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An in vitro method for longitudinal evaluation of root canal sealers was developed and applied. A newly introduced cell culture chamber was used to evaluate the cytotoxic effects of test samples immediately after mixing and for an extended period of time thereafter. A ranking of the test materials, based on their cytotoxicity, was allowed by the method.
This article discusses various aspects of mechanical testing for podiatric applications. Included is a brief overview of the terminology used to describe a variety of mechanical tests, suggestions for the preparation and storage of specimens, and an overview of various mechanical testing techniques that have been used to collect data on internal fixation and osteotomy stability.
Preclinical studies are defined as experiments other than clinical trials that are conducted in test systems under laboratory conditions for determining the safety of test materials for anticipated human use. It is known that preclinical studies are an indispensable requisite for but constitute time/resource-consuming processes in research and development of new pharmaceuticals. Therefore, they must be designed and conducted in a manner to satisfy the criteria that the obtained data are mutually acceptable among various countries to avoid unnecessary duplication of testing. The purpose of the International Conference on Harmonisation (ICH) has been directed towards the resolution of this issue. Major scientific issues in preclinical studies comprise the interpretation of test data with respect to prediction of potential adverse effects of a test material in humans. Mechanistic consideration of the toxic effects occurring in animals given a test material can usually provide a scientific basis for evaluating the potential hazard of the material in humans. For example, when a test material was found to exhibit a carcinogenic effect in a long-term animal test, one will attempt to determine, on the basis of data from genotoxicity studies, repeated dose toxicity tests, toxicokinetic studies or pharmacology studies on the substance, whether the carcinogenic effect is due to its genotoxicity (genotoxic carcinogen) or a sequela of some secondary mechanisms (non-genotoxic carcinogen). In the cases where a test material was shown to exert toxic effects with either functional manifestation or non-neoplastic morphological manifestation, elucidation of the mechanism will also be useful for extrapolation of animal data to the human situation. It is known that pharmaceuticals induce their toxic effects through various mechanisms such as covalent binding of active intermediates with macrolecules of target cells, oxidative stress-mediated effects, hormone-mediated effects or cytokinemediated effects. As shown in hepatocarcinogenesis or elevation of plasma transaminase activities in rodents attributable to activation of PPAR-alpha, nuclear receptors or ligand-dependent transcription factors are, now, regarded as important targets for toxicity evaluation of pharmaceuticals.
PURPOSE: The aim of this study was to evaluate four recording materials (polyether, polyvinyl siloxane, acrylic resin, and wax) for their ability to accurately record, maintain, and reproduce the vertical interocclusal relationship. MATERIALS AND METHODS: A metallic apparatus was used to represent the opposing arches; its epoxy resin duplicate represented the working casts. The vertical discrepancies produced because of the presence of the records were measured both after repositioning them on the metal apparatus and after transferring them onto the casts. Two-way ANOVA was performed. RESULTS: Closure through the interocclusal recording materials produced small vertical discrepancies ranging from 24 to 74 microm. When repositioned on the apparatus, the vertical discrepancies were greater. The lowest discrepancy was displayed by polyvinyl siloxane (101 microm) and polyether (107 microm), and the greatest was displayed by wax (168 microm). When records were transferred onto casts, the discrepancies were approximately 0.5 mm, without significant differences among materials. CONCLUSION: Closure through interocclusal recording materials and removal and repositioning of the records on the apparatus produced small vertical discrepancies with clinically insignificant differences between the materials tested. When records of all materials tested were transferred onto casts, vertical discrepancies of approximately 0.5 mm were found, which is of clinical concern.
Sodium azide, when added to wells adjacent to untreated wells, caused an increase in the reversion rate of Salmonella typhimurium TA100 in a 12-well plate format. Increases in the reversion frequency in adjacent, untreated wells were observed when a single well on the plate was treated with as little as 1 microg of sodium azide. This effect is probably caused by the hydrolysis of sodium azide to form hydrazoic acid. Hydrazoic acid has a boiling point of 37 degrees C and, thus, would become a diffusible gas during the incubation of the plates. Our findings suggest that a diffusible gas is present and that this gas has the ability to contaminate nearby wells when using the multiwell version of the Ames assay. Furthermore, it may be prudent to isolate all positive controls and negative controls on separate plates with no test material since a volatile test material could produce spurious results in the Ames miniscreen.
Fly ash samples from a mixed hazardous waste (MHW) incinerator were subjected to solidification and stabilization (S/S) studies using ordinary Portland cement (OPC) as the binder. Additives (i.e., activated carbon and rice husk) were also homogenized with the binder and waste to determine the effectiveness of the immobilization of heavy metals. The toxicity characteristics leaching procedure (TCLP), Japanese Leaching Test (JLT-13) and the American Nuclear Test 16.1 (modified) ANS 16.1 were used to gauge the leaching of heavy metals from the solidified matrixes. Compressibility strength of the solidified matrixes was also tested using the American Standard Testing Material (ASTM) test procedure for the compressive strength of hydraulic cement mortars.
Cd-sulphate and a 38% dimethoate containing insecticide formulation (BI 58 EC) were used as test material in a teratogenicity test in chicken after administration as a single compounds or in combination. The incubated chicken eggs were directly exposed to the applied test materials with injection into the air-chamber in a volume of 0.1 ml/egg before the starting of incubation. Applied concentration of Cd-sulphate was 0.01% and the concentration of pesticide was 0.1%. Evaluation was done on day 19. In test of individual toxicity after injection on day 0 of incubation Cd-sulphate did not cause a significant reduction in body mass of embryos. The rate of embryonic mortality was 26%. After the administration of dimethoate containing insecticide formulation on day 0 of incubation no decrease occurred in embryonic body mass. The rate of embryonic mortality was 31%. The developmental anomalies observed in the different treatment groups occurred sporadically. The simultaneous administration of Cd-sulphate and the dimethoate containing insecticide formulation on day 0 of incubation resulted in expressed embryonic mortality. The rate of embryonic mortality was 93%. In summary, it can be established that the simultaneous administration of Cd-sulphate and the dimethoate containing insecticide formulation on day 0 in studies of chemical interaction exerted an adverse effect on embryonic mortality.
Current in vivo models for testing biomaterials are time and labor intensive as well as expensive. This article describes a new approach for testing biomaterials in vivo using the chorioallantoic membrane (CAM) of the developing chicken embryo, as an alternative to the traditional mammalian models. Fertilized chicken eggs were incubated for 4 days, at which time a small window was cut in the shell of the egg. After 1 week of incubation, the CAM received several test materials, including the endotoxin LPS, a cotton thread and a Silastic tubing. One day and 1 week later, the tissue response to the test materials was assessed using gross, histological, and scanning electron microscope evaluations. The inflammatory response of the chorioallantoic membrane to biomaterials was fully characterized and found to be similar to that of the mammalian response and was also seen to vary according to test materials. We also found that the structure and geometry of the test materials greatly influenced the incorporation of the samples in the CAM. The similarity of the tissue response of the CAM with the mammalian models, plus the low cost, simplicity, and possibility to continuously visualize the test site through the shell window make this animal model particularly attractive for the rapid in vivo screening of biomaterials.
The dissolution rates of rare earth oxides and two types of rare earth containing functional materials into water, saline solution, and Gamble's fluid were measured in order to evaluate the biological effects of rare earth-containing functional materials. The tested materials were yttrium, lanthanum, cerium and neodymium oxides, and neodymium-boron-iron magnet alloy (NdBFe) and lanthanum-mish-metal-nickel-cobalt (LmNiCo) hydrogen-containing alloy. The dissolution rates of the rare earth oxides were very low, resulting in concentrations of rare earth elements in the test solutions of the order of ppb. In the most extreme case, Gamble's fluid dissolved 1,400 times more of the rare earth oxides than pure water. Fairly high concentration of neodymium were found in the dissolving fluids, which means that trace neodymium present as an impurity in each rare earth oxide dissolved preferentially. For yttrium oxide, the ratio of neodymium to yttrium that dissolved in the saline solution was greater than 78,000 to 1, taking into account the amount of each that was originally present in the yttrium oxide.
Self-etching dentin adhesive systems, a new generation of dental-bonding agents, were investigated for their ability to block nerve conductance in the rat sciatic nerve model. Clearfil SE Bond, Mac Bond and FL Bond were used as test materials. Isolated rat sciatic nerves obtained from female albino rats were placed between two electrodes in a bath containing Tyrode solution. The bonding agents were brought into contact with the nerves and the evoked compound action potentials were recorded versus time before and after contact with the materials. Statistical analysis was performed using the Friedman and Wilcoxon Signed-Ranks tests (P = 0.01) to compare the mean percentage of inhibition between test materials versus time. All test materials were able to block nerve transmission rapidly (3.3 +/- 0.5, 5.1 +/- 2.3 and 8.0 +/- 1.9 min for SE Bond, Mac Bond and FL Bond, respectively). Significant differences were found between FL Bond and SE and Mac Bond (P < 0.01). These results indicated that the bonded systems tested, intended primarily as dentinal tubule occluders, may also exert some direct desensitizing effect on intratubular or pulpal nerve terminals in extremely deep cavities or pulpal microexposures, contributing to decreased postoperative pain.
BACKGROUND: Skin prick tests of native spices (commercial powdered spices) are common in patients with allergy to birch or mugwort pollen. Clinical symptoms from spices are infrequent but occasionally severe. OBJECTIVE: To compare the skin prick test results with native spices and spice extracts and to determine the clinical relevance of test material. METHODS: Skin prick tests with the native spices coriander, caraway, paprika, cayenne, mustard, and white pepper were made twice at 2-month to 2.9-year intervals in 49 patients. During the latter time, tests were also made with spice extracts and spice-specific serum IgE was measured. RESULTS: The reproducibility of skin test results with native spices was 67% to 100%. Spice extracts, except white pepper, elicited positive skin test reactions in half those with positive reactions to native spices. Higher specific IgE concentrations (> or = 3.5 PRU/mL) were seen in cases where the skin tests were positive to the corresponding spices with 5% extracts of > 8 kD Mw. Three-fourths of the patients with positive skin tests to native spices were positive to birch pollen and one-half to a vegetable. Mild clinical symptoms from spices were reported by one-third. CONCLUSIONS: Spice allergens partly crossreact with those of pollens and vegetables. A minority of spice allergens may give clinical symptoms. The > 8-kD 5% extracts may be relevant skin prick test materials for identifying patients at risk of developing severe symptoms from ingested spices.
CONTEXT: In proficiency testing surveys, there are differences in the values reported by users of various analytic methods. Two contributors to this variation are calibrator bias and matrix effects of proficiency testing materials. OBJECTIVES: (1) To quantify the biases of the analytic methods used to measure thyroid-stimulating hormone, thyroxine, triiodothyronine, free thyroxine, and free triiodothyronine levels; (2) to determine if these biases are within allowable limits; and (3) to ascertain if proficiency testing materials correctly identify these biases. DESIGN: A fresh frozen serum specimen was mailed as part of the 2003 College of American Pathologists Ligand and Chemistry surveys. The means and SDs for each analytic method were determined for this sample as well as for a proficiency testing sample from both surveys. In the fresh frozen serum sample, target values for thyroxine and triiodothyronine were determined by isotope dilution/liquid chromatography/tandem mass spectrometry. All other target values in the study were the median of the means obtained for the various analytic methods. MAIN OUTCOME MEASURES: Calibration biases were calculated by comparing the mean of each analytic method with the appropriate target values. These biases were evaluated against limits based on intra- and interindividual biological variation. Matrix effects of proficiency testing materials were assessed by comparing the rank of highest to lowest analytic method means (Spearman rank test) for each analyte. PARTICIPANTS: Approximately 3900 clinical laboratories were enrolled in the College of American Pathologists Chemistry and Ligand surveys. RESULTS: The number of methods in the Ligand Survey that failed to meet the goals for bias was 7 of 17 for thyroid-stimulating hormone and 11 of 13 for free thyroxine. The failure rates were 12 of 16 methods for thyroxine, 8 of 11 for triiodothyronine, and 9 of 11 for free triiodothyronine. The means of the analytic method for the proficiency testing material correlated significantly (P < .05) only with the fresh frozen serum means for thyroxine and thyroid-stimulating hormone in the Chemistry Survey and free triiodothyronine in the Ligand Survey. CONCLUSIONS: A majority of the methods used in thyroid function testing have biases that limit their clinical utility. Traditional proficiency testing materials do not adequately reflect these biases.
The cytotoxicity of hydroxyapatite (HA), tricalcium phosphate (TCP), and two types of apatite-containing glass-ceramics designated A.W-GC and A.W.CP-GC was evaluated by the direct contact method using V79 cells. Compatibility of the cells was assessed as a function of cellular attachment and subsequent growth using scanning electron microscopy. Although all of the tested materials have surfaces available for cellular attachment, cell growth was markedly inhibited by HA sintered at 600 degrees C and 900 degrees C, and slightly inhibited by HA sintered at 1200 degrees C, TCP and the glass-ceramics. In attempts to clarify the cause of this toxicity, the interactions of the ceramics with culture medium was assessed by measurement of calcium (Ca), inorganic phosphate (P), magnesium (Mg), pH and albumin content in the medium. The grade of toxicity corresponded to the degree of reduction of Ca, P, and albumin in the medium. Furthermore, surface reactions of the ceramics were demonstrated to vary in both mode and degree depending on their chemical structure and level of microporosity. Thus, the surface reactivity of ceramic materials should be always taken into account in discussing their biocompatibility in vivo.
Roughened titanium (Ti) surfaces have been widely used for dental implants. In recent years, there has been the tendency to replace Ti plasma-sprayed surfaces by sandblasted and acid-etched surfaces in order to enhance osseous apposition. Another approach has been the utilization of hydroxyapatite (HA)-coated implants. This study examines the effect of two roughened Ti dental implant surfaces on the osteoblastic phenotype of human bone-derived cells (HBDC) and compares this behavior to that for cells on an HA-coated surface. Test materials were an acid-etched and sandblasted Ti surface (Ti-DPS), a porous Ti plasma-sprayed coating (Ti-TPS), and a plasma-sprayed porous HA coating (HA). Smooth Ti machined surfaces served as control (Ti-ma). HBDC were grown on the substrata for 3, 7, 14, and 21 days, counted and probed for various bone-related mRNAs and proteins (type I collagen, osteocalcin, osteopontin, osteonectin, alkaline phosphatase, and bone sialoprotein). All dental implant surfaces significantly affected cellular growth and the temporal expression of an array of bone-related genes and proteins. HA-coated Ti had the most effect on osteoblastic differentiation inducing a greater expression of an array of osteogenic markers than recorded for cells grown on Ti-DPS and Ti-TPS, thus suggesting that the HA-coated surface may possess a higher potency to enhance osteogenesis. Furthermore, Ti-DPS surfaces induced greater osteoblast proliferation and differentiation than Ti-TPS.
Alginate (Alg), chitosan (Chi), collagen (Col), gelatin (Gel), and the mixtures of every two of them were screened to determine their suitability for hepatocyte culture. The test materials were fabricated as films and then evaluated on the basis of their abilities to promote the attachment and functions of rat hepatocytes cultured on them. Cellular attachment on Col and Gel was favorable. However, cellular viability, cytoskeleton organization and function, as evaluated by albumin production, ureagenesis, and enzyme activity of cytochrome P450 as well as expression levels of hepatocyte nuclear factor 4 alpha deteriorated. Reverse cellular behavior was observed on Alg and Chi. Two blends, composed of Chi and Col or Gel, were found to be superior to other materials and sustained viability and differentiated functions of hepatocyte.
A polyetherurethane (PU) was modified using fluorinated surface-modifying macromolecules (SMMs). A double radiolabel method was used simultaneously to measure the number of adhered platelets ((51)Cr) and the quantity of adsorbed Fg ((125)I), in a cone-and-plate instrument. The objectives were to determine if adsorbed Fg levels correlated to platelet adhesion on the surfaces, and to assess if any reductions in platelet adhesion for the SMM-treated surfaces resulted from surface-induced platelet lysis, rather than changes directly related to lower platelet activation and attachment on the novel surfaces. Platelet lysis was determined from lactate dehydrogenase (LDH) and unbound (51)Cr released into plasma isolated from whole blood exposed to test materials. The corresponding Fg adsorption, evaluated under the same platelet adhesion conditions, did not account for the reduced platelet adhesion on the treated surfaces. LDH and (51)Cr platelet release were very low and indicated no statistically significant differences between the materials. It was therefore concluded that platelet lysis did not contribute to the reduction in platelet adhesion characteristic observed on the SMM-treated surfaces. More importantly, the work emphasizes that the platelet activation cannot be inferred to by assessing the quantity of fibrinogen as is commonly done in the literature. The finding suggests a much more complex mechanism of action for the SMM surface modifiers. On-going work is investigating other Fg parameters such as protein binding affinity and protein conformational state in order to establish the mechanism by which the fluorinated surface modifiers may be reducing platelet adhesion via intermediary changes in initial protein adsorption.
The peroxidase-antiperoxidase (PAP) complex method has repeatedly been claimed to be more sensitive and antibody efficient than the indirect peroxidase labeled antibody method. However, most studies comparing these methods used tissue sections as the test material. However, test systems with known amounts of antigen will allow more reliable comparison of these methods and quantitative evaluation of method sensitivity. We therefore compared the antibody efficiency and sensitivity of these methods for the detection of human chorionic gonadotropin in an enzyme linked immunosorbent assay (ELISA), an antigen spot test (AST) and tissue sections of choriocarcinoma. In the PAP technique rabbit PAP and goat anti-rabbit antibody were applied. The same antibody was peroxidase-labeled with the periodate technique and used in the labeled antibody method. In the ELISA the PAP method resulted in slightly higher antibody efficiency than the labeled antibody method. At low primary antibody dilutions the intensity of the reaction decreased with the PAP method but remained high with the labeled antibody method, in the ELISA as well as on tissue sections. In the AST the labeled antibody method and the PAP method appeared to be equally sensitive.
The Department of Defense issued a Request for Proposal (RFP) for its next generation Picture Archiving and Communications System in January of 1997. The RFP was titled Digital Imaging Network-Picture Archiving and Communications System (DIN-PACS). Benchmark testing of the proposed vendors' systems occurred during the summer of 1997. This article highlights the methods for test material and test system organization, the major areas tested, and conduct of actual testing. Department of Defense and contract personnel wrote test procedures for benchmark testing based on the important features of the DIN-PACS Request for Proposal. Identical testing was performed with each vendor's system. The Digital Imaging and Communications in Medicine (DICOM) standard images used for the Benchmark Testing included all modalities. The images were verified as being DICOM standard compliant by the Mallinckrodt Institute of Radiology, Electronic Radiology Laboratory. The Johns Hopkins University Applied Physics Laboratory prepared the Unix-based server for the DICOM images and operated it during testing. The server was loaded with the images and shipped to each vendor's facility for on-site testing. The Defense Supply Center, Philadelphia (DSCP), the Department of Defense agency managing the DIN-PACS contract, provided representatives at each vendor site to ensure all tests were performed equitably and without bias. Each vendor's system was evaluated in the following nine major areas: DICOM Compliance; System Storage and Archive of Images; Network Performance; Workstation Performance; Radiology Information System Performance; Composite Health Care System/Health Level 7 communications standard Interface Performance; Teleradiology Performance; Quality Control; and Failover Functionality. These major sections were subdivided into workable test procedures and were then scored. A combined score for each section was compiled from this data. The names of the involved vendors and the scoring for each is contract sensitive and therefore can not be discussed. All of the vendors that underwent the benchmark testing did well. There was no one vendor that was markedly superior or inferior. There was a typical bell shaped curve of abilities. Each vendor had their own strong points and weaknesses. A standardized benchmark protocol and testing system for PACS architectures would be of great value to all agencies planning to purchase a PACS. This added information would assure the purchased system meets the needed functional requirements as outlined by the purchasers PACS Request for Proposal.