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At least 19 recordsLinked to original sources
PubMed2006

Effects of calcium hydroxide and calcium chloride addition to bentonite in iron ore pelletization.

Pyrite ash is created as waste from the roasting of pyrite ores during the production of sulphuric acid. These processes generate great amounts of pyrite ash waste that is generally land filled. This creates serious environmental pollution due to the release of acids and toxic substances. Pyrite ash waste can be utilized in the iron production industry as a blast furnace feed to process this waste and prevent environmental pollution. The essential parameters affecting the pelletization process of pyrite ash were studied using bentonite as a binder. Experiments were then carried out using bentonite and a mixture of bentonite with calcium hydroxide and calcium chloride in order to make the bentonite more effective. The metallurgical properties of pyrite ash, bentonite, calcium hydroxide, calcium chloride, a mixture of these and sintered pellets were studied using X-ray analysis. The crushing strength tests were carried out to investigate the strength of pyrite ash waste pellets. The results of these analyses showed that pyrite ash can be agglomerated to pellets and used in the iron production industry as a blast furnace feed. The crushing strength of the pellets containing calcium hydroxide and calcium chloride in addition to bentonite was better than the strength of pellets prepared using only bentonite binder.

Bentonite↗
PubMed1993

Bio-microscopical observation of dystrophic calcification induced by calcium hydroxide.

Calcium hydroxide paste was introduced into a rabbit ear chamber, and the effect of calcium hydroxide on the vascular tissue was observed under a bio-microscope continuously up to 14 weeks. Many precipitates were observed at the border of living tissue, after the dissolution of microvessels around the paste. They increased both in size and number to combine like a river bank in the first 48 h. After 1 week, microcirculation recovered, and newly-formed capillaries approached the precipitate-bank, the edge of which became smoother as weeks went by. The bank was stable and compatible to microvessels during the observation period. By SEM observation, the width of the bank was from 200 to 400 microns, and the tissue-side of the bank appeared like amorphous lamellae, while the inner-side showed particle-like appearance. EDX examination revealed high peaks of Ca and P similar to calcium phosphate at the tissue-side of the bank, but only Ca peak at the inner-side. The precipitates seemed to have the potential to induce dystrophic calcification by absorbing Ca and P from the tissue.

Animals↗
PubMed1990

Apical closure of mature molar roots with the use of calcium hydroxide.

Calcium hydroxide may induce apical root closure in affected mature teeth as well as in immature teeth. Once an apical hard tissue barrier is formed, a permanent root canal filling can be safely condensed. Two cases are described in which calcium hydroxide induced apical root closure in mature molar teeth where the apical constriction was lost because of chronic inflammatory process.

Adult↗
PubMed1990

Review of calcium hydroxide.

Calcium hydroxide is a material which has been used for a variety of purposes since its introduction into dentistry in the early part of the twentieth century. In its pure form, the substance has a high pH, and its dental use relates chiefly to its ability to stimulate mineralization, and also to its antibacterial properties. A range of products has been formulated with different therapeutic actions, the effects of which are partially dependent upon the tissue to which they are applied. The material is reviewed under the following general headings: biochemical actions; dental formulation; uses.

Calcium Hydroxide↗
PubMed1998

Simultaneous sulfur dioxide and nitrogen dioxide removal by calcium hydroxide and calcium silicate solids.

At conditions typical of a bag filter exposed to a coal-fired flue gas that has been adiabatically cooled with water, calcium hydroxide and calcium silicate solids were exposed to a dilute, humidified gas stream of nitrogen dioxide (NO2) and sulfur dioxide (SO2) in a packed-bed reactor. A prior study found that NO2 reacted readily with surface water of alkaline and non-alkaline solids to produce nitrate, nitrite, and nitric oxide (NO). With SO2 present in the gas stream, NO2 also reacted with S(IV), a product of SO2 removal, on the exterior of an alkaline solid. The oxidation of S(IV) to S(VI) by oxygen reduced the availability of S(IV) and lowered removal of NO2. Subsequent acidification of the sorbent by the removal of NO2 and SO2 facilitated the production of NO. However, the conversion of nitrous acid to sulfur-nitrogen compounds reduced NO production and enhanced SO2 removal. A reactor model based on empirical and semi-empirical rate expressions predicted rates of SO2 removal, NO2 removal, and NO production by calcium silicate solids. Rate expressions from the reactor model were inserted into a second program, which predicted the removal of SO2 and NOx by a continuous process, such as the collection of alkaline solids in a baghouse. The continuous process model, depending upon inlet conditions, predicted 30-40% removal for NOx and 50-90% removal for SO2. These results are relevant to dry scrubbing technology for combined SO2 and NOx removal that first oxidizes NO to NO2 by the addition of methanol into the flue duct.

Air Pollutants, Occupational↗
PubMed1998

Sealing ability of composite resin placed over calcium hydroxide and calcium sulphate plugs in the repair of furcation perforations in mandibular molars: a study in vitro.

The purpose of this study was to evaluate in vitro the sealing ability of various materials in the repair of furcation perforations in mandibular molars by measuring coronal microleakage with Indian ink. Ninety extracted mandibular molars were embedded individually into a plaster of Paris block, with the roots surrounded by a simulated periodontal ligament of silicone. Subsequently, a standard coronal access opening was prepared, the root canal orifices were located and a perforation was made with a size 012 round bur in a water-cooled high-speed handpiece directly into the centre of the floor of the pulp chamber. The perforations were repaired with amalgam, composite resin, calcium sulphate under composite resin and calcium hydroxide under composite resin. The teeth were coated with two layers of nail polish, leaving the access opening area uncovered, and immersed in Indian ink for 4 days at 37 degrees C. The teeth were sectioned longitudinally and dye penetration measured from the coronal level of the repair material to the apical end of the perforation. All experimental groups revealed dye penetration in varying degrees, but there was no significant difference amongst them (Kruskal-Wallis test P < 0.05). Calcium sulphate and calcium hydroxide prevented overextrusion of composite resin when used under this repair material.

Analysis of Variance↗
PubMed1990

[Comparison of calcium hydroxide and calcium oxide for intracanal medication].

The authors show how the proper use of the root canal medication based on calcium oxide is determinant for causing a perfect asepsis of the root canal in the 58 teeth, taken in consideration, the calcium oxide is more efficacious than the calcium hydroxide not only because it produces a remarkable decrease of the bacterial quantity, but also because the recovery time of the lesion before the filling up of the root canal, is less than half time in comparison with that one got by means of the calcium hydroxide.

Adolescent↗
PubMed2002

An in vitro comparison of pH changes in root dentine following canal dressing with calcium hydroxide points and a conventional calcium hydroxide paste.

AIM: This study aimed to measure and compare pH changes at apical and cervical sites on the external root surface of extracted teeth dressed with calcium hydroxide in two different formulations. METHODOLOGY: Root canals of 45 single-rooted extracted human teeth were accessed and shaped using a step-down technique with rotary instrumentation. Standard cavities were prepared on the external root surface at specific apical and cervical sites. The teeth were randomly allocated to three groups. Teeth in group A were dressed with calcium hydroxide points, those in group B were dressed with an aqueous calcium hydroxide paste and teeth in group C were left unfilled. Following storage in humid conditions, the pH of the dentine at apical and cervical sites was measured at baseline and then at 24 h, 72 h, 1 week, 10 days, 2 weeks and 3 weeks. RESULTS: The pH of the root dentine at both apical and cervical sites was significantly greater (P < 0.001) in teeth dressed with aqueous calcium hydroxide paste compared with those dressed with calcium hydroxide points, when averaged out across all time periods. For all groups, there was a significant difference between the mean apical and cervical pH values for each tooth with lower values for the apical sites (P < 0.001). CONCLUSION: The results of this study indicate that an aqueous calcium hydroxide paste was more effective than calcium hydroxide points at raising the pH on the external root surface of extracted teeth.

Analysis of Variance↗
PubMed1989

The alkalizing properties of calcium hydroxide compounds.

Calcium hydroxide compounds are available in various forms, such as in aqueous suspensions or as cements, liners, pastes or filled resins. When such compounds are exposed to water, the calcium hydroxide dissociates and the pH value shifts to the basic. In this study the compounds Pulpdent, Dycal, Hydroxyline, Gangraena Merz and Prisma VLC-Dycal were subjected to analysis, including quantitative measurement of the amount and the chronological course of ion release following exposure to water, qualitative analysis of the alkalizing effects at the dentin surface and examination of antimicrobial properties. The results showed that calcium hydroxide compounds differed greatly. The strongest degree of ion release, combined with definite antimicrobial properties, was found for the aqueous calcium hydroxide suspension (Pulpdent). The cement (Dycal) demonstrated significantly weaker activity. The liner and the paste (Hydroxyline and Gangraena Merz), as well as the calcium hydroxide filled resin (Prisma VLC-Dycal), were largely lacking in both ion release and antimicrobial properties under the experimental conditions.

Calcium Hydroxide↗
PubMed2004

Apatite-forming ability of alginate fibers treated with calcium hydroxide solution.

Calcium alginate fibers were prepared by extruding an aqueous sodium alginate solution into an aqueous calcium chloride solution. The fibers were treated with a saturated aqueous calcium hydroxide solution for various periods and their apatite-forming ability was examined in a simulated body fluid (SBF). The calcium alginate fibers were treated with the aqueous calcium hydroxide solution for periods longer than five days formed apatite on their surfaces in SBF, and their apatite-forming ability improved with increasing calcium hydroxide treatment time. The amount of calcium ions released from the fibers also increased with increasing calcium hydroxide treatment time, resulting in acceleration of nucleation and growth of apatite on the fiber surfaces. The resultant apatite-alginate fiber composite is expected to be useful as a flexible bioactive bone-repairing material.

Alginates↗
PubMed1996

Effect of calcium hydroxide and combinations of Ledermix and calcium hydroxide on inflamed pulp in dog teeth.

The effects of Ledermix+calcium hydroxide (Ca(OH)2) or Ca(OH)2 alone on inflamed pulp tissues of dogs were studied. Fifty-nine upper incisor teeth of 10 dogs were used. Class V cavities were prepared and filled with amalgam after placement of decayed dentin particles. After 7 days, the decayed dentin and alloy were removed, and the pulps of the teeth were exposed. Ledermix and Ca(OH)2 mixtures or Ca(OH)2 alone were applied to the cavities. At the end of 7, 30, and 90 days, the teeth were extracted and examined histopathologically. Inflammation was found to be more prevalent in the 7- and 30-day groups that were treated with the Ledermix+Ca(OH)2 combination, whereas fibrosis and necrosis were nearly similar in both groups. In the 90-day groups, no inflammation was seen. No difference between the two 90-day groups with regard to reparative dentin was found.

Animals↗
PubMed1998

Dentin penetration of 2 calcium hydroxide combinations.

OBJECTIVE: Calcium hydroxide is a common intracanal medicament. The powder can be mixed with different vehicles for placement in canals. This study examines pH changes in dentin with 2 different calcium hydroxide preparations. STUDY DESIGN: The combinations used were calcium hydroxide + distilled water and calcium hydroxide + glycerin (1/7 distilled water). One hundred forty extracted teeth with single canals were used. pH changes in dentin after the intracanal placement of these combinations were evaluated at different dentin thicknesses by measuring the pH of the external environment. RESULTS: For all dentin thicknesses and at all time periods, the calcium hydroxide + glycerin combination showed significantly higher pH values than the calcium hydroxide + distilled water combination. CONCLUSIONS: Considering pH elevations, we propose the use of a calcium hydroxide + glycerin combination.

Calcium Hydroxide↗
PubMed2006

Removal efficiency of calcium hydroxide intracanal medicament with two calcium chelators: volumetric analysis using spiral CT, an in vitro study.

The vehicles used to carry calcium hydroxide intracanal medicament are many and may affect the retrieval. Access cavities were prepared in 40 single rooted anterior teeth, cleaning and shaping was done and filled with either Metapex or pure calcium hydroxide powder in distilled water. After 7 days the calcium hydroxide was retrieved using either 17% EDTA or 10% citric acid in combination with ultrasonic agitation. Volume analysis was done using spiral computed tomography. The percentage difference was calculated and statistically analyzed using Kruskal-Wallis and Mann-Whitney U test. 10% citric acid showed better removal efficiency than 17% EDTA for Metapex (p = 0.003). The 17% EDTA showed excellent removal efficiency of powder form of calcium hydroxide in distilled water than Metapex (p < 0.001). Ten percent citric acid removed powder form of calcium hydroxide in distilled water better than Metapex (p = 0.05).

Calcium Hydroxide↗
PubMed2007

An in vitro study of the pH of three calcium hydroxide dressing materials.

Calcium hydroxide is widely used as a root canal dressing material because of its favorable alkalinizing effect. It has been suggested that the action comes from diffusion of hydroxyl ions through the apical foramen. The purpose of this in vitro study was to test the pH changes that occurred over a period of 30 days using a mixture of calcium hydroxide and distilled water and two commercial calcium hydroxide products in a simulated periapical environment. The materials were inserted in glass tubes closed at one end, which were placed in individual vials containing distilled water at a pH 7.4. Unfilled glass tubes were used as controls. Alkalinity changes of the medium were measured at 1 and 24 h and 15 and 30 days. The alkalinizing properties of all materials showed a rapid increase at 1 and 24 h followed by a continuous but more gradual increase from 15 to 30 days. The control tubes did not cause a change in pH of the medium, which remained at pH 7.4. At the end of the observation period, the alkalinizing properties of Calasept and Ultracal XS were significantly higher (P < 0.05) than the calcium hydroxide/distilled water paste.

Analysis of Variance↗
PubMed1995

Effect of four vehicles on the pH of calcium hydroxide and the release of calcium ion.

Nonsetting calcium hydroxide pastes are commonly used in endodontic practice. The desired therapeutic effect of such a paste is in part dependent on the dissociation of calcium hydroxide into hydroxy ion and calcium ion. This in turn is influenced by the vehicle used to make the paste. This investigation attempts to quantitatively estimate the release of hydroxyl ion and calcium ion from pastes made by using distilled water, normal saline solution, camphorated monochlorophenol and also an experimental vehicle, propylene glycol. The results of this study indicate that propylene glycol induces the most favorable release characteristics of the two ionic species.

Calcium↗
PubMed2005

Calcium hydroxide: a review.

Calcium hydroxide is a multipurpose agent, and there have been an increasing number of indications for its use. Some of its indications include direct and indirect pulp capping, apexogenesis, apexification, treatment of; root resorption, iatrogenic root perforations, root fractures, replanted teeth and interappointment intracanal dressing. The purpose of this paper is to review the properties and various indications for the use of calcium hydroxide.

Anti-Bacterial Agents↗