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Biomedical subjects

M S Gale

Publications and source records attributed to M S Gale.

12 recordsLinked to original sources
PubMed1999

Thermal cycling procedures for laboratory testing of dental restorations.

OBJECTIVES: Exposure of restorations in extracted teeth to cyclic thermal fluctuations to simulate one of the many factors in the oral environment has been common in many tracer penetration, marginal gap and bond strength laboratory tests. Temperature changes used have rarely been substantiated with temperature measurements made in vivo and vary considerably between reports. Justification and standardization of regimen are required. DATA, SOURCES AND STUDY SELECTION: An assessment of reports describing temperature changes of teeth in vivo is followed by an analysis of 130 studies of laboratory thermal cycling of teeth by 99 first authors selected from 25 journals. A clinically relevant thermal cycling regimen was derived from the in vivo information, and is suggested as a benchmark standard. CONCLUSIONS: Variation of regimens used was large, making comparison of reports difficult. Reports of testing the effects of thermal cycling were often contradictory, but generally leakage increased with thermal stress, although it has never been demonstrated that cyclic testing is relevant to clinical failures. However, should this be done, the standard cyclic regimen defined is: 35 degrees C (28 s), 15 degrees C (2 s), 35 degrees C (28 s), 45 degrees C (2 s). No evidence of the number of cycles likely to be experienced in vivo was found and this requires investigation, but a provisional estimate of approximately 10,000 cycles per year is suggested. Thermal stressing of restoration interfaces is only of value when the initial bond is already known to be reliable. This is not the case for most current restorative materials.

Benchmarking↗
PubMed1999

Dentine permeability and tracer tests.

OBJECTIVES: This paper reviews the evidence for dentine's permeability in order to clarify and emphasize its confounding effect on leakage test measurements, and hence the need to use special test designs to avoid its effects. METHODS: The literature on the subject between 1887 and 1997, including 249 articles. CONCLUSIONS: The prerequisite condition for any tracer penetration test is that unflawed specimens are themselves impermeable to tracer. Entry of tracer then can be used to indicate correctly the location or severity of flaws. The relative impermeability of intact dental enamel permits such testing of the enamel-restoration interface seal, but the same is not true when using dentine, which is usually frankly porous to most tracers through its tubules. False positive results are very likely. Recent intense interest in dentine bonding agents has increased the need and frequency of these tests with dentine, but this serious confounding factor has so far generally remained unstated, and has only been controlled adequately in one study. If tracer penetration test results are to be meaningful, then adequate control is required.

Animals↗
PubMed1997

Controlling dentine penetration in computer microleakage tracer mapping.

OBJECTIVES: Microleakage tracer penetration tests in dentine with simple sectioning are often confounded by dentine tubule penetration into the interface, leaching of water soluble tracers on wet sectioning, lack of standardized cavity dimensions affecting stresses, inadequate sectioning missing important tracer regions and airlocks obstructing tracer entry. The present aim was to create high resolution maps of stained interfaces without these confounding factors. METHODS: Ten intact extracted permanent upper central incisors were horizontally sectioned through the upper root, one third of the root length from the mid-buccal enamel limit. A dentine-bonded resin composite (Scotchbond MP, Z100, 3M) restoration was placed in a cylindrical cavity milled centrally in the root face of the coronal portion of five teeth. Tubules were angled at a mean of 12.5 +/- 4.8 degrees to the root face, and travelled approximately radially from the interface, such that tubule penetration was directed sufficiently radially outward to be distinguished from vertical interface penetration. Waterfast silver nitrate staining was applied with initial vacuum at 30 mmHg. A precision grinding machine serially removed approximately 100 microns increments of the tooth until no tracer remained, and computer image analysis data for the 18 revealed surfaces were used to construct detailed interface tracer maps. RESULTS: Control specimen tubule penetration was directed sufficiently radially outward to permit tubule penetration to be isolated from vertical interface penetration in test specimens, and ignored. Interface penetration ranged from approximately 0.3 to 1.6 mm in depth, and 0.90 to 5.09 mm2 in area. CONCLUSIONS: This method provided quantitative standardized high resolution mapping of interface tracer penetration, unconfounded by dentine penetration. None of the interfaces was fully sealed.

Coloring Agents↗
PubMed1994

Efficient retrovirus transduction of mouse pluripotent hematopoietic stem cells mobilized into the peripheral blood by treatment with granulocyte colony-stimulating factor and stem cell factor.

Cytokine-mobilized peripheral blood cells have been shown to participate in hematopoietic recovery after bone marrow (BM) transplantation, and are proposed to be useful targets for retrovirus-mediated gene transfer protocols. We treated mice with granulocyte colony-stimulating factor (G-CSF) and stem cell factor (SCF) to mobilize hematopoietic progenitor cells into the peripheral blood. These cells were analyzed for the number and frequency of pluripotent hematopoietic stem cells (PHSC). We found that splenectomized animals treated for 5 days with G-CSF and SCF showed a threefold increase in the absolute number of PHSC over normal mice. The number of peripheral-blood PHSC increased 250-fold from 29 per untreated mouse to 7,200 in peripheral-blood PHSC in splenectomized animals treated for 5 days with G-CSF and SCF. Peripheral blood PHSC mobilized by treatment with G-CSF and SCF were analyzed for their ability to be transduced by retroviral vectors. Peripheral-blood PHSC from splenectomized animals G-CSF and SCF were transduced with a recombinant retrovirus containing the human MDR-1 gene. The frequency of gene transfer into peripheral blood PHSC from animals treated for 5 and 7 days was two-fold and threefold higher than gene transfer into PHSC from the BM of 5-fluorouracil-treated mice (P < .01). We conclude that peripheral blood stem cells mobilized by treatment with G-CSF and SCF are excellent targets for retrovirus-mediated gene transfer.

Animals↗
PubMed1994

Three-dimensional reconstruction of microleakage pattern using a sequential grinding technique.

Dye penetration tests are very commonly used to detect the absence of a fluid seal at the tooth-restoration interface. Airlocks in the marginal gap, leaching of water-soluble tracers during processing, and the failure of only a few sections to allow interpretation of the full pattern, limit these tests to low reproducibility and precision. The purpose of this present study was to generate high-resolution three-dimensional images of waterfast tracer patterns. Cylindrical class V (3 mm diameter, 2 mm deep) dentine-bonded resin composite restorations in buccal coronal dentine were thermally cycled (1000 x, 8 degrees C, 55 degrees C, 30 s dwell at each temperature) and then silver stained using an initial vacuum (100 mmHg pressure). Each restoration was sequentially abraded from the free surface on wet 180 grit silicon carbide paper, producing up to 30 parallel surfaces at approximately 0.15 mm separation through the restoration down to the pulp. Images of the ground surfaces were captured, and assembled by a computer image analyser program to give a three-dimensional model of the tracer pattern. The maximum depths of tracer penetration below the reference surfaces were 3.00 mm, 2.09 mm, 3.16 mm and > 2.29 mm for the four specimens. Projections of the models were viewed from several directions with sections in various locations to allow investigation of the full tracer pattern. This method allows the creation of high-resolution three-dimensional tracer patterns.

Composite Resins↗
PubMed1979

Extended hospital care as treatment of choice.

A review of the histories of six patients who failed to adapt to community living after hospital discharge identified six factors that are predictive of serious maladjustment in the community. The are the absence of a family or soical network, repeated threats of violent behavior, previous hospitalization, poor previous functioning, inability to take responsibility for medical and mental health treatment, and suffering. Patients identified by two or more factors are likely to be unable to cope with life outside the hospital. The authors question whether attempting to maintain such patients in the community is desirable in terms of economic cost and patient suffering.

Adaptation, Psychological↗
PubMed1977

Interactional approach to the difficult emergency department patient.

An area of emergency medicine often overlooked is the management of physician-patient relationships. In the Department of Emergency Medicine, University of Cincinnati Medical Center, we use a method for facilitating difficult physician-patient interactions that includes presentation of case-study vignettes followed by recommendations for preventing or ameliorating undesirable interactions. Five of these vignettes are examined here, followed by commentary specific to the individual cases. General principles of action include letting patients or relatives have their say, remaining calm, empathic, courteous, objective and sharing information with patients.

Adolescent↗
PubMed1976

Psychiatric training for emergency medicine residents on a multidisciplinary team.

The Cincinnati General Hospital Emergency Department has a training program for emergency medicine residents on a multidisciplinary emergency psychiatry team. This essential training should occur in the emergency department setting rather than in psychiatric inpatient units of state hospital settings. There are advantages and disadvantages to this arrangement. Nonmedical members of the emergency psychiatry team train and support emergency medicine residents in a multidisciplinary approach to treatment. Some observations are made about how the emergency medicine residents deal with emotionally disturbed patients. Finally, 80% of emergency medicine residents responded to questionnaire on their reactions to the multidisciplinary emergency psychiatry team.

Attitude of Health Personnel↗