Effects of a sodium fluoride solution and a varnish with different fluoride concentrations on enamel remineralization in vitro

Abstract – To study the efficacy of sodium fluoride varnishes and a NaF solution in remineralization of enamel, 120 slabs of non-carious human enamel enamel were presoftened for 6 h and randomly divided into six groups. The slabs were stored in synthetic saliva for 9 days, except for a daily 30-min immersion in 0.1 M lactic acid-NaOH buffer. During the 9-day period, one group of the slabs received no treatment, and the rest were treated once or three times with 2.3% or 1.1% sodium fluoride varnish Duraphat, or nine times with a 0.1% NaF solution. Finally, the slabs were demineralized for 1 h, and the amount of dissolved Ca and F was determined. Microhardness of enamel was determined initially, after presoftening, after the 9- day period, and after the 1-h demineralization. All fluoride treatments prevented enamel softening almost completely during the 9 days, but the control slabs softened markedly. Fluoride varnishes were more effective than NaF solution. Three applications of 2.3% Duraphat were slightly more effective than any of the other varnish treatments, but one treatment with 2.3% varnish was not more effective than treatments with 1.1% varnish. Enamel treated three times with 1.1% varnish showed the greatest acid resistance during the 1-h demineralization. The results suggest that the efficacy of the varnish was not proportional to the fluoride concentration but rather to the number of applications. Fluoride uptake by enamel was greatest with the most concentrated varnish. Enamel solubility was not, however, directly proportional to the fluoride content of enamel.     

Effects of different amine fluoride concentrations on enamel remineralization

Objectives

The aim of this study was to investigate the effects of decreasing fluoride concentrations on repeated demineralizing challenges on human enamel.

Materials and methods

In 24 teeth, 3 mm × 3 mm windows were prepared on the buccal and lingual sides and treated in a cycling demineralization–remineralization model. Remineralization was achieved with 100, 10 and 0.1 ppm fluoride from anime fluoride. Coronal sections were cut through the artificial lesions, and three sections per tooth were investigated using polarized light microscopy and scanning electron microscopy with quantitative element analysis.

Results

The morphology of the lesions was studied, and the extensions of the superficial layer and the body of the lesion were measured. Using element analysis, the Ca, P and F content were determined. The body of the lesion appeared remineralized after application of 100 ppm fluoride, while remineralization of the lesion was less successful after application of 10 and 0.1 ppm fluoride. The thickness of the superficial layer increased with decreasing fluoride concentrations, and also the extension of the body of the lesion increased. Ca and P content increased with increasing fluoride concentrations.

Conclusions

The effectiveness of fluoride in enamel remineralization increased with increasing fluoride concentration.

Clinical relevance

A consistently higher level of fluoride in saliva should be a goal in caries prevention.     

Evaluation of different fluoride concentrations supplemented with trimetaphosphate on enamel de- and remineralization in vitro

Trimetaphosphate (TMP) effects on demineralized bovine enamel were studied after 15 days of pH cycling. Treatments included 30 wt% (weight percent) dilutions of 0, 500, 1,500 or 3,000 μg F/g aqueous NaF solutions with or without 3% TMP. Treated specimens were assessed by transverse microradiography. With the exception of the 3,000 μg F/g case, 3% TMP addition provided significant additional overall remineralization compared with F alone. Mineral content profiles differed significantly between corresponding F and F + TMP groups. Fluoride alone resulted in more remineralization in the original demineralized zone, whereas F + TMP caused less demineralization in the underlying, originally sound enamel.     

Potential remineralization of demineralized enamel after application of fluoride varnish

PURPOSE: To evaluate remineralization effects of a topical fluoride varnish applied over a caries-like lesion compared to around a caries-like lesion. METHODS: Caries-like lesions were created on 30 molar surfaces. Sections were cut through each lesion, photographed under polarized light microscopy, and quantitated with a computerized imaging system. The sections were repositioned with only the lesion exposed. Half were painted with a 5% NaF varnish, including the surface of lesion. The remaining half were painted excluding the surface of the lesion. The sections were placed in artificial saliva for 30 days, re-photographed and re-quantitated. RESULTS: Using a student t-test for analysis, the results demonstrated the mean (+/- S.E.) percent remineralization of lesion size to be 10.8 (4.8) for lesions completely covered by the fluoridated varnish and 9.5 (2.9) for lesions that had the fluoridated varnish surrounding the lesion. Both application techniques indicated remineralization effects, yet there was no significant difference between the two application techniques evaluated in this study (P < 0.05). The data from this in vitro study indicated that there was no significant difference in methods of application for fluoridated varnish. Both application techniques demonstrated effective remineralization.     

含氟涂料和含氟牙膏对釉面再矿化和抗酸作用的实验研究

目的：观察含氟涂料与含氟牙膏对釉质表面再矿化和抗酸作用。方法：取牛恒切牙制备釉质片;统一酸蚀脱矿后随机分为4组（n＝3）;分别为生理盐水（A组对照）、Duraphat含氟涂料（B组）、Fluor Protector含氟涂料（C组）、含氟牙膏规律处理（D组）;处理期间标本置于人工唾液孵育2周;再次酸蚀;各阶段均用显微硬度仪测定釉面显微硬度、扫描电镜观察釉面,图像分析电镜下釉面微孔隙面积差异;统计分析。结果：首次酸蚀后釉面明显脱矿。分组处理2周,A组釉面再矿化不明显;B组和C组釉面形成涂料保护层;D组釉面可见明显再矿化。再次酸蚀后：A组和D组显微硬度下降,B组和C组涂料保护层有明显抗酸作用。再次酸蚀后,A组和D组釉面微孔隙面积增加（P＜0．05）,但D组小于A组（P＜0．05）;B组、C组无显著变化（P＞0．05）。结论：含氟涂料在釉面形成保护层,具有抗酸蚀和促进釉面再矿化作用;含氟牙膏能促进脱矿釉面再矿化,抗酸作用较弱。     

氟涂料用于固定矫治后釉质脱矿再矿化治疗的效果

目的评价氟浓度为2.26 mg/mL的氟涂料应用于正畸固定矫治后釉质脱矿再矿化治疗的临床效果。方法对正畸固定矫治结束并拆除托槽的患者进行牙釉质脱矿状况检查,选择符合纳入标准的110例受试者,随机分为2组,试验组在脱矿牙面上涂布氟涂料,对照组在脱矿牙面上涂布蒸馏水,每个月1次,持续6个月,在拆除托槽当天（基线）和拆除托槽3个月、6个月分别对唇颊面釉质脱矿区域进行临床视诊检查,使用临床视诊指数进行评分。结果基线、3个月、6个月时试验组的视诊指数分别为（2.22±0.42）分、（2.18±0.43）分、（2.15±0.41）分;对照组的视诊指数分别为（2.15±0.36）分、（2.14±0.38）分、（2.14±0.38）分。基线（t=2.470,P=0.228）、拆除托槽3个月（t=0.651,P=0.516）及6个月（t=0.149,P=0.882）试验组与对照组的差异均没有统计学意义。试验组的临床视诊指数在拆除托槽3个月、6个月与基线比较差异均有统计学意义（P＆lt;0.05）,但第3个月与第6个月的差异没有统计学意义（t=1.860,P=0.083）。结论应用2.26 mg/mL的氟涂料对固定矫治后出现的釉质脱矿进行再矿化治疗后,牙釉质脱矿程度有所降低,但再矿化效果不够显著。     

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 bovine enamel remineralization and fluoride uptake from two dentifrices containing different fluoride concentrations

In this study, the differences in lesion remineralization and fluoride uptake after brushing with a 300 ppm F or a 1000 ppm F dentifrice (as NaF) were investigated. Twenty volunteers with partial dentures in their lower jaws were divided into two groups. Bovine enamel slabs with artificial lesions were mounted in the dentures. After a test period of six weeks, the slabs were taken out and analyzed. There was no statistically significant difference between the two groups, in F-uptake and susceptibility of the enamel to demineralization, although the findings favored the 1000 ppm F toothpaste. The microradiograms in the 300 ppm F group showed lesions more pronounced than those in the 1000 ppm group. The present study cannot support the presumption that the fluoride content of regular NaF dentifrices can be lowered to 300 ppm F without undesirable effects on lesion arrest and remineralization.     

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.     

玻璃离子保护膜与氟保护漆对牙釉质脱矿的预防和再矿化作用

目的: 比较玻璃离子保护膜与氟保护漆对牙釉质脱矿的预防和再矿化作用。方法: 选择122颗正畸减数拔除的前磨牙,制成釉质块,随机选择2个,进行扫描电镜（SEM）观察,其余用于两部分实验。①釉质脱矿预防实验 （实验A）—选择60个釉质块,随机分为3组（n=20）,分别使用玻璃离子保护膜（A1组）、氟保护漆（A2组）,对照组（A3组）不予处理;②釉质再矿化实验（实验B）—选择60个釉质块,预脱矿72 h后,随机分为3组(B1、B2、B3,n=20),处理方法同预防釉质脱矿各组。实验A、B共6组样本均经人工脱矿液和人工唾液交替pH循环处理30 d。采用SEM观察釉质表面形貌,显微硬度计测定釉质表面显微硬度（SMH）变化,X线能谱分析仪分析釉质表面钙磷比。采用SPSS 26.0软件包对数据进行统计学分析。结果: 釉质脱矿预防实验,未作处理的牙釉质表面平坦、均匀,A1组釉质表面基本完整,A2组釉质表面可见大量片状沉积物,A3组呈现典型的脱矿导致的蜂窝状结构。各组间ΔSMH两两比较,A1组A2组>A3组(P<0.05)。釉质再矿化实验,SEM结果显示,B1、B2组均有沉积物附着于釉质表面,B3组釉质表面凹凸不平,呈蜂窝状。各组间ΔSMH两两比较,B1组>B2组>B3组(P<0.05)。钙磷比值依次为B1组>B2组>B3组(P<0.05)。结论: 玻璃离子保护膜和氟保护漆均可预防和治疗牙釉质脱矿,玻璃离子保护膜由于其耐磨、持久,具有更好的保护和再矿化作用。     

Prevention of rat fissure caries by sodium fluoride varnish (Duraphat) with different fluoride concentrations

125 Osborne-Mendel rats were weaned at 22-23 days, inoculated with Streptococcus sobrinus and fed a cariogenic diet for 40 days. The control group received no treatment; the study groups received applications of Duraphat containing 2.3, 1.1, or 0.6% fluoride or a placebo varnish on days 21-23. The placebo varnish had no effect on caries. Fissure caries was significantly reduced by the 2.3 and 1.1% fluoride varnishes, whereas the caries reduction found after treatment with the 0.6% fluoride varnish was not statistically significant. These results suggest that reducing the fluoride content of Duraphat by half does not significantly reduce its caries-preventive effect, but the progress of caries seems to be somewhat slower with the 2.3% fluoride varnish.     

含氟牙膏对离体脱矿恒牙再矿化作用的实验研究

目的评价含氟牙膏促进离体脱矿恒牙再矿化的作用。方法选取和制作牙体硬度170KHN左右的16颗离体年轻脱矿恒牙标本,随机分成A、B两组(P>0.05)。A组用无氟Crest牙膏作再矿化处理,B组用含氟的Crest牙膏作再矿化处理,同时将A、B组标本浸泡于人唾液中。用微硬度测量仪测定并记录每个牙标本的硬度。结果A组脱矿牙的硬度平均值为151.9±38.3,而再矿化后牙齿的硬度平均值为143.4±18.8,两组比较P>0.05。B组脱矿牙的硬度平均值为160.1±16.5,而再矿化后牙齿的硬度平均值为200.5±21.3,两组比较P<0.05。再矿化后AB两组的硬度值比较P<0.001。结论含氟牙膏对离体脱矿恒牙有较明显的再矿化作用。     

The influence of fluoride on in vitro remineralization of bovine enamel

Remineralization experiments using bovine enamel were carried out with 2 ppm fluoride or no fluoride added to the remineralizing solutions. The group without fluoride showed (quantitative microradiography) significantly more remineralization in the first 50 microns of the lesion than the fluoride group. It is suggested that fluoride may inhibit remineralization.     

In vitro fluoride uptake by enamel from different amine fluoride concentrations

The aim of this in vitro study was to examine whether the concentration of amine fluoride solution influences the uptake of fluoride by enamel after topical treatment. Four slabs were prepared from each of 31 impacted third molars and selected at random so that one slab from each tooth was present in each group. One group of slabs served as an untreated control (D). The slabs of the other three groups were shaken for 3 min in an amine fluoride solution on 3 successive days: group A (1% F), group B (0.5% F) and group C (0.25% F). The amounts of KOH-soluble fluoride produced with 1 and 0.5% amine fluoride solution did not differ significantly and were superior to 0.25% amine fluoride solution. A statistically significant increase in structurally bound fluoride was observed in groups A, B and C compared with control group D. The difference in the amounts of structurally bound fluoride was significant only between 1 and 0.25% F concentrations. These data suggest that the fluoride content in an amine fluoride solution (1%) can be decreased by half without reducing its ability to form alkali-soluble or structurally bound fluoride. The results of this study are consistent with those of previous clinical studies.     

Effect of tooth-bound fluoride on enamel demineralization/ remineralization in vitro

The effect of tooth-bound fluoride (F) on enamel caries formation was investigated under the condition that loosely bound F was essentially absent. Eighteen thin enamel sections, prepared from the lingual or buccal surfaces of extracted human molars, were embedded in acrylic resin with the enamel surfaces exposed. The sections were placed in a pH 7 remineralizing solution (RS; 1.2 mmol/l Ca, 0.72 mmol/l P, 30 mmol/l KCl, 50 mmol/l HEPES) for 5 days, and were randomly divided into 3 groups: (1) control group that received no treatment, (2) acidulated phosphate fluoride (APF) group that received 5 cycles of a 4 min treatment with APF gel followed by immersion in the RS for 2 days (RS changed daily) and (3) dicalcium phosphate dihydrate (DCPD) - APF group that received 5 cycles of a 4-min pH 2.1 DCPD-forming solution followed by 4 min APF gel and then placed in the RS for 2 days. After the treatment cycles, the sections were washed in a constant composition F titration system to remove loosely bound F. An in vitro model, which consisted of cycles of de- (6 h) and remineralization (18 h) each day for 5 days, was used to produce caries-like lesions in the specimens. The DeltaZ (mineral loss) values, measured by quantitative microradiography, of the lesions formed in the three groups were (mean +/- standard deviation; n = 6) 91.2+/-12.3 microm for the control group, 41.3+/-10.1 microm for the APF group and 21.2+/-4.8 microm for the DCPD-APF group. The same system produced lesions in untreated shark enamel with a mean DeltaZ of 4.4+/-0.3 microm (n = 12). One-way fixed-effects ANOVA indicated that mineral loss was significantly different among the different groups (p<0.05). The results showed that enamel resistance to lesion formation increased with increasing tooth-bound F content. Shark enamel was much more resistant to demineralization than human enamel.     

Influence of salivary macromolecules and fluoride on enamel lesion remineralization in vitro

The aim of this study was to investigate the influence of salivary macromolecules on enamel lesion remineralization in the presence or absence of fluoride. Paraffin-stimulated whole saliva was centrifuged, and the supernatant was dialyzed in 1,000 molecular-weight cutoff dialysis tubes, first against a phosphate buffer and then against a mineral solution containing Ca and phosphate. Artificial subsurface lesions of human enamel, created in pH 4.5 acetate buffer, were remineralized for 28 days in 4 remineralizing solutions: group C--mineral solution as a control; group S--mineral solution + dialyzed saliva; group F--mineral solution + 1 ppm F; group SF--mineral solution + dialyzed saliva + 1 ppm F. Changes in relative mineral concentration in the lesions were assessed by transverse microradiography. The results showed statistically significant mineral gains in the lesion body in groups C (DeltaZ = 3,254 +/- 1,562% x microm) and SF (DeltaZ = 2,973 +/- 1,349% x microm), but not in groups S (DeltaZ = 5,192 +/- 1,863% x microm) and F (DeltaZ = 4,310 +/- 1,138% x microm) compared with the baseline group (DeltaZ = 5,414 +/- 461% x microm). It was also found that the mineral density at the surface layer in group F (75.0 +/- 15.7%) was greater than that in the baseline group (30.1 +/- 12.3%) with statistical significance, but not in group SF (39.9 +/- 16.5%). It was concluded that the macromolecules inhibited lesion remineralization fundamentally but that these molecules, in the presence of fluoride, seemed to play an important role in the continuation of remineralization by reducing mineral gains at the surface layer.     

The effect of topically applied fluoride on enamel remineralization in vitro

The effect of fluoride applied to mildly etched enamel was studied in a remineralizing system in vitro utilizing ³²P labelled neutral phosphate buffer to assess change. Blocks of intact surface enamel were cut from teeth and divided among eight treatment groups. The blocks were mounted in specially constructed holders which permitted identical placement of the blocks in a gas flow counter. The findings showed increased ³²P exchange in etched enamel. Exposure of etched enamel to a mineralizing solution for 24 hr after a 24 hr treatment with 2.2 per cent sodium fluoride or without fluoride treatment did not result in a significant reduction in ³²P exchange. Exchange was significantly reduced in etched enamel which was treated for four minutes with a 2.2 or 0.022 per cent sodium fluoride or for 24 hr with 0.022 per cent sodium fluoride prior to exposure to a mineralizing solution.     

Influence of fluoride and carbonate on in vitro remineralization of bovine enamel

The influence of fluoride, carbonate, and fluoride in combination with carbonate on the in vitro remineralization of bovine enamel was investigated with the use of a sandwich technique. After demineralization, enamel slices were subjected for 610 h to remineralizing solutions with 0.03 or 1.0 ppm fluoride. At each fluoride level, either 0, 1, 10, 20, or 25 mmol/L carbonate was tested. After 0, 22, 62, 126, 192, 329, and 610 h of remineralization, contact microradiographs were made by Cu K alpha-radiation. At 0.03 ppm fluoride, carbonate had an inhibiting influence on remineralization. At 1.0 ppm fluoride, the inhibiting influence of carbonate changed into a stimulation of remineralizatization at 20 and 25 mmol/L carbonate. At 0, 1, and 10 mmol/L carbonate, fluoride had an inhibiting influence on remineralization. The differences in remineralization between the groups were explained by events concerning crystal growth, i.e., different types of minerals might have precipitated with differences in precipitation rates, and retardation of a precipitation step might have occurred under the various remineralization conditions. There was a mutual influence of fluoride and carbonate on the remineralization process. We conclude that the composition of the remineralizing solution with respect to fluoride and carbonate concentrations is important for the remineralization process.