Quantitative proteomic analysis in symptomatic and asymptomatic apical periodontitis.

AIM: To quantitatively and qualitatively compare the host proteomic profile in samples of symptomatic and asymptomatic apical periodontitis (AP) using nano-liquid chromatography-electron spray tandem mass spectrometry. METHODOLOGY: Samples were obtained from 18 patients with radiographically evident AP, divided into symptomatic and asymptomatic groups (nine per group) according to clinical characteristics. After sample collection, protein extraction, purification and quantification of the samples were performed, which were analysed by reverse-phase liquid chromatography coupled to mass spectrometry. Label-free quantitative proteomic analysis was performed by Protein Lynx Global Service software. Differences in expression of proteins between the groups were calculated using the Monte Carlo algorithm, considering P < 0.05 for down-regulated proteins and 1 - P > 0.95 for up-regulated proteins. Proteins were identified with the embedded ion accounting algorithm in the software and a search of the Homo sapiens UniProt database. RESULTS: A total of 853 individual human proteins were identified. In the quantitative analysis, common proteins to both groups accounted for 143 proteins. Differences in expression between groups resulted in 51 up-regulated proteins (1 - P > 0.95) in the symptomatic group, including alpha-1-antitrypsin, protein S100-A8, myeloperoxidase, peroxiredoxin and lactotransferrin. This group also had 43 down-regulated proteins (P < 0.05), comprising immunoglobulin, neutrophil defensin, pyruvate kinase and alpha-enolase. The qualitative analysis considered only the exclusive proteins of each group. For the symptomatic group, 318 complete proteins and 29 fragments were identified, such as dedicator of cytokinesis protein, intersectin, prostaglandin, phospholipase DDHD2 and superoxide dismutase. For the asymptomatic group, 326 complete proteins and 37 fragments were identified, including azurocidin, C-reactive protein, collagen alpha, cathepsin, heat shock and laminin. CONCLUSIONS: Quantitative differences in the expression of common proteins in cases of symptomatic and asymptomatic AP were found, which were mostly related to host immune response in both groups. Exclusive proteins in the symptomatic group were mainly related to the host response to the presence of viruses in endodontic infections, oxidative stress and proteolytic enzymes. The results provide a basis for a better understanding of cellular and molecular pathways involved in AP, establishing specific proteomic profiles for symptomatic and asymptomatic conditions.

Review of Fluoride Intake and Appropriateness of Current Guidelines.

Since the classical epidemiological studies by Dean, it has been known that there should be an optimum level of exposure to fluoride that would be able to provide the maximum protection against caries, with minimum dental fluorosis. The "optimal" daily intake of fluoride for children (0.05-0.07 mg per kilogram bodyweight) that is still accepted worldwide was empirically determined. In the present review, we discuss the appropriateness of the current guidance for fluoride intake, in light of the windows of susceptibility to caries and fluorosis, the modern trends of fluoride intake from multiple sources, individual variations in fluoride metabolism, and recent epidemiological data. The main conclusion is that it is very difficult to think about a strict recommendation for an "optimal" range of fluoride intake at the individual level in light of existing knowledge of 1) the mechanisms of action of fluoride to control caries, 2) the mechanisms involved in dental fluorosis development, 3) the distinct factors that interfere in the metabolism of fluoride, and 4) the windows of susceptibility to both dental caries and fluorosis development. An "optimal" range of fluoride intake is, however, desirable at the population level to guide programs of community fluoridation, but further research is necessary to provide additional support for future decisions on guidance in this area. This list includes the effect of factors affecting fluoride metabolism, clinical trials on the effectiveness of low-fluoride dentifrices to prevent caries in the primary dentition, and validation of biomarkers of exposure to fluoride.

In situ Effect of Chewing Gum with and without CPP-ACP on Enamel Surface Hardness Subsequent to ex vivo Acid Challenge.

The erosion-protective effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) is controversial. This study aimed to investigate the ability of CPP-ACP chewing gum to prevent a single event of erosive demineralization in situ. Bovine enamel blocks (n = 120) were randomly assigned to 3 phases according to the baseline surface hardness: phase I (PI) - chewing gum with CPP-ACP, phase II (PII) - chewing gum without CPP-ACP, and control phase (PIII) - salivary effect without stimulation (no gum). Nineteen volunteers participated in this study during 3 crossover phases of 2 h. In PI and PII, the volunteers wore intraoral palatal appliances for 120 min and chewed a unit of the corresponding chewing gum for the final 30 min. In the control phase the volunteers wore the appliance for 2 h, without chewing gum. Immediately after intraoral use, the appliances were extraorally immersed in a cola drink for 5 min to promote erosive demineralization. The percentage of surface hardness loss was calculated. The data were analyzed by ANOVA models and Tukey's test. Lower enamel hardness loss was found after the use of chewing gum with CPP-ACP (PI: 32.7%) and without CPP-ACP (PII: 33.5%) compared to the salivary effect without stimulation (PIII: 39.8%) (p < 0.05). There was no difference between PI and PII (p > 0.05). The results suggest that the use of chewing gum immediately before an erosive demineralization can diminish enamel hardness loss. However, the presence of CPP-ACP in the chewing gum cannot enhance this protective effect.

Total fluoride intake and excretion in children up to 4 years of age living in fluoridated and non-fluoridated areas.

Fractional fluoride retention is important during the early years of life when considering the risk of development of dental fluorosis. This study aimed to measure fractional fluoride retention in young children. The objectives were to investigate the relationships between fractional fluoride retention and total daily fluoride intake, age, and body mass index (BMI). Twenty-nine healthy children, up to 4 yr of age, participated; 14 lived in a fluoridated area (0.64 µg ml(-1) of fluoride in drinking water) and 15 lived in a non-fluoridated area (0.04 µg ml(-1) of fluoride in drinking water). The total daily fluoride intake of each child was calculated from the daily dietary fluoride intake and toothpaste ingestion (if fluoride toothpaste was used). Total daily fluoride excretion was measured by collecting voided urine and faeces over a 24-h period, and fractional fluoride retention was calculated by dividing the amount of fluoride retained in the body (total daily fluoride intake minus total daily fluoride excretion) by the total daily fluoride intake. Nine children were excluded from data analysis because of suspected invalid samples. Mean (range) fractional fluoride retention for the remaining 20 children was 0.61 (0.06-0.98). There were no statistically significant correlations between fractional fluoride retention and either age or BMI. However, fractional fluoride retention was correlated with total daily fluoride intake: fractional fluoride retention = 1 - exp (-C × total daily fluoride intake), where C = 28.75 (95% CI = 19.75-37.75). The wide variation in fluoride retention in young children could have important implications when recommendations for fluoride use are being considered.

Different protocols to produce artificial dentine carious lesions in vitro and in situ: hardness and mineral content correlation.

This study compared dentine demineralization induced by in vitro and in situ models, and correlated dentine surface hardness (SH), cross-sectional hardness (CSH) and mineral content by transverse microradiography (TMR). Bovine dentine specimens (n = 15/group) were demineralized in vitro with the following: MC gel (6% carboxymethylcellulose gel and 0.1 M lactic acid, pH 5.0, 14 days); buffer I (0.05 M acetic acid solution with calcium, phosphate and fluoride, pH 4.5, 7 days); buffer II (0.05 M acetic acid solution with calcium and phosphate, pH 5.0, 7 days), and TEMDP (0.05 M lactic acid with calcium, phosphate and tetraethyl methyl diphosphonate, pH 5.0, 7 days). In an in situ study, 11 volunteers wore palatal appliances containing 2 bovine dentine specimens, protected with a plastic mesh to allow biofilm development. The volunteers dripped a 20% sucrose solution on each specimen 4 times a day for 14 days. In vitro and in situ lesions were analyzed using TMR and statistically compared by ANOVA. TMR and CSH/SH were submitted to regression and correlation analysis (p < 0.05). The in situ model produced a deep lesion with a high R value, but with a thin surface layer. Regarding the in vitro models, MC gel produced only a shallow lesion, while buffers I and II as well as TEMDP induced a pronounced subsurface lesion with deep demineralization. The relationship between CSH and TMR was weak and not linear. The artificial dentine carious lesions induced by the different models differed significantly, which in turn might influence further de- and remineralization processes. Hardness analysis should not be interpreted with respect to dentine mineral loss.

Validation of fingernail fluoride concentration as a predictor of risk for dental fluorosis.

The aim of this study was to validate the use of fingernail fluoride concentrations at ages 2-7 years as predictors of the risk for developing dental fluorosis in the permanent dentition. Fifty-six children of both genders (10-15 years of age) had their incisors and premolars examined for dental fluorosis using the Thylstrup-Fejerskov index. Fingernail fluoride concentrations were obtained from previous studies when children were 2-7 years of age. Data were analyzed by unpaired t test, ANOVA, and Fisher's exact test when the fingernail fluoride concentrations were dichotomized (≤ 2 or >2 µg/g). Children with dental fluorosis had significantly higher fingernail fluoride concentrations than those without the condition, and the concentrations tended to increase with the severity of fluorosis (r(2) = 0.47, p < 0.0001). Using a fingernail fluoride concentration of 2 µg/g at ages 2-7 years as a threshold, this biomarker had high sensitivity (0.84) and moderate specificity (0.53) as a predictor for dental fluorosis. The high positive predictive value indicates that fingernail fluoride concentrations should be useful in public health research, since it has the potential to identify around 80% of children at risk of developing dental fluorosis.

The role of matrix metalloproteinases in dental erosion.

This review discusses the role of matrix metalloproteinases (MMPs) in the development of dentin erosion and the protective effects of MMP inhibitors, based on recent evidence from in vitro and in situ studies. MMPs are present in both dentin and saliva and play an important role in dentin erosion progression. Enzymatic removal of the organic matrix by MMPs increases the demineralization process, since the demineralized organic matrix has been shown to hamper ionic diffusion after an acidic challenge. Recent evidence from in vitro and in situ studies has shown a protective role of MMP inhibitors against dentin erosion and erosion plus abrasion. The inhibitors tested were green tea and its active epigallocatechin-gallate (EGCG), ferrous sulfate, and chlorhexidine. They have been tested in dentifrices, solutions, and gels. The latter led to a more pronounced protective effect against dentin erosion and erosion plus abrasion. The protection was long-lasting and could be observed after up to 10 days of severe erosive and erosive-plus-abrasive challenges in situ. Thus, the use of MMP inhibitors has emerged as an important preventive tool against dentin erosion. Clinical studies should be conducted to confirm the results obtained and to give support to the establishment of clinical protocols of use.

Factors associated with fluoride concentrations in whole and parotid ductal saliva.

BACKGROUND/AIMS: There are still uncertainties regarding the use of whole and parotid ductal saliva as indicators of chronic exposure to fluoride. This study evaluated the effect of water fluoride concentration, age, gender, geographical area and localization (urban/rural) on fluoride concentrations in whole and ductal saliva. METHODS: Subjects (n = 300) aged 3-7, 14-20, 30-40 and 50-60 years, from five communities (A-E) with different fluoride concentrations in the drinking water, participated in the study. Two samples of drinking water and parotid and whole saliva were collected for each subject and were analyzed for fluoride using appropriate electrode techniques. RESULTS: Mean water F concentrations (±SE, mg/l, n = 60) were 0.09 ± 0.01, 0.15 ± 0.01, 0.66 ± 0.01, 0.72 ± 0.02, and 1.68 ± 0.08 for A-E, respectively. Mean F concentrations (±SE, mg/l, n = 15) ranged between 0.014 ± 0.002 (A, 3-7 years) and 0.297 ± 0.057 (D, 14-20 years) for whole saliva and 0.009 ± 0.001 (C, 30-40 years) and 0.284 ± 0.038 (E, 50-60 years) for parotid saliva. Results of multivariate linear regression analysis showed that geographical area and water fluoride concentration exerted the strongest influence in whole and ductal saliva F concentrations, respectively. CONCLUSION: Therefore, parotid ductal saliva seems to be a more appropriate biomarker of fluoride exposure, and factors like age and localization should also be considered when using this biomarker.

Activity of matrix metalloproteinases in bovine versus human dentine.

Metalloproteinases (MMPs) have been implicated with metabolism of collagen in physiological and pathological processes in human dentine. As bovine teeth have been used as a substitute for human teeth in laboratory analysis, this study evaluated the activity of MMP-2 and -9 in bovine versus human dentine. Bovine and human dentine fragments, from crowns and roots, were powderized. Protein extraction was performed by two protocols: a neutral extraction with guanidine-HCl/EDTA (pH 7.4) and an acidic extraction with citric acid (pH 2.3). Gelatinolytic activities of extracts were revealed by zymography. MMP-2 and -9 were detected in crown and root dentine from bovine and human teeth. Total activities of MMP-2 were 11.4 ± 2.2, 14.6 ± 2.0, 9.7 ± 1.2 and 12.4 ± 0.9 ng/ml for bovine root, human root, bovine crown and human crown dentine, respectively. Corresponding activities for MMP-9 were 14.9 ± 2.0, 15.3 ± 1.3, 15.4 ± 1.3 and 15.5 ± 1.3 ng/ml, respectively. Bovine dentine was found to be a reliable substrate for studies involving the activity of MMP-2 and -9.

Safety and In Situ Antierosive Effect of CaneCPI-5 on Dental Enamel.

The sugarcane cystatin (CaneCPI-5) was recently cloned and showed strong binding force to dental enamel and protection against initial erosion. However, evaluations on its safety and efficacy in a situation closer to the clinical condition are necessary. In the present study we analyzed 1) the cytotoxicity of CaneCPI-5 on human gingival fibroblasts (HGFs); 2) the ability of CaneCPI-5 to reduce enamel erosion and erosion+abrasion in situ. In part 1, HGFs were treated with CaneCPI-5 (0.025, 0.05, 0.1, 0.5 or 1.0 mg/mL) or no treatment (control). The cytotoxicity was assessed after 60 s and 24 h by mitochondrial activity (MTT), confocal microscopy, and hematoxylin/eosin staining. In part 2, 15 volunteers participated in a double-blind crossover protocol consisting of 3 phases, according to the following treatments: 1) 0.1 mg/mL CaneCPI-5; 2) SnCl2/NaF/AmF (Elmex; positive control); 3) water (negative control). The volunteers wore an appliance containing 4 bovine enamel specimens for 5 d. Each day, the specimens were individually treated with 50 µL of the tested solutions per 60 s and then subjected to erosive challenges (0.1% citric acid, pH 2.5, for 90 s, 4 times per day). After the first and last erosive challenge each day, 2 samples were abraded (toothbrushing, 15 s). Enamel wear was measured by contact profilometry. One or two-way analysis of variance (ANOVA)/Tukey's or Sidak's tests (P < 0.05) were applied. Regardless of the concentration and the experimental time, CaneCPI-5 did not decrease the cell viability compared to the negative control (P < 0.05). Erosion+abrasion led to significantly greater wear compared to erosion only. For both conditions, the lowest wear was found for SnCl2 and CaneCPI-5, which did not differ significantly from each other, but showed significant protection when compared to the negative control. In conclusion, CaneCPI-5 is safe on HGFs and reduces enamel erosive wear to the same extent as a commercial solution used to control erosive tooth wear (ETW).

Preventive effect of commercial desensitizing toothpastes on bovine enamel erosion in vitro.

This study evaluated in vitro commercial desensitizing toothpastes with respect to the prevention of erosion and explored the effect of their agents alone or in combination with fluoride. Bovine enamel blocks were randomly allocated to five groups of 20 and exposed to: Sensodyne ProNamel (1,425 ppm F as NaF, 5% KNO(3)), Sensodyne Original (no fluoride, 10% SrCl(2)), Colgate Sensitive (1,450 ppm F as sodium monofluorophosphate, 5% K citrate), Crest (fluoride-only toothpaste, 1,100 ppm F as NaF) and water (negative control). A second experiment was conducted with experimental dentifrices containing fluoride (NaF, 1,100 ppm F), 10% SrCl(2), 5% KNO(3 )or 5% K citrate alone or the latter three combined with F. The samples were submitted to four cycles, alternating demineralization (cola, 10 min) and remineralization (artificial saliva, 1 h). Before and between cyclic de- and remineralization, blocks were treated with slurries of the respective toothpastes or water (1 min). Erosive tissue loss was analyzed by profilometry. Data were analyzed by Kruskal-Wallis and Dunn's tests (p < 0.05). The mean erosion depth (+/- SE, mum) was significantly less for Colgate Sensitive (0.04 +/- 0.00), Sensodyne Original (0.06 +/- 0.01) and Crest (0.07 +/- 0.01) than for Sensodyne ProNamel (2.36 +/- 0.25) or water (2.92 +/- 0.24), which did not significantly differ from each other. Both F and the desensitizing agents alone reduced erosion, but no additive effect was found. In addition, the combination of F and KNO(3) did not reduce erosion. These in vitro results suggest that the presence of fluoride or desensitizing substances in toothpastes, alone or in combination, can reduce erosion of enamel, but this is not valid for all the formulations.

Low-fluoride acidic dentifrice: a randomized clinical trial in a fluoridated area.

BACKGROUND: Low-fluoride dentifrices have been suggested as alternatives to reduce dental fluorosis risk, but there is no consensus regarding their clinical effectiveness, which has been suggested to be increased when their pH is acidic. AIMS: This single-blind randomized clinical trial evaluated the caries increment during the use of a low-fluoride acidic liquid dentifrice. METHODS: Four-year-old schoolchildren (n = 1,402) living in a fluoridated area (0.6-0.8 ppm F) were randomly allocated to 4 groups differing according to the type of dentifrice used over a 20-month period. Group 1 (n = 345): liquid dentifrice, 1,100 ppm F, pH 4.5. Group 2 (n = 343): liquid dentifrice, 1,100 ppm F, pH 7.0. Group 3 (n = 354): liquid dentifrice, 550 ppm F, pH 4.5. Group 4 (n = 360): toothpaste, 1,100 ppm F, pH 7.0. At baseline and after 20 months, clinical examinations were conducted (dmfs index) and caries increment was calculated. Data were analysed by GLM procedure using classrooms (cluster) as unit of analysis (p < 0.05). RESULTS: The mean ± SD (95% CI) net increments found were as follows. Group 1: 2.06 ± 2.38 (1.8-2.3); group 2: 2.08 ± 2.87 (1.7-2.4); group 3: 2.05 ± 2.79 (1.7-2.4), and group 4: 2.08 ± 2.34 (1.8-2.4). No significant differences were detected among the groups. CONCLUSION: In a population with high caries risk living in a fluoridated area, as the selected sample, and according to the present protocol, the low-fluoride acidic liquid dentifrice seems to lead to similar caries progression rates as conventional 1,100 ppm F toothpaste.

Effect of iron on matrix metalloproteinase inhibition and on the prevention of dentine erosion.

It is known that some metal salts can inhibit matrix metalloproteinase (MMP) activity, but the effect of iron has not been tested yet. On the other hand, it has recently been suggested that MMP inhibition might influence dentine erosion. Based on this, the aims of this study were: (1) to test in vitro the effect of FeSO(4) on MMP-2 and -9 activity, and (2) to evaluate in situ the effect of FeSO(4) gel on dentine erosion. MMP-2 and -9 activities were analysed zymographically in buffers containing FeSO(4) in concentrations ranging between 0.05 and 1.5 mmol/l or not. Volunteers (n = 10) wore devices containing bovine dentine blocks (n = 60) previously treated with the following gel treatments: FeSO(4) (1 mmol/l FeSO(4)), F (NaF 1.23%; positive control) and placebo (negative control). The gels were applied once and removed after 1 min. Erosion was performed extraorally with Coca-Cola 4 times per day for 5 min over 5 days. Dentine wear was evaluated by profilometry. The data were analysed by Kruskal-Wallis and Dunn's tests (p < 0.05). FeSO(4) inhibited both MMP-2 (IC(50) = 0.75 mmol/l) and MMP-9 (IC(50) = 0.50 mmol/l) activities. In the in situ experiment, the mean wear (+/- SD) found for the F gel (0.79 +/- 0.08 microm) was significantly reduced in more than 50% when compared to the placebo gel (1.77 +/- 0.33 microm), but the FeSO(4) gel completely inhibited the wear (0.05 +/- 0.02 mum). Since FeSO(4) was able to inhibit MMP in vitro, it is possible that the prevention of dentine wear by the FeSO(4) gel in situ might be due to MMP inhibition, which should be investigated in further studies.

Cross-sectional microhardness of human enamel subjected to erosive, cariogenic or combined erosive/cariogenic challenges.

This in situ study evaluated the interaction between caries and erosion processes. In the first phase, enamel specimens were subjected to erosion without dental plaque (EO) or to erosion with plaque (EP); in the second phase, they were subjected to erosion plus cariogenic challenge (EC) or cariogenic challenge (CO), both with plaque accumulation. Cross-sectional hardness data (10-330 microm depth) were tested using ANOVA (alpha = 0.05). EO and EP showed surface softening to 10 microm depth. CO and EC produced subsurface lesions, of similar depth (up to 220 microm), with CO showing higher integrated loss of hardness than EC, indicating that cariogenic and erosive challenges did not have an additive effect.

Comparison of cross-sectional hardness and transverse microradiography of artificial carious enamel lesions induced by different demineralising solutions and gels.

The aims of this study were: (1) to correlate surface (SH) and cross-sectional hardness (CSH) with microradiographic parameters of artificial enamel lesions; (2) to compare lesions prepared by different protocols. Fifty bovine enamel specimens were allocated by stratified randomisation according to their initial SH values to five groups and lesions produced by different methods: MC gel (methylcellulose gel/lactic acid, pH 4.6, 14 days); PA gel (polyacrylic acid/lactic acid/hydroxyapatite, pH 4.8, 16 h); MHDP (undersaturated lactate buffer/methyl diphosphonate, pH 5.0, 6 days); buffer (undersaturated acetate buffer/fluoride, pH 5.0, 16 h), and pH cycling (7 days). SH of the lesions (SH(1)) was measured. The specimens were longitudinally sectioned and transverse microradiography (TMR) and CSH measured at 10- to 220-microm depth from the surface. Overall, there was a medium correlation but non-linear and variable relationship between mineral content and radicalCSH. radicalSH(1) was weakly to moderately correlated with surface layer properties, weakly correlated with lesion depth but uncorrelated with integrated mineral loss. MHDP lesions showed the highest subsurface mineral loss, followed by pH cycling, buffer, PA gel and MC gel lesions. The conclusions were: (1) CSH, as an alternative to TMR, does not estimate mineral content very accurately, but gives information about mechanical properties of lesions; (2) SH should not be used to analyse lesions; (3) artificial caries lesions produced by the protocols differ, especially considering the method of analysis.

Environmental and individual factors associated with nail fluoride concentration.

Nails have been suggested as suitable biomarkers of exposure to F, with the advantage of being easily obtained. The effect of water F concentration, age, gender, nail growth rate and geographical area on the F concentration in the fingernail and toenail clippings were evaluated. Volunteers (n = 300) aged 3-7, 14-20, 30-40 and 50-60 years from five Brazilian communities (A-E) participated. Drinking water and nail samples were collected and F concentration was analyzed with the electrode. A reference mark was made on each nail and growth rates were calculated. Data were analyzed by ANOVA and linear regression (alpha = 0.05). Mean water F concentrations (+/- SE, mg/l) were 0.09 +/- 0.01, 0.15 +/- 0.01, 0.66 +/- 0.01, 0.72 +/- 0.02, and 1.68 +/- 0.08 for A-E, respectively. Mean F concentrations (+/- SE, mg/kg) ranged between 1.38 +/- 0.14 (A, 50-60 years) and 10.20 +/- 2.35 (D, 50-60 years) for fingernails, and between 0.92 +/- 0.08 (A, 14-20 years) and 7.35 +/- 0.80 (E, 50-60 years) for toenails. Among the tested factors, geographical area and water F concentration exerted the most influence on finger- and toenail F concentrations. Subjects of older age groups (30-40 and 50-60 years) from D and E showed higher nail F concentrations than the others. Females presented higher nail F concentration than males. Water F concentration, age, gender and geographical area influenced the F concentration of finger- and toenails, and hence should be taken into account when using this biomarker of exposure to predict risk for dental fluorosis.

The effect of different fluoride concentrations and pH of dentifrices on plaque and nail fluoride levels in young children.

To evaluate the influence of dentifrice pH and fluoride (F) concentration on F uptake by plaque and nails, two sets of 5- to 6-year-old children were randomly allocated into four groups, according to the type of dentifrice they had been using for 1 year: (1) experimental liquid dentifrice (ELD), 1,100 ppm F, pH 7.0; (2) ELD, 1,100 ppm F, pH 4.5; (3) ELD, 550 ppm F, pH 4.5, and (4) commercial toothpaste, 1,100 ppm F, pH 7.0. In one set of children, nails were clipped. In the second, plaque samples were collected 1 h after the last use of dentifrice. F concentration in plaque and nails was analyzed. Plaque F concentration was significantly lower in group 4 than in groups 1-3. Nail F concentration was significantly higher in group 4, and significantly lower in group 3, than in group 1 or 2. Plaque F uptake was influenced significantly by dentifrice consistency and nonsignificantly by pH and F concentration. Reduction of dentifrice pH did not affect nail F concentration.

Fluoride Mode of Action: Once There Was an Observant Dentist . . .

The discovery and implementation of fluoride in the prevention of dental caries is often praised as one of the most important achievements in health care. In the early 20th century, it took 30 y to identify fluoride as the cause of enamel mottling but also of reduced caries prevalence in a population drinking water containing fluoride. Similarly, from 1960 to 1990, it took major efforts to unravel the working mode of fluoride in such detail that a rational scheme of caries prevention could be formulated. This article describes the scientific struggle leading to a consensus on the topic. For a historic purpose, the field, the actors, and their main research achievements are described. Ultimately it was generally agreed that the effect of fluoride is primarily topical by fluorides in the oral fluids rather than systemic by incorporation of fluoride in the enamel mineral crystals. Fluoride concentrations, even <1 mg/L, enhance the deposition of calcium phosphates during remineralization of enamel (and dentin). Similarly, such low levels of fluoride are effective in reducing the dissolution of the calcified tissues. This understanding has led to the development of fluoride-containing caries-preventive products that had an undisputed beneficial effect on the levels of dental caries.

The use of fluoride for the prevention of dental erosion and erosive tooth wear in children and adolescents.

BACKGROUND: Erosive tooth wear (ETW) has gained increasing clinical relevance. It is estimated that worldwide 30-50% of deciduous and 20-45% of permanent teeth are affected. One of the most important nutritional factors causing ETW is the overconsumption of soft drinks, but also patient-related factors like reflux or eating disorders can lead to erosive lesions. Whether acids lead to erosive demineralisation depends on their degree of saturation with respect to tooth mineral at their actual pH. REVIEW: Fluoride compounds like sodium or amine fluoride seem to be of limited efficacy against erosion, the main reason for this is the missing biofilm in the erosive process as well as the lower pH of the acids compared to bacterial acids. This means that to achieve some kind of preventive effect it would be necessary to use products with higher fluoride concentration, which is not an appropriate option for small children, and/or to increase the frequency of application. In addition, the fluoride compound plays a role as promising effects were found when fluoride is combined with titanium or stannous ions. TiF4 can cause acid-resistant surface coatings and when Sn2+/F- formulations are applied, Sn is not only found on the surface but is also incorporated into enamel and dentine. Both effects make the tooth surface more resistant against acid demineralisation. Different fluoride-containing vehicles have been tested to prevent erosion/ETW, such as toothpastes, rinses, gels and varnishes. Toothpastes offer some degree of protection, especially Sn2+-containing formulations, but effects of the active ingredients are sometimes counteracted by the presence of abrasives. CONCLUSION: Detecting associated factors and influencing them is the main instrument in arresting erosive tooth wear. Additionally, patients at risk for dental erosion should always use an additional fluoride source preferably containing Sn2+.

Fluoride uptake by plaque from water and from dentifrice.

It has been suggested that fluoride retention in plaque is limited by available binding sites. We determined the effects of fluoridated or placebo dentifrices on plaque and salivary fluoride concentrations [F]s in communities with different water fluoride concentrations (0.04, 0.85, 3.5 ppm). After one week of dentifrice use, samples were collected 1.0 and 12 hrs after the last use of dentifrices. After the use of fluoridated dentifrice, plaque fluoride concentrations were higher at both times, except at 12 hrs in the 3.5-ppm community. Plaque concentrations at 1.0 hr after the use of fluoridated dentifrice increased almost constantly (6.5 mmol/kg), but then decreased approximately 50% at 12 hrs in each community. Unlike previous studies, the present findings suggest that the use of fluoridated dentifrice is likely to increase plaque fluoride concentrations significantly for up to 12 hrs in areas where the water contains fluoride close to 1.0 ppm. As previously reported, plaque fluoride concentrations were directly related to calcium concentrations.