Fluoride, remineralization and root caries

This paper reviews the probable mechanism of dental caries and the role of fluoride in the inhibition or reversal of that process. The initial stages of root caries are comparable to enamel caries, being the acid dissolution of mineral resulting from acids generated by bacterial metabolism. The fermentation of carbohydrates by oral bacteria including mutans streptococci and lactobacilli initiate the root caries process, removing mineral from among the organic matrix which is primarily composed of collagen. Subsequent to this demineralization, the organic material can be further broken down by bacterial enzymes. Fluoride inhibits mineral loss during the acid dissolution process and enhances remineralization in a similar manner to that which occurs in dental enamel.     

The effect of fluoride on Streptococcus sanguis 7863 IgA1 protease production and activity

Fluoride was found to affect the production of the bacterial IgA1 protease but to have no effect on IgA1 protease activity. The concentrations of fluoride that do affect Streptococcus sanguis growth and IgA1 protease production are higher than those normally seen in vivo under normal circumstances. The concentrations of fluoride in dental plaque following use of a fluoride rinse or dentifrice would be sufficient to reduce Strep. sanguis IgA1 protease production.     

Recognition of a non-standard base pair by thermostable DNA polymerases

Fluoride is a potent preventive agent of caries. It acts at two levels: local and systemic. At the local level it prevents the surface demineralisation of enamel by strengthening the superficial layers, and inhibiting the local bacterial activity. At the systemic level it improves the resistance of the enamel by forming with calcium, fluorapatite which is stronger than hydroxyapatite. Main sources are naturally fluorinated water, artificially enriched water, fluorinated salt, and fluoride medication. Recommended mean daily intake is 0.05 mg/kg, the risk of dental fluorosis occurring when daily intake exceeds 1 mg/kg. The large benefits of regular fluoride supplementation on children dental health must not live down the risk of dental fluorosis resulting from over administration. Therefore when prescribing fluoride to a child, the practitioner must carefully examine his/her possible other fluoride sources.     

Activity of the plasma membrane H(+)-ATPase and optimal glycolytic flux are required for rapid adaptation and growth of Saccharomyces cerevisiae in the presence of the weak-acid preservative sorbic acid

The weak acid sorbic acid transiently inhibited the growth of Saccharomyces cerevisiae in media at low pH. During a lag period, the length of which depended on the severity of this weak-acid stress, yeast cells appeared to adapt to this stress, eventually recovering and growing normally. This adaptation to weak-acid stress was not due to metabolism and removal of the sorbic acid. A pma1-205 mutant, with about half the normal membrane H+-ATPase activity, was shown to be more sensitive to sorbic acid than its parent. Sorbic acid appeared to stimulate plasma membrane H+-ATPase activity in both PMA1 and pma1-205. Consistent with this, cellular ATP levels showed drastic reductions, the extent of which depended on the severity of weak-acid stress. The weak acid did not appear to affect the synthesis of ATP because CO2 production and O2 consumption were not affected significantly in PMA1 and pma1-205 cells. However, a glycolytic mutant, with about one-third the normal pyruvate kinase and phosphofructokinase activity and hence a reduced capacity to generate ATP, was more sensitive to sorbic acid than its isogenic parent. These data are consistent with the idea that adaptation by yeast cells to sorbic acid is dependent on (i) the restoration of internal pH via the export of protons by the membrane H+-ATPase in an energy-demanding process and (ii) the generation of sufficient ATP to drive this process and still allow growth.     

Adverse Effects of Fluoride on Hydrometallurgical Operations

This review addresses the detrimental effects of fluoride on the various steps which constitute any hydrometallurgical operation. It focuses on the specific examples of apatite flotation, copper bioleaching, zinc electrowinning, and the manufacture of phosphoric acid. The presence of fluoride modifies the surface characteristics of minerals altering their effective flotation. Toxicity of fluoride to bacteria directly affects the mechanisms of bioleaching. Fluoride can interfere with the adhesion of metals to cathodes and affect deposit morphology during electrodeposition. In phosphoric acid synthesis from phosphate ores, fluoride affects production efficiency by altering the crystal morphology of the gypsum by-product.     

The influence of a mineralizing mouthrinse on the mineral contents and on the pH of dental plaque

The main objective of this study was to evaluate the effects of a single use of a mineralizing mouthrinse on dental plaque pH and on its mineral contents: an additional objective was to examine the effects of an oral prophylaxis and scaling on the same response variables. A total of 22 volunteer dental students (14 female and 8 male) participated in the study. The mineralizing mouthrinse contained calcium, phosphate, strontium and fluoride ions. Following a 48-hour period without oral hygiene and 2 hours after breakfast, dental plaque was collected twice from each participant for the evaluation of the effects of the oral prophylaxis and scaling, and twice more for the evaluation of the effects of the mineralizing mouthrinse. The pH was measured in vitro with a microelectrode and the mineral contents were determined by atomic emission spectrometry. The results demonstrate that the average post-prophylaxis pH was higher than the average pre-prophylaxis pH, and that a variation of the average contents of some minerals in the dental plaque was also observed after prophylaxis compared to the contents prior to prophylaxis. Although there was a significant reduction in the Fe content after the rinse with the mineralizing solution, no significant variation on the average pH was detected.     

The effect of bicarbonate/fluoride dentifrices on human plaque pH

The acidogenic response in dental plaque after rinsing with sodium bicarbonate/fluoride dentifrice slurries was studied using three intra-oral models. In the first model, resting plaque pH was monitored in mesiobuccal plaque on upper molars and premolars in six healthy subjects after abstinence from normal oral hygiene for three days. These measurements were followed by a three-minute rinse with 10% sucrose and, following a two-minute interval, a three-minute rinse with a test dentifrice slurry. After the test dentifrice rinse, pH was monitored at regular intervals up to 60 minutes. Flow rate, pH and buffer capacity of stimulated saliva were also determined. Changes in resting pH, plaque pH minima, and maximum pH drop were calculated. A clear elevation in the resting pH was observed after bicarbonate/fluoride dentifrice rinses, and a significant increase was obtained in the pH minima. The smallest pH drop also was found after treatment with the bicarbonate/fluoride dentifrice rinse treatment (p < 0.02). A second model using telemetric partial dentures with interproximally placed micro-antimony pH electrodes was used to study the effects of rinsing with increasing concentrations of sodium bicarbonate and calcium carbonate solutions, and with a fluoride dentifrice containing sodium bicarbonate. The response to these treatments was found to be rapid, dose-dependent, and was the greatest from the sodium bicarbonate. A third model used 24 subjects to assess the effects of sodium bicarbonate/fluoride dentifrice on plaque pH before and after a glucose challenge. The use of the bicarbonate/fluoride dentifrice resulted in significantly less measurable plaque acid than the fluoride dentifrice treatment. Collectively, these results indicate bicarbonate in dentifrice to be an effective buffering agent for stabilizing the pH and neutralizing plaque acids in dental plaque.     

Fluoride in osteoporosis: still an experimental and controversial treatment

Fluoride has been used in the treatment for osteoporosis for more than 30 years but its use is still controversial. Fluoride stimulates the osteoblasts to form new bone tissue. However, the new bone has an abnormal texture and is less mineralized and relatively less strong. In patients with osteoporosis treated with fluoride, the bone mineral density of the skeleton increases. On the other hand, the effects of fluoride treatment on the incidence of fractures are controversial and in some studies an increased fracture incidence was observed. In addition, fluoride often causes upper gastrointestinal complaints and a lower extremity pain syndrome, which is caused by stress fractures and may last for several months. For these reasons, fluoride treatment should only take place in the framework of clinical trials.     

Effectiveness of autologous blood replacement in rheumatoid arthritis surgery--a report of 10 years experience

The use of a wood stick (meswak or chewing stick) for brushing the teeth continues to be an important tool for oral hygiene care in many Afro-Asian communities. It is inexpensive, customary and used for religious reasons as well. Despite the wide use of meswak, information on its chemical and pharmaceutical contents are scant, particularly in regard to an anticaries effect. In the present study, sticks from Salvadora persica, the most common source for meswak, were analyzed for their soluble and total content of fluoride, calcium, phosphorus and silica. Results showed that the fluoride released from meswak soaked in water was negligible (< 0.07 microgram/ml). Approximately 39% of the total fluoride in the sticks was in a form that could be leached out. The leached calcium and phosphorus averaged 582 micrograms/ml and 34 g/ml, respectively, representing 19.6% and 26.4% of their total content in the sticks. There was a substantial amount of silica in the ashes of meswak. It appears that meswak is probably not particularly active against caries through its fluoride content, but it does act as a brush for removing dental plaque and polishing the teeth.     

Potential adverse outcomes of psychotropic and narcotic drug use in Canadian seniors

Infants who ingest high amounts of fluoride can be at risk of dental fluorosis. The authors analyzed the fluoride concentration of 238 commercially available infant foods. Fluoride concentrations ranged from 0.01 to 8.38 micrograms of fluoride per gram, with the highest fluoride concentrations found in infant foods containing chicken. Infant foods, especially those containing chicken, should be considered when determining total fluoride intake.     

Does the presence of xylitol in a sorbitol-containing chewing gum affect the adaptation to sorbitol by dental plaque?

It is known that xylitol inhibits sorbitol metabolism in some bacteria in vitro. The effect of xylitol/sorbitol-containing chewing gum on sorbitol adaptation of dental plaque was therefore examined. Ten subjects used this chewing gum for 12 wk, and plaque was collected before (control plaque) and after (test plaque) the exposure to sorbitol/xylitol. The metabolism of sorbitol by the plaque was examined with 14C-labeled sorbitol, and the radioactive metabolites were detected by high-performance liquid chromatography (HPLC). A considerable individual variation in acid formation was found. The mean values of total acids in the test plaque increased, as compared with the control plaque. An adaptation of dental plaque to sorbitol thus occurred in spite of the presence of xylitol in the chewing gum. The concentration of acetic acid predominated over other acids in both the control and test plaques. The proportions of acids expressed in percentage of total acids differed only slightly. Thus, long-term use of xylitol/sorbitol-containing chewing gum did not eliminate the adaptation of dental plaque to sorbitol.     

Fluoride profiles in dental calculus from Japanese, Chinese and British residents

Whether the fluoride concentrations and profiles differ in human dental calculus obtained from different countries was investigated. A total of 203 dental calculus deposits on 203 permanent teeth from residents (mean age, 52.1 years) of Nagoya (Japan), Shanghai (China), Leeds (Great Britain) and the Wuhan mountainous area (China, fluoridated area) were analysed. An abrasive microsampling procedure was used to examine fluoride distribution. There were five types of fluoride profiles in dental calculus in each area/country (designated types L, J, U, T, W). In supragingival calculus, type L (highest in the outermost layers) and type J (highest in the innermost layers) both had significantly higher values than type U (high in the surface and innermost layers) but were relatively identical. In subgingival calculus, type W (high in the outermost, mid and innermost layers) was characteristics. Calculus from the Wuhan mountainous area (fluoridated) had the highest fluoride concentration, followed by Leeds (non-fluoridated), and Nagoya and Shanghai (non-fluoridated) calculus had the lowest. Fluoride concentrations in supragingival calculus were higher in teeth extracted because of periodontal diseases than dental caries. It is concluded that fluoride concentrations and distribution in dental calculus differ from country to country, probably due to different fluoride environments.     

Chewing gum and saliva in oral health

The crucial role played by many properties of saliva in preventing dental caries, maintaining the plaque pH and controlling the equilibrium between enamel de- and remineralization has been demonstrated. This has been documented by the effects of salivary dysfunction on caries incidence and by the distribution of sites of caries predilection in areas where saliva presence is restricted. The use of sugar-free chewing gum has been increasingly accepted as one adjunct to oral hygiene procedures. It has become part of an anti-caries prevention program, especially in patients suffering from xerostomia. Chewing gum not only acts as a salivary stimulant but may also be a useful vehicle for some agents such as fluoride, chlorhexidine and calcium phosphate. Moreover, in some countries gum containing nicotine has been used to substitute the nicotine from cigarettes to reduce the effects of nicotine withdrawal reaction from people attempting to stop smoking.     

Cancer of the larynx: correlation of clinical characteristics, site of origin, stage, histology and diagnostic delay

Fluoride mouthrinses have generally proved to be effective in controlling caries in clinical studies. Caries reductions in North American studies have averaged about 30%. Large-scale school-based mouthrinse programs conducted during the 1970s, however, used historical controls at a time when caries rates were now known to be declining. Post-hoc analysis of the absolute (not relative) caries reductions in these studies showed that school-based fluoride mouthrinse programs were of questionable benefit from a cost standpoint. Fluoride mouthrinses have been shown to reduce demineralization and enhance remineralization of enamel adjacent to orthodontic bands and brackets. Benefits in adults have been less well documented. Use of fluoride mouthrinses by young children is discouraged until they have mastery of their swallowing reflexes. This paper recommends the use of fluoride mouthrinses for patients at increased or high risk for dental caries, but cautions that school-based programs be undertaken only in communities with a high population caries rate.     

Pharmacokinetics of fluorine contained in the Royale Saint-Yorre mineral water

The pharmacokinetics of oral fluoride supplied by one half liter of Royale Saint-Yorre water, which contains 8.50 mg fluoride per liter, were studied in ten healthy volunteers. Fluoride plasma kinetics and urinary excretion of fluoride were determined over 24 hours. After ingestion of one half liter Royale Saint Yorre mineral water, mean peak serum fluoride level was 159 +/- 22 micrograms/l. Time to peak serum level was 1 h (0.9 +/- 0.21 h) and area under the curve from 0 to 24 hours was 1,040 +/- 168 micrograms/l/h. Mean urinary fluoride was 2.57 +/- 0.4 mg (range 1.90 to 3.32 micrograms). The authors compared their findings with previously published data on fluoride pharmacokinetics after oral administration of an enteric-coated sodium fluoride tablet containing 11.35 mg elemental fluoride (12 healthy volunteers). Both peak serum level standardized for the dose of elemental fluoride and time to peak serum level were greater with the water than with the tablet. The authors cannot conclude as to which of the two types of fluoride exhibits the best bioavailability because their absorption coefficients have not been determined. This study demonstrates that Royale Saint Yorre mineral water is a valuable source of fluoride. Additional prospective studies are needed to determine whether it has therapeutic potential.     

Comparison of the clinical anticaries efficacy of an 1100 NaF silica-based dentifrice containing triclosan and a copolymer to an 1100 NaF silica-based dentifrice without those additional agents: a study on adults in California

Recent years have seen much work in the development of dentifrices containing the antimicrobial agent triclosan, a broad spectrum antibacterial agent manufactured for use in oral products by the Ciba-Geigy Corporation. Studies have shown that the incorporation of this agent into dental products, in combination with a PVM/MA copolymer (the non-proprietary designation for a polyvinylmethyl ether/maleic acid copolymer), can provide several important dental therapeutic benefits, including an antigingivitis effect. Much research on the therapeutic benefits of such dentifrices has been reported in the literature. The present study is a component of a large-scale program of clinical research to investigate the anticaries effectiveness of fluoride dentifrices containing 0.3% triclosan and 2.0% PVM/MA copolymer. The study included two treatment groups, each consisting of adults living within a 50 mile radius of Loma Linda, California, who were assigned to the use of one of the following sodium fluoride (NaF) dentifrices: 1) a dentifrice containing 0.3% triclosan and 2.0% PVM/MA copolymer in a 0.243% NaF/silica (1100 ppm F) base; or 2) a dentifrice containing 0.243% NaF/silica (1100 ppm F). Conducted in accordance with the guidelines for caries clinical studies published by the Council on Dental Therapeutics of the American Dental Association, the study employed clinical diagnostic criteria as described in the August, 1987 National Institute of Dental Research (NIH/NIDR) publication. Dental radiographs were not employed. Principal comparisons of the dentifrices tested were implemented through the construction of 90% confidence intervals for the ratio of mean 3-year caries increments, using Fieller's theorem. Of those subjects who met the initial inclusion/exclusion criteria for this study, 1,542 were available for the 36-month examination. DFS (resp., DFT) increments over this period were 2.07 (0.63) for the triclosan/copolymer dentifrice, and 2.16 (0.68) for the dentifrice without those additives. The confidence interval calculations for both incremental DFS and DFT support the conclusion that a dentifrice containing 0.3% triclosan and 2.0% PVM/MA copolymer in a 0.243% NaF/silica (1100 ppm F) base provides a level of anticaries efficacy which is "at least as good as" that provided by a dentifrice containing 1100 NaF/silica without those additive agents. As such, the results of this clinical study clearly indicate that the addition of triclosan and a copolymer to a 1100 NaF/silica dentifrice does not compromise its anticaries efficacy.     

Comparison of the clinical anticaries efficacy of a 1500 NaF silica-based dentifrice containing triclosan and a copolymer to a 1500 NaF silica-based dentifrice without those additional agents: a study on adults in Israel

Recent years have seen much work in the development of dentifrices containing the antimicrobial agent triclosan, a broad spectrum antibacterial agent manufactured for use in oral products by the Ciba-Geigy Corporation. Studies have shown that the incorporation of this agent into dental products, in combination with a PVM/MA copolymer (the non-proprietary designation for a polyvinylmethyl ether/maleic acid copolymer), can provide several important dental therapeutic benefits, including an antigingivitis effect. A considerable amount of the research on the therapeutic benefits of such dentifrices has been reported in the literature. The present study is a component of a large-scale program of clinical research to investigate the anticaries effectiveness of fluoride dentifrices containing 0.3% triclosan and 2.0% PVM/MA copolymer. The study included two treatment groups, each consisting of adults living near the Kiryat Gat area in Israel, who were assigned to the use of one of the following sodium fluoride (NaF) dentifrices: 1) a dentifrice containing 0.3% triclosan and 2.0% PVM/MA copolymer in a 0.331% NaF/silica (1500 ppm F) base; or 2) a dentifrice containing 0.331% NaF/silica (1500 ppm F). Conducted in accordance with the guidelines for caries clinical studies published by the Council on Dental Therapeutics of the American Dental Association, the study employed clinical diagnostic criteria as described in the August, 1987 National Institute of Dental Research (NIH/NIDR) publication. Dental radiographs were not employed. Principal comparisons of the dentifrices tested were implemented through the construction of 90% confidence intervals for the ratio of mean 3-year caries increments using Fieller's Theorem. Of those subjects who met the initial inclusion/exclusion criteria for this study, 1,296 were available for the 36-month examination. DFS (resp., DFT) increments over this period were 5.21 (1.30) for the triclosan/copolymer dentifrice, and 5.23 (1.39) for the dentifrice without those additives. The confidence interval calculations for both incremental DFS and DFT support the conclusion that a dentifrice containing 0.3% triclosan and 2.0% PVM/MA copolymer in a 0.331% NaF/silica (1500 ppm F) base provides a level of anticaries efficacy which is "at least as good as" that provided by a dentifrice containing 1500 NaF/silica, without those additive agents. As such, the results of this clinical study clearly indicate that the addition of triclosan and a copolymer to a 1500 NaF/silica dentifrice does not compromise its anticaries efficacy.     

Biochemical and histological changes in blood, erythrocytes and tissue of rats on feeding Dryopteris juxtaposita fern

One tenet of successful orthodontic therapy is to complete treatment without decalcification, hypocalcification, or discoloration of the natural dentition. Fluoride application has been shown to reduce demineralization of enamel. The purpose of this study was to see if fluoride could be incorporated into enamel before orthodontic bracketing without adversely affecting bond strength. Forty extract adolescent human premolars were randomly divided into two equal groups with 20 teeth each. Group 1 served as control group, and group 2 (experimental) was immersed in 1.23% acidulated phosphate fluoride for 4 minutes after acid etching. The buccal surfaces of all 40 teeth were then bonded with the same type of metal bracket and debonded with an Instron machine. The debonding interface was observed with scanning electron microscopy (SEM). The mapping was calculated with energy dispersive x-ray spectrometry. The results showed that the bond strength of group 1 was significantly greater than that of group 2. The enamel detachment (enamel fracture) was found in the experimental group only. Although the application of acidulated phosphate fluoride to a tooth can prevent dental decay or decalcification, the bond strength decreases and enamel detachment is found after debonding. The result shows that the application of acidulated phosphate fluoride after acid etching enamel has an adverse effect on orthodontic bond strength of human enamel.