Effect of timing of administered calcium lactate on the sucrose-induced intraoral demineralization of bovine enamel.

A number of soluble calcium salts are known to reduce the demineralization of enamel in the mouth. The present study was undertaken to examine the effects of rinses containing different concentrations of calcium lactate, and the time of giving the rinses with respect to sucrose challenges. Subjects wore palatal appliances containing blocks of bovine enamel whose surfaces were covered with Streptococcus mutans IB 1600, and rinsed with 10% sucrose for 1 min. Changes in iodide penetrability of the enamel, and the pH and extracellular ion concentrations of the streptococcal plaque were determined. When added to the sucrose rinse, 100 or 150 mM calcium lactate reduced demineralization by about 35%, although the plaque pH was not affected. Plaque calcium was elevated but diffused away rapidly so that concentrations after 45 min were close to control values. Plaque inorganic phosphate and lactate were not affected. Ongoing demineralization appeared to be stopped when 100 mM calcium lactate was given 15 min after the sucrose rinse. When the lactate was given 15 min before the sucrose rinse, demineralization was reduced by only about 25%, consistent with the rapid diffusion of plaque calcium. The combination of (i) pretreatment with calcium lactate and (ii) admixture of calcium lactate with sucrose was most effective. Demineralization was reduced about 55% with 100 mM calcium lactate under these conditions, and protective effects were seen with as little as 25 mM. In summary, the findings demonstrate the enamel-protective effect of relatively low concentrations of calcium lactate, and point to the need to sustain a high plaque calcium during periods of maximum acidogenicity.     

Accumulation of enamel constituents in Streptococcus mutans plaque during intraoral demineralization

Studies were carried out with an intraoral demineralizing system in order to determine whether calcium and inorganic phosphate (Pi) accumulate in plaque during active demineralization of enamel. Blocks of bovine enamel were coated with Streptococcus mutans and were carried in palatal appliances worn by human volunteers. Demineralization was determined as changes in the iodide penetrability (delta Ip) of the enamel surfaces. Ca and Pi were determined in the extracellular spaces of the synthetic plaque. Delta Ip increased with time after administration of rinses containing 5% (w/v) sucrose, while plaque pH dropped and then returned toward neutrality. Ca increased to 10.9 +/- 2.8 mmol/l at 30 min, while Ca2+ and Pi rose to 3.0 +/- 2.1 and 9.5 +/- 3.1 mmol/l, respectively. The Ca:Pi ratio was 1.15. Rinses with 10% (w/v) sucrose gave similar results. Concentrations of Ca and Pi were considerably higher than those in saliva. Accumulation of the mineral constituents was shown to be dependent on metabolic activity of the S. mutans plaque, and experiments in which enamel blocks were replaced with blocks made of acrylic plastic gave Ca and Pi concentrations of 2.5 +/- 0.6 and 6.6 +/- 2.4 mmol/l, respectively, demonstrating that most of the Ca and about one-third of the Pi were derived from enamel. The data suggested, furthermore, that Ca and Pi were partially bound to complex macromolecules, and that part eventually recrystallized as mineral within the plaque.     

Protein and mineral changes in bovine enamel during in-vitro demineralization

Mineral distributions with and without a softened surface layer were studied. The molar Ca:P ratio of released material was due to preferential Ca-loss significantly higher from surface-softened enamel than from lesions. The molecular weight (less than 1800) distributions of released proteinaceous matter were similar. The protein release during surface softening contained more large peptides, whereas its amino-acid composition was more acidic amino acids compared with lesion formation. The protein content of released material during demineralization, acetic acid-soluble protein (at pH 4.5) and total protein of sound enamel showed that (i) enamel proteins were partially soluble in an acetic acid-buffer under mild acidic conditions and (ii) enamel proteins soluble in acetic acid-solution were partially released during demineralization. It is postulated that during enamel demineralization the dissolution of acid-soluble proteinaceous matter and its partial adsorption on newly-created sites of partially-dissolved crystals may explain the partial release of acid-soluble proteins. In case of lesion formation on the other hand new adsorption sites on new crystal surfaces formed in the surface layer are formed as well, which may account for the differences in mol.wt distribution and amino-acid composition.     

Protein loss of bovine dental enamel during in-vitro subsurface demineralization

A chemical system based on the dialysis principle was used to study protein loss of dental enamel during demineralization with an acetic-acid buffer solution containing calcium and phosphate, in which the fluoride-ion activity was kept constant. This resulted in a subsurface lesion, with a depth of about 130 microns. After demineralization, protein material was isolated from the demineralization solution. u.v. Spectra of the protein showed strong absorbance between 240 and 300 nm. Amino-acid composition showed high glycine, glutamic acid, proline, serine and aspartic acid contents. After 10 days demineralization, the total protein loss was 3 micrograms cm-2; the mineral loss was 16 mg cm-2. Compared with the total enamel-protein content (0.06-0.09 wt per cent) protein loss (0.018 per cent of total lost material) was not proportional to the mineral loss, when a subsurface lesion was formed.     

Kinetics of enamel demineralization in vitro.

Previously, we reported that the rate (R) of hydroxyapatite dissolution in acetic, lactic, and phosphoric acid solutions is a function of the degree of saturation with respect to the dissolving mineral, DS (defined as the ratio of the mean ionic activity product for hydroxyapatite [Ca5OH(PO4)3] in solution to its solubility product constant), and the sum of the acid activities (sumBiH) in solution: R = K(1-DS)m(sumBiH)n. The present study was undertaken to explore the general validity of this model in describing the kinetics of enamel demineralization. Thin sections of human enamel were exposed to partially saturated 0.1 mol/L lactic acid solutions, at two different DS levels, and at pH values of 4.3 to 6.0. Thin sections of human enamel were also exposed to solutions with four different concentrations of acetic and lactic acids (pH 4.3) with three different DS values and, at one DS value, to solutions of propionic acid. Mineral loss was monitored by quantitative microradiography. In solutions with pH values of 4.3 and 5.0, "lesions" were formed with well-defined surface layers, whereas, in solutions with pH 6.0, "lesions" were produced with no apparent surface layers. The formation of relatively intact surface layers was consistent with predicted phase transformations. Rates of mineral loss were found to be inversely proportional to both the degree of saturation with respect to enamel mineral, DS(En), and the pH of the solution and increased with increased activities of each organic acid, consistent with the proposed model. However, at the same DS(En) and acid activity, rates of demineralization were the same in the acetic and propionic acid solutions, whereas rates of demineralization in lactic acid were greater. It is suggested that specific interactions of acid species with enamel mineral may modify the rate of enamel demineralization. These in vitro findings suggest that relatively small differences in DS(En) values found in plaque fluid may result in very significant differences in the rate of enamel demineralization in vivo.     

不同种类茶对牛牙的釉质脱矿影响的体外初步研究

目的：比较不同种类茶对牛牙的釉质脱矿作用。方法采用微量化学分析法测定茶在处理釉质后,茶中钙和磷含量的变化。采用SPSS 16.0软件包对结果进行双因素方差分析。结果：不同种类茶对牛牙的釉质脱矿程度差异有统计学意义（P〈0.05）。几种茶与人工唾液对釉质脱矿程度不同,差异也具有统计学意义（P〈0.05）。随着茶对牙作用时间的延长,釉质的脱矿程度减弱。结论：茶饮料对釉质有脱矿作用,但其脱矿程度较人工唾液小（P〈0.05）,说明其脱矿并不严重,是一种比较理想的饮料。     

氟以及表面活性剂对牛牙釉质脱矿的影响

本研究旨在进一步了解氟化物以及表面活性剂（SAA）对牛牙釉质脱矿的影响。在体外模拟酸蚀模型，采用自制的钙离子选择性微电极测试不同处理组的钙离子浓度，并进行分析评价。结果显示：①牙釉质经氟化钠处理后其脱矿率明显低于单用酸蚀液组（P＜0．01）；②SAA和氟化钠合用与单用氟化钠组之间无显著差异（P＞0.05）。提示氟可通过增强牙齿组织的抗酸性，降低釉质表面的溶解度而抗龋；SAA的抗龋作用有待进一步研究。     

Microradiographic study on the effects of salivary proteins on in vitro demineralization of bovine enamel

The aim of this investigation was to evaluate the effects of various proteins on in vitro demineralization of bovine enamel. From each of 100 bovine incisors two samples were prepared. The specimens were embedded in epoxy resin and polished up to 4000 grit. Subsequently, the specimens' surfaces were partly covered with nail varnish, thus serving as control of sound enamel. The specimens were divided randomly into five groups (n = 40) and demineralized in a solution of constant composition (pH 5.0; 10 days). For each subgroup of specimens (n = 10) 4 L were taken and either low (50% of medium conc.), medium, or high (150%) concentrations of the proteins [human albumin (100% conc. = 7 mg L(-1)), mucin (577.5 mg L(-1)), immunoglobulin G (IgG) (46 mg L(-1)), casein isolated from bovine milk (1.2 g L(-1))] or amino acid [l-Proline (7 mg L(-1))] were added to 1 L of the demineralizing solution, whereas 1 L served as control. Mineral loss and lesion depth (LD) were evaluated from microradiographs of thin sections (110 mum) by a dedicated software package (TMR 1.24). No differences were found between the five control groups (P > 0.05; ANOVA). Albumin, l-Proline, and IgG did not affect enamel demineralization, whereas the addition of both casein and mucin resulted in significant reductions of both mineral loss and LDs (P < 0.01; Tukey's test). Within the limitations of an in vitro study, the present investigation indicates that casein and mucin seem to affect enamel demineralization significantly. Thus, these proteins might be helpful as an additive to saliva substitutes or mouthwashes if the quality of saliva is altered.     

Rate and mechanism of enamel demineralization in situ.

In this paper, data are presented on the in situ demineralization of human enamel as a function of the demineralization period. To quantify the mineral loss parameters versus time, it is important to obtain information on the kinetics, and thus on the mechanism of dental caries. The results show that for in situ enamel demineralization, the lesion depth as well as the mineral loss parameter both vary linearly with the demineralization time. This is in contrast to in vitro lesion formation where the third power, or the square power of the lesion depth is linearly related to the demineralization time. In in situ demineralization, the rate-determining step of the demineralization process is the inhibitor-controlled dissolution process at the enamel crystallite surfaces, while the inhibitor content (F-, proteins etc.) in the lesion originating from the plaque, saliva and enamel is high. Furthermore, the study indicates that in in situ demineralization, interprismatic mineral loss is very important.     

Correlation between physical changes in tooth enamel and changes in iodide penetrability following in vitro or intraoral demineralization

Demineralization of bovine tooth enamel was assessed by various physical means, and results were compared to measured changes in penetrability to iodide ions (delta Ip). Blocks of bovine enamel were exposed in vitro to lactate buffer (pH 4.3) containing 25 mM CaCl2 and 10 mM KH2PO4 for up to 4 days. Delta Ip increased over a wide range with time. A plot with respect to microhardness exhibited a pronounced inflection, with delta Ip rising rapidly at indentation depths greater than 2.5 microns. Microradiography and polarized light microscopy demonstrated subsurface lesions coincident only with the higher delta Ip values. The limited demineralization during the early time periods, therefore, was associated with only minimal changes at or near the enamel surface, yet could be detected readily with the delta Ip system. Demineralization produced intraorally in subjects rinsing with 5% sucrose was accompanied by increases in delta Ip, but no changes in surface microhardness or microscopic appearance of the enamel. It appeared that, under these conditions, demineralization was limited to the surface and corresponded to the very early phases of lesion formation.     

Fluor Protector抑制饮料致牛牙釉质脱矿的实验研究

目的 :研究FluorProtector对饮料导致牛牙釉质脱矿的抑制作用。方法 :将 40个牛牙标本分成实验组和对照组 ,每组又分为 2个亚组。实验组在FluorProtector预处理釉质后用不同种类饮料处理 ,对照组未经FluorProtector预处理而直接用饮料处理。饮料的处理是 5min/次 ,5次 /d ,共处理 7d。采用微量化学分析法测定饮料在处理牙釉质后 1～ 7d饮料中钙和磷浓度的变化。结果 :实验组与对照组经同种饮料处理后钙、磷溶出的浓度明显不同 ,表现为实验组低于对照组 ,差异具有显著性 (P <0 .0 5 )。结论 :FluorProtector对饮料所致的牙釉质脱矿具有明显的抑制作用 ,并随时间的延长而减弱。     

研究牙釉质脱矿的实验方法

牙釉质表面脱矿是龋病及其他非龋性牙体病变（酸蚀症等）的主要病理改变之一,随着近年来饮料的种类和消耗量的逐年上升,其对牙齿的危害也逐渐引起人们的重视.本文对近年来牙釉质脱矿检测的实验方法作一综述.     

Effect of bovine lactoferrin on enamel demineralization and acid fermentation by Streptococcus mutans

The purpose of this study was to evaluate the effects of bovine lactoferrin on acid fermentation and enamel demineralization using Streptococcus mutans in a culture system and an artificial mouth model system. The antibacterial activity of bovine lactoferrin (bLF) against S. mutans was analyzed by a radial diffusion assay. In the culture system, the effect of bLF on the synthesis and adherence of water insoluble glucan (WIG) and the adherence of S. mutans to a glass surface was examined by a batch culture. In the artificial mouth model system, cell suspension of S. mutans, heart infusion broth supplemented with sucrose, and PBS or lactoferrin solution were supplied separately and constantly for 21 hours. The following parameters were determined for evaluation: the amount of artificial biofilm, the changes in pH underneath the biofilm; and the changes in enamel microhardness measured by a Vicker's hardness tester. The antibacterial activity of bLF against S. mutans was observed. The amounts of bacterial cells in the total adherent fractions were inhibited by bLF in a dose dependent manner. The amounts of WIG in a firm-adherent fraction were significantly inhibited by 0.1–1.0% bLF. The changes in microhardness on enamel slabs in the bLF group (2.4 ± 0.8) showed significantly less hardness reduction than those in the control group (22.3 ± 2.5) (P < 0.001). The artificial biofilm accumulation was not reduced by bLF. The results of this study suggest that bLF might have inhibitory effects against acid fermentation and demineralization of enamel by S. mutans.     

Effect of Galla chinensis extract and chemical fractions on demineralization of bovine enamel in vitro

OBJECTIVE: To evaluate the demineralization inhibition property of extracts and chemical fractions of Galla chinensis in vitro. METHODS: Seventy sound bovine enamels blocks were prepared and randomly divided into seven groups. These samples were pH-cycled for 12 times in 6 days. Each daily cycle included 2x 5 min application with one of the seven treatments: 1000 ppmFaq. (as NaF, positive control); deionized water (negative control); or 4000 ppm aqueous solutions of five G. chinensis extracts (GCEs): GCE, GCE-A, GCE-B, GCE-C or GCE-D. Surface enamel microhardness was measured on the enamel blocks before and after pH-cycling, and the reduction of surface microhardness (DeltaSMH) was calculated. The acidic buffers were retained for calcium analysis. RESULTS: There were significant differences between the GCE groups and the two controls (p<0.01). Among all the GCE groups, the reduction of surface microhardness (DeltaSMH) in GCE group was the least (p<0.01). No significant differences were found between the GCE group and GCE-C group in CDR, as well as the other three GCE groups (GCE-A, GCE-B and GCE-D) (p>0.05). CONCLUSIONS: The present study has demonstrated the potential of the GCE to effect the demineralization under dynamic pH-cycling conditions. None of the chemical fractions was as effective as GCE. Combined with its anti-bacterial properties, the demineralization inhibition of GCE suggests that this material could be a useful source for the development of promising anti-cariogenic agents.     

Laser-matrix-fluoride effects on enamel demineralization

Laser and fluoride have been shown to inhibit enamel demineralization. However, the role of organic matrix and their interactions remains unclear. This study investigated the interaction among CO2 laser irradiation, fluoride, and the organic matrix on the demineralization of human enamel. Twenty-four molars were selected and cut into halves. One half of each tooth was depleted of its lipid and protein. The other half served as a matched control. Each tooth half had two window areas, treated with a 2.0% NaF gel. All left windows then received a laser treatment. Next, the tooth halves were subjected to a four-day pH-cycling procedure that created caries-like lesions. Tooth sections were cut from the windows, and microradiographs were used for quantification of the demineralization. The combined fluoride-laser treatment led to 98.3% and 95.1% reductions in mineral loss for enamel with and without organic matrix, respectively, when compared with sound enamel.     

Effects of Galla chinensis on inhibition of demineralization of regular bovine enamel or enamel disposed of organic matrix

Objective

This in vitro study was undertaken to assess the effects of Galla chinensis extract on inhibition of enamel caries-like demineralization and to elucidate the role of the organic matrix of enamel in this process.

Design

Either regular or enamel disposed of its organic matrix both of bovine origin were exposed to a demineralizing solution for 3 days (pH 4.5). Specimes were additionally treated with either 4 g/L of G. chinensis extraction (GCE) or double distilled water (DDW) four times daily for 5 min each time. Regular enamel exposed accordingly to sodium fluoride (1 g/L) during the demineralizing period served as positive control. After exposure mineral loss and lesion depth of all samples were analysed by transversal microradiography. One-way ANOVA and Student-Newman-Keuls test were used to compare the differences amongst groups. A factorial ANOVA was chosen to test the interaction between GCE and enamel organic matrix.

Results

Mineral loss and lesion depth of specimens in the positive control group were significantly lower compared to all other groups. Regular enamel treated with GCE showed significantly lower values compared to regular enamel treated with DDW or to enamel disposed of its organic matrix (p < 0.05). These three groups revealed similar values (p > 0.05). Significant interaction between GCE and enamel organic matrix with respect to both outcomes could be observed (p < 0.05).

Conclusions

G. chinensis inhibits enamel caries-like demineralization in vitro. However, its potential seems to be weaker compared to sodium fluoride. The organic matrix of enamel was shown to play a substantial role in the observed mechanism.     

Effect of salivary pellicle on enamel subsurface demineralization in vitro.

Diffusion fluxes of two anionic species through hydroxyapatite membranes were found to be reduced up to 50% by the presence of adsorbed salivary pellicles developed on the membrane surfaces. By contrast, water fluxes were only marginally affected, indicating that salivary pellicles display ionic permselectivity. This property is used to explain a remarkable protection of the enamel observed when salivary pellicles were developed on extracted teeth before exposure to acid lactate buffers.