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At least 811 records · Page 45Linked to original sources
PubMed1985

Chemical mutagenesis testing in Drosophila. II. Results of 20 coded compounds tested for the National Toxicology Program.

Results are presented from mutagenesis testing in Drosophila of 20 coded compounds. Two compounds were positive in the sex-linked recessive lethal test, and two were inconclusive. The positive compounds were calcium chromate in adult feeding experiments and ferrocene after adult injection. The two inconclusive compounds were 2,4-diaminophenol dihydrochloride and hexachlorocyclopentadiene. Compounds that produced a positive response were assayed for chromosome breakage using the conventional translocation test. Calcium chromate was negative in the translocation test, and ferrocene was positive. Many of the test compounds were poorly soluble in water, raising questions regarding the effective concentration to which the flies were exposed.

Animals↗
PubMed1998

High-level chloroquine resistance of Plasmodium berghei is associated with multiple drug resistance and loss of reversal by calcium antagonists.

The chloroquine resistance of Plasmodium falciparum is reversed in vitro by numerous compounds, including calcium antagonists, which could enhance the accumulation of the drug in the parasite food vacuole. However, this mechanism of resistance could be insufficient when the resistance level increases. Using in vitro drug trials on strains of Plasmodium berghei displaying various chloroquine-resistance levels, we confirmed previous results obtained in vivo in the chloroquine-resistant strains of P. berghei are cross-resistant to related drugs (amodiaquine, quinine and mefloquine), the resistance levels to these drugs being related to their analogy to chloroquine. Furthermore, we showed that high-level resistant lines were associated with a loss of drug potentiation by verapamil and nicardipine in vivo, but that the reversal rates obtained in vitro are of low significance. We conclude that the parasite is able to escape the activity of these reversing agents.

Animals↗
PubMed1999

Medical management of secondary hyperparathyroidism in uremia.

The prevention and treatment of the secondary hyperparathyroidism of chronic renal failure by medical means relies on a number of different possible approaches, which should be tailored to each patient's individual needs. Schematically, prevention should start early during the course of chronic renal failure (ie, when plasma intact parathyroid hormone is normal or only slightly elevated). Small calcium supplements prevent the development of a calcium deficit and may prevent parathyroid hormone oversecretion. The various therapeutic options that are available at present include: oral or intravenous vitamin D and vitamin D derivatives, in particular the 1alpha-hydroxylated vitamin D compounds; oral calcium supplements (calcium carbonate and calcium acetate) to avoid calcium depletion and also to bind phosphate in the intestinal lumen; aluminum-containing phosphate binders, the use of which should be restricted; oral magnesium salts (magnesium carbonate and magnesium hydroxide), which often are not well tolerated; general measures, such as dietary restriction of phosphate intake; and, in the case of resistance to all these approaches, the possibility of attempting ultrasound-guided ethanol injection of grossly hyperplastic parathyroid glands. Finally, it is encouraging to know that new drugs are in development, including calcium-free, aluminum-free, nonabsorbable oral phosphate binders, potentially nonhypercalcemic vitamin D derivatives, and calcimimetics. Some of them already have entered the stage of clinical evaluation, and preliminary results are promising.

Aluminum Compounds↗
PubMed2006

Conductometric study of precursor compound formation during wet-chemical synthesis of nanocrystalline hydroxyapatite.

Conductometry was employed to study the phase evolution of calcium phosphate compounds during the wet-chemical synthesis of hydroxyapatite (HA). Calcium hydroxide and orthophosphoric acid were used to prepare HA at various temperatures ranging from 30 to 95 degrees C. The electrical conductivity and pH of the reaction mixture were measured at regular intervals of time during acid addition, and the rate of change of conductivity was used to decipher the end point of the reaction. Our previous studies have shown that the end product of this reaction route yields mildly carbonated crystalline HA. The trend of the change in conductivity with time was similar at all temperatures. The conductivity curves were divided into three regions based on the variation in slope of the curves. The slope of the curves decreased with increasing temperatures in the first two regions, and the slope is greater in the second region than in the first. From the conductivity and pH measurement results, the possible precursor phase was identified and it had the composition Ca(3)(PO(4))(2). The kinetics of phase transformation was also analyzed and compared to previous work. The similarities between this work and the traditionally adapted experimental work for phase formation and transformation kinetics are highlighted, and the novelty in the current work is discussed.

Acids↗
PubMed2005

Arsenic release provided by MTA and Portland cement.

OBJECTIVE: The aim of the present study was to determine the release of arsenic from 2 gray Portland cements, a white Portland cement, and 2 MTAs (ProRoot and MTA-Angelus). STUDY DESIGN: The materials were manipulated and placed in plastic tubes, and the tubes were immersed in glass flasks containing water with grade reagent, pH 5.0. After 3 and 168 h, the water in which the material had been immersed was analyzed regarding the presence of arsenic by atomic absorption spectrophotometry with hydride generation. RESULTS: The levels of arsenic released were similar for Portland cements and MTAs, and were well below those considered to be harmful. CONCLUSIONS: MTA and Portland cements showed very low arsenic presence. The results suggest that MTAs and Portland cements are safe for use in clinical practice in terms of the presence of arsenic.

Aluminum Compounds↗
PubMed2005

Postoperative pain after root-end resection and filling.

OBJECTIVE: To evaluate the pain experience following root-end resection and filling with Mineral Trioxide Aggregate or Intermediate Restorative Material. STUDY DESIGN: Referred adult patients recruited using strict entry criteria were randomly allocated to receive either material. A standardized surgical technique was employed. Postoperative instructions and a pain questionnaire were given to each patient to record the severity of their pain at 3 time intervals-3-5 hours, 24 hours, and 48 hours after surgery-on a standard visual analog scale (VAS). Patients were also asked to record consumption of any self-prescribed analgesics, the type, and dosage. RESULTS: At 3-5 hours after surgery, regardless of the material used, 90% of all patients experienced some level of postoperative pain. Twenty-four hours after surgery 82% of patients experienced pain, as did 72% after 48 hours. Thirty-seven percent of patients did not take any analgesics at all. In order of popularity, the analgesics taken were ibuprofen, acetaminophen, and acetaminophen plus codeine phosphate. The VAS measurements were reduced over time in both treatment groups (P < .001). There was no statistically significant difference in the proportion of subjects taking analgesics in each treatment group. Patients who used analgesics showed higher median VAS measurements at all time periods (P < .05). CONCLUSIONS: There was no significant difference in the pain experienced by both treatment groups. The postoperative pain was of a relatively short duration, at its maximum intensity early in the postoperative period but progressively decreased with time. Even if pain relief medication was needed, nonprescription analgesics were adequate and effective.

Adult↗
PubMed1994

Dye leakage of four root end filling materials: effects of blood contamination.

The purpose of this study was to compare the amount of dye leakage (in the presence versus absence of blood) in root end cavities filled with amalgam, Super EBA, IRM, and a mineral trioxide aggregate. After removing the anatomical crowns of 90 extracted human teeth, their roots were instrumented and obturated. Except for their apical 2 mm, the root surfaces were sealed with nail polish. After removal of the apical 2 to 3 mm of each root, a standardized root end cavity was prepared. Five root ends were filled with gutta-percha and no sealer, and another five root ends were filled with sticky wax. These served as positive and negative controls, respectively. The remaining 80 roots were divided into four equal groups and filled with the test materials. For each material, half of the root end cavities were dried prior to placing the filling material. The remaining half were filled after they were contaminated with blood. All 90 roots were then immediately placed in 1% methylene blue dye for 72 h. Finally, the roots were split and linear dye penetration was measured and statistically analyzed (analysis of variance). Presence or absence of blood had no significant effect on the amount of dye leakage. However, the results showed that there was a significant leakage difference between the root end filling materials (p < 0.0001). Mineral trioxide aggregate leaked significantly less than other materials tested with or without blood contamination of the root end cavities.

Aluminum Compounds↗
PubMed1995

Cytotoxicity of four root end filling materials.

Leakage and scanning electron microscopic studies have shown that a mineral trioxide aggregate (MTA) used as root end filling material permits significantly less leakage and has better adaptation than other commonly used root end filling materials. Because these materials are in contact with the periradicular tissues, their cytotoxicity should be evaluated before in vivo tests. Using the agar overlay and radiochromium methods, the cytotoxicity of amalgam, Super EBA, IRM, and the MTA was evaluated. Statistical analysis of the data from the agar overlay technique shows that freshly mixed and set amalgam were significantly less toxic than the rest of tested materials (p< 0.00005). Fresh and set MTA ranked second when tested for cytotoxicity with this technique. Similar statistical tests revealed a significant statistical difference between the toxicity of freshly mixed and set materials after 24 h of incubation with radiochromium-labeled mouse L929 cells. The degree of cytotoxicity of fresh and set materials was MTA least toxic followed by amalgam, Super EBA, and IRM. Based on the results of the cell culture methods used in this study it appears that MTA is a potential root end filling material and warrants further in vivo evaluations.

Agar↗
PubMed1998

Tissue reaction to implanted root-end filling materials in the tibia and mandible of guinea pigs.

The purpose of this study was to examine the tissue reaction to implanted mineral trioxide aggregate (MTA), amalgam, Intermediate Restorative Material, and Super-EBA in the tibias and mandibles of guinea pigs. After anesthetizing 20 guinea pigs, raising tissue flaps, and preparing bony cavities, the test materials were placed in Teflon cups and implanted in the tibias and 10 days later in the mandibles. The animals were euthanized 80 days later and the tissues prepared for histological examination. The presence of inflammation, predominant cell type, and thickness of fibrous connective tissue adjacent to each implant were recorded. The tissue reaction to MTA implantation was the most favorable observed at both sites; as in every specimen, it was free of inflammation (p < 0.01). In the tibia, MTA was the material most often observed with direct bone apposition. Based on these results, MTA seems to be a biocompatible material.

Aluminum Compounds↗
PubMed2004

Effects of physiological environments on the hydration behavior of mineral trioxide aggregate.

Utilizing scanning electron microscope, X-ray diffraction (XRD) and microhardness tests, we evaluated how various physiological environments affect the hydration behavior and physical properties of mineral trioxide aggregate (MTA). We found that the microstructure of hydrated MTA consists of cubic and needle-like crystals. The former comprised the principal structure of MTA, whereas the later were less prominent and formed in the inter-grain spaces between the cubic crystals. MTA samples were hydrated in distilled water, normal saline, pH 7, and pH 5. However, no needle-like crystals were observed in the pH 5 specimens, and erosion of the cubic crystal surfaces was noted. XRD indicated a peak corresponding to Portlandite, a hydration product of MTA, and the peak decreased noticeably in the pH 5 group. The pH 5 specimens' microhardness was also significantly weaker compared to the other three groups (p<0.0001). These findings suggest that physiological environmental effects on MTA formation are determined, in part, by environmental pH and the presence of ions. In particular, an acidic environment of pH 5 adversely affects both the physical properties and the hydration behavior of MTA.

Aluminum Compounds↗
PubMed1999

Osteoblast biocompatibility of mineral trioxide aggregate.

This study investigated the biocompatibility of variants of mineral trioxide aggregate (MTA), by culturing human MG63 osteosarcoma cells in the presence of materials, observing cytomorphology and cell growth, and then assaying cytokine expression from the cells. Reference materials were employed. Cell growth was quantified by preparing samples (n = 6) at 2, 4 and 7 days, for viewing by scanning electron microscopy and then scoring the amount of material that was covered by healthy cells. Subsequently, samples of culture media were tested using ELISA assays for expression of Interleukin (IL)-1alpha, IL-6, IL-8, IL-11 and macrophage colony stimulating factor (M-CSF). These assays were compared with controls where no material was present, and where media and fetal calf serum had not been exposed to cells. Results showed good cell growth on MTA. Expression of IL-6 from cells was only evident in the presence of MTA and Interpore 200. Interleukin-8 was expressed in high concentrations only in the presence of MTA. There was no evidence of expression of IL-1alpha or IL-11 with any material. Production of M-CSF was high for all materials. It appears that the variants of MTA are biocompatible and suitable for use in clinical trials.

Aluminum Compounds↗
PubMed2004

Influence of the thickness of mineral trioxide aggregate on sealing ability of root-end fillings in vitro.

The purpose of this study was to compare the ability of different thicknesses of mineral trioxide aggregate (MTA) to prevent apical leakage through the use of a protein-dye complex with Coomassie Brilliant Blue G. Sixty-four teeth were divided into 4 groups, then filled with MTA to depths of 1, 2, 3, or 4 mm. Two teeth served as the positive controls. Another 2 teeth served as the negative controls. Root-filled teeth were mounted in an apparatus and then challenged with protein solution. The evaluation was conduced at 24-hour intervals for 60 days. The 1-mm-thick MTA was the least effective in preventing apical leakage (P <.05). No significance difference was found between 2- and 3-mm-thick MTA (P >.05). Four-millimeter-thick MTA was significantly more effective than the other thicknesses tested (P <.05). The results of this study suggest that the thickness of 4 mm is most adequate for the use of MTA as a root-end filling material.

Aluminum Compounds↗
PubMed2003

Effect of root resection on the apical sealing ability of mineral trioxide aggregate.

OBJECTIVE: The purpose of this in vitro study was to determine the minimum depth of mineral trioxide aggregate (MTA; ProRoot; DENTSPLY/Tulsa Dental, Tulsa, Okla) required to maintain an apical seal following root resection. Study design. In 10 instrumented teeth, MTA was used to obturate the apical 6 mm of the root canal and was allowed to set for 48 hours. Leakage was determined by means of a fluid filtration method at a pressure of 20 cm H(2)O. Leakage was measured before root resection, and after 3, 4, 5, and 6 mm apical resections. Data were analyzed by means of a Kruskal-Wallis one-way analysis of variance with P <.05. RESULTS: Fluid leakage was shown to increase after each resection, but did not reach statistical significance (P <.05) until 4 mm of the apex had been removed. CONCLUSION: The results indicate that root resection did not significantly affect the sealing ability of MTA when at least 3 mm of the MTA remained. Although there was a statistically significant difference in leakage following the 4 mm resection, it is unknown what the biological difference would be between the 3 mm and 4 mm resections.

Aluminum Compounds↗