Uptake and retention of fluoride by intact enamel in vivo after application of neutral sodium fluoride

abstract – The uptake and retention of fluoride in surface enamel in vivo after a single topical application of a neutral 2 % NaF solution was studied on the basis of 2–3 μm thick enamel biopsies from maxillary central incisors in adults and children. The biopsy technique included delimiting of the sampling area by means of abrasive-resistant, adhesive tape, punched with perforations of known sizes admitting of two biopsies on different places on the same tooth surface. This method made it possible to calculate the depth of each biopsy and to perform the comparative studies with intradental control. The F uptake was estimated by comparing F concentrations in biopsies taken before and 1 week after topical treatment. In teeth of 10- to 11-year-old children the F concentration increased 259 ± 393 parts/10⁶, which is statistically significant ( P < 0.002). The mean uptake in teeth of adults, 22–27 years of age, was 179 ± 401 parts/10⁶ which did not exhibit statistical significance ( P > 0.10). The F concentrations in biopsies taken 1 week and 8 weeks after treatment from teeth in children were almost identical, indicating that the acquired F is firmly fixed in the enamel for 2 months or longer.     

Fluoride concentration in plaque in adolescents after topical application of different fluoride varnishes

The aim of the study was to measure the fluoride (F) concentration in plaque after a single topical application of different fluoride varnishes with contrasting levels of F. Thirty adolescents (12–17 years) with fixed orthodontic appliances were randomly assigned to one of three groups: Bifluoride (6% F), Duraphat (2.23% F) and Fluor Protector (0.1% F). The varnishes were applied after professional cleaning in one upper quadrant, leaving the opposite quadrant untreated according to the split-mouth technique. Pooled plaque samples from each quadrant were collected at baseline and 3 days, 7 days and 30 days after the varnish treatment, and fluoride was analysed by microdiffusion. All fluoride varnishes increased the fluoride concentration in plaque compared with baseline, and the mean values varied between 23 and 138 ng F/mg after 3 days, depending on varnish F concentration. Compared with the control quadrant, statistically significant elevations were recorded for Bifluoride after 3 days and 7 days and Duraphat after 3 days, while no significant differences were revealed in the Fluor Protector group. The fluoride concentration in plaque was back to baseline levels for all participants in the Duraphat group after 7 days, while some individuals in the Bifluoride and Fluor Protector groups still registered slightly increased levels after 30 days. The results suggest that fluoride varnish treatments resulted in elevated fluoride levels in plaque adjacent to fixed orthodontic appliances for a period of up to 1 week, although different patterns was disclosed for the various brands. Received: 5 October 1999 / Accepted: 18 November 1999     

Effect of strontium in combination with fluoride on enamel remineralization in vitro

Previous studies showed that strontium (Sr) as well as fluoride (F) can enhance enamel remineralisation. The aim of this study was to evaluate the effects of Sr in combination with F on enamel remineralisation in vitro. Sixty enamel specimens obtained from caries free human premolars were demineralised to produce caries-like lesions. Half of each lesion was covered with nail varnish as an untreated control. The specimens were then randomly divided into F and Sr + F treatment groups. The F group was exposed to remineralising solutions (1.5 mM CaCl₂, 0.9 mM KH₂PO₄) containing 1 ppm, 0.1 ppm or 0.05 ppm F. The Sr + F treatment group was exposed to the same solutions including 10 ppm Sr. After 2 weeks, lesion depth, mineral loss and percentage enamel remineralisation were determined using transversal microradiography. There was a significant decrease in mineral loss in all groups (p < 0.001). Lesion depth was significantly reduced for all groups (p < 0.05) with the exception of group F. Remineralisation was significantly affected by F concentration (p = 0.000). The participation of Sr resulted in a significant enhancement of remineralisation (p < 0.001) with a synergistic effect of the Sr + F combination (p < 0.01). It was concluded that while the remineralising process was affected by the concentration of F, there was also an interaction between F and Sr when they were used in conjunction.     

矿化液、低浓度氟化物溶液和氟泡沫再矿化作用比较

目的本研究对矿化液、低浓度氟化物溶液和氟泡沫再矿化作用进行了比较,从而寻找出一种再矿化效果较好的制剂.方法采用实验室研究,分别用三种制剂处理表面脱矿釉质.应用显微硬度仪检测处理前后的釉质表面硬度值,通过对比前后硬度差异反映脱矿釉质的再矿化的情况.结果矿化液处理后的釉质表面硬度明显增加,有显著性统计学意义.低浓度氟化物溶液和氟泡沫处理后釉质的表面硬度无明显改变.结论在体外,矿化液的再矿化效果优于低浓度氟化物溶液和氟泡沫.它可用于治疗正畸过程中早期釉质脱矿.     

A field biopsy method for fluoride determinations in human surface enamel

ABSTRACT An enamel biopsy method was developed that is especially intended for use under primitive clinical conditions in field studies. Three successive enamel layers, each of 1 μm or less, were etched off the same delimited area of 3 mm² by means of perchloric acid, using a microsampler with disposable tips. The biopsy technique was applicable to the vestibular surface of almost all teeth, causing no perceptible damage to the enamel surface. Based on cumulated data from the successive enamel layers, curves were drawn from which F levels at various depths in the outer 3 μn of the enamel could be interpolated. F levels in surface enamel of maxillary first premolars in 40 12–13-year-old children in a locale with 0.5 mg F/l in the drinking water were found to be 3,800, 2,400 and 2,000 parts/10⁶ in three successive enamel layers of 0.6, 1.0 and 1.1 μm, respectively, demonstrating a decrease in F concentration of about 1,800 parts/10⁶ within this depth interval. Identical F concentrations were found in bilateral premolars.     

Effect of three fluoride agents on remineralization and fluoride uptake on enamel lesion

This study is to compare the fluoride uptake of three fluoride agents and the effect of remineralization on artificial enamel lesions. Eight human third molars were all divided into four slabs. The slabs were randomly assigned to the following four groups: group A (9,040 ppm F, APF gel), group B (968 ppm F, SnF₂ home gel), group C (22,600 ppm F, fluoride varnish, FV) and a control group. After 72-hour demineralizing and 10-day pH-cycling period with the application of corresponding fluorides. The distribution of fluoride and mineral change was analyzed with EPMA and CMR respectively. There was a significant increase in the amount of F uptake after the application of the three fluoride agents compared to the control group. Group A showed an extremely greater F uptake compared to group C and B. The amount of F uptake from group C was greater than that of group B. The three tested groups showed signs of significantly greater amounts of remineralization as compared to the control group. Remineralization of group C was detected to be the greatest, followed by group A and group B, but there was no significant difference in them under statistical analysis. It can be concluded that all of the tested agents were effective in regaining mineral loss. FV may be recommended as a professional topical fluoride. It is as effective, if not more so, as traditionally used APF gel. Also 0.4% SnF₂ home gel is an efficient self-applied topical fluoride for daily use.     

Structural studies on calcium fluoride formation and uptake of fluoride in surface enamel in vitro

abstract — The structural changes in human enamel during exposure to an acetate buffer, pH 4, containing 150 parts/10⁶ fluoride have been studied using scanning electron microscopy and polarized light microscopy. After exposure for 2 h the enamel surface was covered by a fine-granular layer of calcium fluoride. The underlying enamel was highly eroded with an increased pore volume in the outer layer. Following an equilibration period of 3 months the uptake of fluoride in the apatite lattice had resulted in a highly mineralized, 100-μm-thick surface layer rich in fluoride covering a subsurface porous zone with an unchanged fluoride content. The deeply located, caries-like porous zone may have provided calcium and phosphate for saturation of the liquid     

3种氟制剂对邻面去釉后牙釉质再矿化效果的影响

目的 比较3种氟制剂对邻面去釉后牙釉质再矿化效果的影响,为临床选择预防邻面去釉后牙釉质脱矿的最佳氟制剂提供参考.方法 收集正畸减数拔除的前磨牙60颗,行近远中邻面去釉,牙冠颊舌向劈开后共120个标本,随机分为4组.对照组单纯用人工唾液进行再矿化,A组加用0.1 mol/L氟化钠溶液处理,B组加用6 000 mg/L(6 000 ppm)氟化泡沫处理,C组加用氟含量0.1％(质量分数)的氟保护漆处理.每4周处理1次,共处理3次.应用显微硬度仪测量每个标本再矿化前及再矿化后4周去釉面的显微硬度值,并进行统计学分析.结果 再矿化前、后牙釉质显微硬度差值在对照组为(3.42 ±2.27) kg/mm2,A组为(13.06 ±4.22) kg/mm2,B组为(20.21±4.96)kg/mm2,C组为(16.05 ±5.51) kg/mm2.各组再矿化前、后的显微硬度变化均有统计学意义(P＜0.01).再矿化前、后显微硬度差值在4组间的差异有统计学意义(F =26.168,P=0.000);两两比较,A、B、C3组与对照组的差异均有统计学意义(P＜0.01),B组和A、C组间的差异有统计学意义(P＜0.01),A组和C组间的差异无统计学意义(q=2.142,P=0.139).结论 氟化钠溶液、氟化泡沫、氟保护漆对去釉后的牙釉质再矿化均具有良好的促进作用,其中氟化泡沫的效果优于其他2种制剂.     

In vivo uptake of fluoride by surface enamel of cleaned and plaque-covered teeth

abstract – Utilizing a newly developed biopsy method, the F uptake in the outer 3 μm of enamel from a single topical application of neutral NaF or amine F solution was tested on cleaned and plaque-covered premolars in 12- to 14-year-old children. Cleaned teeth treated with neutral NaF acquired only insignificant amounts of F. The presence of plaque seemed to enhance the deposition of F in surface enamel. The findings were discussed in relation to the possible mechanisms of action of topically applied fluorides. Topical treatments with amine F increased surface enamel F considerably more than the NaF. The F uptake was similar in cleaned and plaque-covered teeth. It was suggested that the usually performed plaque-removing procedures prior to topical F applications are superfluous and may even be disadvantageous.     

Stability of fluoride levels in surface layer of normal enamel during a 21-month fluoride mouthrinsing program

A 21-month trial of the caries-preventive effect of a 0.2% NaF mouthrinse included monitoring changes in the concentration of F in normal enamel. Subsamples of 25 children were randomly selected from groups receiving either normal dental treatment (Control group); additional fortnightly professional prophylaxes (Test group); or prophylaxes plus fortnightly 2-min fluoride rinses (Test + F group). At the start of the trial the sound labial surface of tooth 24 (occasionally 23 or 22) was etched with 2 N HCL and the etchant analysed for F, Ca and phosphate. The contralateral tooth was sampled at the end of the trial. The caries increments (DFS) for the three groups over 21 months were Control, 2.88; Test, 2.51 and Test + F, 1.77, the last being significantly less than the others (P<0.05). The average sound enamel surface F concentrations were similar for the three groups at the start and the end of the trial. F parameter calculations showed that all differences were non-significant. Thus this factor could not explain the reduced caries increment due to F mouthrinsing. F biopsies for the purpose of predicting likely-clinical effectiveness of neutral 0.2% NaF mouthrinsing will find little application in public health dentistry.     

Morphologic changes in the rat enamel organ following a single intraperitoneal injection of sodium fluoride

abstract — Enamel organs in developing teeth of young rats were studied after single intra peritoneal injections of a high dose of sodium fluoride (60 mg NaF/kg body wt.). The study employed primarily light microscopy, but electron microscopy was used to clarify some of the light microscopic findings. The pathogenesis of the fluoride-induced changes was followed during 72 h. Cellular changes were consistently found in the molars, but were never seen in the incisors. In the maxillary molars, ameloblastic injury was most commonly seen on the mesial surfaces of the cusps. One hour after injection, the most prominent findings were swollen mitochondria in the secretory ameloblasts and cleft formations between the ameloblasts and the enamel matrix. The clefts were filled with a stippled material. Some of the clefts gradually expanded to cystic cavities. The stippled material began to calcify after 24 h and formed small, darkly stained globules. After 72 h dearranged ameloblasts were found as islands intermingled with calcified rounded structures in the stellate reticulum. In stratum intermedium numerous atypic autophagic vacuoles appeared 2 h after injection. No light microscopic changes were observed in the postsecretory ameloblasts.     

In vitro studies of fluoride uptake in human enamel

abstract — In a closed agitated system, which included an enamel surface and a continuously magnetically stirred buffer at pH 4.0, 5.0, 6.0 and 7.0, the reaction (Ca₅(PO₄)₃OH)_S+F−→(Ca₅(PC₄)₃F)_S+OH− was investigated kinetically by measuring the fluoride ion activity. The buffers initially contained 1 part/10⁶ fluoride. Six experiments were carried out at each pH. It was found that the reaction followed first order kinetics. The rate of the reaction was very slow at pH 7.0, but increased considerably when pH was lowered, and at pH 4.0 it was 100 times that at pH 7.0. In supplemental experiments it was found that reducing the area of the enamel surface reduced the rate of the reaction. The results are discussed with reference to equilibrium conditions in water-apatite systems, assuming that equilibrium cannot be attained when hydroxyapatite is dissolving and fluorapatite is being formed. The findings are considered to explain the increased amount of fluoride present in the residual apatite in developing carious lesions, and may initiate new principles in the local treatment of teeth with fluorides.     

Calcium fluoride formation on enamel and its influence on uptake of fluoride in the apatitic lattice

abstract – Human dental enamel was exposed to a pH 4 buffer containing 150 parts /10⁶ fluoride. It was found that due to the arising degrees of saturation with respect to calcium fluoride and appetites, surface enamel dissolved coincident with a formation of calcium fluoride. The calcium fluoride redissolved while it kept the liquid saturated with respect to tiiis salt. During this second period, fluorapatite was formed while hydroxyapatite dissolved. Finally, all calcium Ouoride was dissolved and the unreacted fluoride was taken up in the apatidc lattice. The results are discussed with reference to the conditions of the oral cavity and enamel solubility experiments.     

Influence of chlorhexidine on in vitro uptake of fluoride in dental enamel

ABSTRACT – Chlorhexidine gluconate and sodium fluoride were found to be compatible in the concentration range of interest in clinical use. Admixture of chlorhexidine to sodium fluoride solutions did not interfere with the fluoride uptake in clinically intact premolars in vitro .     

Microhardness of dentine in primary teeth after topical fluoride applications

OBJECTIVES: This study measured the microhardness of arrested dentinal caries on primary teeth receiving regular fluoride applications after 30 months. METHODS: Caries on primary upper anterior teeth of preschool children were randomly assigned to receive 38% silver diamine fluoride every 12 months or 5% sodium fluoride varnish every 3 months. Lesions that were hard on probing were considered arrested. At 30 months, very mobile teeth were extracted, sectioned, and polished and they underwent Knoop hardness number (KHN) measurements at sites below the surface at the center of the carious lesion every 25 microm toward the pulp. Three sets of measurements were made on parallel tracks approximately 150-200 microm apart, and the median KHN at each depth were analyzed. RESULTS: Five arrested and five soft carious lesions were examined. Within the outer 25-200 microm, the median KHN of arrested carious lesions (range, 20-46 or 196-451 MPa) were greater than those of soft carious lesions (range, 5-20, or 49-196 MPa). The difference between them, however, was not statistically significant. At a distance of 225 microm or more from the surface of the lesion, the median KHN of both groups were between 20 and 30 (196-294 MPa). CONCLUSIONS: The outermost dentinal surface of carious lesions that had been arrested by topical fluoride application was harder than that of active carious lesions. At a distance of 225 microm or more from the lesion surface, the microhardness of both arrested and soft dentinal caries was similar.     

An in vitro study of fluoride release from a resin-modified glass ionomer cement after exposure to toothpaste slurries of different pH

. The aim of the study was to evaluate the fluoride release from an aged resin-modified glass ionomer (Vitremer) after exposure to five toothpaste slurries with different pH values. Cylindrical specimens of the material were leached in de-ionized water for 3 months and then exposed for 30 min daily for 10 days to three dentifrice slurries (20 specimens/group) containing 0.05% fluoride with pH values of 2.6, 5.7 and 8.3 and two non-fluoridated slurries with pH values of 2.5 and 5.7. A neutral NaF solution (0.05% F) was used as a control. During the 30 min exposure time, the fluoride concentration was gradually decreased in order to imitate the clinical situation. Thereafter, specimens were immersed individually in de-ionized water and the fluoride release determined. After the first day of exposure, all groups except one without fluoride (pH 5.7) showed significantly (P<0.05) increased fluoride release. After exposure to the fluoridated toothpaste slurry with pH 5.7, significantly (P<0.05) more fluoride was released compared to the toothpaste slurry with pH 8.3. Low pH (2.5 or 2.6) of the slurry resulted in a significantly (P<0.05) higher fluoride release, regardless of whether it was fluoridated or not. The total amount of fluoride released after exposure to the more acidic fluoride toothpaste slurry was greater than that released from the more acidic non-fluoride toothpaste and the less acidic fluoride toothpaste. Our data indicate that the fluoride release from the resin-modified glass ionomer studied may be in-creased after treament with an acidified NaF-toothpaste. Received: 24 January 2000 / Accepted: 20 July 2000     

不同氟处理方法釉质表面超微结构观察

目的观察托槽粘结前应用不同方法氟处理以及去托槽后，釉质表面超微结构的变化。方法挑选因正畸需要而拔除的96颗双尖牙，随机分为对照组，酸蚀前加氟组，酸蚀液中加氟组，酸蚀后加氟组，每组牙釉质经酸蚀和不同方法氟处理后做扫描电镜观察并进行统计学分析。结果酸蚀中加氟组和酸蚀后加氟组釉质表面产生的反应物较多且去托槽后残留较多。结论酸蚀剂中加氟和酸蚀后加氟方法可能对固定正畸治疗中防止釉质脱矿有较好的效果。     

离子导人促进乳、恒牙牙釉质表层氟渗透的比较分析

目的：应用离子导入技术对乳牙及恒牙牙釉质进行氟离子导入,观察离子导入对乳牙及恒牙牙釉质表层氟分布及含量的影响,比较离子导入促进氟在不同牙釉质表层的渗透效果。方法：分别收集30例无龋下颌乳中切牙及下颌恒前磨牙,将乳牙及恒牙样本沿唇舌向正中切开,分为对照组与实验组,对照组样本应用2％氟化钠溶液浸润,实验组样本用离子导入仪进行2％氟化钠溶液离子导入。利用电子探针检测乳牙及恒牙牙釉质表层200μm内的氟分布变化并进行统计学分析。结果：电子探针分析显示在对照组与实验组乳牙牙釉质表层均可见高密度氟分布,而恒牙牙釉质,两组样本的氟分布未见明显变化。统计分析显示乳牙实验组样本的氟含量在釉质表层100μm、150μm处明显高于对照组（P〈0．05）,而两组恒牙样本釉质中氟含量无显著差异（P〉0．05）,在釉质表层200μm内离子导入促进乳牙氟渗透的效果明显高于恒牙（p〈0．01）。结论：在实验技术指标相同的情况下,离子导入技术能够有效促进氟离子在乳牙釉质表层的渗透,而对于恒牙釉质表层氟的分布无明显影响。     

Organic structures of developmental origin in human surface enamel

Abstract – The aim of this study was to examine the distribution of organic material in mature enamel surfaces immediately prior to eruption. Thirty-six samples of buccal or lingual enamel from unerupted third molars were prepared for transmission electron microscopy by a method involving demineralization of the enamel after embedding in Epon. The results showed that at time of eruption human surface enamel is a highly porous structure containing large amounts of developmental protein which appear as a variety of triangular, funnel-shaped, or invaginated configurations extending into the enamel. The implications of this finding may be of importance to the understanding of early caries lesion formation in the enamel since organic structures may modify the diffusion of ions in and out of the tissue.     

Fluoride concentrations of the surface enamel of children living in an optimally fluoridated community

Abstract – The present study was undertaken in a community, where the tap water has been optimally fluoridated since 1959 (1.0–1.2 ppm). The material consisted of 92 children and adolescents including 30 sibling-couples. The mean age of the participants was 11.8 ± 2.45 (SD) yr. 56 children had consumed fluoridated water all their life, the others only a part of the developmental period of their permanent dentition. Enamel biopsies were taken from 212 permanent teeth and 33 primary teeth by etching the tooth surface for 6 or 30 s. The etch depth was calculated from the mean of dissolved enamel calcium and phosporus. The fluoride concentration in the outermost enamel was almost similar in the teeth of the lifelong residents and the rest of the children. Towards the deeper layers the amount of fluoride decreases depending on its availablity during the development of the enamel. There was no striking similarity neither in the fluoride concentration nor in the amount of dissolved enamel between the siblings when compared with the other children. The posteruptive incorporation of fluoride takes place only on the outermost surface of the enamel. The results suggest that in subsurface layers the fluoride exposure during tooth formation is the dominating determinant of enamel fluoride concentration.