Demineralization Rate Research Articles

To compare the rate of demineralization using carbopol 907 system with carbopol 2050 system

To compare the rate of demineralization using carbopol 907 system with carbopol 2050 system

Imaging natural and artificial demineralization on dentin surfaces with polarization sensitive optical coherence tomography.

The purpose of this study was to assess the potential of polarization sensitive optical coherence tomography (PS-OCT) to measure non-destructively the severity of natural and artificial caries lesions in dentin and determine the efficacy of intervention with anti-caries agents. Although several studies have demonstrated the utility of PS-OCT to image caries lesions in enamel and to quantify the lesion severity, only a few studies have focused on lesions in dentin. In this study images of natural root caries lesions on extracted human teeth were acquired with PS-OCT. In addition artificial lesions were produced in dentin after 12 days of exposure to a demineralization solution at a pH of 5.0. Before exposure, three incisions were made on the sample surfaces using Er:YAG laser irradiation and selected areas were treated with topical fluoride. PS-OCT images were acquired using a high power (45-mw) 1310-nm superluminescent diode with a bandwidth of 35-nm. PS-OCT was able to measure demineralization in dentin to a depth of ~ 1 mm. Polarized light microscopy and microradiography were used to measure lesion severity on histological thin sections for comparison. PS-OCT successfully measured the inhibition of demineralization by topical fluoride. Er:YAG laser irradiation did not significantly increase or decrease the rate of dentin demineralization.

Adsorption behavior of statherin and a statherin peptide onto hydroxyapatite and silica surfaces by in situ ellipsometry

The salivary protein statherin is known to adsorb selectively onto hydroxyapatite (HA), which constitutes the main mineral of the tooth enamel. This adsorption is believed to be crucial for its function as an inhibitor of primary (spontaneous) and secondary (crystal growth) precipitation of calcium phosphate salts present in saliva. A fragment corresponding to the first 21 N-terminus amino acids of statherin (StN21) was previously found to reduce the rate of demineralization of HA. Therefore, the interfacial properties of this peptide and statherin onto silica, hydrophobized silica and HA discs was studied by in situ ellipsometry. Their reversibility induced by dilution and elutability induced by buffer and sodium dodecyl sulfate (SDS) was also determined. The results revealed that statherin adsorbed at a greater extent onto the HA as compared to StN21, suggesting that the hydrogen bonding between the uncharged polar residues at the C-terminal region of statherin and HA contributes to its adsorption. However, on both silica surfaces the peptide adsorption appeared to proceed in a similar way. Onto the hydrophobized silica the adsorption of both peptides was suggested to occur either via multilayer formation or adsorption of aggregates from solution, while onto the hydrophilic silica adsorption of peptide aggregates from solution was the suggested mechanism. Further, both peptides were observed to be strongly adsorbed onto HA, even after SDS treatment, in comparison to the layers adsorbed onto hydrophobized silica. Both peptide layers were found to be weakly adsorbed onto the hydrophilic silica surface as they were totally removed by buffer dilution.

Peptides Selected for the Protein Nanocage Pores Change the Rate of Iron Recovery from the Ferritin Mineral

Pores regulate access between ferric-oxy biomineral inside and reductants/chelators outside the ferritin protein nanocage to control iron demineralization rates. The pore helix/loop/helix motifs that are contributed by three subunits unfold independently of the protein cage, as observed by crystallography, Fe removal rates, and CD spectroscopy. Pore unfolding is induced in wild type ferritin by increased temperature or urea (1-10 mM), a physiological urea range, 0.1 mM guanidine, or mutation of conserved pore amino acids. A peptide selected for ferritin pore binding from a combinatorial, heptapeptide library increased the rate of Fe demineralization 3-fold (p<0.001), similarly to a mutation that unfolded the pores. Conjugating the peptide to Desferal (desferrioxamine B mesylate), a chelator in therapeutic use, increased the rates to 8-fold (p<0.001). A second pore binding peptide had the opposite effect and decreased the rate of Fe demineralization 60% (p<0.001). The peptides could have pharmacological uses and may model regulators of ferritin demineralization rates in vivo or peptide regulators of gated pores in membranes. The results emphasize that small peptides can exploit the structural plasticity of protein pores to modulate function.

Comparison of the Behavior of Two Nanofiltration Membranes for Sweet Whey Demineralization

Nanofiltration is a process used to separate mineral salts from lactose, having previously removed the proteins by ultrafiltration. Both proteins and lactose can be used as raw materials to prepare a variety of products. In this paper, we studied the feasibility of demineralizing sweet whey obtained from the cheese industry of the Comunidad Valenciana (Spain) using membrane technologies. The NF200 membrane showed the highest volumetric flux and solute rejection values, whereas the DS-5 DL membrane showed the lowest values. The volumetric fluxes obtained with the NF200 and DS-5 DL membranes in these experiments with the ultra-filtered whey demonstrated significant differences between membranes. Concerning solute rejection, the highest values were obtained using the NF200 membrane. The chosen parameter to evaluate the demineralization capability was solute flux. In this way, the values obtained for chloride ion were 9.90 and 32.42 g/ (m2·h) for the NF200 and DS-5 DL membranes, respectively, with the highest demineralization rates being achieved with the DS-5 DL membrane.

Fluorine uptake into human enamel around a fluoride-containing dental material during cariogenic pH cycling

Using PIGE (TIARA, JAPAN) technique, we measured fluorine (F) uptake into the tooth enamel around a fluoride-containing material during caries progression using pH cycling. Class I cavities in the buccal surfaces of 6 extracted human teeth were drilled and filled with fluoride-containing material; a glass ionomer cement (Fuji IX(GC)). Three 300 μm sections through the material were obtained from each tooth. Two of these specimens were utilized to measure the F distribution in enamel adjacent to the material. A 1.7 MeV proton beam accelerated by the TIARA single-ended accelerator was delivered to a micro-beam apparatus. The beam spot size was about 1 μm with a beam current of about 100 pA. A nuclear reaction, 19F(p, αγ) 160, was used to measure the F concentration and the gamma-rays from this reaction were detected with a 4” NaI detector. X-rays induced by proton were detected with a Si(Li) detector to measure calcium concentration and the beam intensity was monitored with the X-ray yield from a copper foil for quantitative analysis. After measurement of F uptake, all specimens were polished to a thickness of 120 μm. In order to simulate daily acid challenges occurring in the oral cavity, the pH cycling (pH6.8–pH4.5) was carried out for 1, 3 and 5 weeks, separately. The duration that the solution remained below pH 5.5 was 37 min per cycle. The cycles were repeated 6 times per day with 2 h interval between cycles, and the specimens were kept in remineralizing solution for the rest of pH cycle. After pH cycling, F and calcium distribution of each specimen was evaluated using PIGE technique. The F distribution of the specimens before pH cycling clearly showed the F uptake from fluoride-containing material into enamel adjacent to the material. After pH cycling, the caries progression in all specimens was observed by the image of transverse microradiography (TMR). The depth of caries and mineral loss progressed with increasing the duration of pH cycling, although the enamel adjacent to the material remained a caries inhibition zone due to low rate of demineralization. With caries progression, fluorine accumulated in the subsurface of the caries lesion, while the outermost surface of the caries lesion gradually dissolved under increasing pH cycling. The data obtained using PIGE (TIARA, JAPAN) technique were useful to understand the fluorine benefit for preventing dental caries by means of fluoride-containing dental materials.

Demineralisation of Permeable Hydroxyapatite with Alternating Water and Acidic Buffer: Scanning Microradiographic Study of Effect of Switching Period

Permeable hydroxyapatite (HAP) blocks were exposed for equal times alternately to pH 4.0 buffer and water for 237 h. Rates of HAP loss with time (determined from changes in X-ray attenuation) were measured as a function of switching period τ (the time for a complete cycle) from 0.5 to 6 h and with a continuous buffer flow. The mean rate of HAP loss decreased markedly as τ increased, and for large τ was about half the rate for continuous buffer flow. We propose that demineralising conditions through the depth of the HAP are influenced by the extent of retention of buffer within its pores which will depend on τ. A mathematical model with parameters R₀ and Δt was developed, where R₀ is the rate of demineralisation for continuous flow, and Δt a time added to each τ/2 buffer exposure to account for its retention in the HAP pores. Experimental data fitted the model with Δt ∼8 to ∼10 min and with R₀ close to the rate observed for continuous buffer flow. The model predicts that the rate decreases and approaches R₀/2 as τ → ∞, as was found experimentally to be the case. This type of study could potentially give information about subsurface porosity and transport processes during acidic dissolution of permeable solids, for example in dental caries and dental erosion.

In situ tracing the process of human enamel demineralization by electrochemical impedance spectroscopy (EIS)

The purpose of this study was to in situ characterize the demineralization (namely dissolution of hydroxyapatite) on the surface of the human enamel using electrochemical impedance spectroscopy (EIS) technology. Fresh human third molars extracted without visible evidence of caries, were used in this study. After they were immersed in a demineralizing solution prepared from lactic acid and carboxy methyl cellulose sodium (Na-CMC) buffering at pH 4, demineralization happened on their surfaces. EIS of the specimens were measured at a series of immersed interval. X-ray diffractometer (XRD) were used to distinguish the microstructure of the surface layer of the specimens. The depositions that appeared in the demineralizing solution after 46 h immersion were analyzed by fourier transform infrared spectrometer (FTIR). XRD analysis revealed that the percentage of intensity (I%) of HAP gradually decreased with the elapsed immersing time, which indicated the dissolution of HAP columns of enamel. Nyquist spectra were fitted with an equivalent circuit characterized by some parameters, such as Q and R(p) (error<0.1%). Changes of the parameters' values revealed that the rate of demineralization accelerated at the forepart of the demineralization, but slowed down beyond 70 h immersion. The results suggested that EIS was proved to be a useful method for in situ investigating and in vivo detecting the demineralization of the enamel.

Production of chitin from red crab shell waste by successive fermentation with Lactobacillus paracasei KCTC-3074 and Serratia marcescens FS-3

Successive two-step fermentation was carried out from red crab shell wastes for biological extraction of chitin in combination of the 1st step with a lactic acid bacterium Lactobacillus paracasei subsp. tolerans KCTC-3074 and the 2nd step with a protease producing bacterium Serratia marcescens FS-3, and vice versa. In the 1st step fermentation with KCTC-3074, the pH decreased rapidly from pH 6.90 to 3.31 and TTA increased rapidly to 10.99 for 5 days. At day 7 in the 2nd step fermentation with FS-3, pH further dropped to 2.82 and TTA also dropped to 1.71. In the 1st step fermentation using FS-3, the pH decreased slightly from pH 6.90 to 5.89, and TTA was low as indicated by 1.50 at 5 days. At day 7 in the 2nd step fermentation with KCTC-3074, the pH value was 3.62, and TTA increased to 8.95. The successive fermentation in the combination of FS-3 and KCTC-3074 gave the best result in co-removal of CaCO 3 and proteins from crab shells. In this combination, the rates of demineralization and deproteinization were 94.3% and 68.9%, respectively, at the end of fermentation. To date, this is the 1st report on successive fermentation for biological extraction of chitin from crustacean shells.

Enamel Demineralization in Primary and Permanent Teeth

Although enamel demineralization is important for our understanding of caries formation, no consensus has been reached regarding the possible differences in susceptibility of primary and permanent enamel. We used the constant composition (CC) technique to investigate the acid-induced demineralization of these tissues at a relative undersaturation with respect to hydroxyapatite (HAP) of 0.902, pH = 4.5, and ionic strength = 0.15 mol L(-1). The demineralization rates showed significant differences, primary enamel having the greater susceptibility to dissolution during an initial linear stage: 1.5 +/- 0.5 x 10(-10) mol mm(-2) min(-1) compared with 2.6 +/- 0.5 x 10(-11) mol mm(-2) min(-1) for permanent enamel. During the reactions, we observed nanosized crystallites which attached to the enamel surfaces or escaped into the bulk solution. These nanosized crystallites were kinetically protected against further dissolution, even though the solutions remained undersaturated. It is hypothesized that they may contribute to the remarkable mechanical and dynamic characteristics of enamel.

Acidic demineralization of apatites studied by scanning X-ray microradiography and microtomography

AbstractThe mineral in bones and teeth is an impure form of hydroxylapatite (HAP), the principal impurity being 2—5 wt.% carbonate. This mineral dissolves during remodelling of bone and also in dental caries as a result of the action of acids produced by osteoclasts and by bacteria, respectively. In enamel, demineralization proceeds with preferential loss of carbonate relative to phosphate. Surprisingly, in the early stages, the demineralization is subsurface. In order to facilitate the understanding of physical chemical aspects of these processes, we have undertaken studies of demineralization in model systems. We give three examples here. The first two used scanning microradiography in which the specimen is stepped across a 10—30 μm diameter X-ray beam. Intensity measurements allow calculation of the mineral mass per unit area in the X-ray path through the specimen. In the first experiment, porous HAP sections were separated from a reservoir of acidic buffer by a column initially filled with water (the diffusion length) and scanned with the X-ray beam perpendicular to the axis of the diffusion length. The rate of total loss of mineral along each profile was calculated from the scans. The rate of demineralization fell as the diffusion length increased. We believe the explanation is that the rate-controlling step is the diffusion of dissolved HAP away from the solid to the buffer reservoir. In the second experiment, demineralizing solution and water were pumped alternately, for equal lengths of time, past blocks of porous HAP or enamel. The X-ray beam was perpendicular to the exposed surface. As the rate of switching between solutions decreased, the mean rate of demineralization also fell. We propose that this effect is due to retention of acid in the pores of the HAP during the time when water flows, allowing further demineralization to take place during this time. The third study used X-ray microtomography, a form of 3D microscopy, to study the loss of mineral in compacted carbonate apatite powders. The powders were packed in six 10 mm internal diameter acrylic cylinders to a depth of 4 mm (after pressing). One end was covered with a porous polyethylene disc and each tube placed in acidic buffer for 70 days. Periodic examination by microtomography showed the development of subsurface demineralization. Infrared spectroscopy of the dissected-out surface layers showed preferential loss of carbonate over phosphate by comparison with deeper layers. Rietveld analysis of X-ray powder diffraction data showed changes in the crystallographic structures of the apatites between the initial and dissected-out apatite.

Relationship between electrical conductivity and demineralization rate during electroacidification of cheddar cheese whey

Electrical conductivity is used as a simple method to monitor demineralization of food systems during conventional electrodialysis treatments. However, during bipolar membrane electroacidification, the H + generated at the bipolar membrane, have a higher conductivity contribution in comparison with all other cations. The objective of the present work was to develop an equation correlating conductivity and temperature to the demineralization rate in cheddar cheese whey during bipolar membrane electroacidification treatment. It appeared that conductivity data were not directly correlated with experimental demineralization rate. Thus a second order polynomial equation appropriate for whole and skim whey, was developed in order to predict demineralization rate ( D) as a function of conductivity ( C) and temperature ( T): D = 153.42 − 64.45 C + 5.55 T + 2.97 C 2 − 0.03 T 2 ( R 2 = 0.946). Mathematical models were also calculated from data of diluted whey solutions and these equations allowed evaluation of dilution phenomenon due to dead volume in electrodialysis cell prior to electroacidification. This work will allow the use of conductivity and temperature measurements to indicate, more precisely, the demineralization rate of cheddar cheese whey during electroacidification with bipolar membrane.

Electrodialysis of calcium and carbonate high concentration solutions and impact on composition in cations of membrane fouling

Fouling, which is the accumulation of undesired solid materials at the phase interfaces of permselective membranes, is one of the major problems in electrodialysis. The objectives of the present work were to investigate the effect of the composition in calcium and carbonate of a model solution to be treated by conventional electrodialysis on their migration kinetics and the composition in cations of the membrane fouling. In the absence of sodium carbonate in the solution, no fouling was visually observed on anion-exchange membranes (AEM) and fouling was observed only at 1600 mg/L CaCl 2 on cation-exchange membrane (CEM), while at only 800 mg/L CaCl 2 with sodium carbonate, a deposit was observed on both membranes. This difference could be explained by the fact that carbonate has a high buffer capacity, and the time to reach pH 4.0 was then longer than the one without carbonate. Consequently, the migration of the ionic species was carried out over a longer period of time during ED treatment with sodium carbonate addition and in extent the demineralization rates were higher: 43 vs 86%. For treatment with sodium carbonate and 1600 mg/L CaCl 2, the higher migration during ED treatment, increased the concentration of calcium, from 14.24 to 93.38 mg/g dry membrane and from 0.74 to 10.27 mg/g dry membrane for CEM and AEM, respectively. Due to the basic pH on the side of the membrane in contact with the NaCl solution, the calcium would precipitate to form calcium hydroxide on CEM while the calcium migrated through the CEM was blocked by the AEM where it formed another fouling.

Enhanced tobacco polyphenol electromigration and impact on membrane integrity

Previous work has shown the feasibility of removing polyphenols from tobacco extracts by electrodialysis using monopolar membranes. However, the low migration rates obtained for polyphenols were not sufficient to demonstrate that it was a practical technology. In the present work three anionic membranes of the same type, AM-4 or AM-2, were stacked in a cell and the duration of treatment was extended to 4 h. Trends previously observed during electromigration treatments for these membranes were confirmed. The AM-4 and AM-2 membranes gave final demineralization rates of 86.5 and 89.5%, respectively. High polyphenol migration rates were obtained with these membranes: for the AM-4 and AM-2 membranes the rates were, respectively, for chlorogenic acid 90.8 and 86.5%, for scopoletin 66.7 and 23.2%, and for rutin 81.3 and 31.1%. These results confirmed that ED has the potential for efficient separation of tobacco polyphenols. However, for both membranes, the mass balance showed a large (90%) decrease in nicotine in the treated tobacco extract, indicating a high level of nicotine electromigration. Measurements of the membrane characteristics before and after treatment were consistent with the AM-2 membrane becoming fouled during treatment.

Scanning microradiographic study on the influence of diffusion in the external liquid on the rate of demineralization in hydroxyapatite aggregates

Subsurface demineralization in enamel caries is known to entail diffusion of reagents and products both within the lesion and within the plaque biofilm external to the lesion. However, development of a predictive mathematical model for subsurface demineralization is hindered by limited quantitative understanding of the effects of these diffusion processes. The purpose of this quantitative study was to investigate and understand the effect of external diffusion length on the rate of demineralization in a simple model system. Ten, 500-microm thick sections cut from a porous hydroxyapatite (HAP) pellet were inserted in scanning microradiography (SMR) cells. The exposed thin edges of the sections were initially separated by columns of water (diffusion lengths) of 0-0.9 cm from a 1-l reservoir of demineralizing buffer (pH 4). Buffer was found to diffuse from the reservoir through the increasing diffusion lengths to the exposed HAP surface, whilst dissolved product diffused along the reverse path. Rates of HAP loss (from SMR measurements) decreased as the diffusion length increased. Experimental data were fitted to a general diffusion-reaction model. This showed that the solution near the HAP surface was almost completely saturated with HAP, and that the diffusion of dissolution products, rather than of buffer species, was rate limiting.

Demineralization of crab shells by chemical and biological treatments

To achieve demineralization of crab shell waste by chemical and biological treatments, lactic acid and lactic acid bacterium were applied. In 5.0 and 10% lactic acid, pH rapidly decreased from 6.8 to 4.2 and from 4.5 to 2.4 at day 3, respectively, and thereafter the pH remained at an almost constant level. In a 10% lactic acid bacterium inoculum, pH lowered to 4.6 at day 5. Relative residual ash content rapidly decreased to 49.1 and 16.4% in 5 and 10% lactic acid treatments, respectively, for the initial 12 h. In 2.5, 5 and 10% lactic acid bacterium inoculums, relative residual ash content rapidly decreased to 55.2, 40.9 and 44.7%, respectively, on the first day. Residual dry masses were 76.4, 67.8 and 46.6% in 2.5, 5 and 10% lactic acid treatments, respectively, for the initial 12 h. After a one-time exchange of the lactic acid solution, in the 5.0% lactic acid treatment, residual dry mass rapidly decreased from 66.0 to 41.4%. In 2.5, 5 and 10% lactic acid bacterium inoculums, residual dry masses decreased to 67.6, 57.4 and 59.6% respectively, on the first day. Protein contents after demineralization ranged from 51.3–54.7% in the chemical treatments and decreased to 32.3% in the lactic acid fermentation process. A negative relationship was shown between pH and demineralization rate in lactic acid and lactic acid bacterium treatments. These results suggest that lactic acid fermentation can be an alternative for demineralization of crab shells, even though the rate and efficiency of the demineralization is lower than the chemical treatment.

Reaction and diffusion during demineralization of animal bone

AbstractThe demineralization of animal bone is investigated. Experimental results show an increase in penetration rate of hydrochloric acid into animal bone particles, and thereby increased demineralization, at increasing temperature and concentration of HCl. Fick's law is used to calculate the effective diffusivities of HCl in animal bone from these experimental results, showing a decrease in effective diffusivity at increased HCl concentration, which proves Fick's law unsuitable for describing the process, whereas a Maxwell–Stefan‐based model is used successfully. This model is able to take into account gradients in composition as well as electrical potential, and also addresses the frictional resistances between the various components in the multicomponent system. The results of the Maxwell–Stefan model are in good agreement with the experimental data. From the Maxwell–Stefan model and the experiments, it follows that at high concentrations of HCl, the friction between the diffusing ions (H+, Cl−, H2PO, and Ca2+) becomes more important and lowers the increase of demineralization rate caused by the increase in the concentration gradient. © 2004 American Institute of Chemical Engineers AIChE J, 50:2682–2690, 2004

Microwave exposure increases bone demineralization rate independent of temperature

There is a long-standing controversy regarding an effect of microwaves, independent of increasing temperature, on the rate of bone demineralization. In this study, we exposed standardized samples of gerbil femur to constant microwave exposure while maintaining the demineralizing solution (ethylenediamine tetraacetic acid, EDTA) at 20 degrees C. Random samples were selected at 3 h intervals, embedded in plastic and sectioned for histological evaluation to determine the extent of demineralization. The time to complete demineralization was significantly faster with microwave exposure (33 h) compared to non-exposure on a tissue rotator (45 h) in a limited amount (5 mL/24 h) of EDTA. The presence of bone marrow was a significant barrier to the rate of demineralization and resulted in an asymmetrical pattern of mineral extraction. Samples without bone marrow were completely demineralized after 21 h of exposure to microwaves and EDTA. Additional comparisons were made between samples exposed to an effectively infinite supply of demineralizing agent (bone marrow intact). There was a significant increase in rate with unlimited demineralizing agent with (24 h) or without (30 h) microwaves when compared to tissue demineralized on the rotator. Our results establish a positive effect of microwaves on the rate of bone demineralization which is independent of temperature.

Electromigration of tobacco polyphenols

Polyphenols in tobacco are known precursors for bioactive phenolic compounds in cigarette smoke. Electrodialysis has been tested as a means of selectively extracting polyphenols from aqueous tobacco extracts. Seven commercial membranes were tested in an electromigration configuration. This exploratory study showed the potential application of AM-2 and AM-4 membranes for the migration of polyphenols. During 3-h trials with a single membrane in an electrodialysis cell, both AM-2 and AM-4 membranes achieved a 77% demineralization rate. The migration rates for the AM-2 and AM-4 membranes were for chlorogenic acid 24.7 and 28.7%, respectively, for scopoletin 8.6 and 18.8%, and for rutin −10.3 and 10.3%.

Bipolar electrodialysis for glycerin production from diester wastes

Diester plants produce large quantities of glycerin solutions, whose commercial exploitation requires sodium sulphate elimination. Bipolar electrodialysis (BED) has been investigated for its capability to both demineralize solutions and to produce alkali and acid solutions. Demineralization rates above 80% were achieved with glycerin loss below 2%. Alkali and acid solutions were obtained with a final concentration of about 2 N and an energy cost of about 0.5 kWh/kg of pure glycerin. The treatment of waste solutions could be realized with a membrane area of 100 m 2. Economic evaluation demonstrates the suitability of BED since demineralization allows the upgraded solution to be sold at a price 1.4 times higher than the initial solution.