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Biomedical subjects

J R Dunn

Publications and source records attributed to J R Dunn.

At least 37 records · Page 2Linked to original sources
PubMed1994

Psychosocial effects of PCB contamination and remediation: the case of Smithville, Ontario.

A cross-sectional study design was used to investigate psychosocial effects in the population exposed to PCB contamination and remediation in Smithville, Ontario, Canada. Psychosocial effects were defined as the complex of distress, dysfunction and disability manifested in a wide range of psychological, social and behavioural outcomes as a consequence of actual or perceived contamination. This paper describes the results of logistic regression analyses conducted to investigate the determinants of psychosocial effects of exposure. The data come from an epidemiologic survey of a sample (N = 272) of Smithville households within 3 km of the site, and a sample from a matched comparison community (N = 263). Two types of outcome variables were used as indicators of psychosocial effects. Scores on the general measures of psychosocial health and well-being (the GHQ-20 and the somatic complaints checklist of the SCL-90) for the Smithville sample did not differ from those expected in a 'normal' population, nor did they differ from those in the comparison community. Scores on these outcomes were associated with plausibly linked independent variables, but were not associated with exposure to the PCB site. Results for site-specific outcome measures (concern and health concern) showed that moderate levels of concern reported by Smithville respondents were explained by concern about another local hazardous waste issue and could not be explained by PCB site exposure. We conclude from these results that local community context exerts an important influence on psychosocial effects of environmental contamination. Furthermore, the types of outcome measures employed and the timing of the research in the context of the site history were important factors in our ability to detect psychosocial effects of the PCB contamination and remediation in Smithville.

Adult↗
PubMed1993

Fracture resistance of amalgam and composite resin cores retained by various intradentinal retentive features.

The fracture strengths of amalgam and composite resin cores retained by three types of intradentinal retentive features were compared with the fracture strength of cores retained by four self-threaded retentive pins. Composite resin cores had significantly greater resistance to fracture than amalgam cores with any of the retentive features. The fracture strength of amalgam cores retained by retentive pins was comparable to that of amalgam cores retained by a post with a countersink, but significantly higher than the strength of those retained by slots or channels. The fracture strength of composite resin cores retained by retentive pins was significantly higher than that of composite resin cores retained by any of the alternative intradentinal retentive features.

Analysis of Variance↗
PubMed1992

Marginal leakage of cast gold crowns luted with an adhesive resin cement.

The microleakage of cast gold complete crowns cemented with Panavia EX cement was evaluated and compared with those luted with a standard zinc phosphate cement. The effect of water immersion of specimens for 30 and 90 days was also investigated. The finding of this study indicated that crowns cemented with Panavia EX cement exhibited substantially less marginal leakage than those cemented with zinc phosphate cement. No significant difference in marginal leakage was observed between 30-day and 90-day water immersion of crowns cemented with Panavia EX cement.

Adhesives↗
PubMed1992

Fracture resistance of composite and amalgam cores retained by pins coated with new adhesive resins.

This study determined the effects of coating pins with either Panavia EX or with 4-META (Cover-Up) materials on the fracture resistance of pin-retained amalgam and composite cores. Gold-plated stainless steel (TMS) and titanium (Filpin) self-threading pins were used. Findings of this study corroborated the findings of several other studies that the use of pins reduces the fracture resistance of restorations. However, coating the pins with adhesion promoters such as Panavia EX and 4-META materials has been found to be effective in improving the fracture resistance. Cross-preference was observed between TMS and Filpin pins; that is, Panavia material coating was more effective with TMS pins, while 4-META was more effective with Filpin pins.

Adhesives↗
PubMed1991

Microleakage of composite resin cores treated with various dentin bonding systems.

Composite resin post and cores have gained widespread acceptance as an alternative for cast-gold post and core systems. A prefabricated metal post is generally used. Substantial microleakage at the interface between the composite resin core and the dentin substrate may occur. A tight and impervious bond between the dentin and the restorative material is critical for the longevity of core restorations. This study compared the microleakage of composite resin cores treated with various dentin bonding agents, including the recently developed Gluma, Tenure, and Scotchbond 2. The results indicated that Tenure and Scotchbond 2 bonding agents were most effective in reducing microleakage, followed by Gluma and conventional Scotchbond (Dual Cure) bonding agents. Although all proprietary dentin bonding systems used in this study significantly reduced microleakage, no system was capable of preventing microleakage completely.

Analysis of Variance↗
PubMed1990

Microleakage at gingival dentin margins of Class V composite restorations lined with light-cured glass ionomer cement.

This study compared the microleakage of light-cured and auto-set glass ionomer liners used in Class V composite laminated glass ionomer restorations by determining the amount of microleakage at the gingival cementum/dentin margins. Standardized nonundercut V-shaped Class V cavities with gingival margins below the cementoenamel junction were prepared on the mesial and distal surfaces of 40 molars, establishing a total of 80 cavities, which were randomly divided into four groups. Each was lined with glass ionomers: group 1, Ketac-Bond (ESPE-Premier), which served as the control; group 2, XR-Ionomer (Kerr); group 3, XR-Ionomer with polyacrylic acid (PAA) pretreatment (Kerr); and group 4, Vitrabond (3M). Specimens were thermocycled for 300 cycles in 0.5% aqueous solution of basic fuchsin between 4 and 55 C with a 1-minute dwell time, and individually embedded in an epoxy resin. Statistical analysis indicated no differences among groups using the light-cured glass ionomer (groups 2 to 4), and they showed significantly less leakage than the control (group 1) at P less than 0.00001). Removal of the smear layer using 10% polyacrylic acid solution did not influence microleakage in restorations with light-cured glass ionomer liners.

Acid Etching, Dental↗
PubMed1989

Microleakage patterns of porcelain and castable ceramic laminate veneers.

This investigation evaluated the microleakage of conventional porcelain and Dicor castable ceramic laminate veneers bonded either entirely on acid-etched enamel or with the cervical margins on dentin. Three brands of light-activated composite resin cement systems were used and compared. Laminate veneers were bonded to extracted human maxillary central incisors and the extent of the marginal microleakage was measured. The findings indicated minimal marginal microleakage under both types of ceramic veneers bonded to all-enamel preparations. A markedly greater leakage at the dentin-composite resin interface was observed in veneers with cervical margins placed on dentin.

Acid Etching, Dental↗
PubMed1988

Temperature rise produced by various visible light generators through dentinal barriers.

This study evaluated and compared the heat generated by seven brands of light-curing units by measuring the temperature elevation from the ambient temperature through the use of a digital thermocouple-thermometer with a needle probe placed at three locations in the dentin. The results of this study indicated a wide range of differences in temperature rise among the tested light-curing units. In all three locations of probe placement, the Translux unit produced the least temperature elevation.

Dental Restoration, Permanent↗
PubMed1981

Lysosomal cathepsin B: correlation with metastatic potential.

Although lysosomal enzymes are implicated in the processes of tumor invasion and metastasis, their cellular origin within the tumor is unclear. The activity of the lysosomal proteinase cathepsin B is significantly elevated in a variant of the B16 melanoma with high metastatic potential. The cathepsin B activity is localized to the lysosomes of the tumor cells.

Animals↗
PubMed1975

Purification, properties and kinetics of sheep and human renin substrates.

Sheep plasma renin substrate was purified 1,200-fold by using nephrectomised sheep plasma, followed by DEAE-Sephadex chromatography and gel filtration. The purified substrate contained 8 mu-g angiotensin II/mg protein and had an estimated molecular weight of 52,000. The kinetic characteristics of the purified substrate were identical both to those of unpurified nephrectomised sheep plasma and to normal sheep plasma substrates. At pH 7.5, K-m of the human renin-sheep substrate reaction was 0.29 mu-M and for sheep renin-sheep substrate, 2.0 mu-M. Sheep substrate was susceptible to peptic digestion with generation of pepsitensin. Human renin substrate was less readily purified. DEAE-Sephadex chromatography of plasma from pregnant women at 36-40 weeks' gestation produced a 70-fold increase in purity (0.9 mu-g angiotensin II/mg protein). No further increase was achieved with gel filtration. Human renin substrate behaved as a larger (mol. wt. 82,000) more anionic protein than sheep substrate and was resistant to the proteolytic actions of both pepsin and sheep renin. K-m for the human renin-human substrate reaction was high and could not be accurately determined (range 3-8 mu-M, mean 5.7 mu-M). The presence of human substrate in a human renin-sheep substrate system did not alter the measured initial velocity. In both sheep and man, the normal concentration of renin substrate is considerably less than K-m and must therefore be considered a determinant of angiotensin production rate in vivo.

Angiotensin II↗
PubMedDate not supplied

Self-collection of antepartum anogenital group B streptococcus cultures.

BACKGROUND: Group B streptococcus (GBS) from the maternal perineum is a leading cause of serious neonatal infection. Recommendations by the Centers for Disease Control and Prevention include cultures from anogenital swabs on all pregnant women between 35 and 37 weeks' gestation. This study examines whether a significant difference in test results exists between GBS cultures from swabs done by physicians and those done by patients, and whether patients prefer to perform the swab themselves, with the potential of enhancing patient satisfaction and decreasing utilization of health care resources. METHODS: Study design was a comparison of 250 obstetrics patients attending a military community hospital family medicine clinic. Patients were assigned on an alternating basis to perform an anogenital culture swab before or after the physician performed a swab. Patients were designated to complete a preference survey before or after the swabs were performed. Descriptive statistics, chi square, and McNemar's test corrected for multiple comparisons, and the Kruskal-Wallis test on effect of order on test outcome were used to analyze the data. RESULTS: Forty-two of 250 patients had positive cultures. There was no statistically significant difference between swab results done by patients and those done by physicians. There was no significant difference between results of first swabs and results of second swabs. Of the 250 patients 145 preferred self-collection. There was no statistically significant relation between preference and order of completion of the questionnaire. CONCLUSIONS: Patient-collection technique is as accurate as physician collection. A majority of patients in this study population preferred self-collection of GBS swabs.

Adult↗
PubMedDate not supplied

Toward a lexicon of population health.

Despite its undeniable currency in research and policy circles, there remains considerable confusion about what 'population health' is. We propose a lexicon for population health in the hope of clarifying issues and advancing this important research emphasis and policy agenda. It distinguishes population health in its literal meaning from a population health perspective, population health research, a population health framework, and a population health approach to policy. Population health is more than just thinking in aggregate terms or about identifying vulnerable or at-risk subpopulations. A population health perspective is fundamentally concerned with the social nature of health influences. The social structures that shape health experiences transcend the characteristics or actions of any one individual, providing population health with analytic advantages over individualistic-oriented approaches to health and to health policy.

Canada↗