The fluoride concentrations and acid solubility of teeth from fluoridated (1ppm) and low-fluoride areas.
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The objective of this study was to analyse fluoride uptake and microhardness alteration of carious-like demineralised enamel after application of differently concentrated acidulated sodium fluoride gels and to determine the effect of fluoridation on enamel resistance against subsequent demineralisation. Artificial caries-like lesions of bovine enamel specimens were treated with sodium fluoride gels of different concentration (group A: 1.25%, group B: 0.62%, group C: 0.31%, group D: 0.15%; n=20 each group) for 5 min and stored in artificial saliva for 24 h. This cycle was carried out three times. Subsequently, KOH-soluble and structurally bound fluoride (determined at depths of 30, 60, and 90 microm) were analysed. In the second part of the study, for each 12 enamel specimens surface microhardness was determined before and after demineralisation, after fluoridation with the differently concentrated gels A-D, and after a second demineralisation. With all groups uptake of KOH-soluble and structurally bound fluoride resulted in higher levels than baseline content. Statistical analysis revealed significant differences between fluoride uptake among the groups, with highest uptake for the 1.25% gel and lowest for the 0.15% gel. Moreover, with all gels highest uptake was observed in the outermost enamel layer (P<0.05). Microhardness values after second demineralisation increased with increased concentration of the applied sodium fluoride gel. Increasing concentration of the applied gel implies better protection of the enamel specimens against subsequent demineralisation (P<0.05). It is concluded that differently concentrated acidulated sodium fluoride gels resulted in concentration-related significant uptake of fluoride in carious-like demineralised enamel, leading to a better demineralisation protection with increasing fluoride concentration in the gel.
Vinyl fluoride is used widely in the manufacture of fluoropolymers. Based in part on the structural similarity of vinyl fluoride to the hepatocarcinogens vinyl chloride and vinyl bromide, a TSCA Section 4 test rule mandated the testing of vinyl fluoride for oncogenicity. This report presents the results of a 90-day inhalation study in rats and mice with vinyl fluoride designed to set test concentrations for a subsequent oncogenicity study. Groups of 15 male and female rats and mice were exposed 6 hr per day, 5 days per week for approximately 90 days to target concentrations of 0, 200, 2000, or 20,000 ppm vinyl fluoride. Clinical chemical, hematological, and urine analyses were performed on rats after 45 and 90 days of exposure. A hematological evaluation was performed on mice following 45 and 90 days of exposure. A complete gross and microscopic evaluation was conducted at the end of the study. After 93 days on test, groups of five rats and five mice per sex were implanted with osmotic minipumps containing [3H]thymidine and were exposed for an additional 5 days to measure cell proliferation in liver, kidney, lung, and nasal cavity tissues. Results of the histopathological, clinical chemical, and hematological evaluations showed no significant effects of vinyl fluoride exposure at any concentration following either 45 or 90 days of exposure. A concentration-related increase in fluoride ion in urine was observed in rats at 45 and 90 days of exposure. A plateau in urinary fluoride excretion was observed at approximately 2000 ppm, suggesting saturation of vinyl fluoride metabolism. Vinyl fluoride-related cell proliferation effects were largely restricted to liver. Hepatic cell proliferation in male and female rats and mice was elevated at all concentrations. The response was similar at concentrations of either 2000 or 20,000 ppm and was consistent with concentration-response relationships for other haloethylenes. Taken together, the urinary fluoride excretion and hepatic cell proliferation data suggest a mechanistic link between the two effects. On the basis of these findings and experience with other haloethylenes, concentrations of vinyl fluoride to be tested for oncogenicity should be chosen such that the full linear range of the concentration-response curve is evaluated. The present study demonstrates through example the value of incorporating cell proliferation studies in standard testing protocols.
OBJECTIVES: The aim of the current in vitro study was to evaluate the effect of CO(2)-laser treatment immediately after applying amine fluoride solution on enamel. It was hypothesized that such a treatment would increase enamel fluoride uptake, and reduce dissolution rate and thermal surface alterations. METHODS: Fluoride uptake was determined in 40 human enamel sections randomly assigned to four groups (n=10), which were either left untreated (1), exposed to a 1% amine fluoride solution for 15s without irradiation (2), irradiated for 15s with a continuous-wave carbon dioxide laser (3), or laser-treated for 15s through the amine fluoride solution applied immediately beforehand (4). Fluoride uptake was determined with an ion selective electrode after acid dissolution of the specimens (surface and subsurface layers). For the determination of acid resistance, another 40 enamel sections were treated according to the above protocol. Acid resistance was determined in surface and subsurface layers by measuring eluted calcium upon 3% lactic acid exposure with atomic absorption spectrometry. Enamel surface alterations after laser irradiation were monitored using scanning electron microscopy. RESULTS: Laser irradiation through the fluoride solution led to significantly higher fluoride contents in the surface enamel layer compared to fluoride treatment alone or laser treatment alone (p=0.002). Laser treatment with or without fluoride resulted in an increased acid resistance of enamel specimens. Fewer surface alterations were observed upon SEM examination of specimens irradiated through the amine fluoride solution compared to counterparts treated with laser only. CONCLUSIONS: CO(2) laser light application through an amine fluoride solution may be useful and effective in the prevention of caries.
The compressive strength, fluoride releases and recharge profiles of 15 commercial fluoride-releasing restorative materials have been studied. The materials include glass ionomers (Fuji IX, Ketac Molar, Ketac Silver, and Miracle Mix), resin-modified glass ionomers (Fuji II LC Improved, Photac-Fil, and Vitremer), compomers (Compoglass, Dyract AP, F2000, and Hytac) and composite resins (Ariston pHc, Solitaire, Surefil and Tetric Ceram). A negative linear correlation was found between the compressive strength and fluoride release (r(2)=0.7741), i.e., restorative materials with high fluoride release have lower mechanical properties. The fluoride-releasing ability can be partially regenerated or recharged by using a topical fluoride agent. In general, materials with higher initial fluoride release have higher recharge capability (r(2)=0.7088). Five equations have been used in curve fitting to describe the cumulative fluoride release from different materials. The equation [F](c)=[F](I)(1-e(-bt))+betat best describes the cumulative fluoride release for most glass ionomers, resin-modified glass ionomers, and some high fluoride-releasing compomers and composites, whereas [F](c)=[F](I)/(t(1/2)+t)+alphat best describes the cumulative fluoride release for most compomers and composite resins. The clinic applications of different fluoride-releasing materials have also been discussed.
OBJECTIVES: To determine firstly, if sustained fluoride release can be achieved from five orthodontic adhesives: Ketac-Cem, Fuji ORTHO LC, Sequence, Transbond and Right-On, with daily exposure to fluoride mouthrinse in vitro, and secondly, if sustained fluoride release can be re-established from the same specimens, after an interruption in mouthrinse exposure. METHODS: Ten brackets were bonded to bovine incisors using each adhesive. Each adhesive group was divided equally into a test and a control sub-group. In phase 1 (42 days), the test sub-groups were exposed for 1min daily to fluoride mouthrinse (225 ppm), followed by immersion in de-ionised water for 42 days to deplete their fluoride reserves. Mouthrinse exposure was then resumed in phase 2 (28 days). Mean cumulative fluoride release (MCFR) was calculated for days 0-21 of phase 1 and for the plateau portion of the fluoride release curves in phase 1 (days 21-42) and phase 2 (days 7-28). RESULTS: During phase 1, the MCFR for each test sub-group was significantly greater than its control (p<0.05). There was no significant difference in MCFR between the curve plateau portion of phases 1 and 2 for all adhesives except Transbond, for which MCFR was less in phase 2 (p<0. 05). CONCLUSIONS: Sustained fluoride release occurred for each adhesive exposed daily to fluoride mouthrinse, at a level significantly greater than its control. After fluoride exhaustion, re-exposure to daily fluoride mouthrinse produced sustained fluoride release levels comparable to those prior to exhaustion, for all adhesives except Transbond.
The aim was to determine the fluoride concentration in saliva after intake of a dinner meal prepared with fluoridated salt. The investigation had a randomized cross-over design, and 10 healthy adolescents with natural fluoride content (1.06 ppm) in their drinking water participated after informed consent. After a run-in week, the subjects were served a standardized dinner of spaghetti with minced meat sauce prepared with either fluoridated salt (test arm) or non-fluoridated salt (control arm). The fluoride concentration of the test salt was 250 ppm. Samples of stimulated whole saliva was collected at baseline, directly after eating (0 min) and then after 10, 30 and 180 min. After a 1-week wash-out period, the experimental procedure was repeated with the opposite salt. Fluoride concentration in saliva was measured with a fluoride-specific electrode and the post-ingestion levels were compared with baseline using repeated-measures ANOVA. The mean baseline concentrations were 10.9 and 8.0 microg/l in the test and control arms, respectively. Immediately after the intake, the mean fluoride values increased significantly to 81.6 microg/l in the test arm and to 31.5 microg/l in the control arm (p<0.05). The fluoride levels remained elevated (p<0.05) for 30 min after ingestion of the test meal but not following the control meal. In conclusion, consumption of a dinner meal prepared with fluoridated salt increased the salivary fluoride levels for about 30 min.
OBJECTIVE: To study fluoride release and its impact on flexural strength of fluoride-containing composites. METHODS: Experimental composite resins containing 0.3%, 0.6% and 1.2% fluoride (w/w) respectively and non-fluoride control composites were selected, including a compomer and its control composites. The amount of fluoride release in vitro was determined with fluoride ion-sensitive electrode in a 30 day consecutive period. The flexural strength was measured by Autograph Machine before and after releasing fluoride in water. RESULTS: The amount of fluoride release increased (0, 21.98, 43.98 and 99.91 micrograms.cm-2 respectively) and the flexural strength decreased (101.70, 94.29, 82.03 and 79.84 MPa respectively) while fluoride-contents in resins increased (0%, 0.3%, 0.6% and 1.2% respectively). With fluoride release, the flexural strength decreased significantly (P < 0.05). CONCLUSION: Fluoride release affects mechanical properties of fluoride-containing composites.
AIM: To determine the concentration of fluoride in saliva and supragingival dental plaque at designated time intervals after consumption of snacks prepared with a standardised amount of fluoridated salt. STUDY DESIGN: The investigation had a single blind prospective crossover design. METHODS: A group of 11 healthy young adults volunteered to participate after verbal and written information and consent. After a 1-week fluoride depletion period, the subjects consumed popcorn prepared with either fluoridated (250 mg/kg) or non-fluoridated salt during 30 minutes. Unstimulated whole saliva and samples of supragingival plaque were collected before consumption (baseline) and at 30, 60 and 120 minutes after the intake. Fluoride concentration was determined with a fluoride-specific electrode and the post-ingestion levels were compared with baseline by ANOVA. RESULTS: In saliva, the mean fluoride concentrations at baseline ranged from 0.021 to 0.027 mg/L and after the 30 minutes consumption of fluoride prepared snacks a 15-fold increase (p<0.001) was found. The same pattern was disclosed in the plaque samples. In both saliva and plaque, the fluoride levels remained significantly elevated after 2 hours (p<0.001 and p<0.05, respectively). CONCLUSION: Consumption of snacks prepared with fluoridated table salt resulted in significantly increased fluoride levels in saliva and supragingival plaque for a period of at least two hours.
PURPOSE: The objectives of this study were to investigate the fluoride levels in plaque and saliva before and after applying fluoride-containing pit and fissure sealants, and compare the fluoride release of 2 types of sealants at the different time intervals. METHODS: Eighteen children ages 6 to 9 years were randomly divided into 2 groups: Group 1--sealant containing fluorosilicate glass (Helioseal-F); and group 2--sealant containing methacryloyl fluoride-methyl methacrylate copolymer (Teethmate-F). Saliva and plaque samples were collected before and after the sealants were placed on their 4 first permanent molars. Fluoride levels were determined using the microdiffusion method. Fluoride concentrations before and after placing the sealants were analyzed by paired t test, and the fluoride concentrations between the 2 sealants were compared by t test, with the level of significance at 0.05. RESULTS: There was no significant difference between salivary fluoride levels before and after sealant placement application in both groups. The plaque fluoride level of Helioseal-F group at 24 hours was significantly higher than the baseline level (P = .03), and was not different afterwards. The plaque fluoride levels after sealant with Teethmate-F were not significantly different when compared to the baseline. However, there were no significant differences between salivary and plaque fluoride levels of the 2 groups at different time intervals. CONCLUSIONS: The groups sealed with sealant containing fluorosilicate glass showed significant increase of plaque fluoride level only at 24 hours after sealant placement.
This report shows results of a survey on dental caries in the canton of Vaud in the years 1970 and 1974. In this canton fluoridation was carried out by means of fluoride tablets distributed at school until 1969/70 and in subsequent years by adding 250 mg F/kg fluoride to domestic salt. For comparison, results from adjoining and other cantons are also presented. In 1970 the 3 communities in the canton of Vaud (Moudon, Grandson and Vevey) showed a remarkably low overall caries level due to the distribution of fluoride tablets, supplemented in Grandson with regular brushings with fluoride solutions. When the fluoride tablets were discontinued in 1968/70 and fluoridated domestic salt containing 250 mg F/kg NaCl was introduced, caries incidence reached an even lower level. In these 3 communities caries prevalence fell to the lowest level reached, so far, by means preventive measures in Bettlach (canton of Solothurn, toothbrushing with fluoride solutions 6 times per year combined with information, fluoride tablets on every school day, and in addition consumption of table salt fluoridated at a suboptimal level of 90 ppm). The children in the control communities Romont (canton of Fribourg), St-Aubin (canton of Neuchâtel) and Châtel-St-Denis (canton of Fribourg) also showed decreases of caries levels from 1970 to 1974. This decrease is attributed to the distribution of fluoride tablets started at the schools of this community in the late sixties. Caries incidence in the age spans 8 to 12 and 10 to 14 years was estimated. Children from the canton of Vaud where fluoridated table salt was practically the only preventive measure showed a smaller DMF increase than those from the cantons of Fribourg and Neuchâtel. By means of a method combining DMF means of various age groups it was possible to obtain sufficiently large numbers of children for a study of the caries prevalence in each community. All communities showed a decrease of caries levels. In the canton of Vaud this reduction started in 1970 at an already low level and in 1974 reached consistently lower values than those of the control communities of the cantons of Fribourg and Neuchâtel.
The purpose of this study was to examine the effect that brushing with a fluoridated dentifrice (Crest--Procter and Gamble) has on the fluoride release of restorative materials. Thirty standardized discs were fabricated; 10 were P-50 (3M) nonfluoridated composite resin (control), ten were Heliomolar Radiopaque (Ivoclar/Vivadent) fluoride releasing composite resin, and ten were Ketac Fil (ESPE) glass ionomer cement. Specimens were placed into separate containers of 10 mL deionized water. Half the specimens from each group were brushed with fluoridated dentifrice for two minutes twice per day and rinsed. The fluoride level of each specimen was evaluated for thirty days, using a fluoride specific ion analyzer. An analysis of variance (ANOVA) and Duncan's test (p < 0.05) indicated significant differences in fluoride release. The brushed glass ionomer was significantly higher than all other groups and the glass ionomer not brushed was significantly higher than all composite groups. Glass Ionomer Cement-brushed > Glass Ionomer Cement > Fluoridated Composite Resin-brushed = Fluoridated Composite Resin = Composite Resin-brushed = Composite Resin. Brushed glass ionomer appears to release the highest fluoride level, acting as a fluoride reservoir from the dentifrice for subsequent fluoride release.