A comparison of the influence of lanthanum and fluoride on de- and remineralization of bovine enamel in vitro

The influence of fluoride and lanthanum on enamel softening was compared by hardness measurements and by determination of the calcium content in the solution. The addition of lanthanum to an acetate buffer solution (0.05 mol/L, pH = 5.0) had no significant influence on the change of the indentation length and on the calcium release, compared with those of the control group. In the fluoride group, a moderate increase of the indentation length and a reduced calcium loss were observed. In a second experiment, surface-softened bovine enamel was treated with calcifying solutions (Ca/P ratio = 1.67). Differences in treatment were created by the addition of traces (2 ppm) of lanthanum, fluoride, or both. The acid resistance of the treated enamel was evaluated by two successive softening steps (0.1 mol/L acetate buffer, pH = 5.5). Alterations of the enamel surface were longitudinally followed with a hardness tester. The addition of fluoride, lanthanum, or both significantly improved the rehardening of surface-softened enamel, compared with that of the control group. A 2 x 2 factorial analysis of variance showed that lanthanum and fluoride had a highly significant main effect and a significant negative interaction effect on the rehardening of surface-softened enamel. Subsequent acid treatments revealed that only samples treated with a fluoride-containing solution were adequately protected from further dissolution. The enamel surfaces treated with a solution containing both lanthanum and fluoride were covered with an acid-resistant surface coating. SEM observation of this surface layer revealed the presence of globular and spherulite structures.     

3种溶液对早期釉质龋再矿化作用的扫描电镜观察

目的观察比较碳酸氢钠溶液、氟化钠溶液及碳酸氢钠与氟化钠混合液对人工釉质龋的再矿化作用。方法选择因正畸拔除的前磨牙制备成牙釉质标本,用凝胶酸蚀法形成人工釉质龋模型,脱矿标本分别经碳酸氢钠溶液、氟化钠溶液及碳酸氢钠与氟化钠混合液及双蒸水浸泡1周后,扫描电镜观察比较经不同溶液处理的脱矿釉质标本表面形态差异。结果经碳酸氢钠溶液、氟化钠溶液及碳酸氢钠与氟化钠混合液浸泡的脱矿釉质表面均有不同程度矿物质沉积,其中,经碳酸氢钠与氟化钠混合液浸泡的脱矿釉质表面形成的沉积物更规则、明显。结论碳酸氢钠溶液能够促进脱矿釉质再矿化,且能增强氟化钠溶液对早期釉质龋的再矿化作用。     

Increased fluoride uptake and acid resistance by CO2 laser-irradiation through topically applied fluoride on human enamel in vitro

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.     

Uptake of fluoride into enamel and its effect on acid resistance by application of fluoride-releasing sealant--Part 1. Comparison with acid phosphate fluoride

The newly developed fluoride-releasing sealant (F + sealant) used in this experiment is expected to have the combined cariostatic effects of a sealant and fluoride. The purpose of this study was to investigate F + sealant's effects on the enamel in regard to the uptake of fluoride and resistance to acid. F + sealant's effect was compared to that of acid phosphate fluoride (APF) which has effect as topical fluoride applicant. Bovine teeth applied with F + sealant or APF were immersed for 4 weeks in a pH 7.0 phosphate buffer at 37 degrees C. After 4 weeks of immersion, each tooth was biopsied with pH 1.0 sodium acetate-hydrochloric acid buffer. The fluoride and calcium in the biopsy samples were analyzed by means of fluoride ion electrode and atomic absorption spectroscopy, respectively. The following results were obtained: (1) The fluoride in the enamel was significantly increased by the incorporation of fluoride from the F + sealant. Almost all fluoride in the surface enamel was found to be fluorapatite by the method of alkaline extraction. (2) The amount of fluoride increased by APF application was about 50% of that of F + sealant application. (3) The calcium released from the enamel treated with F + sealant or APF decreased by 13% and 9%, respectively, compared to that without treatment.     

Influence of carbamide peroxide on enamel fluoride uptake

OBJECTIVE: Aim of the study was to evaluate the influence of carbamide peroxide (CP) on enamel fluoride uptake by comparing enamel fluoride uptake from a 1% amine fluoride (AmF) gel with the fluoride acquisition from a 10% carbamide peroxide agent supplemented with 1% AmF. MATERIALS AND METHODS: Three enamel cylinders (4mm in diameter) were prepared from the buccal surfaces of 60 bovine incisors. One sample of each tooth was used for determination of baseline fluoride content of the respective tooth. The two remaining samples were allocated to the experimental series 1 or 2, respectively. Each series consisted of five experimental groups (A-E, n=12) and differed with respect to the length of the treatment period with the gels (A-D). The experimentally designed gels (pH 5.5) used in the study were as follows: A (10% CP), B (10% CP, 1% F(-) as AmF), C (1% F(-) as AmF), D (no CP, no F(-)) and were formulated on the same basis. The enamel samples were covered for 4h with the respective gel at 37 degrees C and were then transferred to artificial saliva for 20 h (series 1). The samples of group E served as controls and were not treated with a gel. In series 2, treatment with the gels and storage in saliva was conducted seven times. Finally, the samples were assessed for KOH-soluble and structurally bound fluoride. RESULTS: Only the enamel samples treated with the fluoridated bleaching gel (group B) and with the amine fluoride gel (group C) exhibited significant fluoride acquisition. Thereby, both gels showed significantly lower uptake in series 1 as compared to series 2. Both KOH-soluble and structurally bound fluoride acquisition was significantly higher in group C than in group B. CONCLUSION: Treatment with a carbamide peroxide gel supplemented with amine fluoride causes less fluoride acquisition in enamel than a pure amine fluoride gel. Under the conditions of the study, it is assumed that carbamide peroxide seems to influence enamel fluoride uptake.     

窝沟封闭前局部用氟对离体牙窝沟侧壁氟含量的影响

目的研究窝沟封闭前局部使用酸性磷酸氟（APF）对窝沟侧壁氟含量的影响。 方法收集第三恒磨牙共9对18颗,随机一侧为对照组、对侧同名牙为酸性磷酸氟处理组。（1）对照组：酸蚀60 s,窝沟封闭;（2）处理组：酸性磷酸氟溶液处理4 min后,酸蚀60 s,窝沟封闭。用电子探针显微分析（EPMA）对窝沟侧壁进行点检测,所得数据进行配对t检验统计学分析。 结果酸性磷酸氟处理组的窝沟侧壁氟含量为（0.50 ± 0.09）%,明显高于对照组含量（0.24 ± 0.12）%,差异有统计学意义（t=-4.670,P= 0.002）。 结论窝沟封闭前局部使用酸性磷酸氟溶液,可提高窝沟侧壁氟含量。     

Fluoride profiles in dental plaque in vivo formed on fluoride pre-treated human enamel

Using a novel device capable of generating plaque in vivo on a natural enamel substrate, it has been possible to determine fluoride profiles from the saliva-plaque interface towards the enamel surface. Fluoride profiles in dental plaques tended to fall from the saliva-plaque interface towards the enamel. The device also offered the possibility of examining fluoride distributions after pre-treatment of the enamel with fluoride in vitro. Fluoride profiles were determined in plaque generated in vivo on enamel surfaces, which had been previously treated with a 900-ppm fluoride solution. The results showed the previously reported fall from the plaque surface, but in addition, a further rise towards the enamel surface was seen. The data imply that enamel loaded with fluoride can release some of this fluoride back into the plaque and may act as a fluoride reservoir.     

Effects of systemic fluoride and in vitro fluoride treatment on enamel crystals

Systemically administered fluoride at a concentration of 75 ppm increases the surface roughness of developing enamel crystals in rats, which may be significant in advancing our understanding of the biological mechanism of fluorosis. Thus, the aim of this study was to investigate whether the increased surface roughness may be a result of surface restructuring by the direct action of fluoride at the crystal surface. We examined the fluoride dose-dependent roughening of enamel crystal surfaces in vivo, in the rat, and whether this roughening could be mimicked by the in vitro treatment of rat enamel crystals with neutral pH fluoride solutions. Our results showed that enamel crystal surface roughness increased after treatment with increasing fluoride ion concentrations, whether applied in vitro or administered systemically. This suggests a mechanism, alongside others, for the increased surface roughness of crystals in fluorotic enamel.     

Mineral flux of surface enamel and root surfaces in acidified gelatin gels

Gels of crude gelatin were dialyzed to eliminate fluoride, and then acidified with 75 mM lactic and 25 mM acetic acid at pH 4.2 and interfaced with enamel and root surfaces in gel-surface ratio of 0.2 ml/0.15 cm². Enamel and root surface to gel mineral flux was reduced by initial inclusion of 0.5 and 1.0 mM fluoride with 2.5 mM calcium and 1.5 mM phosphate in gels at pH 4.2. Inclusion of 0.25 mM fluoride in the gels without added mineral ions had no effect in the first 22-day interface. The 0.25, 0.5 and 1.0 mM fluoride remarkably increased remineralization in a second 12-day interface. This indicated that the first fluoride exposure initiated formation of fluorapalites in the enamel which required a lower degree of gel saturation for enhanced remineralization in the second acid exposure. Fluoride had the same effect, but greater effectiveness on enamel than root-surface remineralization. Gels of crude gelatin may contain sufficient mineral ions to alter remineralization-demineralization of enamel and root surface.     

脉冲Nd:YAG激光加氟化钠对离体人牙釉质超微结构及氟离子分布水平的影响

目的　探索脉冲Nd:YAG激光结合氟化钠使用的防龋机制。方法　选择24颗健康离体人恒前磨牙制成牙釉质标本。扫描电镜(SEM)、电子探针分别观察和分析激光加氟化钠组、激光组、氟化钠组、空白组(不处理)牙釉质表面超微结构及牙釉质内部氟离子分布水平。结果　①SEM观察:激光加氟化钠组牙釉质表面玷污物全部去除,并呈部分熔融状和空泡状改变;牙釉质表面散在分布着细小的白色颗粒;熔融灶、裂纹、微孔呈白色高度阻射。 ②电子探针分析:激光加氟化钠组中氟离子平均重量百分比值增加明显,5μm处氟离子平均重量百分比值最高,明显高于空白组、激光组和氟化钠组(P<0·001);氟离子进入牙釉质的有效深度约15μm,高于氟化钠组的5μm。结论　脉冲Nd:YAG激光结合氟化钠作用后引起牙釉质表面部分熔融、改变牙釉质晶体结构、促进牙釉质对氟离子的吸收、去除牙面玷污层,因而具有防龋作用。     

Mineral flux of surface enamel and root surfaces in acidified gelatin gels

Gels of crude gelatin were dialyzed to eliminate fluoride, and then acidified with 75 mM lactic and 25 mM acetic acid at pH 4.2 and interfaced with enamel and root surfaces in gel-surface ratio of 0.2 ml/0.15 cm2. Enamel and root surface to gel mineral flux was reduced by initial inclusion of 0.5 and 1.0 mM fluoride with 2.5 mM calcium and 1.5 mM phosphate in gels at pH 4.2. Inclusion of 0.25 mM fluoride in the gels without added mineral ions had no effect in the first 22-day interface. The 0.25, 0.5 and 1.0 mM fluoride remarkably increased remineralization in a second 12-day interface. This indicated that the first fluoride exposure initiated formation of fluorapatites in the enamel which required a lower degree of gel saturation for enhanced remineralization in the second acid exposure. Fluoride had the same effect, but greater effectiveness on enamel than root-surface remineralization. Gels of crude gelatin may contain sufficient mineral ions to alter remineralization-demineralization of enamel and root surface.     

Effects of CO2 laser on fluoride uptake in enamel

OBJECTIVES: The objective of this study was to investigate the effects of CO(2) laser on fluoride uptake in the loosely- and firmly-bound forms in enamel. METHODS: Five human molars were cut into halves before being treated with 2.0% NaF topical gel. Each half had three windows on the enamel surface, including one control and two experimental windows irradiated by two laser therapies. One half of each tooth was treated with 1 M KOH solution to remove the loosely-bound fluoride (calcium fluoride). A tooth section was obtained from each window and the relative fluorine concentration was analyzed with Secondary Ion Mass Spectrometry (SIMS). The morphology of the enamel surfaces in the windows was examined using an Environmental Scanning Electron Microscope (ESEM). RESULTS: Significant laser-induced increases in the uptake of fluoride were revealed in both loosely-bound and firmly-bound apatitic fluoride, with both laser treatments (all p<0.001). Calcium fluoride-like deposits on the enamel surfaces receiving the combined laser-fluoride treatment were revealed by ESEM. CONCLUSIONS: The finding of this study substantiated the laser effect in increasing the fluoride uptake into enamel.     

The in vitro uptake of fluoride by secretory and maturation stage bovine enamel

The objectives of this study were to determine the specific surface area of secretory-stage and of maturation-stage enamel, to compare the fluoride uptake by isolated enamel at these two stages on a surface-area basis, and to examine the effect of the organic matrix on the fluoride uptake by whole enamel. Fetal bovine secretory and maturation stage enamel samples were collected, and a portion of the enamel at each developmental stage was treated with hydrazine for removal of the organic matrix. The specific surface areas of the enamel mineral, as determined by the multi-point BET method, were 59.3 m2/g in the secretory stage and 37.9 m2/g in the maturation stage. Whole and deproteinated enamel samples were equilibrated in buffered solutions containing 10(-5) to 10(-3) mol/L fluoride, and the uptake was measured with a fluoride specific electrode. The results indicate that the in vitro fluoride uptake was controlled solely by the surface area of the apatitic mineral and that the organic matrix did not contribute to the fluoride uptake.     

局部应用氟化物对酸蚀釉质作用的体外研究

目的：评价局部应用氟化物对酸蚀釉质的作用。方法：收集正畸减数拔除的年轻前磨牙40个，制备釉质样本，随机分成对照组，lg／L氟化钠液组，含氟牙膏组，联合应用组。用饮料对釉质间断性酸蚀1周，然后使用不同的氟化物处理酸蚀的釉质表面1周。采用显微硬度计检测釉质表面显微硬度值（SMH），原子力显微镜（AFM）、扫描电镜（SEM）观察牙体硬组织表面的结构。结果：饮料浸泡后釉质的SMH明显下降。与对照组相比，氟化物处理后各氟化物处理组的釉质SMH均有明显增加（P＜0．001）。AFM和SEM均可见酸蚀后的釉质表面呈典型的蜂窝状结构，SEM观察显示氟化物处理后，各组釉质表面均有一定沉积物。结论：饮料会导致体外釉质表面的脱矿，氟化物能够促进体外酸蚀釉质的再矿化。     

精氨酸牙膏对釉质早期龋再矿化作用的研究

目的 研究精氨酸牙膏对人牙釉质早期龋的再矿化效果。方法 制备人牙釉质龋标本,随机分为 3组：空白组（去离子水处理）,对照组（普通市售含氟牙膏处理,含质量分数 0.14%单氟磷酸钠）,实验组（精氨酸牙膏处理,含质量分数 0.14%单氟磷酸钠和 8%精氨酸）。经体外 pH循环 10 d,测量 pH循环前后各组样本的表面显微硬度,计算其差值;并通过偏光显微镜观察各组样本再矿化前后的形态学改变。pH循环结束后,脱矿处理 2h,测量其表面显微硬度,计算与 pH循环前的差值,评估再矿化处理对釉质抗酸能力的影响。采用酸蚀法测定各组的氟摄入量。结果 与对照组和空白组比较,实验组釉质表面的显微硬度、抗酸能力,以及氟摄入量均明显升高。偏光显微镜下观察,实验组病损深度明显变浅,且有表层下再矿化条带,而空白组与对照组病损无明显变化。结论 精氨酸牙膏能有效促进人牙釉质龋表层及表层下再矿化,在早期龋的防治领域具有较大的临床应用前景。     

Roughness of human enamel surface submitted to different prophylaxis methods

The purpose of this in vitro study was to evaluate alterations in the surface roughness and micromorphology of human enamel submitted to three prophylaxis methods. Sixty-nine caries-free molars with exposed labial surfaces were divided into three groups. Group I was treated with a rotary instrument set at a low speed, rubber cup and a mixture of water and pumice; group II with a rotary instrument set at a low speed, rubber cup and prophylaxis paste Herjos-F (Vigodent S/A Indústria e Comércio, Rio de Janeiro, Brazil); and group III with sodium bicarbonate spray Profi II Ceramic (Dabi Atlante Indústrias Médico Odontológicas Ltda, Ribeir?o Preto, Brazil). All procedures were performed by the same operator for 10 s, and samples were rinsed and stored in distilled water Pre and post-treatment surface evaluation was completed using a surface profilometer (Perthometer S8P, Marh, Perthen, Germany) in 54 samples. In addition, the other samples were coated with gold and examined in a scanning electron microscope (SEM). The results of this study were statistically analyzed with the paired t-test (Student), the Kruskal-Wallis test and the Dunn (5%) test. The sodium bicarbonate spray led to significantly rougher surfaces than the pumice paste. The use of prophylaxis paste showed no statistically significant difference when compared with the other methods. Based on SEM analysis, the sodium bicarbonate spray presented an irregular surface with granular material and erosions. Based on this study, it can be concluded that there was an increased enamel surface roughness when teeth were treated with sodium bicarbonate spray when compared with teeth treated with pumice paste.     

Degradation of surface enamel and formation of precipitates after topical applications of sodium fluoride solutions in vitro

After topical treatment of enamel pieces cut from bovine incisors, the chemical composition of the solution phases and of the topmost layers of enamel were determined by special techniques of elemental and surface analysis. Fluoride seems to degrade surface enamel when applied in acidic and neutral solutions. Calcium remains immobile on the enamel surfaces, whereas phosphate goes into solution. When treated with acidic solutions (0.05-0.5 mol/l fluoride), a calcium-fluoride-rich phase is precipitated on the enamel surfaces.     

Effects of acidic phosphate fluoride on the protein compositions of acquired pellicle in vitro

The human enamel powders treated with acidic phosphate fluoride (APF) were used to react with human mixed saliva and purified proteins. Before and after treated with APF, the changes of fluoride content in the enamel and the salivary proteins adsorbed on the enamel surfaces were noticed. The results are as follows: 1. The post-treated enamel fluoride is increased, and the production is fluorapatite besides a little CaF2. 2. No effect of APF on the kind of salivary proteins adsorbed on the enamel is found. 3. The quantity of salivary proteins adsorbed on the enamel is increased in different percentage and the proportion of the proteins on the enamel surface may be changed. Therefore, we believe that these changes must be one of the APF's mechanisms on caries prevention.     

氟化钠抗碳酸饮料酸蚀乳牙釉质作用的研究

目的：探讨氟化钠抗碳酸饮料对乳牙釉质酸蚀的效果。方法：用人下颌乳切牙制备72个釉质块,将其随机平均分为3组：对照组釉质块不作涂氟处理,实验组两组釉质块分别涂0.6%和1.23%浓度氟化钠;各组再按浸泡在碳酸饮料中的时间不同分成30 min和50 min两个亚组。将各组釉质块分别浸泡于碳酸饮料中30 min或50 min,取出后用去离子水冲洗,将实验组重新涂氟,然后再将釉质块浸泡在碳酸饮料中,如此循环直至12 h。用扫描电镜观察乳牙釉质表面形态改变,显微硬度计测定釉质表面硬度值（surface micro-hardness,SMH）变化,评估氟化钠保护乳牙釉质抗碳酸饮料酸蚀的效果。结果：与对照组比较,经两种浓度氟化钠处理过的乳牙釉质能不同程度地抵抗碳酸饮料的酸蚀作用,SMH值较高（P〈0.05）;随着碳酸饮料浸泡时间的延长,氟化钠保护乳牙釉质抗酸蚀的能力下降;较高浓度的氟化钠的保护效果更好,差异有统计学意义（P〈0.05）。结论：氟化钠能够增强乳牙釉质抗碳酸饮料酸蚀能力。