Effect of low levels of fluoride in solution on enamel demineralization in vitro

The effect of low levels of fluoride in solution on in vitro enamel demineralization has been studied. Extracted human teeth were exposed to 0.1 M lactate solutions (at pH 4.3) which were partially saturated with respect to enamel mineral and which contained between 0.004 and 1 ppm fluoride. Enamel demineralization was monitored using SEM and polarized light microscopy. It was observed that, in the absence of fluoride, rapid enamel demineralization occurred, resulting in the formation of cavitations within 72 hours. Using the same demineralizing medium containing as little as 0.024 and 0.054 ppm fluoride, we observed a remarkable protection of the enamel surface. Subsurface enamel demineralization was, however, observed under these conditions as well as in a solution containing 0.154 ppm fluoride. When the demineralizing solution containing 1 ppm fluoride was used, no mineral loss was detected. The observed inhibition of enamel demineralization was also shown to be associated with a significant uptake of fluoride by the enamel mineral. These observations have been noted to correlate with an increase in solution supersaturation with respect to fluoridated apatitic species. The results obtained were found to be consistent with a proposed hypothesis that the net rate of enamel demineralization will be reduced in a demineralizing medium supersaturated with respect to less soluble fluoridated phases, due to the enhancement of the precipitation rate of fluoridated apatitic phases relative to the rate of dissolution of the original enamel surface.     

Effects of aluminum (III) and fluoride on the demineralization of bovine enamel: a longitudinal microradiographic study

Longitudinal microradiography has been used to determine inhibiting effects of aluminum (III), Al, and fluoride on mineral loss from slices of bovine enamel exposed to a demineralizing solution 4 h daily for 35 days. Inhibitor treatment was 5 min four times daily. For the remaining time, the samples were immersed in a neutral calcium phosphate solution which allowed neither remineralization nor demineralization. This study indicates that a 1-mM (27 ppm) solution of Al in a 0.1-M lactate solution, pH 5, has an inhibitory effect on the in vitro demineralization of bovine enamel. Application of this solution alternating with 20 mM (380 ppm) fluoride gave the same total inhibition as treatment with 20 mM fluoride alone.     

pH-cycling of enamel and dentin lesions in the presence of low concentrations of fluoride

F-dentifrice usage causes slightly elevated fluoride levels in saliva. Therefore, the effects of permanent low fluoride concentrations versus daily dentifrice treatments were studied on enamel and dentin lesions in a pH-cycling model of alternating demineralization and remineralization. Groups received 1) no fluoride treatment. 2) 3 μM (0.06 ppm) F continuously present during re- and demineralization or 3) daily 5–min F-dentifrice treatments. Solutions were analyzed for changes in calcium and fluoride. Cumulative results (10 d) showed that for the non-fluoride group the dentin lesions increased, while for enamel lesions mineral uptake and loss were balanced. Addition of 3 μM F caused small, non-significant, enhancement of remineralization (1–7%). while demineralization was significantly inhibited for both tissues (9–23%). The daily dentifrice treatments resulted in a balance between mineral uptake and loss of dentin, due to inhibited demineralization (-33%) and enhanced remineralization (+ 79%). For enamel, the F-dentifrice treatments resulted in 43% reduction of demineralization, with no significant effect on remineralization. Fluoride loss from the 3 μM F cycling solutions was significant (up to 50%) and constant during the experimental period. Microradiographic analysis showed remineralization at the lesion front in enamel. In dentin, the lesion depth was increased in all groups, with concomitant mineral deposition in the surface region of the dentifrice group. Results indicate that slightly elevated fluoride levels may be considerably less effective in inhibiting lesion progression in dentin than in enamel, and suggest mineral uptake and loss to occur at similar depths for enamel lesions, while demineralization and remineralization occur at different depths in dentin.     

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.     

Elevated fluoride products enhance remineralization of advanced enamel lesions

Caries prevention might benefit from the use of toothpastes containing over 1500 ppm F. With few clinical studies available, the aim of this pH-cycling study was to investigate the dose response between 0 and 5000 ppm F of de- and remineralization of advanced (> 150 microm) enamel lesions. Treatments included sodium and amine fluoride, and a fluoride-free control. Mineral uptake and loss were assessed from solution calcium changes and microradiographs. Treatments with 5000 ppm F both significantly enhanced remineralization and inhibited demineralization when compared with treatments with 1500 ppm F. Slight differences in favor of amine fluoride over sodium fluoride were observed. The ratio of de- over remineralization rates decreased from 13.8 to 2.1 in the range 0 to 5000 ppm F. As much as 71 (6)% of the remineralized mineral was calculated to be resistant to dissolution during subsequent demineralization periods. With 5000-ppm-F treatments, more demineralizing episodes per day (10 vs. 2 for placebo) would still be repaired by remineralization.     

Demineralization of human dentine compared with enamel in a pH-cycling apparatus with a constant composition during de- and remineralization periods.

A comparison was made between the demineralization of enamel and dentine with and without abraded surfaces. This was done in a pH-cycling experiment for different demineralization/remineralization ratios--in the range from 1:1 to 1:4--and for different fluoride additions (up to 2 ppm) in solution. A new automatic pH-cycling system, in which the de- and remineralization solutions have a constant composition during the de- and remineralization cycles, was used to create mineral loss in human dentine and enamel. Changes in mineral content were monitored by means of longitudinal microradiography. A linear correlation was found between the amount of mineral lost and the total demineralization time for both dentine and enamel. The demineralization rates were comparable for abraded enamel and dentine and for polished enamel and dentine, and this rate was roughly doubled by the removal of the outer surface for both tissues. This showed that the presence of the outer surface is equally important to dentine and enamel. Under the pH-cycling conditions used, a logarithmic relation was found between the addition of fluoride and the decrease in demineralization for both enamel and dentine. The inhibitory effect of fluoride on demineralization was most pronounced on abraded enamel, followed by pumice-polished enamel, abraded dentine and pumice-polished dentine. About 2 ppm fluoride was needed under the conditions used to stop enamel demineralization completely; in the case of dentine, however, this amount of added fluoride did not inhibit demineralization.     

不同浓度的含氟涂料对人牙釉质抗酸性的影响

目的：确定4种浓度的含氟涂料对人牙釉质抗酸性的影响。方法：采用22000ppm,10000ppm,5000ppm及2200ppm等4种不同浓度的含氟涂料处理离体人牙釉质后经脱矿实验，然后测量酸蚀液中钙的溶出量，并用激光荧光诊断仪对人工龋损进行定量诊断。结果：22000ppm组与10000ppm组的抗酸性无差别，而其余各组之间均有差别。结论：22000ppm及10000ppm的含氟涂料抑制牙釉质脱矿的效果比5000ppm及2200mmp的含氟涂料好，而将22000ppm的含氟涂料浓度降至10000ppm，并不影响它的防龋效果，因此，在临床应用时，可以考虑适应降低含氟涂氟浓度以提高安全性。     

Effect of 0.02% NaF solution on enamel demineralization and fluoride uptake by deciduous teeth in vitro

The application of 0.02% NaF solution on teeth with a cotton swab instead of brushing with fluoride dentifrice has been suggested for young children to reduce the risk of dental fluorosis, but its anticariogenic effect has not been evaluated. Thus, we studied the in vitro effect of 0.02% NaF solution on enamel demineralization and fluoride uptake in deciduous teeth; non-fluoride dentifrice and fluoride dentifrice (1.100 mug F/g) were used, respectively, as negative and positive controls. The treatment with fluoride dentifrice was more effective in reducing enamel demineralization (p < 0.05) and on fluoride uptake by the enamel (p < 0.05) than the non-fluoride dentifrice and the 0.02% NaF solution. Data suggest that the alternative use of 0.02% NaF solution instead of fluoride dentifrice should be reevaluated especially if dental caries are to be controlled.     

氟化物在预防正畸釉质脱矿中的应用

釉质脱矿是正畸临床中经常伴有的牙体损害,一旦发生,大部分不可逆转,常会影响到牙齿的健康和美观,因此预防釉质脱矿非常重要.氟化物的应用可以抑制釉质脱矿的发生并促进釉质再矿化.氟化物防龋机制主要是降低釉质溶解度、生成氟化钙和氟磷灰石来促进釉质再矿化.本文就氟化物预防正畸釉质脱矿的可能机制和预防方法进行综述.     

Effects of two fluoride gels on fluoride uptake and phosphorus loss during artificial caries formation

Blocks of human enamel were cycled through a demineralization--F-treatment-remineralization procedure and then analyzed for fluoride and the presence of caries-like lesions. Treatments with a sodium fluoride gel (5000 ppm F) increased the enamel fluoride concentration to 6500 ppm F, whereas a stannous fluoride gel (1000 ppm F) increased enamel fluoride to about 1200 ppm F. Although a control treatment (water) allowed caries-like lesions to form, as observed by microradiography, no lesions were found in either of the fluoride-treated groups. When the experiment was repeated with radioactive teeth, mineral loss, as determined by release of 32P, was again greatest in the water-treated control group, but some loss was observed in the fluoride treatment groups. The least loss was found in the sodium fluoride group. It was concluded that the fluoride treatments not only increased enamel resistance but also enhanced remineralization so that calcium phosphate was replaced during the subsequent remineralization phase. Because of the probability that stannous ions were deposited during the stannous fluoride treatments, some of the apparent calcium phosphate re-deposition in this group was probably stannous compounds.     

Enamel demineralization in situ with various frequencies of carbohydrate consumption with and without fluoride toothpaste.

There is little information in the literature on the relationship among the frequency of carbohydrate consumption, the use of fluoride toothpaste, and enamel demineralization. The aim of this investigation was to compare the extent of demineralization of enamel slabs in situ, with a sugar-based solution, consumed in constant amounts but with various frequencies in subjects both with and without the use of fluoride (F) toothpaste. Eight subjects wore removable mandibular appliances carrying an enamel slab cut from white-spot lesions. The subjects were required to drink 500 mL of a 120-gm/L sugar solution either once, 3, 5, 7, or 10 times/day for 30 sec on each occasion, for a period of 5 days while brushing their teeth twice daily with either a F (1450 ppm NaF) or a F-free toothpaste. Mineral analysis revealed that when the subjects used a F toothpaste, net demineralization was evident only with the seven- and 10-times/day regime (ns). When F-free toothpaste was used, statistically significant demineralization was observed when the frequency exceeded 3 times/day. This study demonstrates the importance of F-containing toothpaste in enamel re-/demineralization by varying the frequency of carbohydrate challenge     

Effect of calcium in model plaque on the anticaries activity of fluoride in vitro.

The uptake of calcium by a polysaccharide (agarose) gel used as a model for plaque from a two-step treatment (consisting of a calcium rinse followed by a fluoride treatment) and the effect of the deposited calcium in model plaque on caries lesion formation in enamel were determined. Calcium uptake was measured by treatment of the model plaques with [45Ca]-CaCl2 solutions with or without NaF. A two-step treatment consisting of calcium followed by fluoride produced a 100% increase in calcium content of model plaque, presumably due to the formation of CaF2, compared with a treatment with artificial saliva followed by calcium alone. The effects of these increased plaque minerals on caries lesion formation were studied by subjecting model-plaque-covered enamel blocks to a cyclic demineralization-remineralization treatment. Artificial-plaque-covered enamel blocks were treated daily with 180 ppm calcium for ten min, then 100 ppm fluoride for ten min, followed by demineralization for 16 h, and finally, remineralization for seven h and 40 min. After five days, the blocks were sectioned, and lesion formation was determined by microradiography-microdensitometry. Artificial plaque treated with a calcium rinse followed by a fluoride rinse reduced lesion size by 90%, compared with a 68% reduction by a fluoride rinse alone. When the experiment was repeated with a simulated pre-brush calcium rinse (180 ppm calcium) followed by a fluoride dentifrice suspension (110 ppm fluoride), lesion size was reduced by 46%, compared with a 32% reduction by the fluoride dentifrice suspension alone.     

Combination effect of fluoride dentifrices and varnish on deciduous enamel demineralization

The aim of this study was to evaluate the anticaries potential of 500 or 1100 ppm F dentifrices combined with fluoride varnish using a pH-cycling regimen. Seventy primary canines were covered with nail polish, leaving a 4×4 mm window on their buccal surface, and randomly assigned into 7 groups (n = 10): S: sound enamel not submitted to the pH-cycling regimen or treatment; N: negative control, submitted to the pH-cycling regimen without any treatment; D1 and D2: subjected to the pH-cycling regimen and treated twice daily with 1100 or 500 ppm F dentifrice, respectively; VF: fluoride varnish (subjected to F-varnish before and in the middle of the pH-cycling regimen); and VF+D1 and VF+D2. After 10 days, the teeth were sectioned, and enamel demineralization was assessed by cross-sectional hardness at different distances from the dental surface. Data were analyzed using a two-way ANOVA followed by Tukey's test. Dentifrice with 1100 ppm F and the combination of F-varnish with the dentifrices significantly reduced enamel demineralization compared with the negative control (p < 0.05), but the isolated effects of F-varnish and dentifrice with low concentration were not significant (p > 0.05). The effect of combining F-varnish with the dentifrices was not greater than the effect of the dentifrices alone (p < 0.05). The data suggest that the combination of F-varnish with dentifrices containing 500 and 1100 ppm F is not more effective in reducing demineralization in primary teeth than the isolated effect of dentifrice containing 1100 ppm F.     

酪蛋白磷酸肽-无定形磷酸钙对正畸术后釉质再矿化的效果评价

目的: 比较含氟漱口水、护牙素即酪蛋白磷酸肽-无定形磷酸钙（casein phosphopeptide calcium phosphate complex,CPP-ACP）对正畸治疗后发生釉质脱矿的再矿化效果。方法: 应用Image J图像分析技术观察正畸治疗后釉质的再矿化。将固定矫治器正畸治疗后发生牙釉质脱矿的21例患者（女13例,男8例,84颗患牙）分为3组,每组28颗患牙。对照组仅用含氟牙膏每天刷牙2次,每次3 min。氟化物组用含氟牙膏每天刷牙2次,每次3 min,同时使用20 mL 0.01%氟化物冲洗牙2次。CPP-ACP组用含氟牙膏每天刷牙2次,每次3 min。同时按要求使用CPP-ACP 2次,3组均持续使用6个月。采用SPSS17.0软件包对数据进行统计学分析。结果: 正畸治疗后6个月,3组牙釉质脱矿白斑区域面积均有不同程度减少,3组治疗前、后均有显著差异（P<0.05）。CPP-ACP组效果尤为明显（51.68%）,显著高于氟化物组（44.42%）和对照组（42.71%）。结论: 正畸治疗后6个月内,正确刷牙、氟化物漱口、配合护牙素的使用,对正畸治疗中脱矿牙的再矿化均有一定效果, 而且CPP-ACP可以更有效地减小牙釉质脱矿白斑区域面积。     

The carbonate and fluoride in surfaces of remineralized enamel.

Analyses were made of samples of surface enamel collected before and after acid demineralization and after subsequent remineralization in solutions containing calcium and phosphate and various levels of bicarbonate and fluoride ions. Demineralization caused a preferential loss of carbonates. Remineralization was increased by both fluoride and bicarbonate ions. With no bicarbonate in the calcifying solution, 0.25 to 4.0 mM NaF increased mineral formation and thereby caused a relative reduction of its carbonate content. With 0.5 mM NaF (10 ppm F-) and 5, 15, and 25 mM HCO-3 in remineralizing solutions more carbonate was deposited than in the absence of NaF. Five and 15 mM HCO-3 increased, but 25 mM HCO-3 decreased, deposit of fluoride in enamel.     

氟化泡沫对正畸固定矫治患者牙周指数及牙釉质脱矿的影响

目的:探讨氟化泡沫对正畸固定矫患者牙周指数及牙釉质脱矿的影响。方法:选取2013年6月~2014年6月30例舌侧正畸治疗患者(600颗牙)为研究对象,根据入院时间分为对照组15例(297颗牙)和观察组15例(293颗牙),对照组采取常规口腔卫生措施,观察组在对照组的基础上定期使用1.23%氟化泡沫。随访12 个月,观察两组牙釉质脱矿牙位分布、脱矿指数(EDI)、菌斑指数(PLI)和出血指数(BI)。结果:牙釉质脱矿主要分布于上颌侧切牙、上颌中切牙及下颌前磨牙等;观察组牙釉质釉质脱矿率11.26%明显低于对照组17.51%(χ²=4.666,P<0.05);观察组EDI、PLI、BI等均明显低于对照组(t=9.947, 4.435, 7.789,P<0.05)。结论:舌侧正畸治疗中牙釉质脱矿发生率较高,氟化泡沫有助于减少正畸治疗中的牙釉质脱矿发生,降低牙周指数。     

Current concepts on the theories of the mechanism of action of fluoride

The caries-preventive effect of fluoride is mainly attributed to the effects on demineralization/remineralization at the tooth oral fluids interface. Sub ppm levels of fluoride in saliva are effective in shifting the balance from demineralization, leading to caries, to remineralization. This is attributed to the fluoride-enhanced precipitation of calcium phosphates, and the formation of fluorhydroxyapatite in the dental tissues. Low fluoride levels are found in saliva after toothbrushing with fluoride containing dentifrices. Similar concentrations are ineffective in interfering with processes of growth and metabolism of bacteria, and also do not result in a significantly reduced dissolution of tooth mineral as a result of (firmly bound) fluoride incorporation. Comparative studies of fluoride efficacy have shown that higher concentrations in solution are needed in pH-cycling studies of dentine than in enamel to maintain the mineral balance or to induce remineralization. This is attributed to the greater solubility of the dentine and the smaller size of the dentine crystallites compared to enamel. Fluoride slow-release devices, in the form of fluoride-releasing restorative materials, may serve to increase the fluoride levels in saliva and plaque to levels at which caries can be prevented, also in high-risk patients. Research questions for the next millennium and future perspectives for fluoride applications should be found in the retention and slow release of fluoride after various combinations of fluoride treatment, the combination of fluoride and anti-microbial treatment, the individualization of caries prevention, and the combination of preventive schemes with new developments in caries diagnosis.     

In vitro demineralization of tooth enamel subjected to two whitening regimens

BackgroundThe resistance of bleached enamel to demineralization has not been elucidated fully. In this study, the authors aimed to examine the level of in vitro demineralization of human tooth enamel after bleaching by using two common bleaching regimens: home bleaching (HB) and office bleaching (OB) with photoirradiation.MethodsThe authors bleached teeth to equivalent levels by means of the two bleaching regimens. They used fluorescence spectroscopy to measure the reduction in enamel density and the release of calcium into solution after storing the treated teeth in a demineralizing solution for two weeks. They also visualized and quantified mineral distribution in demineralized bleached enamel over time by using a desktop microcomputed-tomographic analyzer.ResultsEnamel subjected to HB or to photoirradiation without bleaching showed increased demineralization. In contrast, enamel treated with OB was more resistant to demineralization. This resistance to demineralization in teeth treated with OB presumably is due to peroxide's permeating to deeper layers of enamel before being activated by photoirradiation, which enhances mineralization.ConclusionsThe mineral distribution pattern of enamel after treatment plays a critical role in providing resistance to demineralization in whitened teeth.Practical ImplicationsOB confers to enamel significant resistance to in vitro demineralization. Dentists should supervise the nightguard HB process.     

Remineralization potential of a new toothpaste formulation: an in vitro study

The aim of the present study was to determine the ability of a dentifrice containing a mixture of ion-exchange resins (named NMTD), which supplies calcium, fluoride, phosphate, and zinc ions, to promote remineralization and/or inhibit demineralization of dental human enamel in a pH cycling model in vitro. A fluoride toothpaste was used as the control. The enamel specimens were tested for microhardness before and after 10 days and 16 days of the demineralizing and remineralizing treatments. The results of this study showed both dentifrices were effective in limiting in vitro enamel demineralization although the effects were not significantly different from each other. Inclusion of calcium and phosphate ion-exchange resins in the dentifrice containing a fluoride ion-exchange resin maintained a similar net outcome of the conventional dentifrice in the demineralization/remineralization process under the experimental conditions employed.     

CaF2 in enamel biopsies 6 weeks and 18 months after fluoride treatment

Fluoride concentrations were studied in enamel biopsies from maxillary central incisors 6 weeks and 18 months after fluoride treatment. In the short-term study biopsies were obtained prior to and after treatment with acidic sodium or ammonium fluoride. The findings showed that large amounts of fluoride were deposited in enamel from NH4F treatment (mean concentration 84,723 ppm), indicating substantial CaF2 formation. NaF treatment resulted in mean fluoride concentrations of 7,818 ppm. In the 18-month study, biopsies from 58 placebo-treated teeth were analyzed for total fluoride (mean 1,733 ppm). Twenty-five additional biopsies from placebo-treated and 58 from NH4F-treated teeth were analyzed for KOH-soluble (CaF2) and KOH-nonsoluble (apatitic) fluoride. The mean values for total fluoride were 1,669 and 2,085 ppm in the placebo-treated and in the NH4F-treated groups, respectively. The corresponding mean values for KOH-nonsoluble fluoride were 1,467 and 1,731 ppm and for KOH-soluble fluoride 202 and 354 ppm, respectively. The increase in enamel fluoride after fluoride treatment was only marginally significant. Biopsies from the ammonium fluoride treated group were significantly more likely to have high (30 vs. 8%) and moderate (28 vs. 16%) CaF2 levels and less likely to have low levels than biopsies of placebo-treated teeth (chi-square = 8.0 with 2 d.f.; p = 0.018). It is concluded that very substantial amounts of CaF2 are present in enamel 6 weeks after treatment, and small amounts may persist in the surface enamel for as long as 18 months.