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Biomedical subjects

M S Wolff

Publications and source records attributed to M S Wolff.

At least 73 records · Page 4Linked to original sources
PubMed1986

Shear strength of brackets bonded to anterior and posterior teeth.

A study was undertaken to determine the maximum shear strength of brackets bonded to anterior and posterior teeth. Brackets were bonded to two groups comprising 12 incisor and 12 molar teeth. After storage in water at 37 degrees C for 10 days, each bracket was tested to failure in a shear mode in a Instron machine. The mean value for the incisors was 164.3 +/- 35.1 kg/cm2 (16.1 +/- 3.4 MPa) and 115.7 +/- 41.1 kg/cm2 (11 +/- 4.0 MPa) for molars. These values, analyzed in a two-tailed test, were statistically different at the 0.01 level of confidence. It was concluded that differences in etching patterns do not necessarily affect shear bond strength and that the predominantly weak link in the bonding chain was at the bracket/resin interface. The lower values for molar teeth may relate to adaptation of the bracket and nonuniform resin thickness.

Acid Etching, Dental↗
PubMed1985

Oculodermatological findings in workers with occupational exposure to polychlorinated biphenyls (PCBs).

Oculodermatological findings, such as hypersecretion of the Meibomian glands, swelling of the upper eyelids and hyperpigmentation of the conjunctivae are considered typical of "PCB poisoning." They were common clinical manifestations of yusho and yu-cheng, two epidemics in Japan and Taiwan caused by the ingestion of rice cooking oil contaminated with polychlorinated biphenyls (PCBs) and polychlorinated dibenzofurans. To investigate the prevalence of such abnormalities in a population with long term occupational exposure to PCBs, a group of 326 workers employed in two capacitor manufacturing facilities were investigated in 1976, and 195 of these again in 1979. The median blood values of lower homologues of PCBs were 63 ppb (in plasma) in 1976 and 49 ppb (in serum) in 1979, and of the higher homologues 18 ppb and 17 X 5 ppb respectively. The prevalence of oculodermatological findings potentially related to the effects of PCBs were 9 X 4% and 13 X 3% at the two examinations. There was no significant association between such abnormalities and blood plasma/serum concentrations of PCBs. The observations in this work population exposed to PCBs differ from the yusho and yu-cheng experiences in that fewer clinical abnormalities were found. Suggestions are made that it may be inappropriate to extrapolate findings from the well known PCB poisoning episodes to exposures in occupational settings and that attention should be paid to the importance of polychlorinated dibenzofurans as an aetiological factor in human PCB poisoning.

Adult↗
PubMed1985

Occupational exposure to polychlorinated biphenyls (PCBs).

Human occupational exposure to polychlorinated biphenyls (PCBs) with varying chlorine content has been reported by several investigators, using analyses of blood or adipose samples or skin wipes to evaluate levels in the body. The intensity of occupational exposure is related to both duration and intensity of exposure. The qualitative nature of occupational exposure, as well as casual environmental exposure, has been shown to consist of less readily metabolized PCB congeners. The pattern of PCB congeners in human tissues, determined by gas chromatography, may or may not be readily ascribed to specific PCB standard mixtures. The average occupational exposure, as depicted in several studies of blood, plasma or serum concentrations, is approximately 10 to 1000 times that observed in nonoccupationally exposed persons. Currently used methods of PCB quantitation and pattern identification vary widely, with no uniformly administered criteria being applied to characterize human PCB exposure.

Adipose Tissue↗
PubMed1983

Occupationally derived chemicals in breast milk.

Exogenously derived chemicals have been widely reported in breast milk. Chemicals typically found in occupational exposures, including trace metals, solvents, and halogenated hydrocarbons, are reviewed, in terms of milk partition factors, potential infant exposures, and possible infant health effects. In addition to ingestion of a chemical from breast milk, an infant incurs a neonatal body burden of a chemical due to transplacental migration from maternal blood. For trace metals, neonatal blood levels are similar to maternal blood levels. Partition of metals to milk is less efficient, but nevertheless can contribute significantly to an infant's body burden. For lipid-soluble pesticide residues and halogenated biphenyls, neonatal body burden is much less than that of the mother, but transfer to milk is efficient, due to the high proportion of milk fat. It is suggested that potential organic mercury toxicity can be estimated from concentration in maternal blood or milk. For other chemicals, available data are not sufficient to evaluate short- or long-term health effects. However, for many halogenated hydrocarbons, concentrations in normal human milk would permit infant exposure above guidelines for allowable daily intake set by the World Health organization.

Body Burden↗
PubMed1982

Human tissue burdens of halogenated aromatic chemicals in Michigan.

A cross section of the population of Michigan was studied in 1978 to evaluate residual burdens of polybrominated biphenyls (PBBs), a flame-retardant chemical that had contaminated the state's food supply five years earlier. Levels of PBB were measured in serum specimens in 1,681 people and in adipose samples in 844. Ninety-seven percent of the adipose samples had detectable PBB concentrations. Levels of PBB were highest in that part of the state where meat and dairy products had been most contaminated and were lowest in the upper peninsula, farthest from the source. Levels for the rest of the state were in between. Polychlorinated biphenyls (PCB) and 2,2'-bis(p-chlorophenyl)-1, 1-dichloroethylene (p,p'-DDE), a dichlorodiphenyltrichloroethane (DDT) residue, were also measured, and variations of PBB, PCB, and p,p'-DDE levels with age and sex were investigated.

Accidents↗
PubMed1982

Body burden of polychlorinated biphenyls among persons employed in capacitor manufacturing.

In an effort to assess exposure among workers engaged in capacitors manufacture, PCB concentration was determined in plasma (290) and adipose tissue (61). In general, males had higher concentrations of PCBs than females. The correlation of plasma concentration (1-546 ppb) of the more highly chlorinated PCBs, which had been used in past, with total duration of employment suggested accumulation over time. The gc-ec pattern of these PCB peaks was, in most cases, characteristic of exposure to a PCB mixture with 54% chlorine. The less highly chlorinated PCBs, di-, tri-, and tetrachlorobiphenyls, were the source of current exposure, and were observed in concentrations of 6-2530 ppb in plasma. Higher exposure occurred among persons with direct contact with PCBs in jobs such as capacitor filling. Adipose tissue concentrations, for both the more highly chlorinated PCBs (1-165 ppm) and lower chlorinated PCBs (0.6-414 ppm), were proportional to those in plasma.

Adipose Tissue↗
PubMed1979

The neurotoxicity of polybrominated biphenyls: results of a medical field survey.

Neurologic symptoms were the earliest and most prominent symptoms recorded in Michigan farm residents exposed to PBB as compared to a non-PBB exposed control farm population in Wisconsin. In Michigan (particularly among males) those who exhibited the most marked symptoms tended to show diminished performance as assessed by special tests, although population differences in performance were not as marked. Low indices of performance were also significantly correlated with intake of home-produced foodstuffs, particularly during the years 1972--1974 and store-bought products during the years 1975--1976. Between 1972 and 1976 the Michigan farm residents studied made significant changes in their consumption patterns of products suspected to be contaminated with PBB, as compared to those of Wisconsin farm residents. Serum PBB levels were not found to be significantly higher in Michigan males and females exhibiting the most prominent neurologic symptoms. Serum PBB levels were negatively correlated with performance test scores, particularly in males in older age groups.

Adolescent↗