PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Calcium Compounds”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources
PubMed2005

21st century endodontics. Part 4.

The prime objective of this series of papers has been to focus the attention of the reader on the biological principles of root canal treatment. Accurate diagnosis, knowledge of the root canal morphology and the principles of modern preparation techniques are all essential so that appropriate chemical cleaning and disinfection of the entire root canal system may be accomplished. This paper will consider two further aspects of root canal treatment. First, whether the root canal system should be prepared and obturated in a single visit, and, if not, which intervisit medication is appropriate. Secondly, the modern concepts and techniques for obturation of the root canal system.

Aluminum Compounds↗
PubMedDate not supplied

Modern endodontic therapy for an incompletely developed tooth.

An important goal of modern dentistry is to preserve a functional, esthetic, and pain-free dentition. If irreversible pulp pathology occurs in an immature permanent tooth from traumatic or carious exposure, normal apical maturation may be interrupted. Conventional endodontic obturation techniques, if necessary, will be difficult and may not be adequate in such a tooth. The endodontic techniques of apexogenesis and apexification have been successful in achieving adequate root development and apical construction. These conventional techniques and materials are reviewed along with a promising material called mineral trioxide aggregate.

Aluminum Compounds↗
PubMedDate not supplied

Intracoronal sealing comparison of mineral trioxide aggregate and glass ionomer.

OBJECTIVE: The purpose of this study was to determine the effectiveness of mineral trioxide aggregate and glass ionomer when placed coronally as double-sealing materials over gutta percha. METHOD AND MATERIALS: Seventy extracted anterior teeth were cleaned, shaped, and obturated with gutta percha and Sealapex. After removing 4 mm of coronal gutta percha, the teeth were randomly divided into 3 groups. In two experimental groups of 30 teeth each, 4 mm of either mineral trioxide aggregate or glass ionomer was placed in the chamber over gutta percha. A positive control group of 5 teeth received no barrier. A negative control group of 5 teeth was covered completely with sticky wax. All teeth, except the negative controls, were covered with 2 layers of sticky wax except for the access openings. Teeth were immersed in Pelikan ink for 48 hours, and then were decalcified, dehydrated, and cleared. Leakage into the canals was measured in millimeters and statistically analyzed between the two experimental groups using the Mann-Whitney test. RESULTS: Results showed that the glass ionomer group leaked significantly more than the mineral trioxide aggregate group (P < .001). CONCLUSION: It was concluded from this study that mineral trioxide aggregate may be preferred over glass ionomer as a seal intracoronally following root canal treatment to prevent coronal microleakage.

Aluminum Compounds↗
PubMed2002

The calcium-binding properties of pamidronate, a bone-resorption inhibitor.

The title compound, calcium bis(3-ammonio-1-hydroxypropylidene-1,1-bisphosphonate) dihydrate, Ca(2+).2C(3)H(10)NO(7)P(2)(-).2H(2)O, consists of calcium octahedra arranged in columns along the c axis and coordinated by hydrogen-bonded molecular anions. The Ca(2+) cation lies on a twofold axis. Pamidronate adopts a twisted conformation of the hydroxyalkylamine backbone that enables the formation of an intramolecular N-H...O hydrogen bond. The molecular anion is chelating monodentate as well as bidentate, with an O...O bite distance of 3.0647 (15) A.

Bone Resorption↗
PubMed1993

[Struvite stone dietetics: 1. Effect of different feed rations on the urine pH value of cats].

In this investigation the base excess of cat foods (sum of alkalogenic compounds calcium, magnesium, sodium and potassium minus sum of acidifying compounds phosphorus, chloride, methionine and cysteine; base excess in mmol/kg dry matter = Ca*2+Mg*2+Na+K-(met(-)+cys)*2-P*2-Cl) as a method of predicting the influence of food on the urinary pH was tested. The base excess and the effect on urinary pH (feeding experiment with 4 to 6 adult cats per trial) was determined in 10 commercial cat foods (3 moist, 3 dry type foods, 4 struvite diets) as well as the influence of several additives (CaCl2, CaCO3, Ca-lactate, CaHPO4, phosphoric acid in 2 doses, NH4Cl, ascorbic acid). After the intake of commercial cat foods the mean urine pH ranged between 6.58 and 7.89, after the intake of struvite diets it ranged between 6.36 and 7.57. The addition of Ca-carbonate or -lactate led to a significant increase of urine pH, Ca-phosphate and ascorbic acid had no effect, while Ca-Chloride, phosphoric acid and ammonium chloride led to a decrease. There was a highly significant correlation between the base excess in the food (x; mmol/kg dry matter) and the mean urine pH (y; y = 6.72 + 0.0021 x; r = 0.96**).

Animal Feed↗
PubMed1970

Effects of calcium on the contraction of the hypodynamic frog heart.

1. The time course of build-up or decline of twitch tension in response to enhancement or reduction of the external calcium concentration was determined in frog heart ventricles, in the hypodynamic state as well as under non-hypodynamic conditions.2. The tension build-up induced by high calcium was greatly slowed when the heart passed into the hypodynamic state, whereas the decline in low calcium was little altered by this condition.3. The tension decline consisted of two approximately exponential phases, an initial rapid phase (t((1/2)) between 3 and 10 sec) and a later slow phase (t((1/2)) between 50 and 180 sec).4. A similar composite time course of tension build-up only occurred under certain conditions: (a) in ventricles in which the hypodynamic state had not developed; (b) after a conditioning period of exposure to enhanced calcium or reduced sodium concentrations.5. The results are explained on the assumption that contraction is brought about by the co-operative action inside heart cells of two calcium compounds whose concentrations change at different rates after variation of the external calcium concentration.6. Formal relationships describing the dependence of twitch tension on the concentration of these two hypothetical compounds are obtained.A tentative explanation of the development of the hypodynamic state is also proposed.

Animals↗
PubMed1993

Multiple calcium-dependent processes related to secretion in bovine chromaffin cells.

We have used the caged calcium compound DM-nitrophen to investigate the kinetics of calcium-dependent secretion in bovine chromaffin cells. Perfusion with partially calcium-loaded nitrophen often caused a loading transient--slow secretion for up to 1 min due to displacement of Ca2+ by cytoplasmic Mg2+. Flash photolysis elicited 100 microM [Ca2+]i steps that evoked intense secretion, lasting a few seconds. In cells experiencing a loading transient, [Ca2+]i steps evoked an especially fast secretion. A persistent, slow secretion often followed these fast phases. Distinct kinetic components may reflect secretion from pools that are differentially capable of release. Both secretion and movement of vesicles between pools appear to be [Ca2+]i sensitive. Later [Ca2+]i steps sometimes evoked a rapid capacitance decrease, indicating a fast, [Ca2+]i-dependent phase of endocytosis.

Acetates↗
PubMedDate not supplied

Isometric dynamic response of mammalian heart muscle due to step changes in the calcium concentration of the perfusing medium.

The isometric tension transient response of isolated kitten papillary muscle was found to exhibit direction-dependent dynamics when subjected to step changes in the calcium concentration of the bathing medium. The tension transient curves could be resolved into a minimum of two to three exponential components, which could be considered to indicate different calcium compounds or compartments within the muscle. However, a model relating calcium diffusion across the muscle to the dose-response curve indicates that the exponential components of the tension transient curves are due to the properties of calcium diffusion through the extracellular space, and that the direction-dependent dynamics are caused by the nonlinearity of the dose-response curve.

Animals↗
PubMed2002

Synthesis and monolayer characterization of phosphorylated amino acid analogs.

The synthesis of a series of thiols containing phosphorylated and non-phosphorylated serine, threonine, and tyrosine amino acid residues is described. The synthesized molecules, based on 3-mercaptopropionic acid, were assembled onto gold and subsequently characterized using infrared reflection-absorption spectroscopy, ellipsometry, X-ray photoelectron spectroscopy, and contact angle goniometry. The ellipsometric analysis indicates that they form densely packed and well-oriented monolayers on gold, with thicknesses that are in good agreement with estimated values from space-filling models. The bulky and space-demanding phosphorylated threonine analog was, however, found to be an exception. The increase in layer thickness when adding a phosphate group to the threonine is only 35% of that observed for the two other analogs. A detailed infrared examination of the influence of cation coordination to the phosphorylated serine analog using calcium and magnesium reveals structural similarities to those of the inorganic phosphate compound calcium hydroxy apatite. We furthermore discuss the application of these monolayers as soft templates for biomineralization.

Amino Acids↗
PubMed1970

Interaction between heart rate and calcium concentration in the control of contractile strength of the frog heart.

1. The changes in twitch tension during the ascending and descending staircase of the frog heart have been examined under various experimental conditions including the hypodynamic and prehypodynamic state.2. The descending staircase resembles the tension change after reduction of external calcium concentration in showing two consecutive phases, an initial rapid and later slow phase of tension decline.3. The time course of the ascending staircase depends on the condition of the heart; it is slow after, and rapid before, development of the hypodynamic state. It is also rapid when elicited after conditioning periods of increased heart rate.4. The tension transients in response to brief concentration steps of external calcium concentration were examined at various levels of heart rate. The results indicate that at high heart rates the sensitivity of heart cells to external calcium is increased.5. The results are interpreted along the lines of a previous hypothesis relating tension development to the cooperative action of two intracellular calcium compounds. The additional assumption is made that an intermediary exists which facilitates calcium movements in heart cells to an extent depending on the level of heart rate.

Animals↗
PubMed1993

[The effect of bone-seeking metal salts on the biodistribution of tumor-seeking heavy metal complexes].

This work attempted to overcome the problem of unwanted bone radioactivity after injection of tumour-affine heavy-metal compounds (prototype 169Yb-citrate) by pre-application of stable yttrium- and calcium-compounds into tumour-bearing mice in doses of 1 mg metal/kg body weight. The pre-application of stable yttrium and calcium resulted in a smaller bone radioactivity. The most favourable results were achieved by injecting the metal salts simultaneously at or within 5 h before the 169Yb-citrate. On the other hand a strong radioactivity increase in the RES (liver and spleen) by a factor of 2 to 4 was observed after yttrium-preapplication.

Animals↗
PubMed1988

Inactivation and block of calcium channels by photo-released Ca2+ in dorsal root ganglion neurons.

Calcium channels are inactivated by voltage and intracellular calcium. To study the kinetics and the mechanism of calcium-induced inactivation of calcium channels, a "caged" calcium compound, dimethoxy-nitrophen was used to photo-release about 50 microM calcium ion within 0.2 millisecond in dorsal root ganglion neurons. When divalent cations were the charge carriers, intracellular photo-release of calcium inactivated the calcium channel with an invariant rate [time constant (tau) approximately equal to 7 milliseconds]. When the monovalent cation sodium was the charge carrier, photorelease of calcium inside or outside of the cell blocked the channel rapidly (tau approximately equal to 0.4 millisecond), but the block was greater from the external side. Thus the kinetics of calcium-induced calcium channel inactivation depends on the valency of the permeant cation. The data imply that calcium channels exist in either of two conformational states, the calcium- and sodium-permeant forms, or, alternatively, calcium-induced inactivation occurs at a site closely associated with the internal permeating site.

Animals↗
PubMed1995

Crystalline composition of equine urinary sabulous deposits.

The composition and crystal morphology of 141 equine sabulous deposits were determined by infrared spectroscopy (IR), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The IR analysis revealed that all investigated deposits contained calcium carbonates (calcite, CaCO3, and/or vaterite, CaCO3) as major constituents; 42 samples were composed of calcite and vaterite, 33 of calcite, 18 of calcite/vaterite and calcium oxalate, and 17 of vaterite. The remaining specimens contained calcite/vaterite and other compounds (calcium phosphates, sulphate and/or oxalates and/or silica). The examination of 44 selected samples by means of SEM/EDX, revealed the characteristic morphology and elemental composition of the constituents of the sabulous deposits. Calcite crystals showed a typical spherical shape, as well as other less common rhombohedral habit. Vaterite displayed a "flower" or "star" appearance and also a "mulberry" shape. Less frequent was a spherular habit for vaterite resembling that of calcite. Elemental analysis of both calcite and vaterite crystals showed, besides calcium, varying proportions of magnesium and potassium. It is concluded that calcite and vaterite were mainly present in a substituted form. Calcium oxalate dihydrate crystals showed their characteristic bipyramidal morphology. Calcium oxalate monohydrate crystals, which were less frequent, exhibited "dumbbell" or "hour-glass" shape.

Animals↗