Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Laboratory Procedures”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 919 records · Page 51Linked to original sources
PubMed2004

Flexible denture flanges for patients exhibiting undercut tuberosities and reduced width of the buccal vestibule: a clinical report.

Buccal undercut of the maxillary tuberosity together with reduced width of the buccal vestibule can complicate denture fabrication. This clinical report describes the treatment options for this situation, the rationale for the design and use of flexible denture flanges in the maxillary posterior buccal vestibule, and the laboratory procedure for incorporation of flexible denture flanges in the undercut area.

Biocompatible Materials↗
PubMed2005

Effect of glazed and polished surface finishes on the friction coefficient of two low-fusing ceramics.

STATEMENT OF PROBLEM: All-ceramic and metal-ceramic dental restorations are potentially harmful because they may wear opposing enamel. Wear is a multifactorial process; however, laboratory procedures can minimize the wear process, thus benefiting clinicians and manufacturers. PURPOSE: This in vitro investigation of wear evaluated the physical and tribological characteristics of 2 low-fusing ceramics and dental enamel. MATERIAL AND METHODS: Quantitative and qualitative analyses of 2 low-fusing ceramics (IPS d.Sign and Vita Omega 900) and enamel were performed using scanning electron microscopy, x-ray diffraction, and energy-dispersive analyses. Each ceramic was tested using 20 disks (10 mm x 3 mm), of which 10 were glazed and 10 were polished. Ten polished enamel specimens (6 mm x 7 mm) served as the control. The specimens were submitted to a Vickers hardness test for 30 seconds using a 200 g load. The coefficient of friction was determined by using a pin-on-disk test without lubrication (5 N load, 600 seconds, 120 RPM). The data were analyzed using a 1-way analysis of variance and Sheffe analysis (alpha=.05). RESULTS: The same chemical elements were found in both ceramics, and tetragonal leucite was the main component of the crystalline phases. The microhardness of the enamel was significantly different ( P <.05) between the glazed and polished ceramics. There was no significant difference found in the friction coefficient (mean +/- SD) of the enamel (0.286 +/- 0.174), glazed Vita Omega 900 (0.309 +/- 0.085), and glazed IPS d.Sign (0.253 +/- 0.068) specimens. The mean friction coefficient of the polished Vita Omega 900 (0.486 +/- 0.036) and IPS d.Sign (0.446 +/- 0.037) specimens was found to be significantly higher than the enamel and glazed specimens ( P <.05). CONCLUSIONS: Both ceramics tested presented similar chemical-structural and tribological characteristics. When glazed, they showed tribological similarity to dental enamel.

Aluminum Silicates↗
PubMed2005

The use of three different matrices to ensure proper spatial dimension in fabricating definitive implant-supported prostheses.

Implant concepts continue to evolve not only in terms of materials, surfaces, and designs but also in clinical experience and technical management. This article presents a clinical and laboratory procedure describing how to plan, ensure, and achieve proper spatial dimension in fabricating definitive implant-supported prostheses with the use of 3 different matrices. This will in turn aid in restoring the patient with a predictable outcome from the outset of the treatment.

Dental Implantation, Endosseous↗
PubMed2005

Effect of soldering on the metal-ceramic bond strength of an Ni-Cr base alloy.

STATEMENT OF PROBLEM: Although soldering is a common laboratory procedure, the use of soldering alloys may adversely affect metal-ceramic bond strength and potentially decrease the longevity of metal-ceramic restorations. PURPOSE: The purpose of this study was to investigate the effect of soldering on metal-ceramic bond strength of a representative Ni-Cr base metal alloy. MATERIAL AND METHODS: Twenty-eight rectangular (25 x 3 x 0.5 mm) Ni-based alloy (Wiron 99) specimens were equally divided into soldering (S) and reference (R) groups. Soldering group specimens were covered with a 0.1-mm layer of the appropriate solder (Wiron-Lot) and reduced by 0.1 mm on the opposite side. Five specimens of each group were used for the measurement of surface roughness parameter (R(z)) and hardness, and 3 were used for measurement of the modulus of elasticity. Six specimens of each group were covered with porcelain (Ceramco 3) and subjected to a 3-point bending test for evaluation of the metal-ceramic bond strength according to the ISO 9693 specification. The data from surface roughness, hardness, modulus of elasticity, and metal-ceramic bond strength were analyzed statistically, using independent t tests (alpha=.05). RESULTS: Statistical analysis of the R(z) surface roughness parameter (S: 3.4 +/- 0.3 mum; R: 3.7 +/- 0.7 microm; P=.07) and bond strength (S: 46 +/- 3 MPa; R: 40 +/- 5 MPa; P=.057) failed to reveal any significant difference between the 2 groups. The specimens of the soldering group demonstrated significantly lower values both in hardness (S: 128 +/- 11 VHN; R: 217 +/- 4 VHN; P<.001) and in modulus of elasticity (S: 135 +/- 4 GPa; R: 183 +/- 6 GPa; P=.035) than the reference group. CONCLUSION: Under the conditions of the present study, the addition of solder to the base metal alloy did not affect the metal-ceramic bond strength.

Chromium Alloys↗
PubMed2006

Repair of a milled cantilevered implant overdenture bar: a clinical report.

This clinical report of a fractured cantilevered substructure bar describes an alternative treatment to the proposed refabrication of the substructure bar and overdenture prosthesis. This report outlines the clinical and laboratory procedures to repair the fractured bar, eliminating the time and expense of fabricating a new bar and prosthesis.

Aged↗
PubMed2006

Fabrication of a duplicate denture using visible light-polymerized resin as an interim denture base.

This article describes a technique for producing a duplicate denture using a visible light-polymerized (VLP) denture base for support prior to processing. A 2-part mold of the original denture was made, and then a sheet of VLP resin was reduced to a thickness of 0.5 mm and adapted to the fitting surface of the mold to create a denture base. The base was polymerized and the remaining features, such as the teeth and polished surfaces of the denture, were reproduced in wax. This technique may be helpful when performing subsequent clinical and laboratory procedures.

Acrylic Resins↗
PubMed2006

Cellular toxicity of mineral trioxide aggregate mixed with an alternative delivery vehicle.

OBJECTIVE: Mineral trioxide aggregate (MTA) mixed with water has a short working time, delayed setting, and poor consistency. A preliminary study suggested that substituting KY Jelly as a mixing vehicle improves the working properties of MTA. The present study compared the biocompatibility of white MTA mixed with water or with KY Jelly to that of Fuji II cement and of silver amalgam. STUDY DESIGN: Periodontal ligament (PDL) cells were cultured using standard laboratory procedures. Cells were plated in wells at a density of 10,000 cells/well. The test materials were mixed and eluate placed in contact with the PDL cells. Cell viability was determined by measuring mitochondrial enzyme activity using the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenytl)-2H-tetrazolium inner salt assay. Cytotoxicity was also measured in terms of cell lysis using the lactate dehydrogenase assay. The assays were completed in triplicate after time intervals of 24, 48, and 72 h. Mean cell counts were calculated and converted to a percentage of control results. A 2-way analysis of variance and Tukey honestly significant difference post-hoc test were performed to determine statistical significance. RESULTS: Eluate extractions from all materials caused significantly less cell viability and more cell death than control eluate (medium only) at all eluate time points tested. However, at 72 h the MTA/water, MTA/KY, and amalgam eluate extractions led to significantly better cell viability than the Fuji II eluates. However, there was significantly greater cell lysis for all eluates from the tested materials at 72 h than at 24 h. CONCLUSIONS: Within the limitations of this in vitro study, we conclude that MTA/KY, MTA/water, and amalgam have similar biocompatibility regarding effects of their eluates on human PDL cells, and eluates from all 3 materials demonstrate better biocompatibility than eluates derived from a resin-modified glass ionomer cement.

Aluminum Compounds↗
PubMed2004

Method for determination of methane potentials of solid organic waste.

A laboratory procedure is described for measuring methane potentials of organic solid waste. Triplicate reactors with 10 grams of volatile solids were incubated at 55 degrees C with 400 ml of inoculum from a thermophilic biogas plant and the methane production was followed over a 50-day period by regular measurements of methane on a gas chromatograph. The procedure involves blanks as well as cellulose controls. Methane potentials have been measured for source-separated organic household waste and for individual waste materials. The procedure has been evaluated regarding practicality, workload, detection limit, repeatability and reproducibility as well as quality control procedures. For the source-separated organic household waste a methane potential of 495 ml CH4/g VS was found. For fat and oil a lag-phase of several days was seen. The protein sample was clearly inhibited and the maximal methane potential was therefore not achieved. For paper bags, starch and glucose 63, 84 and 94% of the theoretical methane potential was achieved respectively. A detection limit of 72.5 ml CH4/g VS was calculated from the results. This is acceptable, since the methane potential of the tested waste materials was in the range of 200-500 ml CH4/g VS. The determination of methane potentials is a biological method subject to relatively large variation due to the use of non-standardized inoculum and waste heterogeneity. Therefore, procedures for addressing repeatability and reproducibility are suggested.

Bioreactors↗
PubMed2004

Testis-like development of gonads in female moles. New insights on mammalian gonad organogenesis.

Moles are unique among mammals because all females of several species of genus Talpa have bilateral ovotestes (gonads with both ovarian and testicular tissue). Based on the analysis of a large sample of embryos, foetuses and infants over a 13-year period, we have studied the development of the gonads in male and female moles of the species Talpa occidentalis. Several new field and laboratory procedures were developed specifically to obtain and manage this singular material. Our results reveal that gonads of female moles develop according to a testis-like pattern, which includes cord formation and mesonephric cell migration, and begins at the same time as testis differentiation in males. The first signs of sex differentiation do not appear in males but in females. Female (but not male) gonads are regionalised with a cortex (precursor of the ovarian tissue) and a medulla (precursor of the testicular tissue). Germ cells concentrate only in the cortex, so that the medulla soon becomes sterile. Testicular tissue development is transiently retarded in females for about a week before birth, and resumes afterwards. Development of the ovarian tissue in females is considerably delayed with respect to that of testicular tissue in both males and females. The molecular characterisation of peritubular myoid cells, which are exclusive of testes, evidences the presence of testicular tissue in the gonads of female moles, which also contain Leydig cells. However, the absence of fully differentiated Sertoli cells indicates that these cells are not responsible for triggering the differentiation of such a testicular tissue. Our results are also discussed regarding the definition of Sertoli cell morphology and function, and the possible role of germ cells in the sex-reversal process. Differences observed between XX and XY gonad development in moles suggest that the mammalian testis-determining gene, SRY, has an "anti-regionalisation" role during gonadal development, at least in those mammalian species in which regionalisation of the female gonad occurs.

Animals↗
PubMed2004

Computational methods for prediction of T-cell epitopes--a framework for modelling, testing, and applications.

Computational models complement laboratory experimentation for efficient identification of MHC-binding peptides and T-cell epitopes. Methods for prediction of MHC-binding peptides include binding motifs, quantitative matrices, artificial neural networks, hidden Markov models, and molecular modelling. Models derived by these methods have been successfully used for prediction of T-cell epitopes in cancer, autoimmunity, infectious disease, and allergy. For maximum benefit, the use of computer models must be treated as experiments analogous to standard laboratory procedures and performed according to strict standards. This requires careful selection of data for model building, and adequate testing and validation. A range of web-based databases and MHC-binding prediction programs are available. Although some available prediction programs for particular MHC alleles have reasonable accuracy, there is no guarantee that all models produce good quality predictions. In this article, we present and discuss a framework for modelling, testing, and applications of computational methods used in predictions of T-cell epitopes.

Animals↗
PubMed2006

Microbial flora on operating room telephones.

Approximately 500,000 surgical site infections (SSIs) occur each year in the United States. The purpose of this study was to determine if the bacteria most frequently involved in SSIs could be found on telephones in the OR. Twenty-six cultures were taken from telephones in 14 ORs and two substerile rooms at a large teaching medical center. Using standard laboratory procedures, the researchers identified coagulase-negative staphylococci in the cultures. The study found that telephones in the OR can serve as reservoirs for SSI-causing bacteria.

Bacterial Infections↗
PubMed1999

Neuroadaptations in the dopaminergic system after active self-administration but not after passive administration of methamphetamine.

Methamphetamine is a strong and long-lasting stimulant that can be easily synthesized and is effective when taken either orally, intravenously, or smoked as 'ice'. Due to it's escalating abuse, a clear need exists for laboratory procedures to evaluate motivational components of methamphetamine abuse and their underlying neurobiological mechanisms. In the present experiment, we utilized a 'yoked' procedure in which rats were run simultaneously in groups of three, with two rats serving as yoked controls which received an injection of either 0.1 mg/kg methamphetamine or saline which was not contingent on responding each time a response-contingent injection of 0.1 mg/kg methamphetamine was self-administered by the third paired rat. Rats that had actively self-administered methamphetamine for 5 weeks and were then withdrawn from methamphetamine for 24 h showed marked decreases in somatodendritic dopamine D2 autoreceptors levels in the ventral tegmental area (34%) and medial (31%) and dorsal (21%) part of the substantia nigra zona compacta with a corresponding down-regulation of dopamine D1 receptors in the shell of the nucleus accumbens (15%), as measured by in vitro quantitative autoradiography. Since the decreases in levels of dopamine D1 and D2 receptors which occurred in rats self-administering methamphetamine did not occur in littermates that received either yoked injections of methamphetamine or saline, these changes likely reflect motivational states that were present when methamphetamine injection depended on active drug self-administration behavior.

Animals↗
PubMed1991

In vivo and in vitro maturation of human oocytes: effects on embryo development and polyspermic fertilization.

OBJECTIVE: To compare the effects of in vivo and in vitro maturation of human oocytes. DESIGN: Women (n = 60) undergoing follicular stimulation for in vitro fertilization, using long-course analog therapy to suppress endogenous luteinizing hormone (LH), were randomly allocated to a short (34 hour) or long (39 hour) delay between human chorionic gonadotropin (hCG) administration and oocyte retrieval. Each patient's oocytes were divided into two groups that were either inseminated immediately or after 5 hours. RESULTS: The incidence of polyspermic fertilization was highest in oocytes inseminated immediately after a short hCG/oocyte retrieval interval (17/100) and was significantly (P less than 0.05) reduced by preincubation and/or a long hGG/oocyte retrieval interval. Fertilization rates were higher with 39 hours than with 34 hours in vivo maturation (84.2% versus 76.8%; P less than 0.05). The incidence of delayed fertilization was reduced by extending the hCG/oocyte retrieval interval (short, 12.9%; long, 3.9%; P less than 0.001). CONCLUSIONS: Extension of the in vivo maturation time increased fertilization rates and eliminated the requirement for preinsemination incubation, allowing simplification of laboratory procedures.

Chorionic Gonadotropin↗
PubMed1996

Accuracy of semen counting chambers as determined by the use of latex beads.

OBJECTIVE: To assess the accuracy of the Hemacytometer (Hausser Scientific, Horsham, PA), Makler (Sefi-Medical Instrument, Haifa, Israel), Cell-VU (Millennium Sciences Inc., New York, NY), and Micro-Cell chambers (Conception Technologies, San Diego, CA) counting chambers. DESIGN: A solution containing a known concentration of latex beads was used as the standard to perform counts on the four different counting chambers. MAIN OUTCOME MEASURES: Bead counts for the four different chambers were compared with the bead counts of the standard solution. Variability within chambers also was determined. RESULTS: Mean bead concentrations for both the Cell-VU and Micro-Cell chambers were consistently similar to the bead concentration of the standard solution. Both the hemacytometer and the Makler chambers overestimated the actual bead concentration of the standard solution by as much as 50% and revealed significant interchamber variability. CONCLUSIONS: Our data revealed marked differences in the accuracy and reliability of the different counting chambers tested and emphasized the need for standardization and quality control of laboratory procedures.

Humans↗
PubMed1992

Allergenicity of cow milk proteins.

The allergenicity and antigenicity of cow milk proteins are age dependent. Because the nonspecific and specific factors inhibiting the passage of cow milk proteins through the epithelial layer of the intestine are deficient at birth, although developing during early infancy, allergy to cow milk may be acquired during the first year of life. Allergic reactivity to cow milk is lost during childhood in the vast majority of cases. This change may depend at least partly on the development of the local immune system of the gut producing antigen-specific IgA antibodies. Circulating IgG antibodies to cow milk proteins are always produced when an infant has cow milk in the diet but are not associated with allergy; their titer is reduced with age. Clinical challenge tests show that most cow milk-allergic patients react to several protein fractions of cow milk. A patient may have IgE antibodies to several fractions of cow milk, measured either by skin testing or by radioallergosorbent test. Likewise, various tests for cell-mediated immunity may show positive reactions to several fractions. No single major allergen is apparent in cow milk, according to either the challenge tests or laboratory procedures: casein, alpha-lactalbumin, and beta-lactoglobulin all show a high proportion of positive reactions.

Animals↗
PubMed1991

An accelerated technique for casting post and core restorations.

An accelerated technique for casting a direct-pattern post and core restoration is presented. The entire clinical and laboratory procedure may be completed within 1 hour. The necessity for two appointments for completion of the restoration as well as the necessity of making two provisional restorations may be eliminated.

Acrylic Resins↗