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PubMed1993

pH changes in root dentin over a 4-week period following root canal dressing with calcium hydroxide.

Root canals in extracted human teeth were cleaned and shaped and subsequently dressed with a calcium hydroxide root canal dressing. pH Changes in the root dentin were measured over a 4-wk period with microelectrodes in small cavities at apical and cervical levels in inner and outer dentin. The pH increased within hours in the inner dentin, peaking at pH 10.8 cervically and 9.7 apically. However, 1 to 7 days elapsed before the pH began to rise in the outer root dentin, reaching peak levels of pH 9.3 cervically and 9.0 apically after 2 to 3 wk. The results show that hydroxyl ions derived from a calcium hydroxide dressing do diffuse through root dentin. They diffuse faster and reach higher levels cervically than apically. Surface pH measurements showed that hydroxyl ions do not diffuse in more than a minor way through the intact root surface.

Adult↗
PubMed1993

Histological evaluation of therapy using a calcium hydroxide dressing for teeth with incompletely formed apices and periapical lesions.

Periapical tissue response was evaluated histologically in teeth of 6-month-old dogs with incomplete root formation and periapical lesions in order to compare the effects of two calcium hydroxide-containing pastes prepared with different vehicles on induced root apex formation and repair of the periapical region. A group of teeth with no root canal dressing was used as control. After induction of the periapical lesion, the root canals were instrumented and filled with one of the two pastes (Calen and Calasept), which were renewed monthly for 90 days. At the end of the follow-up period (3 months), the animals were killed. Block sections from the actual areas were dissected free and prepared for histopathological analysis. Both calcium hydroxide pastes helped induce apical sealing and repair of the region, but the Calen paste yielded better results than Calasept. The induced mineralized tissue was predominantly of the cementoid type after the use of both pastes, but the inflammatory infiltrate was significantly less intense with the use of the Calen paste. In the control group, the absence of a root canal dressing impaired the process of periapical repair and yielded no apical root closure in any of the cases analyzed.

Animals↗
PubMed1991

Long-term sealing ability of a calcium hydroxide sealer.

A calcium hydroxide sealer (Sealapex) was compared with a zinc oxide and eugenol sealer (Tubli-Seal) over a 32-wk interval to examine solubility in an in vitro simulation. After obturation with gutta-percha and the appropriate sealer, specimens were immediately immersed in a saline solution to challenge the sealers' solubility. The solutions were changed weekly to allow for a continued dissolution of the sealers and to prevent establishment of an equilibrium between the solution and the sealers. The 2- and 32-wk specimens were removed from the solutions, immersed in India ink for 3 days, and then made transparent by a clearing process. Microscopic examination was used to determine the linear penetration of the ink for each tooth. Results revealed that Sealapex statistically had no greater dissolution (based upon linear penetration) than Tubli-Seal at both 2 and 32 wk. It is suggested that Sealapex has a sealing ability comparable to Tubli-Seal and can withstand long-term exposure to tissue fluids without significant leakage. This may allow time for the biochemical action of the calcium hydroxide to stimulate physiological calcification of the apical foramen.

Calcium Hydroxide↗
PubMed1990

Biological evaluation of collagen gels containing calcium hydroxide and hydroxyapatite.

Dentinal chips and different biocompatible materials have been used in the past as apical plugs to enhance healing and simplify obturation. The purpose of this study was to evaluate bone reactions to implants of hydroxyapatite, collagen, and calcium hydroxide, alone or in different combinations. The materials were implanted bilaterally in the mandibles of 36 guinea pigs and the reactions were compared histologically over a period of 16 wk. No major inflammatory reactions were observed in any of the implant combinations. Hydroxyapatite was not resorbed over the examination periods, but calcium hydroxide and collagen implants were partially or totally resorbed and replaced by bony tissue. The results indicate that cylinders which may be useful as apical plugs can be performed and will heal with minimal biological reactions.

Animals↗
PubMed1989

Effectiveness of ultrasonics and calcium hydroxide for the debridement of human mandibular molars.

This study evaluated the ability of ultrasonics and calcium hydroxide to remove pulp tissue debris from the mesial root canals of human mandibular molars. All teeth were instrumented using a standard filing technique and irrigated with an equal volume of 2.6% sodium hypochlorite before the application of the experimental debridement methods. Debridement comparisons were made of both instrumented and uninstrumented controls at the 3-mm and 1-mm levels of the canals and isthmuses. Statistical analysis showed no differences among the experimental groups or the instrumented controls in the canals at either level or isthmuses at the 3-mm level. In the isthmuses at the 1-mm level, no differences were found among the experimental groups, but they were all significantly cleaner than the instrumented controls. These results indicate that calcium hydroxide and ultrasonics are equally effective in debriding the root canal system, and that both are significantly better than standard instrumentation alone in the isthmuses at the 1-mm level.

Calcium Hydroxide↗
PubMed1996

Disinfection by calcium hydroxide pastes of dentinal tubules infected with two obligate and one facultative anaerobic bacteria.

Bovine dentine cylinders were experimentally infected with Actinomyces israelii, Fusobacterium nucleatum, or Enterococcus faecalis. The latter is a facultative anaerobic bacteria and the others are obligate anaerobes commonly found in endodontic infections. The infected specimens were exposed to pastes of calcium hydroxide mixed with saline solution or camphorated paramonochlorophenol for periods of 1 h, 1 day, and 1 week. The viability of bacteria after these exposure times was evaluated by specimen incubation in culture medium to compare the effectiveness of the pastes in disinfecting dentinal tubules. The calcium hydroxide/camphorated paramonochlorophenol paste effectively killed bacteria in the tubules after a 1-h period of exposure, except for E. faecalis that required one day of exposure. In contrast, the calcium hydroxide/saline paste was ineffective against E. faecalis and F. nucleatum even after 1 week of exposure. The results showed that camphorated paramonochlorophenol increased the antibacterial effects of calcium hydroxide.

Actinomyces↗
PubMed1999

Growth inhibition of Streptococcus anginosus (milleri) by three calcium hydroxide sealers and one zinc oxide-eugenol sealer.

The inhibition of growth of Streptococcus anginosus (milleri) by three calcium hydroxide sealers--calciobiotic root canal sealer (Hygienic Corporation, Akron, OH), Sealapex (Kerr Division, Sybron Corporation, Romulus, MI), and Apexit (Vivadent, USA, Amherst, NY)--was compared with a zinc oxide-eugenol sealer: Roth (Roth International, Chicago, IL). Sixteen brain heart infusion agar plates were inoculated with S. anginosus. Each plate was divided into five separate areas. In each area, a 0.1 ml droplet of a given sealer was placed such that each plate had five areas with the same sealer. There were four plates (for each of the four sealers) for a total of 20 observation areas to evaluate each sealer. The plates were incubated at 37 degrees C in a 5% CO2 atmosphere. After varying periods of incubation, the zones of inhibition of bacterial growth were observed and measured. Roth sealer had a statistically significant larger mean zone of inhibition than the calcium hydroxide sealers. However, all of the sealers exhibited clinically relevant antimicrobial activity. It is likely that the eugenol in the Roth sealer is responsible for its greater antimicrobial activity.

Analysis of Variance↗
PubMed2001

Spontaneous nucleophilic addition of hydroxide ions to the meso-position of high-valent antimony-oxo porphyrin complexes.

Bimolecular reactions of the antimony(V) porphyrin complexes SbO(tpp)OH, 1 and SbO(oep)OH, 2 with tetra-n-butylammonium hydroxide were investigated at 298 K in acetonitrile solution (tpp, dianion of 5,10,15,20-tetraphenylporphyrin and oep, dianion of 2,3,7,8,12,13,17,18-octaethylporphyrin). Spontaneous nucleophilic addition of hydroxide ions to the non-oxidized porphyrin macrocycle leads to novel hydroxyphlorin derivatives, which contain a saturated meso-carbon bridge. While this process is a reversible equilibrium reaction for the TPP derivative, the OEP complex undergoes subsequent demetallation and oxidative ring cleavage in the presence of dioxygen. Possible implications for the competitive inhibition of heme-oxygenase by high-valent metalloporphyrin therapeutics are discussed.

Animals↗
PubMed1999

Haemophilus influenzae type b conjugate vaccine stability: catalytic depolymerization of PRP in the presence of aluminum hydroxide.

The structural stability of the Haemophilus influenzae type b (Hib) capsular polysaccharide, polyribosylribitolphosphate (PRP) in an aluminum hydroxide adsorbed, polysaccharide-protein conjugate vaccine was monitored using modifications of an HPLC assay developed by Tsai et al. [Tsai C-M, Gu X-X, Byrd RA. Quantification of polysaccharide in Haemophilus influenzae type b conjugate and polysaccharide vaccines by high-performance anion-exchange chromatography with pulsed amperometric detection. Vaccine 1993;12:700-706.]. As applied to products containing PRP conjugated to the outer membrane protein complex (OMPC) from Neisseria meningitidis, this assay allows direct measurement of the total PRP content in very complex samples including commercial vaccine products. In addition, with the use of a high-speed centrifugation step, the assay can be used to directly quantify any PRP that is not conjugated to the OMPC carrier protein. These results provide evidence of what appears to be a catalytic reaction taking place between the phosphodiester bond of PRP and the aluminum hydroxide adjuvant that results in hydrolysis of the PRP polymer into smaller chain lengths and liberation of PRP oligomers from the conjugate particle. The reaction approaches an asymptotic limit after approximately two years at 2-8 degrees C. Clinical studies which span this time period confirm that the modest decrease in conjugated PRP content over time does not impact the overall clinical effectiveness of PRP-OMPC-containing vaccines.

Adsorption↗
PubMed1988

Reversal of aluminum-related bone disease after substituting calcium carbonate for aluminum hydroxide.

Aluminum-related osteodystrophy, a crippling disease in patients with renal failure, can develop from the long-term ingestion of aluminum hydroxide gels. We present a diabetic patient treated with continuous ambulatory peritoneal dialysis (CAPD) who developed markedly elevated plasma aluminum levels but no musculoskeletal symptoms. Bone biopsy revealed features of the aplastic form of aluminum-related disease with significant aluminum staining, decreased osteoblastic osteoid, and decreased bone formation by double tetracycline labeling, but no excess accumulation of unmineralized osteoid. Aluminum hydroxide gels were discontinued and the patient received calcium carbonate to control hyperphosphatemia; 9 months later, a bone biopsy showed marked improvement of the aluminum-related bone disease, and at 2 to 10 months, plasma aluminum had decreased from 208.7 +/- 10.3 (SE) to 55.7 +/- 3.9 micrograms/L.

Aged↗
PubMed2003

Calcium hydroxide's association with different vehicles: In vitro action on some dentinal components.

OBJECTIVE: Calcium hydroxide, Ca(OH)(2), is a common intracanal medicament. Ca(OH)(2) powder can be mixed with different vehicles and used as a paste for temporary intracanal treatment. The vehicle may influence the dissociation of calcium hydroxide into ions. We sought to evaluate the level of pH and to quantitatively estimate the release of proteins, hydroxyproline, and phosphorus from pieces of radicular dentin kept in different Ca(OH)(2) solutions. STUDY DESIGN: Twenty-eight extracted incisors were maintained for 35 days in Ca(OH)(2) aqueous solutions prepared in chlorhexidine digluconate, propylene glycol (PG), anesthetic solution, camphorated monochlorophenol (CMCP), and CMCP-PG. The control solution contained Ca(OH)(2) without vehicle. RESULTS: The pH values changed little during the experiment. The concentrations of proteins, hydroxyproline, and phosphorus rose for all the solutions under study. Statistical analysis of the data from the control and the experimental groups revealed an increase in the concentration of proteins when chlorhexidine, anesthetic solution, and PG were used; a rise in hydroxyproline levels when CMCP-PG, CMCP, and PG solutions were used; and an increase in phosphorus when PG and chlorhexidine vehicles were used. CONCLUSION: The test solutions with the root dentin remained alkaline. A release of proteins, hydroxyproline, and phosphorus was observed.

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↗
PubMed1997

Periapical repair and apical closure of a pulpless tooth using calcium hydroxide.

A case with a wide-open apex and a large cystlike periapical lesion in an adult is presented. The lesion formed as a result of necrosis from trauma to a maxillary central incisor 12 years ago. After nonsurgical endodontic treatment with calcium hydroxide paste and a calcium hydroxide-containing root canal sealer, apical closure and significant healing of the periapical lesion within 15 months were observed. This report suggests that even large periapical lesions (likely cystic) could respond favorably to nonsurgical treatment.

Adult↗
PubMed1995

Structure and function analysis of Escherichia coli inorganic pyrophosphatase: is a hydroxide ion the key to catalysis?

Using site-directed mutagenesis, we have completed replacing all 17 putative active site residues of Escherichia coli inorganic pyrophosphatase (PPase). We report here the production of 11 new variant proteins and their initial characterization, including thermostability, hydrophobicity, oligomeric structure, and specific activity at pH 8. Studies of the pH-rate profiles of 12 variants containing substitutions for potentially essential residues showed that the effect of the mutation was always to increase the pKa of a basic group essential for both substrate binding and catalysis by 1-3 pH units. The D70E variant had the lowest activity at all pHs; the K29R, R43K, and K142R variants also had low kcat/Km values. The principal effect seen in the other variant proteins was higher and sharper pH optima; their pH-independent kcat and kcat/Km values changed at most by a factor of 8. Our results suggest that the most likely candidate for the essential basic group affected by all mutations in the active site is a hydroxide ion stabilized by coordination to the essential Mg2+ ions. Analyzing our results using the structure recently obtained for E. coli PPase [Kankare et al. (1994) Protein Eng. 7, 823-830] led us to identify a group of residues, centered around Asp70 and including Tyr55, Asp65, Asp67, Asp102, and Lys104, that we believe binds the magnesium ions that are critical for the activity, possibly by stabilizing the essential hydroxide. Others, including Lys29, Arg43, and Lys142, are more spread out and more positively charged. They appear to be involved in binding substrate and product. Tyr55 is also a key part of the hydrophobic core of E. coli PPase; when it or residues that interact with it are conservatively mutated, there are changes in the overall structure of the enzyme as assayed by thermostability, hydrophobicity, or oligomeric structure.

Bacterial Proteins↗
PubMed2001

First computational evidence for a catalytic bridging hydroxide ion in a phosphodiesterase active site.

Phosphodiesterases are clinical targets for a variety of biological disorders, because this superfamily of enzymes regulates the intracellular concentration of cyclic nucleotides that serve as the second messengers playing a critical role in a variety of physiological processes. Understanding the structure and mechanism of a phosphodiesterase will provide a solid basis for rational design of the more efficient therapeutics. Although a three-dimensional X-ray crystal structure of the catalytic domain of human phosphodiesterase 4B2B was recently reported, it is uncertain whether a critical bridging ligand in the active site is a water molecule or a hydroxide ion. The identity of this bridging ligand is theoretically determined by performing first-principles quantum chemical calculations on models of the active site. All the results obtained indicate that this critical bridging ligand in the active site of the reported X-ray crystal structure is a hydroxide ion, rather than a water molecule, expected to serve as the nucleophile to initialize the catalytic degradation of the intracellular second messengers.

Binding Sites↗
PubMed2004

Lithium-catalyzed hydroxide attack at the carbon atom of methyl phosphate.

The spontaneous hydrolysis of phosphate ester monoanions is relatively easy, but the reaction of water with simple phosphate ester dianion appears to be the slowest biomimetic reaction whose spontaneous rate has been measured in water, with an estimated half time of approximately 1012 years at room temperature in the absence of a catalyst. Here, we report an alternative mode of cleavage of methyl phosphate that involves hydroxide attack at the carbon atom of methyl phosphate and proceeds at a rate proportional to the square of the concentration of lithium hydroxide.

Anions↗
PubMed2005

Spectroscopic characterization of hydroxide and aqua complexes of Fe(II)-protoheme, structural models for the axial coordination of the atypical heme of membrane cytochrome b6f complexes.

Electronic absorption and resonance Raman (RR) spectra are reported for hydroxide and aqua complexes of iron(II)-protoporphyrin IX (Fe(II)PP) respectively formed in alkaline and neutral aqueous solutions. These compounds with weak axial ligand(s) represent a biomimetic approach of the unusual coordination of the atypical heme c(i) of membrane cytochrome b6f complexes. Absorption spectra and spectrophotometric titrations show that Fe(II)PP in alkaline aqueous cetyltrimethylammonium bromide (CTABr) binds one hydroxide ion, forming a five-coordinated high-spin (HS) complex. In alkaline aqueous ethanol, we confirm the formation of a dihydroxy complex of Fe(II)PP. In the RR spectra of Fe(II)PP dissolved in neutral aqueous CTABr, a mixture of a four-coordinated intermediate spin form with an HS monoaqua complex (Fe(II)PP(H2O)) was observed. The spectroscopic information obtained for Fe(II)PP(OH-), Fe(II)PP(H2O), and Fe(II)PP(OH-)2 was compared with that previously reported for the 2-methylimidazole and 2-methylimidazolate complexes of Fe(II)PP, representative of the most common axial ligation in HS heme proteins. This investigation reveals a very remarkable analogy in the spectral properties of, in one hand, the Fe(II)PP(H2O) and mono-2-methylimidazole complexes and, in the other hand, the Fe(II)PP(OH-) and mono-2-methylimidazolate complexes. The comparisons of the absorption and RR spectra of Fe(II)PP(OH-) and Fe(II)PP(OH-)2 clearly establish that both a redshift of the pi-pi electronic transitions and an upshift of the v8 RR frequency are spectral parameters indicative of porphyrin doming in HS ferrous complexes. Based upon isotopic substitutions (16OH-,16OD-, and 18OH-), stretching modes of the Fe-OH bond(s) of a ferrous porphyrin were assigned for the first time, i.e., at 435 cm(-1) for Fe(II)PP(OH-) (nu(Fe(II)-OH-)) and at 421 cm(-1) for Fe(II)PP(OH-)2 (nu(s)(Fe(II)-(OH-)2). The spectroscopic and redox properties of Fe(II)PP(H2O), Fe(II)PP(OH-), and heme c(i) were discussed and favor a water coordination for the heme c(i) iron.

Cetrimonium↗
PubMed2005

Layered copper hydroxide n-alkylsulfonate salts: synthesis, characterization, and magnetic behaviors in relation to the basal spacing.

A series of hybrid inorganic-organic copper(II) hydroxy n-alkylsulfonate with a triangular lattice, Cu(2)(OH)(3)(C(n)H(2)(n)(+1)SO(3)) (n = 6, 8, 10), are prepared by anion exchange, starting from copper hydroxy nitrate Cu(2)(OH)(3)NO(3). These compounds show a layered structure as determined by X-ray diffraction, with interlayer distances of 14.3-34.8 A in alternation with interdigitated bilayer packing. Magnetic properties have been investigated by means of dc and ac measurements. All the compounds show similar metamagnet behaviors, with a Neel temperature of about 11 K. A subtle difference in the ac magnetic susceptibility among the compounds is understood by the existence of hydrogen bonding between the sulfonate headgroup and the hydroxide anion. A detailed molecular structure of the alkyl chains incorporated to the inorganic copper hydroxide layer is also discussed from the FTIR data.

Copper↗