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PubMed2002

Obturating teeth with wide open apices using mineral trioxide aggregate: a case report.

The conventional approach in handling a tooth with a wide open apex requiring endodontic treatment is by means of a procedure called apexification. The objective of treatment is to introduce calcium hydroxide mixed with sterile water or local anaesthetic into the root canal to create a hard-tissue-like formation or an apical plug to prevent extrusion of filling materials during obturation of teeth with wide open apices. This procedure may take anything from 6 months to 2 years. In 1999 a new material called mineral trioxide aggregate (MTA) was introduced to the dental profession for clinical use which has the ability to create an apical plug within a few weeks.

Aluminum Compounds↗

PubMed2004

Transmittance of a bioceramic dental restorative material based on calcium aluminate.

This article investigates the transmittance of a new ceramic filling material as a function of time, thickness, wavelength, and addition of pigments. In the hardened state the ceramic material is composed of hydrates, calcium aluminate, and glass fillers. The radiopacity of the investigated material is also measured. The results of the transmittance are compared to a commercial glass ionomer cement (Fuji II) and resin composite (Tetric Ceram). The transmittance increased with time from low values after 1 h to values close to the glass ionomer cements after 1 week. The resin composite had almost twice the transmittance as the calcium aluminate material and the glass ionomer cement. The amount of light passing through the material was dependent on both the sample thickness and the wavelength. Samples of 0.5-mm thickness transmitted almost twice as much as 1-mm-thick samples. Regarding the wavelength, blue light was scattered very effectively (low transmittance), whereas red light was not (high transmittance). Addition of pigments lowered the transmittance. The radiopacity was slightly higher than that of enamel.

Aluminum Compounds↗

PubMed2005

Hydration process of cement in the presence of a cellulosic additive. A calorimetric investigation.

In the cement industry, the extrusion technique is used to produce flat shapes with improved resistance to compression. Extrusion is a plastic-forming process that consists of forcing a highly viscous plastic mixture through a shaped die. The material should be fluid enough to be mixed and to pass through the die, and on the other hand, the extruded specimen should be stiff enough to be handled without changing in shape or cracking. These characteristics are industrially obtained by adding cellulosic polymers to the mixture. The aim of this work is to understand the action mechanism of these additives on the major pure phases constituting a typical Portland cement: tricalcium silicate (C(3)S), dicalcium silicate (C(2)S), tricalcium aluminate (C(3)A), and tetracalcium iron-aluminate (C(4)AF). In particular, a methylhydroxyethyl cellulose (MHEC) was selected from the best-performing polymers for further study. The effect of this additive on the hydration kinetics (rate constants, activation energies, and diffusional constants) was evaluated by means of differential scanning calorimetry (DSC) while the hydration products were studied by using thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). MHEC addition in calcium silicate pastes produces an increase in the induction time without affecting the nucleation-and-growth period. A less dense CSH gel was deduced from the diffusional constants in the presence of MHEC. Moreover, CSH laminar features and poorly structured hydrates were noted during the first hours of hydration. In the case of the aluminous phases, the additive inhibits the growth of stable cubic hydrated phases (C(3)AH(6)), with the advantage of the metastable hexagonal phases being formed in the earliest minutes of hydration.

Aluminum Compounds↗

PubMed2002

The use of MTA in teeth with necrotic pulps and open apices.

Three clinical cases have been treated with the use of an apical plug of MTA for apexification. All three cases were central incisors that had suffered premature interruption of root development as a consequence of trauma. According to the treatment protocol, the root canals were rinsed with 5% NaOCl; then, calcium hydroxide paste was placed in the canals for 1 week. Consequently, the apical portion of the canal (4 mm) was filled with MTA. The remaining portion of the root canals was then closed with thermoplastic gutta-percha. At 6-month and 1-year follow-up period the clinical and radiographic appearance of the teeth showed resolution of the periapical lesions. MTA appears to be a valid option for apexification with its main advantage being the speed at which the treatment can be completed.

Adolescent↗

PubMed2006

Treatment of pulp floor and stripping perforation by mineral trioxide aggregate.

Mineral trioxide aggregate (MTA) has been widely used to repair various kinds of tooth perforations, but its use for obturation of the entire root canal has not been reported. We report two cases of tooth perforation successfully repaired with MTA. The first patient was a 78-year-old male with calcified canal and pulp floor perforation in the left maxillary first premolar. After bypass of the calcified palatal canal, both buccal and palatal canals were filled with gutta percha, and the pulp floor perforation was repaired with MTA. Clinical success with no evident radicular lesion was found at the 18-month follow-up. The second patient was a 51-year-old female with a stripping perforation in a C-shaped root canal of the right mandibular second molar detected after removal of a post. Following root canal debridement and calcium hydroxide therapy to control inflammation at the stripping perforation site, apical and furcation bone healing were observed by radiographic examination. The stripping perforation was repaired by obturation of the entire C-shaped root canal with MTA. Observation at the 9-month follow-up revealed bone healing without any clinical symptoms and signs. These cases suggest that MTA is an alternative root canal obturation material for treatment of stripping perforation in a C-shaped root canal and for repair of pulp floor perforation.

Aged↗

PubMed2005

Synthesis of ettringite: a way to deal with the acid wastewaters of aluminium anodising industry.

Synthesis of ettringite from acid wastewaters of the aluminium anodising industry has been studied as a possible route of reducing the emissions to the environment, recovering at the same time resource materials as a useful marketable mineral. Wastewaters of different concentrations have been subjected to the process of synthesis suspending calcium oxide and calcium aluminate powders at different time and pH conditions. High caustic alkalinity (pH approximately 12) and low sulphate concentrations (<0.1 M) are the most suitable conditions to synthesise ettringite. The mineral characterisation has been performed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential thermal analysis (DTA), proving the high purity of the pursued solid product when hydrated in the appropriate sodium hydroxide concentrations. In such conditions, around 90% of the aluminium initially present in the wastewater solutions is recovered in the form of ettringite.

Aluminum↗

PubMedDate not supplied

A strategy for controlling deposition of struvite in municipal wastewater treatment plants.

This paper presents strategies to reduce the risk of struvite deposition by controlling its location of formation. Two technical routes were investigated: (1) to fix the phosphate into the dewatered sludge cake, and (2) to remove phosphate from centrate or filtrate. Chemicals used include magnesium hydroxide [Mg(OH)2], both of reagent grade and reclaimed from a flue gas desulfurization system, magnesium chloride (MgCl2), calcium hydroxide [Ca(OH)2], ferric chloride (FeCl3) and aluminum sulfate [Al2(SO4)3]. Research results indicate that (1) for anaerobically well-digested sludge, Mg(OH)2 is effective in fixing phosphate into sludge cake and improving sludge dewaterability, and (2) adding Mg(OH)2 into a reactor, located between the sludge dewatering facilities and the centrate or filtrate discharge line, and using air for mixing and carbon dioxide stripping, proves feasible in reducing struvite deposition in centrate or filtrate discharge lines and can generate a potentially valuable plant fertilizer--struvite.

Alum Compounds↗

PubMed2006

Evolution of iron speciation during hydration of C4AF.

It is now well accepted and demonstrated that calcium silicate, calcium aluminate and calcium sulfo aluminate (ettringite, AFm) phases exhibit a good capability to fix metals and metalloids. Unfortunately the role of minor phases and especially calcium-ferric aluminate phase, shorthand C4AF is not well defined. In other systems like in soils or sediments iron phases play a key role in the fixation of pollutant. In cement sorption isotherms, indicated that various metals can be retained by the C4AF hydrated products. Therefore the capabilities of those phase to retain heavy metal should not be neglected. Previous investigations have shown that the minerals formed during the hydration of C4AF are similar to those formed from C3A (pure tri-calcium aluminate) under comparable conditions. Nevertheless no investigation was conducted at the molecular level and there is still a controversy whether Fe substitutes for Al in the hydrated minerals in whole or in part, or if it forms FeOOH clusters scattered throughout the matrix. In this context we have conducted XAS experiments using synchrotron radiation. It was found that the hydration of C4AF forms C3AH6 (hydrogarnet) in which Fe randomly substitutes for Al as well as an amorphous FeOOH phase. Intermediate products like AFm (i.e., an ill organized lamellar phase) are also formed but rapidly evolve to C3AH6; iron does not seem to be incorporated in the AFm structure.

Aluminum Compounds↗

PubMed2000

Phosphate immobilization using an acidic type F fly ash.

Batch equilibration experiments using a low calcium ( approximately 1 wt.% as CaO), acidic (pH approximately 4.5) Type F fly ash demonstrated phosphate immobilization on the order of 100% to 75% for 50 and 100 mg P/l solutions, respectively. A loosely compacted column of fly ash similarly removed 10 mg P/l for over 85 pore volumes. While the interactions between phosphate and calcium-rich (Type C) ashes are relatively well understood, insight into the mechanisms of phosphate immobilization in Type F ash necessitated a review of the phosphate chemistry and interactions with acidic geomedia. Phosphate adsorption was subsequently modeled using a constant capacitance model approach (CCM) excluding precipitation reactions. Our CCM predictions of total phosphate immobilization (20%) were substantially less than the results of the batch equilibration experiments and phosphate adsorption predicted by other researchers examining near pure natural and synthetic geomedia due to the compositional heterogeneity of the fly ash. Nevertheless, for the amorphous and crystalline phases studied, the immobilization of phosphate in the Type F fly ash is attributed to the formation of insoluble aluminum and iron phosphates at low to medium values of pH.

Adsorption↗

PubMed2001

Measurement of cadmium(II) and calcium(II) complexation by fulvic acids using 113Cd NMR.

Aquatic and terrestrial fulvic acids are environmentally important in pollution transport because they affect the bioavailability and transport of metal ions. The complexation of the metal ions, Cd(II) and Ca(II), with several fulvic acids is examined in this study using 113Cd NMR. Our results indicate that Cd(II) predominately binds to the oxygen containing functional groups of the fulvic acids. A single 113Cd NMR resonance is observed in NMR spectra of Cd(II)-fulvic acid solutions indicating fast exchange between free and complexed cadmium species. An average association equilibrium constant, K(Cd), is determined from NMR spectra measured for the titration of fulvic acid with Cd(II). The K(Cd) values determined for the four fulvic acids studied range between 1.2 and 3.5 x 10(3) M(-1). Competitive binding between Ca(II) and Cd(II) is used to indirectly determine an average association equilibrium constant, K(Ca), for Ca(II) with each fulvic acid. Overall K(Ca) values range from 4.6 to 7.8 x 10(2) M(-1).

Benzopyrans↗

PubMed2005

A three year follow-up of posterior doxadent restorations.

A new direct restorative material, a calcium aluminate cement, was introduced in the year 2000 and sold under the name Doxadent (Doxa AB, Uppsala, Sweden). The aim of this study was to evaluate Doxadent used in class I and II cavities. A total of 63 restorations were evaluated clinically, according to sligthly modified USPHS criteria, at baseline, after 6 mths, 1, 2 and 3 yrs. Four of the patients reported post-operative sensitivity. At 3 yrs, 62 restorations were evaluated. At 6 mths 9.5% non-acceptable Doxadent restorations were observed, 17.5% at 12 mths, 24.2% at 2 yrs and 21% at 3 yrs, which resulted in a cumulative failure frequency of 72.6% at the end of the 3-years for the new restorative material. Main reasons for failure were material or tooth fracture. It can be concluded that Doxadent showed a non-acceptable clinical failure rate as a posterior restorative, especially in class II cavities.

Adult↗

PubMed2006

An alternative to Portland Cement for waste encapsulation--the calcium sulfoaluminate cement system.

Currently, Portland Cement (PC) is used extensively in the solidification/stabilisation of a wide variety of wastes. In the nuclear industry, low and intermediate level radioactive wastes are encapsulated or immobilised within composite PC cement systems based on high replacement with blast furnace slag or fly ash. However, the high alkalinity of these PC-based systems will corrode reactive metals found in some wastes releasing hydrogen and forming expansive corrosion products. Alternative cement systems could provide a different hydration chemistry, which would allow wastes containing these metals to be encapsulated with lower reactivity. Calcium sulfoaluminate (CS A) cement is one such cement. It combines economy of cost and low emission of CO(2) with rapid strength gain and compatibility with other construction materials. Hydration provides an internal pore solution where the pH is considerably lower than that of PC. The main hydration product, ettringite, can incorporate a number of ions into its crystal structure, making it an ideal candidate for waste immobilisation. This paper details some results from a commercial CS A system that examines aspects of mixing, hydration of different formulations and aluminium corrosion behaviour. The fluidity of mixes can be adjusted by changing the formulations. All designed mixes were set within 24 h with little bleeding and the pH values were in the range of 10-11.5. In addition, a significant reduction in Al corrosion was observed compared to a composite OPC system. Although these results provide encouragement for the idea that CS A cement can provide a possible alternative to PC in the immobilisation of difficult and reactive wastes, further investigation is needed.

Aluminum↗

PubMed2006

Improvement of the agitation granulation method to prepare granules containing a high content of a very hygroscopic drug.

This study describes a new approach to the preparation of a granulate with a high content of a very hygroscopic powder or drug, using the agitation granulation method, and the development of a tablet formulation using these granulates. A Chinese medicine extract, Hatimi-zio-gan, was used as the model of a very hygroscopic drug. Among the several excipients tested, only porous calcium silicate could be used to prepare granules, with a mixing ratio (extract to porous calcium silicate) from 2:1 to 20:1. With other excipients, very large lumps were formed during the granulation process. The best mixing ratio of extract to porous calcium silicate was 6:1. For preparation of the granules, water could be added to the mixed powder within a range of 1- to 4-times the amount of porous calcium silicate. From these results, it was concluded that the ability of porous calcium silicate to hold large amounts of water in its numerous pores may allow for the preparation of granulates with a high content of very hygroscopic drugs. Starch with partial alpha-links, carboxymethyl starch sodium salt and crospovidone were used for selection of the disintegration agent. When crospovidone was used as a disintegration agent, tablets containing about 70% of the Chinese medicine extract disintegrated in less than 7 min, with good dissolution rates. The same process was applied to extracts of Hotyu-ekki-to, Syo-seiryu-to, Boi-ogi-to and Bohu-tusyo-san. The absorption of paeoniflorin, a characteristic monoterpene glucoside contained in Hatimi-zio-gan extract, was evaluated in beagle dogs after oral administration of the Hatimi-zio-gan tablets prepared in this study. The values of C(max) and AUC obtained after administration of the tablets prepared in this study were significantly greater than those obtained for commercial tablets.

Administration, Oral↗

PubMed2005

Interleukin-1 levels in gingival crevicular fluid adjacent to restorations of calcium aluminate cement and resin composite.

OBJECTIVES: The aim of this clinical study was to intra-individually compare Class V restorations of a calcium aluminate cement (CAC), resin composite and enamel with respect to the adjacent levels of interleukin (IL)-1alpha, IL-1beta and IL-1 receptor antagonist (IL-1ra) in gingival crevicular fluid (GCF). The hypothesis was that there are higher IL-1 levels adjacent to resin composite, compared with CAC and enamel. MATERIALS AND METHODS: In 15 subjects, at least one set of two Class V restorations with subgingival margins, one CAC and one universal hybrid resin composite, and one control surface of enamel were included. In a cross-sectional study and on days 0, 3 and 7 of an experimental gingivitis study, GCFs were collected with Periopaper for 30 s. The GCF concentrations of IL-1alpha, IL-1beta and IL-1ra were quantified with enzyme linked immunosorbent assays. RESULTS: Neither the cross-sectional study nor the experimental gingivitis study showed any significant differences in the levels of IL-1alpha, IL-1beta and IL-1ra between CAC, resin composite and enamel sites (p>0.05). In the cross-sectional study, low IL-1 concentrations were observed. The IL-1 levels increased significantly during the experimental gingivitis. CONCLUSION: Regardless of CAC or resin composite, the restorations per se did not affect the GCF levels of IL-1 and IL-1ra, neither at healthy gingiva, nor at initiation of plaque-related gingival inflammation.

Adult↗

PubMed2005

Dimensional change of a calcium aluminate cement for posterior restorations in aqueous and dry media.

OBJECTIVES: A calcium aluminate cement has recently been developed, with claims of being an alternative to dental amalgam and resin composites in posterior cavities. However, its' mechanical properties are not well evaluated and the aim of the study was therefore, to evaluate its' dimensional stability over time. METHODS: The dimensional changes of the cement, Doxadent, and two composite resins, Esthet-X and InTen-S, were tested during 360 d. The specimens were stored at 37+/-1 degrees C either in 100% air humidity (dry) or immersed in distilled water (wet), except for the first 24h when all specimens were stored at 100% air humidity and 37+/-1 degrees C. RESULTS: During the first 24h, Doxadent decreased in volume with 0.04%, while InTen-S and Esthet-X decreased with 1.60 and 1.75%, respectively. From d 1-360, the dry Doxadent specimens increased in volume with 2.0% and in weight with 5.5%, while the corresponding increase for the wet specimens were 4.1 and 6.3%, respectively. The volume of both composites increased 0.8% or less in dry and wet conditions, while the increase in weight for InTen-S was 1.2% for the wet specimens and 0.6% for the dry. The corresponding figures for Esthet-X were 0.7 and 0.2%. SIGNIFICANCE: Doxadent was less dimensionally stable than the composites tested. Doxadent increased 2 times more in volume immersed in water than in 100% air humidity, while the increase in weight was almost similar. The clinical implications of the results found in the present study are uncertain. A material that continues to absorb water during prolonged periods and continues to react is questionable for clinical use.

Absorption↗

PubMedDate not supplied

Water-soluble and solid-state speciation of phosphorus in stabilized sewage sludge.

Three chemicals, ferrous sulfate (Fe-sul), calcium oxide (CaO), and aluminum sulfate (alum), were used to stabilize phosphorus (P) in fresh, anaerobically digested sewage sludge (FSS). The chemically stabilized sludge materials and biosolids compost (BSC) were compared with the FSS with respect to water-soluble phosphorus (WSP) content in its inorganic (WSP(i)) and organic (WSP(o)) forms as well as water-soluble organic carbon (DOC). Solid-state P speciation was further probed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy-dispersive X-ray elemental spectrometry (EDXS). Water-soluble P was effectively controlled by a wide range of Fe-sul or CaO additions to the sludge (Ca to P ratio = 3.47-17.72, Fe to P ratio = 1.01-16.53), but by only a narrow range (Al to P ratio = 1.04-2.87) of alum addition. The WSP content in the BSC was also depressed, but to a lesser extent. The pH in the treated sludge ranged from 3.0 to 12.5 and served as a key factor to control P chemistry. No correlation was observed between DOC and WSP(o). No crystallized Ca-P minerals were detected in the CaO-stabilized sludge, but brushite crystallization seemed to be obtained by low addition of Fe-sul and alum. Variscite and strengite crystallization was obtained following high addition of Fe-sul or alum, as detected by XRD and SEM-EDXS. Adsorption of P by newly formed Fe-hydroxide seems to play an important role in the Fe-sul-stabilized sludge. We concluded that administration of the tested chemicals at the proper rate can effectively reduce the hazard of P release and leaching from sludge.

Adsorption↗

PubMed2001

The carbon dioxide absorption capacity of Amsorb is half that of soda lime.

UNLABELLED: A new CO(2) absorbent, Amsorb (A), which does not contain monovalent bases, is ideal because it does not degrade volatile anesthetics to either Compound A (from sevoflurane) or carbon monoxide (from desflurane, enflurane, or isoflurane). The CO(2) absorption capacity of A, however, has not been investigated under clinical conditions. In this study, we compared the longevity (time to exhaustion) and CO(2) absorption capacity (the volume of CO(2) absorbed before CO(2) rebreathing occurs) of A under low-flow anesthesia (1 L/min) with those of two soda lime absorbents-Medisorb (M) and Sodasorb (S)-by using a 750-mL ADU canister and a 1350-mL Aestiva 3000 canister. In the study with the ADU canister, the longevity of A was 213 +/- 71 min, significantly less than those of M (445 +/- 125; P < 0.01) and S (503 +/- 89; P < 0.001). The CO(2) absorption capacity (L/100 g absorbent) of A was 5.5 +/- 1.2, significantly less than those of M (10.7 +/- 1.7) and S (12.1 +/- 1.8; P < 0.001). In the study with the Aestiva 3000 canister, the longevity of A was 218 +/- 61 min, significantly less than those of M (538 +/- 136) and S (528 +/- 103; P < 0.001). The CO(2) absorption capacity (L/100 g absorbent) of A was 7.6 +/- 1.6, significantly less than those of M (14.4 +/- 1.8) and S (14.8 +/- 2.3; P < 0.001). These results indicate that the CO(2) absorption capacity of A is half that of M or S and that the difference in the CO(2) absorption capacity between A and M or S is almost constant, regardless of the canister design. IMPLICATIONS: The CO(2) absorption capacity of Amsorb is half that of Medisorb and Sodasorb under clinical low-flow (1 L/min) anesthesia with either a 750-mL Ohmeda ADU compact or a 1350-mL Ohmeda Aestiva 3000 canister.

Absorption↗

PubMed1990

[The synthesis and biological activity of substituted tetrahydroisoquinoline compounds].

Tetrandrine possesses calcium antagonistic and hypotensive effects. It was cleaved into two compounds O-methylcoclaurine (I) and N-methylarmepavine (II) by Na/NH3. Pharmacological test indicated that I and II showed weaker calcium antagonistic activity but having alpha-adrenoceptor antagonistic effect. With I and II as lead compounds as well as integration of some structural feature of calcium antagonists and SAR of antiarrhythmic drugs, two kinds of substituted tetrahydroisoquinoline derivatives III, IV were designed and synthesized in order to search for novel cardiovascular drugs. Tetrahydroisoquinoline compounds were first synthesized by the Bischler-Napiraski cyclization with substituted phenethylamine and aromatic acetic acid or substituted cinnamic acid as starting materials. N-alkylsubstituted tetrahydroisoquinoline compounds were prepared by the reaction of 4 with alkyl halide to produce 5, then reduction of 5 by KBH4 to give III13-25. The synthesis of N-alkylaminoethyl substituted tetrahydroisoquinoline compounds involved the reaction of 6 with chloroacetyl chloride to obtain IV1-3, the reaction of IV1-3 with secondary amine to produce 9, and then reduction of 9 with LiA1H4 to give IV16-19. Preliminary tests showed that most of these compounds exhibited varied degree of alpha-adrenoceptor antagonistic effect, and some of them possess calcium antagonistic activity. In anesthetic normal rats III15, 19 showed certain degree of hypotensive effect. IV10, 11 exhibited significant protective effect on experimental arrhythmic animals. The results of quantum chemical calculation of some compounds demonstrate that the compounds might act with alpha 1-adrenoceptor by forming charge-transfer complex.

Adrenergic alpha-Antagonists↗