectiveness.

Studies on plaque fluoride after use of F-containing dentifrices

Increased fluoride levels in plaque and saliva have been associated with improved protection against dental caries for dentifrices which contained sodium monofluorophosphate (Duckworth et al., 1992). The main aim of the present work was to test whether oral fluoride retention depended on F source after use of dentifrices containing either NaF or Na2FPO3. In study 1, plaque samples were collected from 474 subjects who had been using one of six test dentifrices for two years, and analyzed by F extraction with water. The dentifrices contained 1000 or 1500 micrograms F/g as either NaF or Na2FPO3. Significantly more fluoride was found in plaque from subjects who were using the NaF dentifrices than in plaque from subjects who were using Na2FPO3 dentifrices of the same F content. Subsets of plaque samples were large enough to divide into two parts for extraction by both acid and water. No significant difference was found between mean fluoride contents, indicating that the majority of fluoride retained in plaque from these conventional dentifrices appears to be relatively labile. The results of two small-scale human enamel studies showed that NaF dentifrices gave elevated F concentrations in plaque and saliva, respectively, compared with Na2FPO3 dentifrices of equivalent F content, consistent with the main plaque study 1. These findings demonstrate that oral F retention from dentifrices is dependent on the source of ionic fluoride and support the view that NaF dentifrices may be more clinically effective than dentifrices which contain the same amount of F as Na2FPO3.

Biological markers: their use in quantitative assessments

Biological markers can be conceptualized in terms of categories of markers that form a continuum representing a sequence of events from exposure to disease. These categories include markers of internal dose, biologically effective dose, early response, and disease. Outside of this sequence are susceptibility factors that can act at any point along the way to modify the effects of external exposures on disease outcomes. Examples of the use of these different types of markers in epidemiologic research are provided. There are many factors that one must consider when selecting a biological marker for use in an epidemiologic study. These factors include: the objectives of the study, the availability and specificity of potential markers, the feasibility of measuring the markers in various biological media, the invasiveness of the techniques necessary to measure the markers, the amount of biological specimen needed for analysis, the time to appearance of the markers in the biological media, the persistence of the markers in biological media, the variability of marker levels within and between individuals, the stability of markers in storage, as well as the cost, sensitivity, specificity, and reliability of the assays used to measure the markers. Each of these characteristics is discussed. The usefulness of biological markers in an epidemiologic study depends on the objectives of the study and whether the properties of the markers fulfill the objectives of the study in a feasible and cost-effective manner.

Composition and cariogenic potential of dental plaque fluid

Our understanding of the chemical events that take place at the tooth-plaque interface has improved greatly through studies of the chemical composition and properties of dental plaque fluid. In the absence of fermentable carbohydrate, plaque fluid has been found to be supersaturated with respect to tooth mineral and other calcium phosphate phases, thus exhibiting the potential to support calculus formation and the remineralization of incipient carious lesions. Following the exposure to fermentable carbohydrate, the degree of saturation of plaque fluid decreases rapidly, primarily due to lactic acid production and the lowering of plaque fluid pH. The extent of these chemical changes has been shown to be associated with differences in caries history. Such studies have been facilitated by the recent development of microanalytical techniques. Unfortunately, little is known about the relationship between the observed chemical changes in plaque fluid and the microbial composition of plaque. Limited information is also available on the association of immune factors in plaque fluid with dental disease.

Effect of intermittent delivery of fluoride to solution on root hard-tissue de- and remineralization measured by 125I absorptiometry

The effect of intermittent fluoride levels on root hard-tissue de- and remineralization was studied once daily for 21 days in a pH-cycling caries model with simulated fluoride clearance curves. Four root hard-tissue blocks, from each of 12 human teeth, were cut out parallel to the cementum surface. During a daily 15-hour period, the blocks were subjected 12 times to pH changes similar to those which occur in plaque after a carbohydrate intake. The fluoride was delivered immediately before a daily nine-hour remineralization period. Four experiments were independently carried out: One block from each tooth was subjected to pH-cycling without and with fluoride delivery, simulating a rinse with 0.025, 0.2, and 1.0% sodium fluoride (NaF), respectively. The mineral change in the blocks was monitored by 125I absorptiometry and expressed as the change in transmission (delta T). The surface between the data points (delta T values) and the x axis (time points) was used as a summary measure, i.e., the area under the curve (AUC). When no fluoride was delivered, the delta T increased over 21 days, indicating loss of mineral. The AUC was, on average, 5.85 +/- 0.68 (mean +/- S.E.) %.day. In the 0.025% NaF-rinse experiment, there was a marked reduction in mineral loss, indicated by an average AUC of 1.66 +/- 0.59%.day. In both the 0.2 and 1.0% NaF-rinse experiments, a decrease in delta T, indicating gain of mineral, was observed from day 2. Negative delta T values occurred after 7 and 3 days, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)