Concentrations Of Calcium Salts Research Articles

EVALUATION OF THE STRUCTURAL-MECHANICAL PROPERTIES OF COMPOSITE PEAR JELLIES PREPARED WITH DIFFERENT GELLING TIME AND CALCIUM SALTS

The aim was to investigate the influence of different calcium salts and gelation times on the structural-mechanical parameters of a pear composite jellies. Calcium citrate and calcium lactate with a concentration of 0.6 % and 1.2 % were used as sources of calcium ions for the gelling time of 24 and 48 h. The changes in the structural-mechanical properties of the jellies were determined from the obtained typical curves through a penetration test using a texture analyzer. The increase in the concentration of calcium ions led to the increasing values of the structuralmechanical parameters of the fruit jellies, except for adhesiveness and rupture deformation. The shape of the penetration curves was determined to a greater extent by the type and concentration of calcium salts and to a lesser extent by the gelation time. The Pearson correlation coefficients for the compressive stress, deformation force and firmness increased compared to the other structural-mechanical properties with an increase in the gelation time and the concentration of calcium salts.

Comparison of the zonal distribution of calcium salt density and fat marrow in bone-healthy and osteoporotic sacra: an image data analysis using quantitative computed tomography and magnetic resonance imaging.

Pathogenesis of sacral fragility fractures is not fully understood. This study investigates zonal distribution of calcium salt and fat marrow in intact bone-healthy and osteoporotic pelvis. In addition, in unilateral sacral fractures, the fracture side was compared with the intact side. CT and MRI images of 37 pelves were analyzed. Zonal calcium salt distribution by Hounsfield units (HU) was recorded for each CT dataset. Fat marrow content was measured in MRI mDixon-Quant sequence. The cohort was divided: intact pelves with (PEO, HU < 100, n = 8) and without osteoporosis (PE, HU ≥ 100, n = 14) based on the mean HU value in LWK5. A third group consisted of patients with osteoporosis and unilateral fractures (PEOFx, n = 10). The results suggest that in PEO sacral alae experience disproportionate skeletal rarefaction. This concerns the sacral ala at the S1 level (- 25 ± 55), whereby the calcium salt content is so low that it corresponds to the S3 level of healthy bone (- 20 ± 21 HU). This explains the occurrence of transalar fractures in the load-transmitting zone S1. In PEOFx, the calcium salt density was higher and the fat content was lower on the fractured side than on the intact side, indicating bony compacting due to lateral compression and fat displacement due to hematoma in the accident mechanism. This study makes an important contribution to the understanding of the development of sacral fragility fractures. Furthermore, impaction of the cancellous bone within the fracture can be demonstrated.

Comparison of Physicochemical Properties of Noodles Fortified with Commercial Calcium Salts versus Calcium Citrate from Oyster Shells.

This study examined the physicochemical effects of the fortification of noodles with 0.25-1.00% (w/w) calcium salts, viz. calcium acetate, calcium carbonate, calcium citrate, and calcium lactate. Fortification with calcium citrate, calcium acetate, and calcium carbonate increased the pH and breaking force of the dried noodles. However, the fortification of noodles with any concentration of calcium did not increase the extent of elongation of the control raw noodles. The L* and b* values of the raw and dried noodle color increased with increasing concentrations of calcium salts, except for noodles with added calcium citrate. Fortification with calcium citrate yielded no significant influence on color, texture, adhesiveness, springiness, flavor, and overall scores for cooked noodles. Noodles fortified with 0.5% calcium citrate made from oyster shells were compared with a control sample of noodles and noodles fortified with commercially available calcium citrate. The particle size of the calcium citrate made from oyster shells (258 nm) was smaller than that of the purchased calcium citrate (2631 nm). Noodles fortified with calcium citrate made from oyster shells showed no significantly difference compared to noodles fortified with commercially available calcium citrate. These results suggest that calcium citrate made from oyster shells may be used as the additive of choice for the manufacture of calcium-fortified noodles.

Three-dimensional electrodes in hybrid electrolytes for high-loading and long-lasting calcium-ion batteries

Aqueous calcium-ion batteries (CIBs) exhibit a reliable long-term cycling and rate performance, but they have a low energy density owing to the narrow electrochemical stability window (ESW) of aqueous electrolytes. Highly concentrated water-in-salt electrolytes offer enhanced stability by limiting the number of free water molecules present within the system. However, CIB electrolytes still suffer from low conductivity and high viscosity due to the high concentration of calcium salt. Hence, to resolve this problem, a series of hybrid aqueous/organic calcium electrolytes were formulated to improve the ESW and long-term reversibility while maintaining a low electrolyte concentration. The best hybrid-electrolyte candidate, which had a calcium perchlorate/water/acetonitrile molar ratio of 1.0:4.0:4.8 (i.e., Ca(ClO4)2/(H2O)4.0(AN)4.8), exhibited a wide ESW (≈3.0 V) and a facile insertion of calcium ions into Prussian green host materials, leading to an impressive 90% capacity retention after 1000 cycles. Nickel foam (NF) was also employed as a cathode current collector to investigate the feasibility of the drop-coated three-dimensional electrodes. Owing to its high-porosity architecture, the NF substrate could accommodate for four to eight times higher mass loading than traditional foil-type collectors, resulting in full cells with much higher energy densities.

How Normalization of the Content of Calcium Salts in Body Tissues Affects the Course of Alzheimer's disease In the Elderly

How Normalization of the Content of Calcium Salts in Body Tissues Affects the Course of Alzheimer's disease In the Elderly

Influence of Normalization of The Content of Calcium Salts in Body Tissues on The Course of Parkinson's Disease in The Elderly Peapls

Calcium plays an important regulatory and structural role in living organisms. Calcium is a common macronutrient in the body of plants, animals and humans. This chemical element is involved in key physiological and biochemical processes of the cell. Calcium ions are involved in blood coagulation processes, and also serve as one of the universal second messengers inside cells and regulate a variety of intracellular processes - muscle contraction, exocytosis, including the secretion of hormones and neurotransmitters. In the body, calcium is found not only in bones and teeth (about 1 kilogram), but also in the blood. Calcium in the bones is mainly needed for our skeleton to be strong and able to support us. Calcium helps muscles contract, nerves carry messages from the brain to every part of the body, blood vessels move blood throughout the body, release hormones and enzymes that affect almost every function in the body, blood clot, regulate blood pressure and bad cholesterol levels. In old age there is an accumulation in the body of minerals, especially calcium. This is expressed in the deposition of calcium salts in the walls of blood vessels, in joints, cartilage and other tissues. The amount of deposited calcium salts on the tissues of the body, including in the tissues of the brain, is very large, if not enormous. Prior to the start of treatment, all patients were diagnosed by bioresonance. The state of the nosode "Parkinson's disease" ("PD"), organ preparations of the brain - Roof of the midbrain, Red nucleus, Substance nigra, Midbrain, Reticular formation, Lenicular nucleus, Paranigra dopaminergic nucleus were assessed. It was established that in all patients all the listed formations were clearly tested, including the nosode "BP", which indicated the presence of PD. After examining patients with PD using the method of resonance diagnostics, patients begin to use only water with a reduced content of calcium salts in their diet. After 7 weeks of treatment, most of the patients testified that they did not see manifestations of PD in themselves. Their examination showed that the nosode BP and the organ preparations tested before the onset of the disease stopped being tested by the method of resonance diagnostics. The parathyroid gland was also tested in all nine patients (prior to the start of treatment, the parathyroid gland was tested in all patients - it was in a state of degeneration). After 10 weeks of treatment, the rest of the patients reported that they had no manifestations of PD, which was combined with the termination of testing by the method of resonance diagnostics of all previously tested organ preparations, the PD nosode and the parathyroid organ preparation.

Technology of production process and encapsulation fruit and berry concentrates

The article presents 2 methods for making concentrates from fruits and berries, which were later used as a filler for alginate capsules. The results of the physicochemical parameters of the obtained concentrates are presented. Of the 15 options for the formulations of fruit and berry concentrates - capsule fillers, 11 formulations were selected, which were divided into categories "up to 7 years" and "7 +" depending on their composition. Under laboratory conditions, the technological regime for the manufacture of alginate capsules by the drop method was worked out. As a result of the single-factor experiment, it was revealed that from the moment a drop of about 6 mm in size is immersed to the formation of a capsule wall with a thickness of about 2.3 mm, 2 minutes are needed in the given experiment parameters: the concentration of alginate in the filler solution is 1 %, the Ph of the filler is 4.2, the concentration of calcium salt, where the drops are immersed to form a sphere - 1 %, the size of the drop is 6 mm, the thickness of the capsules is not less than 2 mm and not more than 2.5 mm. To prevent the process of gelation, it is necessary to heat the spheres in a bath of water at 85 °C for 10 minutes. With such a manipulation, the gelification process stops, and the center of the sphere remains liquid. Prototypes have been developed that are stable if, during storage, they are immersed in a neutral medium of the filler. Based on the results of a sensory assessment of the quality and texture of yogurt from sheep and goat milk mixed with capsules according to M. Bourne, it can be concluded that mixing the homogeneous structure of yogurt with capsules has a positive effect on the taste range, the product acquires a new look and taste, while not losing its quality.

Osmotic regulation and chlorophyll fluorescence characteristics in leaves of wheat seedlings under different salt stresses

The damage mechanism of salt stress on plants has attracted much attention. In order to reveal the damage mechanism of different salt stresses, we compared osmotic regulation and photosynthetic characteristics of seedlings of wheat cultivar Xianhan 3 under sodium salt (150 mmol·L-1) and calcium salt (5, 30 mmol·L-1) treatments alone or in combination. The results showed that sodium salt or calcium salt stress alone significantly inhibited the growth of roots and stems, but increased the amount of soluble sugar and proline, regulatory energy-dissipated electron yield, non-photochemical quenching and relative content of zeaxanthin contents in leaves. In contrast, salt treatments alone significantly decreased the levels of chlorophyll a and chlorophyll b, maximum photochemical efficiency, PSⅡ photochemical efficiency, photochemical quenching and photosynthetic electron transport efficiency. Furthermore, the inhibition of wheat seedling growth was more sensitive to calcium salt than to sodium salt stress, whereas the decreases of chlorophyll content and chlorophyll fluorescence parameters were more prominent in response to sodium salt stress. Except for the amount of soluble protein, lutein and the relative level of zeaxanthin, the changes of other parameters in the leaves due to sodium salt stress were effectively blocked by the application of low calcium concentration, but further increased by the presence of high calcium salt concentration. Taken together, sodium or calcium salt stress alone significantly inhibited seedling growth. The toxicity of sodium salt to wheat seedlings was effectively alleviated by low calcium concentration, but was aggravated by high calcium concentration, which were associated with the changes of photosynthetic pigment content, light energy capture, and photosynthetic electron transport process in the leaves of wheat seedlings. Moreover, osmotic regulators played an important role in enhancing the resistance of wheat seedlings to sodium or/and calcium environment.

Differential effects of excess calcium applied to whole plants vs. excised fruit tissue on blossom-end rot in tomato

Blossom-end rot can cause serious yield and quality losses to processing tomato producers, fresh market growers, and home gardeners alike. Blossom-end rot is often associated with calcium deficiency, though salt stress and even high concentrations of calcium salts can also cause blossom-end rot. The goal of this study was to characterize the negative effects of excess calcium compared to inadequate calcium at the whole plant and cellular level. Four calcium chloride levels (0 ppm, 10 ppm, 100 ppm, and 500 ppm) were applied daily to highly blossom-end rot susceptible processing tomato plants, starting at first flowering. Fruit were harvested 21–22 days after pollination. Blossom-end rot incidence and severity were lowest in the 10 ppm treatment. Blossom-end rot incidence was highest in the 0 ppm treatment and blossom-end rot severity was significantly increased in 500 ppm and 0 ppm treatments compared to 10 ppm CaCl2. No significant difference was found in the calcium content of tomato fruit harvested from plants treated with various levels of calcium. The soil drainage solution from the 500 ppm treatment had the highest conductivity, which was nearly 10 times higher than that of the 0 ppm and 10 ppm treatments. Daily plant water use was reduced in the 500 ppm treatment. Application of moderate calcium to tomato plants effectively reduced blossom-end rot incidence and severity, but excess levels of calcium did not reduce incidence and further increased blossom-end rot severity compared to moderate calcium application. Calcium applied to immature tomato fruit pericarp discs also inhibited blossom-end rot symptom development; however, excess calcium did not induce blossom-end rot symptoms. These results indicate that excess calcium induces blossom-end rot development due to effects at the whole plant level, but not due to excess calcium in the fruit tissue.

Structural analysis of the statocyst and nervous system of Praesagittifera naikaiensis, an acoel flatworm, during development after hatching

Acoel statocysts are fluid-filled chambers formed by two parietal cells underlying basal lamina as a capsule and contain a movable statolith cell called a lithocyte. The statocyst is needed for geotaxis; however, the mechanism of the gravity receptor system has not been elucidated. We focused on the geotactic ability of the acoel Praesagittifera naikaiensis, acquired during the development of the statocyst and its nervous system after hatching, and examined the three-dimensional relationship between the statocyst and its nervous system. Acoel geotactic ability was acquired between 0 and 7 days after hatching. No major changes in neural structures, namely a commissural brain, nerve cords, and commissures, were observed between juveniles and adults. The statocyst-associated commissure (stc), a commissural brain component, was circular and was located ventral to the statocyst but was not observed in neural connections to the capsule’s lumen. Fine structures of the statocyst revealed that the statolith developed after hatching. We hypothesized that geotactic ability needs the following conditions: (1) a sufficient concentration of calcium salt in the statolith; (2) stc must work as afferent neurons; and (3) a ventral polar cell, which is present outside the capsule, must be a sensory cell stimulated by the lithocyte.

Formulation and Characterization of Calcium-Fortified Jelly and Its Proximate Composition and Sensory Analysis.

Calcium is a dynamic mineral. Recent discoveries designate that low intake of calcium generates deficiencies and path to other diseases. Food fortification could play a key role to overcome this problem. To cope with this deficiency problem, jellies were formulated with food-grade calcium salts and chicken eggshell powder. In the present study, three different concentrations of calcium salts, as well as eggshell powder were used to formulate jellies. The results of the sensory evaluation indicated that the two jelly products (A&D) in the current study were suitable for consumers. Results of Atomic Absorption Spectrophotometer revealed Jelly A and jelly D had 151±0.05 ppm and 133±0.06 ppm calcium concentration, respectively. Proximate analysis of Jelly A showed that it has 6.0±0.01% ash, 9.2±0.1% moisture, 0.4±0.01 g crude protein, 82.79±0.001 g crude fiber, and 0.61±0.001 g crude fat, while the jelly D that was made with chicken eggshell powder exhibited 6.0±0.01% ash, 10.1±0.1% moisture, 0.5±0.01 g protein, 84.54±0.01 g crude fiber and 1.61±0.01 g crude fat. Therefore, these two jelly A & D were greatly appreciated among other attributes. In spite of naturally available calcium-rich sources, calcium-fortified jellies can be consumed by individuals who are incapable to take sufficient calcium from their diet.

Study of photocatalytic and electrocatalytic activities of calcium tungstate nanoparticles synthesized via surfactant-supported hydrothermal method

Here, calcium tungstate nanoparticles (CWONPs) were synthesized by the hydrothermal method. The reaction parameters including calcium salt concentration, surfactant concentration, reaction time and temperature have been optimized by Taguchi Design Method for smaller particles size. The morphology, size, crystallinity and chemical structure of nanoparticles were investigated by different methods. The optimized calcium tungstate nanoparticles (opt-CWONPs) with average size of 51 nm were showed outstanding removal effectiveness for three different pollutants including methyl orange, imipenem and imatinib mesylate over UV illumination. Nearly, 100% of methyl orange, 98% of imipenem and 60% of imatinib mesylate are degraded at 1800s over opt-CWONPs with banggap 3.7 eV. In addition, a modified carbon paste electrode was formed with opt-CWONPs and linear sweep voltammetry was used to analyze its electrocatalytical activity in acidic media. The findings showed that the carbon paste electrode modified by opt-CWONPs had a higher current density in the hydrogen evolution reaction (HER) than the bare carbon paste electrode. This article has subsequently revealed a revolutionary method for opt-CWONPs preparation and demonstrated its multifunctionality as photocatalyst and electrocatalyst active ingredients.

The Effect of Calcium and Halide Ions on the Gramicidin A Molecular State and Antimicrobial Activity.

Gramicidin A (gA) forms several convertible conformations in different environments. In this study, we investigated the effect of calcium halides on the molecular state and antimicrobial activity of gramicidin A. The molecular state of gramicidin A is highly affected by the concentration of calcium salt and the type of halide anion. Gramicidin A can exist in two states that can be characterized by circular dichroism (CD), mass, nuclear magnetic resonance (NMR) and fluorescence spectroscopy. In State 1, the main molecular state of gramicidin A is as a dimer, and the addition of calcium salt can convert a mixture of four species into a single species, which is possibly a left-handed parallel double helix. In State 2, the addition of calcium halides drives gramicidin A dissociation and denaturation from a structured dimer into a rapid equilibrium of structured/unstructured monomer. We found that the abilities of dissociation and denaturation were highly dependent on the type of halide anion. The dissociation ability of calcium halides may play a vital role in the antimicrobial activity, as the structured monomeric form had the highest antimicrobial activity. Herein, our study demonstrated that the molecular state was correlated with the antimicrobial activity.

Cultivation and growth dynamics of endophytic fungi in a solid culture medium based on sugar beet pulp

The production of mycelium from endophytic fungi is of interest for applications ranging from inoculants and biofertilizers for crop production to fermentations for enzyme and metabolite production. The purpose of this study was to test the capacity of a solid growth medium based on beet pulp for growing different strains of endophytes. The ergosterol content of inoculated medium was measured to estimate fungal growth. Several parameters related to the preparation of the growth medium, such as water content, calcium salts and incubation time, were evaluated. The greatest fungal biomass production was observed in a medium prepared with a 1:2 (beet pulp:water) ratio, containing calcium sulfate and carbonate. Strains belonging to different fungal species grew well in the growth medium finally selected, producing yields ranging from 50 to 500 g mycelium per kilogram of dry culture, after 22-27 days. Cultures containing up to 400 g beet pulp grew successfully, and could be scaled up. A solid culture medium based on beet pulp supported the growth of diverse taxa of fungal endophytes. Both the water and calcium salt content of the growth medium affected the efficiency of mycelium production. Considering these factors, beet pulp medium was an excellent endophyte cultivation medium because of the high yield of fungal biomass observed, together with its ease of handling and scaling-up production. © 2019 Society of Chemical Industry.

Factors Affecting Bio-cemented Typical Silt from Middle and Lower Reaches of Yellow River

Microbial-induced calcite precipitation (MICP) technique takes advantage of the metabolic process of bacteria bonding soil particles together with an environmentally-friendly and sustainable manner. In this study, the silt from reaches of Yellow River was used for bio-grouting. The effects of temperature, pH, inoculum size and revolving speed on urease activity were studied by single factor method for Sporosarcina pasteurii. Moreover, the effects of different nutrient concentrations on the stabilization for the typical silt were evaluated. Highest urease activity could be obtained under temperature of 32 °C, inoculum size of 5%, pH of 8 and speed of 180 r/min. Besides, higher concentration of calcium salt could generate more calcium carbonate effectively, and calcium carbonate content can reach to 261mg/g with uniaxial compressive strength of 1.7 MPa.

Searching for formalized connections between the consumer properties of sugar and technological process parameters of its production

Until now technological control realization in sugar production has been regulated by the requirements, the fundamental provisions of which were developed in the 80s of the XX century. Over the past period, significant changes happened in the state of sugar market, approaches to quality assurance and food safety; local technology process and control methods have undergonechanges. To reflect adequately changes in the control scheme, it is reasonable to establish a interconnection between the consumerproperties of sugar and technological process parameters of its production. This task was solved by a survey, a group of 25 experts was questioned according to Delphi method, they were proposed to describe the degree of influence of technological process parameters from 39 items on the indicators of sugar, set by industrial consumers from 8 items. Due to mathematical processing, an information model has been obtained showing the existence of such connection and allowing to determine both the indicators of the consumer properties of sugar and technological process parameters for inclusion in the control scheme: turbidity of sugar solution, content of calcium salts, saponin, pH, flock potential; at the stage of juice purification pH of the semi-finished products, alkalinity, calcium salts content, reducing substances. To confirm the results of the information model, structural and parametric modeling of technological process stages of sugar production was carried out by construction of matrices of interconnection between the grouped parameters of the technological process and the indicators of the consumer properties of sugar. The array data of observations from 25 enterprises formed for the optimal production period was statistically processed by the methods of correlation and regression analysis. For every enterprises mathematical models on 12 objects of research were received, which then were transformed into summarized research for each object. The results of structural and parametric modeling were compared with the data of the information model – in 90...95% of cases they coincided with the opinion of experts. Established formalized connections will allow to update the technological control schemes in sugar production.

24-hour urinary constituents in stone formers: a study from Kashmir

Background: Urolithiasis is a common disorder. Studies have shown that metabolic causes of urolithiasis include hypercalciuria, hypocitraturia, high or low pH of urine, hyperuricosuria, hyperoxaluria and hypomagnesuria. We intended to conduct this study with the aim to provide historical data regarding the 24-hour urinary analysis in this part of India with a distinct and different geographical and cultural background.Methods: A total of 186 patients having urinary stone disease attending the departments of Nephrology and Urology in Sher-I- Kashmir institute of medical sciences were included. 26 healthy members of hospital staff were taken as controls. Demographic and clinico-pathological characteristics of each patient were recorded in a questionnaire. Urine was collected for 24-hours from 186 patients and 26 controls. 10ml sample of this urine collection was stored at 20c0 before processing for urinary parameters.Results: The mean concentration of calcium salts, Magnesium, Oxalate and Uric acid in the 24-hour urinary analysis of urolithiasis patients is higher than that of the normal healthy controls and the relation was statistically significant. On comparing the 24-hour urinary constituents among urolithiasis patients and health controls, the concentration of phosphate was almost equal in both cases and controls while the concentration of oxalate was much higher in cases than controls.Conclusions: In present study hypercalciuria is main cause of renal calculi along with hypocitraturia, hypomagnesuria and hyperphosphaturia in our valley. Measurement of 24-hour urine constituents is still gold standard for evaluation of stone formers.

Numerical modelling of sulphate ion concentration in wastewater from a closed cooling system

The paper presents a mathematical model that allows for predicting daily changes of sulphate ion concentration in water circulating in a closed cooling system consisting of condensers and cooling towers. This is an important issue because an excessive and uncontrolled increase in the concentration of SO 4 2− in the circulating water may cause the corrosion of concrete parts of the channels and cooling towers, as well as an increase in the concentration of calcium salts, which can accelerate the process of its deposition on the exchange surfaces inside condensers. The goal of the paper is to propose an original mathematical model, which under certain simplifications poses an analytical solution to this problem. The approach enables calculating the asymptotic value of the sulphate ion concentration in circulating water, as well as the minimal volumetric flow rate of wastewater allowing the SO 4 2− ion concentration to be preserved below legal limits. The simplified analytical solution enables indicating the optimal volumetric flow rate of wastewater fitting the actual number of working power units. This is especially important because the daily amount of water released from the cooling system as wastewater usually reaches a level of several thousand m 3 and its proper management could significantly reduce system maintenance costs.

Effects of Annealing and Concentration of Calcium Salts on Thermal and Rheological Properties of Maize Starch During an Ecological Nixtamalization Process

The objective of the present work was to study the effect of annealing and concentration of Ca(OH)2 (lime) and calcium salts on the thermal and rheological properties of maize starch during an ecological nixtamalization process. Thermal and rheological properties of maize starch changed during the ecological nixtamalization process because of three main causes: the annealing phenomenon, type of calcium salt, and calcium salt concentration. In all treatments thermal properties (To, Tp, and Tf) of nixtamal starch increased owing to the annealing process, whereas the type of salt or lime increased thermal properties and decreased pasting properties in this order: CaCl2 &gt; CaSO4 &gt; Ca(OH)2 ≈ CaCO3. This behavior was because of the dissociation of each salt or lime in water. Anions (OH−) can penetrate much more easily into the starch granule and start the gelatinization process by rupturing hydrogen bonds. Additionally, amylose‐lipid complexes were formed during the nixtamalization processes, as indicated by an increasing peak at 4.5 Å in X‐ray diffraction patterns.

Niveles de erosión del esmalte dentario por efecto de agentes clareadores

Los sistemas clareamiento dental y actualmente el uso de pastas dentales con sustancias clareadoras llevó a plantear el efecto de éstas sobre la superficie del esmalte. La evidencia científica indica que puede ocasionar respuesta en la estructura química con pérdida de sales de calcio. Se midieron las concentraciones de calcio en partes por millón (ppm) en 27 coronas de dientes premolares. La erosión del esmalte fue cuantificada a través de la liberación de sales de Calcio de los especimenes sumergidos en dos tipos de pastas blanqueadoras: Crest Whitening Y Colgate Maxwhite comparadas con un gold estándar, el gel de peróxido de carbamida al 20 %; permaneciendo en contacto directo en una soiución de ellas, las concentraciones de calcio fueron medidas a las 12 h, 24 h y 7 d respectivamente. El método empleado para determinar la concentración de calcio fue la espectrofotometría de absorción atómica. Con el análisis de medias los resultados indican que la pasta Crest Whitening (contiene peróxido) presenta mayor concentración. La de menor concentración de calcio fue la pasta dental Colgate Maxwhite, el gel presenta mayor concentracion de calcio. Existen diferencias significativas entre las concentraciones halladas en las pastas testadas (Anova p&amp;lt;,05) Se concluye que la pasta dental Colgate Maxwhite libera menos sales de calcio que la pasta Gest Whitening cuyo contenido de peróxido al igual que los geles blanqueadores utilizados en el sistema de clareamiento profesional, deben ser de prescripción profesional.