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PubMed1998

The thin electrolyte layer approach to corrosion testing of dental materials--characterization of the technique.

An innovative technique for corrosion testing of metallic dental materials is introduced. The thin electrolyte layer technique (TET) simulates the physical characteristics of the oral environment by employing a still, thin layer of an electrolyte, in contrast to bulk electrolyte techniques (BET) which utilize relatively large quantities of fluid. Limiting current density tests on a platinum electrode revealed a lower surface oxygen content for TET. Borate buffer (pH 6.8) was employed as an electrolyte. The effect of lower oxygen content in TET on passivation and polarization characteristics of 316L SS in 0.9% saline was investigated. The results revealed differences in the polarization resistance and open circuit potential development with time, as well as in anodic and cathodic polarization behavior. Lower O2 concentration in TET was attributed to different electrolyte convection characteristics under both testing conditions. Additionally, use of the TET resulted in better data reproducibility. Overall, this investigation led to a deeper understanding of the electrochemical processes inherent in thin electrolytes such as those found in the oral environment.

Alloys↗

PubMedDate not supplied

Design and application of a test system for viscoelastic characterization of collagen gels.

Characterization and control of the mechanical properties of the extracellular matrix are critical to the interpretation of results of in vitro studies of cultured tissues and cells and for the design of functional engineered constructs. In this work a viscoelastic tensile test system and custom culture chambers were developed and characterized. The system allowed quantification of strain as well as the stresses developed during cyclic viscoelastic material testing. Finite element analysis of the culture chambers indicated that the tensile strains near the actuated ends of the gel were greater than the strains experienced by material in the center of the culture chambers. However, the strain was uniformly distributed over the central substance of the gel, validating the assumption that a homogeneous strain state existed in the central region of the chamber. Viscoelastic testing was performed on collagen gels that were created with three different collagen concentrations. Results demonstrated that there was a significant increase in the dynamic stiffness of the gels with increasing equilibrium strain, collagen concentration, and frequency of applied strain. With increasing strain rate, the phase angle, representing the energy dissipated, dropped initially and then increased at higher rates. Mechanical testing of gels at different time intervals up to 7 days after polymerization demonstrated that the material properties remained stable when appropriate environmental conditions were maintained. The ability to characterize the viscoelastic properties of gels after different periods of culture will allow the quantification of alterations in gel material properties due to changes in cell cytoskeletal organization, cell-matrix interactions, and cellular activity on the matrix. Further, the test device provides a means to apply controlled mechanical loading to growing gel cultures. Finally, the results of this study will provide guidance to the design of further experiments on this substrate.

Biocompatible Materials↗

PubMed2006

Comparative nephrotoxicity of cisplatin and new octahedral Pt(IV) complexes.

PURPOSE: Previously, we have reported that the newly synthesized octahedral Pt(IV) compound, trans,cis-Pt(acetato)(2)Cl(2)(1,4-butanediamine), K101 and trans,cis-Pt(trifluoroacetato)(2)Cl(2)(1,4-butanediamine), K102 showed potent antitumor activities in vitro and in vivo. In order to compare the nephrotoxicity of the newly synthesized Pt(IV) complexes, K102 and K102 with cisplatin, we performed various tests. MATERIALS AND METHODS: We performed a single dose acute toxicity test for LD(50) values determination, biochemical assays in blood serum, acid phosphatase enzyme histochemistry and transmission electron microscopic studies in renal proximal tubular cells in mice in vivo. The route of drugs administration is intraperitoneal injection. RESULTS: In biochemical assays, the serum levels of BUN were significantly elevated at 6 h (p < 0.001), 1 day (p < 0.05) and 3 days (p < 0.001) after injection in cisplatin treated mice (6 mg/kg, single dose, i.p.). On the other hand, the serum levels of BUN were slightly elevated at 6 h (p < 0.01) only in K101 treated mice (8.2 mg/kg, single dose, i.p.), and were significantly raised at 6 h, 1 and 3 days (p < 0.05) after injection in K102 treated mice (6.2 mg/kg, single dose, i.p.). The higher serum BUN level in K102 treated mice is considered that K102 possesses more lipophilic fluoro group than acetyl group in K101. The values of creatinine and uric acid were similar in all groups. The ultrastructural morphological changes of K101- or K102-administrated mice were less remarkable than cisplatin-administrated mice. In acid phosphatase enzyme histochemistry, cisplatin treatment induced relevant changes in the distribution pattern of enzyme activity compared with K101 or K102 treatment at 7 days after injection. CONCLUSIONS: In conclusion, these results show that K101 is less nephrotoxic than cisplatin and a promising new platinum complex.

Acid Phosphatase↗

PubMed1978

Mechanical properties of tissue conditioners. Part II: creep characteristics.

These static creep characteristics indicate that under functional loads Coe-Comfort could behave satisfactorily as a tissue-conditioning material for periods up to 1 week, particularly for the first 24 hours postinsertion. However, the absence of published data on the tissue loads exerted by dentures in their resting state precludes making judgments as to the absolute efficiency of any of these materials as tissue-conditioning agents. When the present results are considered along with those obtained in an earlier study (Part I), the following general conclusions can be made: 1. Coe-Comfort should exhibit the best tissue-conditioning characteristics of the materials tested. 2. F.I.T.T. should perform as the best functional impression material. 3. Lynal is distinctly different from the other two materials in its mechanical properties. Its much greater stiffness coupled with much lower plasticity precludes a prediction of its relative clinical efficacy.

Chemical Phenomena↗

PubMed1989

The occurrence of HIV antibodies in drug addicts autopsied at the University Institute of Forensic Medicine in Copenhagen in 1987.

In 1987 a total of 89 intravenous drug addicts were admitted to medico-legal autopsy at the University Institute of Forensic Medicine in Copenhagen. Totally 10 cases were reactive by the Elisa test and five of these, or 7% of the total material tested, could be confirmed by the immuno-blotting test. The other five cases must be considered as false positive, possibly due to antibodies against cellular antigens. Among the five real positive cases, four were known before-hand while in one case the HIV-positivity was not known. These findings - together with the possibility of false negative reactions - especially regarding persons with acute HIV-infection, requires special precautionary measures when autopsies of drug addicts are performed.

Adult↗

PubMedDate not supplied

Effect of subacromial decompression on laxity of the acromioclavicular joint: biomechanical testing in a cadaveric model.

Subacromial decompression is a well-accepted treatment for impingement syndrome when nonoperative therapies have failed. However, recent clinical data have raised concern that arthroscopic subacromial decompression may lead to laxity of the acromioclavicular joint and, potentially, predispose patients to late postoperative acromioclavicular joint pain. Our goal was to determine whether subacromial decompression with co-planing of the distal clavicle alters the laxity, or compliance, of the acromioclavicular joint in a cadaveric model. Eighteen cadaveric shoulders were dissected and tested in a specially designed rig, driven by a hydraulic materials testing machine. One hundred-Newton loads were applied to the distal clavicle in the superior, posterior, and anterior directions, while acromioclavicular joint motion was recorded with a 3-dimensional infrared optical measurement system. Acromioplasty was performed with a posterior-referenced cutting block technique and included co-planing of the distal clavicle in all specimens. Joint compliance before and after subacromial decompression was compared with the paired t test. Subacromial decompression increased anteroposterior compliance by 13%, from 8.8 +/- 2.9 mm (mean +/- SD) in the intact joint to 9.9 +/- 3.1 mm (P =.001). Subacromial decompression increased superior compliance by 32%, from 3.1 +/- 1.5 mm in the native specimen to 4.1 +/- 1.8 mm (P =.03). These observations may have implications for the technique of acromioplasty. Although the immediate result of acromioplasty with co-planing appears to be an increase in the compliance of the acromioclavicular joint, the clinical significance of these findings has yet to be determined.

Acromioclavicular Joint↗

PubMed1997

The effect of intermittent-release intraperitoneal chemotherapy on wound healing.

OBJECTIVE: Our purpose was to study the effect on wound healing when intraperitoneal chemotherapy was instilled on a daily basis. STUDY DESIGN: Intraperitoneal carboplatin, Taxol, or saline solution was instilled daily into 70 rats after they underwent laparotomy. The animals were killed and analyzed for adhesions. An area measuring 5 x 5 cm including the incision was also harvested for biomechanical testing. The wound thickness was measured, and the Shore Western Materials Testing System (Monrovia, Calif.) was used to test the force required to break the wound, the stress, and the stiffness. RESULTS: Groups of 10 rats received saline solution control, carboplatin 6 mg/kg, 7 mg/kg, 8 mg/kg, or Taxol 2.5 mg/kg, 3.0 mg/kg, or 3.5 mg/kg. The total dose was divided into seven equal amounts, administered daily. No significant adhesions developed in any of the animals. The carboplatin group experienced no significant decrease in wound thickness whereas the higher-dose Taxol group had a significant decrease in thickness from 1.06 mm to 0.72 mm (p = 0.02). The wound-breaking strength (force) also decreased for the highest-dose Taxol group from 710 gm to 411 gm (p = 0.02). The wound stiffness was also decreased from 69 gm/mm to 46 gm/mm (p = 0.01). The other measured parameters for both the Taxol and carboplatin groups were not significantly decreased when compared with those of controls. CONCLUSION: The immediate instillation of divided daily carboplatin did not influence wound strength whereas the use of Taxol on a similar schedule significantly decreased wound strength.

Animals↗

PubMed1998

Development of a simple spectrophotometric method for propylene glycol detection in tablets.

A simple spectrophotometric procedure was developed and validated to indirectly assess the quantities of propylene glycol (PG) remaining in compressed liquid/powder admixtures. Such simplified quantitation may facilitate several testing procedures related to various aspects of formulation development and material testing of pharmaceutical powder excipients using various nonvolatile liquids as the diluents. In the present study, this new and simple approach for PG quantitation was developed as an integral part of a new method termed the liquisolid compressibility (LSC) test, used to characterize the compaction behavior of powder excipients. According to LSC testing, several admixtures of a nonvolatile liquid (in this case PG) and a powder, differing in their PG/powder weight ratio, are compressed in order to assess their compactabilities. The PG content of such compacts may then be directly quantitated by the USP gas chromatographic method or, indirectly, by this new simple spectrophotometric procedure. The new approach involves the addition of a dye marker to the PG prior to its incorporation into the powder. After compression, the PG amount remaining in the compacts may be determined by simply extracting the dye from the tablets and analyzing the extracts spectrophotometrically. In this manner, the dye content thus obtained may be extrapolated to the respective net amount of PG originally added as a dye/PG solution to the powder. Statistical comparison of the results obtained from both methods revealed almost absolute correlation.

Cellulose↗

PubMed2001

Identification of a female-specific, antennally active volatile compound of the currant stem girdler.

We identified (Z)-9-octadecen-4-olide as a female-specific, antennally active compound from the currant stem girdler Janus integer Norton. Female specificity was demonstrated by gas chromatographic comparison of liquid chromatography fractions of male and female volatile emissions and whole body extracts. The gamma-lactone was identified by coupled gas chromatographic-electroantennographic detection (GC-EAD), coupled gas chromatographic-mass spectrometric (GC-MS) analysis, microchemical reactions, and GC and MS comparison with authentic standards. GC-EAD analysis of female volatile emissions and cuticular extracts showed a single peak of activity on male antennae, which was not present in male-derived materials. Female antennae did not respond to any of the tested materials. The hydrogenation product of the natural EAD-active material was a known saturated gamma-lactone. The mass spectrum of the dimethyl disulfide derivative of the natural y -lactone was consistent with a double bond present in the 9 position. Comparison of the natural gamma-lactone and a synthesized racemic mixture of (Z)-9-octadecen-4-olide on a chiral GC column showed the presence of a single enantiomer in the natural material.

Animals↗

PubMedDate not supplied

Lysosomal-storage disorder induced by elmiron following 90-days gavage administration in rats and mice.

Elmiron, a highly sulfated, semisynthetic pentose polysaccharide with properties similar to heparin, is used for the treatment of interstitial cystitis. Thirteen-week gavage studies were conducted by administering the drug in deionized water to F344/N rats and B6C3F1 mice once daily, 5 days per week for up to 13 consecutive weeks, at doses of 0, 63, 125, 250, 500, and 1,000 mg/kg body weight. No significant drug-related effects were observed in body weight, survival, clinical, and necropsy results. Significant organ weight increases were seen in the liver, lungs, and spleen of both species and the kidneys of rats, mainly in groups treated with 250 mg/kg/day and above. Hematological analysis indicated increases for both species in the white blood cell and lymphocyte counts. Sites of toxicity identified histopathologically were the rectum, liver, mesenteric and mandibular lymph nodes (both sexes), spleen (mice only), and lungs and kidneys (rats only). Lesions consisted mainly of infiltration into multiple tissues of vacuolated histiocytes, which, by histochemical investigation, indicated the presence of neutral and acidic mucins and lipidic material within the vacuoles. Transmission electron microscopy identified these vacuoles as lysosomal structures that exhibited a variety of contents. On the basis of our findings, we propose that Elmiron was absorbed through the focally disrupted rectal mucosa, was deposited in the lamina propria, accumulated within macrophages, and then was distributed by these cells or as a free chemical via the lymphatics and blood, to the various organ sites manifesting histiocytic infiltration. The cytoplasmic membrane-bound structures within macrophages were lysosomes containing membranous material of cellular origin and, perhaps, remnants of the deposited test material, Elmiron.

Animals↗

PubMed1979

Correlation of fluorescence intensity and carcinogenic potency of synthetic and natural petroleums in mouse skin.

After standardized topical exposure of mouse skin to synthetic and natural petroleums, the penetration and persistence of the fluorescent components have been quantitated. Carcinogenicity of the same materials was determined by repeated skin application following by a period without treatment ot allow expression of malignantly transformed epidermal cells. No simple correlation was found for the materials between total specific fluorescence in either tissue or the test tube and their observed capacity to elicit skin necrosis or malignancy. The number of test materials was insufficient to allow generalization; however, the results do suggest that before fluorescence can be effectively employed as a tool for assessing potential occupational exposure to complex hydrocarbon mixtures, considerable refinement of the methodology will be required.

Animals↗

PubMed1999

A biomechanical analysis of internal fixation of complex tibial plateau fractures.

OBJECTIVE: To compare the mechanical stability of fixation of an unstable bicondylar tibial plateau fracture with several different fixation techniques in a cadaveric model. DESIGN: Randomized laboratory investigation using a simulated bicondylar tibial plateau fracture with metaphyseal-diaphyseal dissociation. SETTING: Complex tibial plateau fractures were instrumented and tested under ramp and cyclic loading conditions on a servohydraulic materials testing machine. INTERVENTION: Each tibia was instrumented sequentially with a lateral buttress plate, a lateral and a medial buttress plate, and a lateral buttress and an anteromedial antiglide plate for ramp load testing. For cyclic testing, one of the three constructs was used on each specimen. MAIN OUTCOME MEASUREMENTS: Vertical subsidence of the medial tibial plateau was measured in both ramp and cyclic loading in order to evaluate the three internal fixation techniques. RESULTS: No significant difference was measurable between the dual buttress construct and the lateral buttress/anteromedial antiglide construct. However, the lateral buttress plate alone provided significantly less stability. CONCLUSIONS: A lateral buttress plate with an anteromedial antiglide plate may provide equally effective fixation as compared with the dual buttress plating technique in complex tibial plateau fractures. This less invasive technique may also be associated with fewer complications due to the lack of soft tissue stripping that is required for its application.

Aged↗

PubMed2006

Spectral and temporal cues in cochlear implant speech perception.

OBJECTIVE: Taking advantage of the flexibility in the number of stimulating electrodes and the stimulation rate in a modern cochlear implant, the present study evaluated relative contributions of spectral and temporal cues to cochlear implant speech perception. DESIGN: Four experiments were conducted by using a Research Interface Box in five MED-EL COMBI 40+ cochlear implant users. Experiment 1 varied the number of electrodes from four to twelve or the maximal number of available active electrodes while keeping a constant stimulation rate at 1000 Hz per electrode. Experiment 2 varied the stimulation rate from 1000 to 4000 Hz per electrode on four pairs of fixed electrodes. Experiment 3 covaried the number of stimulating electrodes and the stimulation rate to study the trade-off between spectral and temporal cues. Experiment 4 studied the effects of envelope extraction on speech perception and listening preference, including half-wave rectification, full-wave rectification, and the Hilbert transform. Vowels, consonants, and HINT sentences in quiet, as well as with a competing female voice served as test materials. RESULTS: Experiment 1 found significant improvement in all speech tests with a higher number of stimulating electrodes. Experiment 2 found a significant advantage of the high stimulation rate only on consonant recognition and sentence recognition in noise. Experiment 3 found an almost linear trade-off between the number of stimulation electrodes and the stimulation rate for consonant and sentence recognition in quiet, but not for vowel and sentence recognition in noise. Experiment 4 found significantly better performance with the Hilbert transform and the full-wave rectification than the half-wave rectification. In addition, envelope extraction with the Hilbert transform produced the highest rating on subjective judgment of sound quality. CONCLUSIONS: Consistent with previous studies, the present result from the five MED-EL subjects showed that (1) the temporal envelope cues from a limited number of channels are sufficient to support high levels of phoneme and sentence recognition in quiet but not for speech recognition in a competing voice, (2) consonant recognition relies more on temporal cues while vowel recognition relies more on spectral cues, (3) spectral and temporal cues can be traded to some degree to produce similar performance in cochlear implant speech recognition, and (4) the Hilbert envelope improves both speech intelligibility and quality in cochlear implants.

Adult↗

PubMed1992

The isolation and identification of Leptospira interrogans serovar bratislava from a pig in Germany.

During a study on the improvement of selective media for the isolation of leptospires from clinical material, leptospires were isolated from the kidneys of a pig. Test material was cultured in EMJH-medium containing 0.4% rabbit serum and 3 inhibitory substances (Rifampicin 10 micrograms/ml, Amphotericin B 2 micrograms/ml, 5-Fluorouracil 100 micrograms/ml). The cultured leptospira-strain (Berlin 406) was identified to serogroup level using the cross agglutination method and it was further typed to serovar level by MAB's, factor analysis and restriction endonuclease analysis (REA). MAB typing of Berlin 406 gave an agglutination pattern profile typical of serovar bratislava. Factor serum identification clearly identified this strain as serovar bratislava. On REA examination, Berlin 406 gave a profile identical to that of the serovar bratislava type strain Jez Bratislava i.e. genotype B1. This is the first report of a confirmed isolate of Leptospira interrogans serovar bratislava from domestic animals in Germany. There exist a number of possibly important implications as this agent is being incriminated in the cause of clinical disease not only in pigs, but also in horses and dogs in other countries.

Animals↗

PubMed1999

A primary care evaluation of three near patient coagulometers.

AIM: To compare the reliability and relative costs of three international normalised ratio (INR) near patient tests. MATERIALS: Protime (ITC Technidyne), Coaguchek (Boehringer Mannheim), and TAS (Diagnostic Testing). METHODS: All patients attending one inner city general practice anticoagulation clinic were asked to participate, with two samples provided by patients not taking warfarin. A 5 ml sample of venous whole blood was taken from each patient and a drop immediately added to the prepared Coaguchek test strip followed by the Protime cuvette. The remainder was added to a citrated bottle. A drop of citrated blood was then placed on the TAS test card and the remainder sent to the reference laboratory for analysis. Parallel INR estimation was performed on the different near patient tests at each weekly anticoagulation clinic from July to December 1997. RESULTS: 19 patients receiving long term warfarin treatment provided 62 INR results. INR results ranged from 0.8-8.2 overall and 1.0-5.7 based on the laboratory method. Taking the laboratory method as the gold standard, 12/62 results were < 2.0 and 2/62 were > 4.5. There were no statistical or clinically significant differences between results from the three systems, although all near patient tests showed slightly higher mean readings than the laboratory, and 19-24% of tests would have resulted in different management decisions based on the machine used in comparison with the laboratory INR value. The cost of the near patient test systems varied substantially. CONCLUSIONS: All three near patient test systems are safe and efficient for producing acceptable and reproducible INR results within the therapeutic range in a primary care setting. All the systems were, however, subject to operator dependent variables at the time of blood letting. Adequate training in capillary blood sampling, specific use of the machines, and quality assurance procedures is therefore essential.

Anticoagulants↗

PubMed2004

Perceptibility curve test for conventional and colour-coded radiographs.

OBJECTIVE: A colour scale has been developed as a complement to the grey scale in radiographs. The aim of the present study was to compare colour-coded with conventional black-and-white radiographs in terms of the perceptibility curve test. MATERIALS AND METHODS: Twelve digital radiographs were exposed on a test object from low to high exposures and recorded using the DIXI system (Planmeca Oy, Helsinki, Finland). An aluminium test object was used containing ten object details in the form of holes with depths ranging from 0.03 mm to 0.30 mm in steps of 0.03+/-0.01 mm. The new colour scale was used to transform the conventional black-and-white radiographs into colour radiographs by specially designed software. Ten observers were asked to analyse four sets of radiographs, i.e. colour-coded and black-and-white radiographs, and reversed colour-coded and reversed black-and-white radiographs. The object detail having the lowest perceptible contrast in each radiograph was registered for each observer. Perceptibility curves were plotted based on the mean value of observer data. RESULTS: Results from the perceptibility curve test showed that the information in colour-coded radiographs was at least as good as that in black-and-white radiographs. In fact, in the lower exposure range, colour-coded radiographs exhibited better perception than conventional black-and-white radiographs. CONCLUSION: Radiographs that are colour-coded with the applied colour scale may be used as an alternative to conventional black-and-white radiographs.

Absorptiometry, Photon↗

PubMed1999

Attitudes toward colon cancer gene testing: survey of relatives of colon cancer patients.

OBJECTIVES: Various studies have identified psychosocial factors that may influence attitudes toward colon cancer gene testing. Whereas family history of colon cancer has been associated with interest in gene testing, this has not been examined extensively. We hypothesized that the strength of family history of colon cancer is associated with risk perception and willingness to undergo gene testing. MATERIALS AND METHODS: We evaluated attitudes toward colon cancer gene testing among persons who had at least one first-degree relative with colon cancer. A total of 2680 at-risk relatives in 863 kindreds were identified and mailed an extensive survey regarding sociodemographic variables, family history, health behaviors and knowledge, and willingness to take a colon cancer gene test. A total of 56.6% of persons completed and returned surveys. We conducted a brief telephone survey of a random sample of 200 persons who did not respond to the mail survey. RESULTS: The combined study sample of 1373 people was 42% male, had a mean age of 55 +/- 15 years, was 96% white, and had moderate-to-high SES. A total of 77.4% were very likely to take the gene test, and 92.4% were somewhat or very likely to take the gene test. A total of 78% of the sample perceived a higher colon cancer risk, although patterns of risk perception and worry differed significantly between mail survey and telephone survey respondents. More of the telephone survey respondents were also somewhat unlikely or very unlikely to take the gene test compared to the mail survey respondents (13.7% versus 6.9%). In the combined sample, concern about developing colon cancer and risk perception increased with number of relatives with colon cancer (P < 0.0001). Eight percent expressed no concern about developing colon cancer; 4.8% felt their chance of developing colon cancer was lower than others of the same age, sex, and race; and 3.3% felt that they were very unlikely to develop colon cancer in their lifetime. However, there was strong interest in gene testing regardless of the number of affected relatives, and persons with more affected relatives were generally willing to pay more for the gene test (up to $1000). CONCLUSIONS: The strength of family history of colon cancer is associated with risk perception but not with willingness to undergo gene testing.

Aged↗

PubMed2001

In vitro comparison of peak polymerization temperatures of 5 provisional restoration resins.

BACKGROUND: The heat produced by provisional restoration materials may injure the dental pulp. This study measured and compared peak temperatures during polymerization of 5 materials used in the fabrication of provisional restorations. METHODS: The tested materials were 2 self-curing resins (Integrity and Protemp) and 3 dual-cure resins (Iso-Temp, TCB Dual Cure and Provipont DC). A mould the size of a maxillary molar tooth was fabricated to contain 0.5 cc of resin. The temperature rise of the different materials was recorded every 10 seconds over a 10-minute period. RESULTS: The rise in temperature of Integrity (peak temperature of 33.8 degrees C) and Protemp Garant (35.6 degrees C) was significantly higher than the rise in temperature of Iso-Temp (29.5 degrees C), TCB Dual Cure (28.4 degrees C) and Provipont DC (29.5 degrees C). CONCLUSION: Use of the dual-cure resins in provisional restorations may reduce the risk of pulp injury.

Acrylic Resins↗