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PubMed2004

Mechanism of adsorption of hepatitis B surface antigen by aluminum hydroxide adjuvant.

Hepatitis B surface antigen (HBsAg) differs from many antigens because of its associated lipid bilayer that is largely composed of phospholipids. In general, phosphate groups adsorb strongly to hydroxylated mineral surfaces by ligand exchange. The purpose of this study was to investigate the mechanism of adsorption of hepatitis B surface antigen to aluminum hydroxide adjuvant with emphasis on the role of phospholipids in this adsorption. The adsorption of HBsAg by aluminum hydroxide adjuvant exhibits a high affinity adsorption isotherm. The Langmuir equation was used to calculate the adsorptive capacity (1.7 microg/microg Al), which is the amount of HBsAg adsorbed at monolayer coverage and the adsorptive coefficient (6.0 ml/microg), which is a measure of the strength of the adsorption force. The relatively high value of the adsorptive coefficient indicates that adsorption is due to a strong attractive force. Ligand exchange between a phosphate of the antigen and a surface hydroxyl of the adjuvant provides the strongest adsorption mechanism. The adsorption capacity of HBsAg was not affected by increased ionic strength indicating that electrostatic attraction is not the predominant adsorption force. Adsorption was also not affected by the addition of ethylene glycol indicating that hydrophobic interactions were not the predominant adsorption force. The strength of the adsorption force was indicated by the resistance of HBsAg to elution when exposed to interstitial fluid. Less than 5% of the HBsAg adsorbed to aluminum hydroxide adjuvant in a model vaccine was eluted during a 12 h in vitro exposure to interstitial fluid at 37 degrees C. Less than 1% of the adsorbed HBsAg in two commercial vaccines was eluted by in vitro exposure to interstitial fluid for 48 h at 37 degrees C. Thus, it was concluded that adsorption of HBsAg by aluminum hydroxide adjuvant is predominantly due to ligand exchange between the phospholipids in HBsAg and surface hydroxyls in aluminum hydroxide adjuvant.

Adjuvants, Immunologic↗
PubMed2000

Determination of inorganic anions in environmental waters with a hydroxide-selective column.

US Environmental Protection Agency Method 300.0 specifies the use of an IonPac AS4A anion-exchange column with a carbonate-hydrogencarbonate eluent and suppressed conductivity detection for the determination of inorganic anions in environmental waters by ion chromatography. Hydroxide eluents have not typically been used for the routine analysis of common inorganic anions due to the lack of an appropriate hydroxide selective column and the difficulty in preparing contaminant free hydroxide eluents. The use of ion chromatography with a hydroxide-selective IonPac AS17 column, automated eluent generation and potassium hydroxide gradient represents a new approach to the routine determination of inorganic anions in environmental waters. This new approach, which is a modification of Method 300.0, allows equivalent method performance with improved linearity, precision, and method detection limits. The AS17 column provides superior retention of fluoride from the column void volume and improved resolution from small organic acids, such as formate and acetate, compared to the AS4A column. Quantitative recoveries were obtained for all the common inorganic anions spiked into typical environmental waters using this new approach, and the Performance Based Measurement System Tier 1 method validation quality control acceptance criteria are well within the acceptable ranges defined by Method 300.0. In addition, the EG40 eluent generator eliminates the need to manually prepare eluents, increasing the level of automation and ease-of-use of the ion chromatography system.

Anions↗
PubMed1996

Changes in pH at the dentin surface in roots obturated with calcium hydroxide pastes.

The purpose of this study was to determine the pH, after defined periods of time, in cavities prepared in the facial surface of the cervical, middle, and apical regions of roots obturated with calcium hydroxide pastes. Root canal instrumentation was performed on 40 recently extracted, single-rooted human teeth. Cavities 1.5 mm in diameter and 0.75 mm in depth were prepared in the cervical, middle, and apical regions of the facial surface of each root. Teeth were randomly divided into four groups. One group was left unobturated and served as a control. The three remaining groups were obturated with either aqueous calcium hydroxide, calcium hydroxide mixed with camphorated monochlorophenol. or Pulpdent pastes. Access cavities and apical foramina were closed with Cavit. Each tooth was stored individually in a vial containing unbuffered isotonic saline. pH at the surface was measured in the cervical, middle, and apical cavities at 0 and 3, 7, 14, 21, 28, 45, 60, 90, and 120 days. Results indicate that hydroxyl ions derived from calcium hydroxide pastes diffused through root dentin at all regions over the experimental period of 120 days. The pattern of pH change at the tooth surface was similar in all regions of the root, regardless of the type of calcium hydroxide paste used. This was a rapid rise in pH from a control value of pH 7.6, to greater than pH 9.5 by 3 days, followed by a small decline to pH 9.0 over the next 18 days, before finally rising and remaining at, or above pH 10.0 for the remainder of the experimental period. Pulpdent paste in the apical region was the only exception in this pattern, producing a pH rise nearly one full unit below the other pastes, pH 9.3. These results indicate that, for all pastes tested, a high pH is maintained at the root surface for at least 120 days.

Analysis of Variance↗
PubMed1999

Effect of calcium hydroxide and four irrigation regimens on instrumented and uninstrumented canal wall topography.

The topography of instrumented and uninstrumented canal walls exposed to calcium hydroxide and four different irrigation regimens was observed by scanning electron microscopy. After chemomechanical debridement, one tooth in each matched pair was medicated with calcium hydroxide. One week later, the teeth were irrigated and split longitudinally for evaluation. When no calcium hydroxide was used, predentin and pulpal debris covered the dentinal tubules of the uninstrumented surfaces in specimens irrigated with water or EDTA, but was absent on uninstrumented surfaces in specimens irrigated with NaOCl or NaOCl and EDTA. A typical smear layer was absent in instrumented specimens irrigated with NaOCl and EDTA, but covered the dentinal tubules of the instrumented surfaces of the EDTA irrigated specimens (partially) and the water or NaOCl irrigated specimens (completely). Calcospherites or their remnants were seen on the uninstrumented canal walls of specimens irrigated with NaOCl or NaOCl and EDTA, respectively. Calcium hydroxide use did not alter the surface topography in specimens irrigated with water, EDTA, or NaOCl, but seemed to erode the intertubular dentin in specimens irrigated with NaOCl and EDTA. All irrigants seemed to effectively remove most of the calcium hydroxide.

Calcium Hydroxide↗
PubMed1999

Formation of crystals on the surface of calcium hydroxide-containing materials in vitro.

The purpose of the present study was to examine the surface of calcium hydroxide-containing materials when treated in different in vitro conditions. Five calcium hydroxide-containing materials (Dycal, Nu-Cap, Life, Sealapex, and Apexit) and two control calcium hydroxide-free materials (Roth 811 and AH26) were tested. The materials were placed onto Teflon discs or root dentin samples; maintained in distilled water or phosphate-buffered saline, or culture medium supplemented or not supplemented with fetal calf serum; incubated at 37 degrees C in humidified atmosphere containing or not containing 5% CO2; and examined by scanning electron microscope. The results demonstrated precipitation of simple crystal units or organized crystalline structures in the calcium hydroxide-containing specimens treated in all experimental conditions, except those maintained in distilled water without 5% CO2. X-ray elemental microanalysis of the different crystalline structures showed one or two peaks corresponding to calcium or calcium and phosphorus. These data indicate that the crystals formed by reactions of calcium ions released from the calcium hydroxide-containing materials with the environmental ions might modify the material surface, especially in the presence of substrate adhesion molecules, such as fibronectin. This modification might play an important role in the regulation of cell adhesion and the initiation of new matrix synthesis.

Bismuth↗
PubMed2003

Influence of age on the behavior of dental pulp of dog teeth after capping with an adhesive system or calcium hydroxide.

This study evaluated histomorphologically the influence of chronological age of the dog on the dental pulp-healing process after capping with the All Bond 2 system or with calcium hydroxide paste. The animals were divided according to age into young and adult groups. Class 5-type cavities were prepared, and the pulp was submitted to an exposure of a diameter of 0.5 mm. The pulp of the teeth was then protected with the adhesive system or with a calcium hydroxide paste. Sixty days after treatment, the results obtained with the adhesive system in the young group were significantly better than those in the adult group. With calcium hydroxide, the results were similar for both groups. The pulp treated with calcium hydroxide exhibited a complete hard tissue bridge and a pulp without inflammatory reaction, a fact not observed when the adhesive system was used. In conclusion, the chronological age of the pulp influenced the comparative results only for the adhesive system (P = 0.1), and the total results were better with calcium hydroxide than with the All Bond 2 system (P = 0.01).

Age Factors↗
PubMed1991

Enhancement of absorption and effect of glipizide by magnesium hydroxide.

The effects of magnesium hydroxide on the pharmacokinetics and pharmacodynamics of glipizide were studied in eight healthy volunteers in a randomized crossover trial. After an overnight fast, 5 mg glipizide was given with either 150 ml water or water containing 850 mg magnesium hydroxide. Magnesium hydroxide increased the areas under the plasma glipizide concentration-time curves (AUC) from 0 to 1/2 hour and from 0 to 1 hour by 180% (p less than 0.05) and 69% (p less than 0.05), respectively. The peak plasma concentration, time to peak, total AUC, elimination half-life, and mean residence time of glipizide remained unchanged. The incremental plasma insulin area from 0 to 1/2 hour increased by 85% (p less than 0.05), and the time to maximal insulin response was reduced (p less than 0.05) during the magnesium hydroxide phase. The corresponding decremental plasma glucose area increased fourfold (p less than 0.05), and the maximal glucose decrease was 35% greater (p less than 0.05) than during the control phase. We conclude that the concomitant ingestion of magnesium hydroxide and glipizide may result in accelerated absorption of glipizide and increased early insulin and glucose responses.

Adult↗
PubMed2005

Thioester hydrolysis reactivity of zinc hydroxide complexes: investigating reactivity relevant to glyoxalase II enzymes.

A recently reported binuclear zinc hydroxide complex [(L(1)Zn(2))(mu-OH)](ClO(4))(2) (, L(1) = 2,6-bis[(bis(2-pyridylmethyl)amino)methyl]-4-methylphenolate monoanion) containing a single bridging hydroxide was examined for thioester hydrolysis reactivity. Treatment of it with hydroxyphenylthioacetic acid S-methyl ester in dry CD(3)CN results in no reaction after approximately 65 h at 45(1) degrees C. Binuclear zinc hydroxide complexes of the N-methyl-N-((6-neopentylamino-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine (L(2)) and N-methyl-N-((6-neopentylamino-2-pyridyl)methyl)-N-((2-pyridyl)ethyl)amine (L(3)) chelate ligands were prepared by treatment of each ligand with molar equivalent amounts of Zn(ClO(4))(2).6H(2)O and KOH in methanol. These complexes, [(L(2)Zn)(2)(mu-OH)(2)](ClO(4))(2) and [(L(3)Zn)(2)(mu-OH)(2)](ClO(4))(2) (), which have been structurally characterized by X-ray crystallography, behave as 1 : 1 electrolytes in acetonitrile, indicating that the binuclear cations dissociate into monomeric zinc hydroxide species in solution. Treatment of them with one equivalent of hydroxyphenylthioacetic acid S-methyl ester per zinc center in acetonitrile results in the formation of a zinc alpha-hydroxycarboxylate complex, [(L(2))Zn(O(2)CCH(OH)Ph)]ClO(4).1.5H(2)O or [(L(3))Zn(O(2)CCH(OH)Ph)]ClO(4).1.5H(2)O, and CH(3)SH. These reactions, to our knowledge, are the first reported examples of thioester hydrolysis mediated by zinc hydroxide complexes. The results of this study suggest that a terminal Zn-OH moiety may be required for hydrolysis reactivity with a thioester substrate.

Biomimetic Materials↗
PubMed2002

Effects of instrumentation, irrigation and dressing with calcium hydroxide on infection in pulpless teeth with periapical bone lesions.

AIM: The aim of this study was to evaluate the fate of microorganisms in root canals of teeth with infected pulps and periapical bone lesions with and without the use of calcium hydroxide medication. METHODOLOGY: Endodontic samples were cultured and microorganisms were counted and identified in 43 teeth before (sample 1) and after (sample 2) treatment during the first visit and before (sample 3) and after (sample 4) treatment during the second visit. In the first visit teeth were instrumented and half of the teeth were filled with a thick slurry of calcium hydroxide in sterile saline. The other teeth were obturated with gutta-percha and AH-2 6 sealer. After 4 weeks the teeth with calcium-hydroxide were accessed again and after microbiological sampling they were obturated with gutta-percha and AH-26 sealer. RESULTS: The mean total colony forming unit (CFU) counts of positive samples dropped significantly as a result of canal preparation during the first visit from 1.0 x 10(6) to 1.8 x 10(3) (between samples 1 and 2) but increased to 9.3 x 10(3) in the period between the two visits (sample 2 and 3). There was no difference in mean total CFU counts of positive samples between the end of the first (sample 2) and the end of the second visit (sample 4). The most frequently isolated species were Prevotella intermedia, Capnocytophaga spp.. Actinomyces odontolyticus. Propionibacterium acnes and Peptostreptococcus micros. CONCLUSIONS: Although a calcium hydroxide paste was placed in the prepared canals, the number of positive canals had increased in the period between visits. However, the number of microorganisms had only increased to 0.93% of the original number of CFU (sample 1). It is concluded that a calcium hydroxide and sterile saline slurry limits but does not totally prevent regrowth of endodontic bacteria.

Actinomyces↗
PubMed1999

Calcium hydroxide pastes: classification and clinical indications.

REVIEW ARTICLE: Calcium hydroxide has been used in endodontology for many years. The aim of this paper is to review the various formulations of calcium hydroxide that have been described, with specific reference to the vehicle used to carry the compound. The requirements for a vehicle are described, and ex vivo and in vivo studies reviewed. Vehicles can be classified into aqueous, viscous and oily, the clinical properties of calcium hydroxide changing depending on the vehicle. The review also describes the use of various active components that have been added to calcium hydroxide, including antimicrobial and anti-inflammatory agents. This review will help clinicians to make informed judgements about which formulations of calcium hydroxide should be used for specific endodontic procedures.

Animals↗
PubMed2003

Effectiveness of 2% chlorhexidine gel and calcium hydroxide against Enterococcus faecalis in bovine root dentine in vitro.

AIM: To evaluate the effectiveness of 2% chlorhexidine gluconate gel and calcium hydroxide (Ca(OH)2) as intracanal medicaments against Enterococcus faecalis. METHODOLOGY: One hundred and eighty dentine tubes prepared from intact freshly extracted bovine maxillary central incisors were infected in vitro for 7 days with E. faecalis. The specimens were divided into four groups, according to the intracanal medicament used, as follows: Group 1: 2% chlorhexidine gluconate gel; Group 2: calcium hydroxide in a viscous vehicle (polyethyleneglycol 400); Group 3: 2% chlorhexidine gluconate gel + calcium hydroxide and Group 4: Brain Heart Infusion (BHI) broth (control group). The medicaments were placed into the canal lumen and left there for experimental times of 1, 2, 7, 15 and 30 days. After each period, irrigation with sterile saline to remove the medicament was performed and the canals were dried with sterile paper points. Dentine chips were removed from the canals with sequential sterile round burs at low speed. The samples obtained with each bur were immediately collected in separate test tubes containing BHI broth. The tubes were incubated at 37 degrees C and daily observed for microbial growth, visualized by the medium turbidity. RESULTS: Chlorhexidine gel alone completely inhibited the growth of E. faecalis after 1, 2, 7 and 15 days. Calcium hydroxide allowed microbial growth at all experimental times. The combination of chlorhexidine and Ca(OH)2 was effective after 1 and 2 days demonstrating 100% antibacterial action; however, its antibacterial activity reduced between 7 and 15 days. CONCLUSION: Under the conditions of this study, it can be concluded that 2% chlorhexidine gel alone was more effective against E. faecalis than calcium hydroxide (P < 0.05). However, its antibacterial activity depended on how long it remained inside the root canal.

Animals↗
PubMed2002

Antimicrobial activity of extracts of calcium hydroxide points.

The purpose of this study was to evaluate in vitro the antibacterial effect of calcium hydroxide points by using a broth dilution test. Extracts of calcium hydroxide points and a calcium hydroxide paste (Calasept) were tested by using 2 facultative anaerobic bacteria, Streptococcus mutans (ATCC 27352) and Enterococcus faecalis (ATCC 29212). Saline solution was used as a control. Each tested agent was kept in contact with the bacterial species used for the experiment for 5 minutes, 1 hour, 1 day, 2 days, and 5 days. Results showed that Calasept paste was effective in killing the tested bacteria, whereas calcium hydroxide points and saline showed bacterial survival in all experimental periods. It was concluded that calcium hydroxide points extract is not an effective antimicrobial agent against the tested bacteria.

Administration, Topical↗
PubMed2002

In situ antimicrobial effectiveness of chlorhexidine and calcium hydroxide: gel and paste versus gutta-percha points.

The aim of this study was to determine the antibacterial effectiveness of either chlorhexidine or calcium hydroxide integrated in gutta-percha points compared with chlorhexidine or calcium hydroxide delivered as gel or paste, respectively. A total of 70 initially sterile roots with open accesses were carried for 1 week in the oral cavities of two volunteers. The roots were then removed, and samples were taken from the root canals for microbial analysis. The roots were medicated with calcium hydroxide paste, 5% chlorhexidine gel, or a chlorhexidine- or calcium hydroxide-containing gutta-percha point. The accesses were closed with bonding material, and the roots incubated for 1 week. After removal of the antimicrobial agents, roots were again checked for bacterial growth. One thioglycolate-soaked paper point was then introduced into each canal, and roots were incubated for 1 week more to observe bacterial regrowth. After 1 week of medication, the absolute bacterial count revealed significant differences compared with the controls. However, only the chlorhexidine-gel and the calcium hydroxide paste group showed no microbial colonization in a considerable number of samples after 1 and 2 weeks.

Anti-Infective Agents, Local↗
PubMed2003

Effectiveness of stannous fluoride and calcium hydroxide against Enterococcus faecalis.

The objective of this study was to evaluate the antimicrobial activity of stannous fluoride, calcium hydroxide, or the two in combination against Enterococcus faecalis. Fifteen Mueller-Hinton agar plates were used to conduct a disc diffusion susceptibility test. The plates were inoculated with E. faecalis. The groups tested were: (a) stannous fluoride (Stanimax); (b) calcium hydroxide; and (c) a combination of stannous fluoride and calcium hydroxide. Three filter paper discs, each soaked with one of the groups, were placed along with an antibiotic control (ampicillin) on each agar plate. The plates were then incubated at 37 degrees C. The zones of inhibition were measured at 24 and 48 h. One-way ANOVA revealed a statistically significant difference (p < 0.05) between the three groups. Stannous fluoride displayed the widest zone (1.7 mm), followed by the combination of stannous fluoride and calcium hydroxide (1.1 mm), whereas calcium hydroxide by itself displayed a minimal zone of inhibition (0.05 mm).

Analysis of Variance↗
PubMed2003

Efficacy of calcium hydroxide: chlorhexidine paste as an intracanal medication in bovine dentin.

The purpose of this study was to evaluate the antibacterial efficacy of an intracanal medication composed of calcium hydroxide with 2% chlorhexidine. Dentin from 24 bovine incisors was used. The incisors were made into standardized cylindrical segments of dentin and infected with Enterococcus faecalis. They were then treated with an intracanal paste composed of calcium hydroxide and sterile water or an intracanal paste composed of calcium hydroxide and 2% chlorhexidine for 1 week. Dentin shavings were collected, suspended in solution, and spread on brain-heart infusion agar. After incubation, colony-forming units were enumerated. The amount of bacteria per mg of dentin was determined. The calcium hydroxide paste with 2% chlorhexidine was significantly more effective at killing E. faecalis in the dentinal tubules than calcium hydroxide with water.

Animals↗
PubMed1994

Low surface tension calcium hydroxide solution is an effective antiseptic.

The antimicrobial effects of a saturated calcium hydroxide solution, and in combination with 10% and 20% detergent, were evaluated on Streptococcus faecalis, Streptococcus sanguis, Streptococcus mutans, Streptococcus salivarius, Neisseria sp., diphtheroid, Staphylococcus aureus, Lactobacillus sp., Staphylococcus epidermidis, Bacillus subtilis and Candida albicans. The saturated calcium hydroxide solution was effective against only four of the 11 microorganisms studied over a 60-min exposure time. The calcium hydroxide solutions containing detergent killed all 11 test organisms over a 30-min exposure time. This difference was statistically significant (P < 0.01). No statistically significant difference in antimicrobial action was found between the 10% and 20% detergent calcium hydroxide solutions (P > 0.01). However, the low surface tension (46.5 x 10(-3) Nm-1) and high pH (10.8) of the calcium hydroxide solution with 20% detergent establish it as the more effective solution.

Anti-Infective Agents, Local↗
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↗
PubMed1995

Short vs. long-term calcium hydroxide treatment of established inflammatory root resorption in replanted dog teeth.

This study examined, histologically, the healing of intentionally produced inflammatory root resorption of replanted teeth in beagle dogs, treated with short- or long-term placement of calcium hydroxide. Thirty beagle dog incisors were randomly divided into four groups. In group 1 (negative control), uninfected incisors were extracted, the roots were longitudinally grooved and the teeth were replanted within 2 min. In group 2 the root canals were artificially infected followed by extraction, longitudinal grooving, and replantation as in group 1. Radiographs were taken biweekly and at the first signs of inflammatory root resorption or at 4 weeks, the root canals were fully instrumented and medicated with calcium hydroxide. In group 2, the root canals were permanently obturated with gutta-percha and sealer after 1 week of calcium hydroxide. The teeth in group 3 were treated as described in group 2 but after 1 wk the calcium hydroxide dressing was repacked for the duration of the study. In group 4 (positive control) the teeth were treated as described in groups 2 and 3 but no endodontic treatment was performed. Twelve weeks after the initiation of the endodontic treatment, sacrifice and histological preparation were carried out. In group 1, complete cemental repair was seen in all teeth. In group 2, five of ten teeth showed complete cemental repair whereas in group 3 complete cemental repair was seen in nine of ten teeth. None of the teeth in group 4 showed cemental repair. It was concluded that long-term may be more effective than short-term calcium hydroxide treatment of established inflammatory root resorption.

Animals↗