Biomedical subjects

L Björkman

Publications and source records attributed to L Björkman.

At least 19 recordsLinked to original sources

PubMed2005

Environmental and heritable factors in the etiology of oral diseases--a population-based study of Swedish twins.

A population-based twin study is a useful design for quantification of the effects of genes and environmental factors in disease etiology. We used data from 10,000 Swedish twin pairs to quantify genetic and environmental contributions to tooth loss and periodontal health. Oral health information was obtained from telephone interviews. Structural equation models measured the relative importance of genetic and environmental factors. Genetic factors contributed to 14% of variation in tooth loss among women, and 39% among men. Non-shared environmental factors accounted for one-quarter of risk; environmental factors shared by twins comprised the remainder. Heritability estimates of periodontal disease were 39% and 33% for women and men, respectively, while non-shared environmental factors accounted for the remaining variation. Heritability for both conditions varied as a function of age and smoking status. Analysis of data from this large, population-based study demonstrates a moderate role of genetic factors in oral diseases, and suggests potential gene-environment interactions.

Adult↗

PubMed2003

The use of fluorometric assays to assess the immune response to DNA in murine systemic lupus erythematosus.

Antibodies to DNA (anti-DNA) play an important role in the pathogenesis of systemic lupus erythematosus (SLE). In blood, these antibodies may exist in a free, unbound state or as part of complexes with DNA. Furthermore, circulating DNA may be either complexed or free. Because of the central role of these immunoreactants (anti-DNA and DNA) in the disease, monitoring of their levels could provide valuable information for both clinical and investigative purposes. In these studies, we have explored the use of a DNA-binding dye, PicoGreen, for the detection of circulating DNA, either total or immune complex bound. In addition, we have used this dye for Farr-type antibody assays. Using autoimmune MRL/lpr mice as a model, we have shown that, while the levels of free DNA in the plasma of these mice were comparable with those of normal BALB/c mice, the amounts in complexes precipitable by ammonium sulfate were significantly greater. Furthermore, we showed that Farr assays using PicoGreen reliably detect levels of free anti-DNA, with values correlated with anti-DNA levels by an enzyme-linked immunosorbent assay. Together, our results suggest that a fluorometric dye can accurately monitor DNA and anti-DNA antibody levels in SLE and may provide important information on immunopathogenesis.

Ammonium Sulfate↗

PubMed2002

Multidisciplinary examination of patients with illness attributed to dental fillings.

OBJECTIVE AND METHODS: In 1993, a special Amalgam Clinic was established at Huddinge University Hospital. Residents in the Stockholm County area with morbidity attributed to dental fillings ('amalgam disease'), were referred to this clinic. Patients were examined by a dentist (n 428), a physician (n 379), and a psychologist (n 360). Sixty-nine per cent were women and 31% men; the mean patient age was 46 years. RESULTS: Oral symptoms included tender or aching teeth (60%), metallic taste (54%), sore mouth (43%) and dry mouth (43%). Signs of moderate or severe temporomandibular joint dysfunction were found in 81 cases, glossitis in 30 and oral lichen in 26 cases. Common general symptoms included diffuse pain (78%), general weakness (75%), extreme fatigue (68%) and dizziness (68%). Seven per cent of the patients suffered from previously undiagnosed medical conditions (thyroid dysfunction, anaemia, cardiopathy, renal disease, cancer). In 26 subjects, skin patch testing revealed allergy to mercury, gold or palladium. The median concentration of mercury was 10 nmol L-1 in whole blood, 3 nmol L-1 in plasma and 10 nmol L-1 in urine, i.e. normal levels. Earlier mental trauma was common, and in the psychological questionnaire SCL-90, clear tendencies to somatization were found. Only a few cases of severe psychiatric illness were observed. No positive correlation was found between the amount of amalgam and somatic symptoms or psychological effect parameters. CONCLUSIONS: The results do not support the hypothesis that release of mercury from amalgam fillings is the cause of 'amalgam disease', but suggest that there may be various explanations for the patient's complaints.

Acute Disease↗

PubMed2000

Retrospective study of orthodontic bonding without liquid resin.

The aim of this study was to evaluate the retention of fixed orthodontic appliances bonded without liquid resin with the use of a retrospective study design. Patients from each of 2 consultant orthodontists in the same specialty clinic were chosen under strict selection criteria. In the test group (n = 37), composite material (Phase II) without liquid resin was used to bond full arch fixed appliances onto patients' upper teeth. Patients' appliances, which were bonded with Phase II composite and liquid resin, were used as the control group (n = 37). The duration of the appliance survival, from the date of appliance bonding to the date of first accidental bracket loss, was analyzed by Kaplan-Meier product limit method and log-rank test. Our data suggested that supragingival orthodontic metal brackets seemed to bond on healthy enamel surfaces and to work equally well either with or without the use of liquid resin. The total percentages of bond failure, roughly 6%, were similar in both test and control groups. Approximately 73% of all patients in the test group and 57% of the patients in the control group experienced no bond failure at all throughout the entire course of treatment.

Adolescent↗

PubMed2000

In vitro shear bond strength of orthodontic bondings without liquid resin.

This study aimed at evaluating the early shear bond strength of enamel-composite-bracket adhesion accomplished without the use of liquid resin. Orthodontic brackets were bonded to the buccal surfaces of healthy extracted premolars in the test group by Transbond XT (n = 8) and Phase II (n = 8) composites but not the enclosed liquid resins in these products. Brackets bonded with the same materials (n = 8 for each) along with their corresponding liquid resin served as controls. The specimens were tested for shear bond strength after 24-h storage in water at 37 degrees C. The fractured surfaces were graded with Adhesive Remnant Index (ARI) under a 2x-dissection microscope. Enamel of the randomly selected test and control specimens was dissolved by 20% formic acid. Afterwards, the enamel side of the bonding materials in both groups (n = 4) was examined under the scanning electron microscope. ANOVA was used for statistical analyses. Our laboratory data suggest that the enamel adhesion produced by these two commercial materials without the use of liquid resin does not differ significantly in their early in vitro shear bond strength.

Acrylic Resins↗

PubMed2000

Both the environment and genes are important for concentrations of cadmium and lead in blood.

Concentrations of cadmium and lead in blood (BCd and BPb, respectively) are traditionally used as biomarkers of environmental exposure. We estimated the influence of genetic factors on these markers in a cohort of 61 monozygotic and 103 dizygotic twin pairs (mean age = 68 years, range = 49-86). BCd and BPb were determined by graphite furnace atomic absorption spectrophotometry. Variations in both BCd and BPb were influenced by not only environmental but also genetic factors. Interestingly, the genetic influence was considerably greater for nonsmoking women (h(2) = 65% for BCd and 58% for BPb) than for nonsmoking men (13 and 0%, respectively). The shared familial environmental (c(2)) influence for BPb was 37% for men but only 3% for women. The association between BCd and BPb could be attributed entirely to environmental factors of mutual importance for levels of the two metals. Thus, blood metal concentrations in women reflect not only exposure, as previously believed, but to a considerable extent hereditary factors possibly related to uptake and storage. Further steps should focus on identification of these genetic factors and evaluation of whether women are more susceptible to exposure to toxic metals than men.

Aged↗

PubMed2000

New filling materials--an occupational health hazard.

The acrylic content of dental composites poses a risk of adverse reactions. Although the quantities of the substances released are probably too small to cause systemic reactions, local skin or mucosal reactions may arise from direct contact with dental composites. In fact, epidemiological data suggest that most known side effects of dental resins are occupational dermatoses. They may either be due to irritation or allergy. In the Scandinavian countries, occupational dermatoses are relatively common among dental staff, sometimes entailing occupational disability and re-schooling. Most of these reactions can be avoided by observing precautions such as the minimization of the oxygen-inhibited-layer (OIL) in set composites and by using the resin-paste enamel bonding technique. The risk of occupational dermatoses could be reduced by the development of new bonding techniques and careful risk-benefit assessments in the use of dental composites.

Acrylic Resins↗

PubMed1999

Variation in blood concentrations of cadmium and lead in the elderly.

This study aims at characterizing blood concentrations of cadmium (B-Cd) and lead (B-Pb) in a group of 176 men and 248 women, 49-92 years of age (mean 68 years), selected from the Swedish Twin Registry. Metal concentrations were determined using graphite furnace atomic absorption spectrophotometry. B-Cd ranged from 0.05 to 6.8 microg Cd/L (median 0.36 microg Cd/L) and B-Pb from 5.6 to 150 microg Pb/L (median 27 microg Pb/L). As expected, smokers had higher B-Cd than nonsmokers (median 1.3 versus 0.32 microg Cd/L), while B-Pb was not significantly related to smoking habits. Among nonsmokers, women had higher B-Cd than men (median 0.35 versus 0.25 microg Cd/L). In men, but not women, B-Cd increased with age and consequently the gender-related difference in B-Cd was most obvious in the youngest age group. On the other hand, women had lower B-Pb than men (median 24 versus 30 microg Pb/L). In both men and women, B-Pb decreased between 50 and 70 years of age, perhaps reflecting decreased energy intake. In women, the highest B-Pb in the 50-55 years age group is probably related to an increased release of Pb from the skeleton during postmenopausal bone demineralization. After about 70 years, B-Pb tended to increase, which probably is a cohort effect due to much higher Pb exposure 10-30 years ago when leaded gasoline was used.

Aged↗

PubMed1999

In vitro cytotoxicity of orthodontic bonding resins on human oral fibroblasts.

Polymerization of bonding resins is compromised by atmospheric oxygen, giving rise to a layer of low molecular weight chemical species commonly known as the oxygen inhibited layer. The aim of this study was to evaluate the cytotoxic effect of this layer on primary cultures of human oral fibroblast. The cytotoxic effect related to the modes of polymerization of seven commercially available orthodontic bonding resins was also evaluated statistically. Each material was polymerized into 12 resin disks of standardized dimensions. Half of them were washed with 99% acetone to remove the oxygen inhibited layer. In duplicates, human oral fibroblasts were exposed to the intact and washed resin disks in tissue culture inserts. Cell viability was assessed by tetrazolium bromide reduction assay (MTT) 1, 3, and 6 days after exposure. Glass disks served as controls. ANOVA was used to test for statistical significance. Overall, the presence of an oxygen inhibited layer renders bonding resins 33% more cytotoxic (P <.01, F = 11.83, DF = 1). Light-cured and chemically cured 2-pastes materials had their mean cytotoxicities approximating their inert controls over 6 days. In chemically cured liquid-paste materials, the viability of human oral fibroblasts was only 37% (P <.001, F = 26.4, DF = 2) comparing to the control, 64% on day 1, 30% on day 3 and 14% on day 6. This suggested that the oxygen inhibited layer formed on the surface of bonding resins is an important cytotoxic source in vitro. Chemically cured liquid-paste materials were more cytotoxic than light-cured and chemically cured 2-paste materials. Further investigation into the influence of the modes of polymerization on materials' toxicodynamic effect is warranted to verify its clinical implication.

Analysis of Variance↗

PubMed1998

[New dental materials a health risk for dental staff. Acrylates can cause contact allergy and other problems].

The acrylic content of modern dental materials poses a risk of adverse reactions. Although the quantities of the substances released are normally too small to cause systemic reactions, local reactions may occur resulting in damage to the skin. A study, in which 81 dental workers referred to dermatologists for a variety of adverse reactions were patch tested, showed work-related dermatoses to represent a serious problem for dental staff, sometimes entailing occupational disability and re-schooling. Much of this could be avoided by observing special precautions to prevent direct contact with the sensitising substances in composite materials used in dental surgery. Since the use of dental amalgam has been reduced to about 10 per cent of all fillings in Sweden, the prevalence of adverse local reactions to the acrylic composite materials which are used instead may be expected to increase.

Acrylates↗

PubMed1998

Toxicological aspects on the release and systemic uptake of mercury from dental amalgam.

This paper summarizes some recent reports on mercury release from amalgam fillings and resulting concentrations in biological fluids, development of antibiotic resistance, and kidney function. In a series of studies of subjects with amalgam fillings, mercury (Hg) levels were followed in saliva, feces, blood, plasma, and urine before and until 60 d after removal of all of the fillings. The Hg concentrations in saliva remained elevated for at least 1 wk, suggesting that dissolved Hg vapor is not the major source of mercury in mixed saliva. An absorption phase of Hg was seen in plasma during 24 h after amalgam removal. After 60 d the plasma Hg concentration was reduced to 40%, of the baseline level. The decrease per amalgam surface was 0.11 nmol/l (range 0.02 0.40). The Hg level in feces increased two orders of magnitude two days after amalgam removal. At day 60, the median Hg concentration was still slightly higher than the median value of the amalgam free control group. The resistance patterns of the oral and intestinal microflora in these subjects were also studied. In the intestinal microflora, the relative amount of intestinal microorganisms resistant to 50 microM HgCl2 peaked 7 d after removal of the amalgam fillings, with a median value per sample of 6.1%, compared to 1.3% in samples collected prior to the Hg exposure. However, no statistical differences in the resistance pattern of the oral microflora were detected between the control and the experimental groups. A number of sensitive kidney function parameters were measured 1 wk before and 1, 2, and 60 d after amalgam removal. No effects on the various kidney parameters studied were recorded. According to the conclusions of independent evaluations from different state health agencies, the release of mercury from dental amalgam does not present any non-acceptable risk to the general population.

Absorption↗

PubMed1998

Determination of low levels of total mercury in blood and plasma by cold vapour atomic fluorescence spectrometry.

A sensitive and semi-automated analytical method allowing determination of low and normal levels of total mercury in human blood and plasma using cold vapour atomic fluorescence is described. Samples are digested overnight, or at an elevated temperature for 4 h, followed by bromination at room temperature. After reduction with tin (II), analysis is performed using automated continuous flow vapour generation coupled to a fluorescence detector, allowing 20 samples to be analysed per hour. Detection limits for blood and plasma were found to be 0.9 and 0.5 nmol Hg l-1, respectively. The method precision at various concentrations of mercury was determined. For whole blood at 8.1 nmol Hg l-1 and 12.9 nmol Hg l-1, the within-day precision was 5% and 6% and the between-day precision 9% and 6%, respectively. For plasma at 1.3 nmol Hg l-1, the within-day precision was 13% while the between-day precision was 17%. Accuracy was evaluated by an inter-laboratory comparison study. At blood mercury concentrations below 60 nmol Hg l-1 the results from the current method were almost identical to those obtained with radiochemical neutron activation analysis, commonly regarded as a reference method. The present method should have merits in relation to previously used methods using atomic absorption spectrometry.

Bromine↗

PubMed1997

Mercury in saliva and feces after removal of amalgam fillings.

The toxicological consequences of exposure to mercury (Hg) from dental amalgam fillings is a matter of debate in several countries. The purpose of this study was to obtain data on Hg concentrations in saliva and feces before and after removal of dental amalgam fillings. In addition Hg concentrations in urine, blood, and plasma were determined. Ten subjects had all amalgam fillings removed at one dental session. Before removal, the median Hg concentration in feces was more than 10 times higher than in samples from an amalgam free reference group consisting of 10 individuals (2.7 vs 0.23 mumol Hg/kg dry weight, p < 0.001). A considerable increase of the Hg concentration in feces 2 days after amalgam removal (median 280 mumol Hg/kg dry weight) was followed by a significant decrease. Sixty days after removal the median Hg concentration was still slightly higher than in samples from the reference group. In plasma, the median Hg concentration was 4 nmol/liter at baseline. Two days after removal the median Hg concentration in plasma was increased to 5 nmol/liter and declined subsequently to 1.3 nmol/liter by Day 60. In saliva, there was an exponential decline in the Hg concentration during the first 2 weeks after amalgam removal (t 1/2 = 1.8 days). It was concluded that amalgam fillings are a significant source of Hg in saliva and feces. Hg levels in all media decrease considerably after amalgam removal. The uptake of amalgam mercury in the GI tract in conjunction with removal of amalgam fillings seems to be low.

Adult↗

PubMed1996

Resistance of the normal human microflora to mercury and antimicrobials after exposure to mercury from dental amalgam fillings.

The concentrations of mercury in saliva and feces and the resistance pattern of the gastrointestinal microflora were investigated for 20 subjects. Ten patients, with a mean number of 19 amalgam surfaces, had all amalgam fillings removed during one dental session. Ten subjects without amalgam fillings served as a control group. Saliva and fecal samples were collected before amalgam removal and 2, 7, 14, and 60 days afterward. Mercury levels in saliva and feces correlated significantly with the number of amalgam surfaces. No differences in the resistance pattern of the oral microflora were detected between the two groups. In the amalgam group there was an increase in the relative number of intestinal microorganisms resistant to mercury, ampicillin, cefoxitin, erythromycin, and clindamycin on days 7-14. This was not statistically significant in light of the normal variations of the control group. A significant correlation between the prevalence of mercury resistance and multiple antimicrobial resistance in intestinal bacterial strains was observed.

Adolescent↗

PubMed1996

Physical and mental health related to dental amalgam fillings in Swedish twins.

In the past years increasing attention has been paid to possible adverse health effects of mercury exposure from dental amalgam fillings. To evaluate possible health effects from amalgam fillings, dental status registered by specially trained nurses was obtained from 587 subjects included in the ongoing Swedish Adoption/Twin Study of Aging (SATSA). Data on physical and mental health were collected and memory function tested. Mean age was 66 years (SD 9, range 46-89). In the entire material, 25% of the individuals had no own teeth and in the group with own teeth the median number of teeth surfaces filled with dental amalgam was 15 (range 0-65). Analyses of associations between number of surfaces filled with dental amalgam and a number of scales estimating somatic and mental health and memory functions were performed both for the entire group and for individuals having at least 12 teeth. Regardless of the sample, no negative effects on physical or mental health were found from amount of dental amalgam, even after controlling for age, gender, education and number of remaining teeth. When using a co-twin control design with twin pairs discordant for amalgam exposure, no negative health effects associated with dental amalgam were detected. This study does not indicate any negative effects from dental amalgam on physical or mental health or memory functions in the general population over 50 years of age.

Age Factors↗

PubMed1995

Selenium concentrations in brain after exposure to methylmercury: relations between the inorganic mercury fraction and selenium.

Three groups of female monkeys (Macaca fascicularis) were exposed to methylmercury (MeHg, p.o. 50 micrograms Hg/kg body wt per day) for 6, 12, or 18 months. One group was exposed to MeHg for 12 months and kept unexposed for 6 months before sacrifice. Another group of three monkeys was exposed to HgCl2 i.v. for 3 months. Total and inorganic mercury concentrations in occipital pole and thalamus were determined by cold vapor atomic absorption spectroscopy. Selenium concentrations were analyzed by hydride generation atomic absorption spectroscopy. The results indicated an association between concentrations of inorganic mercury and selenium in both occipital pole and thalamus in the MeHg-exposed animals. A linear regression model using concentrations of inorganic mercury (nmol/g wet wt) as independent variable, and selenium concentrations (nmol/g wet wt) as the dependent variable showed significant correlations between the variables in both occipital pole and thalamus (r = 0.85 and r = 0.91, P < 0.0001). The intercept of the regression line was slightly lower (about 2 nmol Se/g wet wt) than the selenium concentrations found in control monkeys (about 3 nmol Se/g wet wt). There was a tendency to a "hockey stick"-shaped relationship between concentrations of selenium and inorganic mercury in the thalamus of monkeys with ongoing exposure to MeHg. An important role for selenium in the retention of mercury in brain is indicated.

Animals↗

PubMed1994

Mercury and selenium distribution in human kidney cortex.

Concentration of mercury and selenium were analyzed in tissue fractions of human kidney cortex samples from seven autopsy cases. Total mercury content ranged between 0.3-9.0 nmol Hg/g wet wt. Between 27-61% of the total mercury was found in the 105,000g supernatant of the tissue homogenate from six cases. In kidney cortex from the seventh case, a decreased dentist with the highest concentration of mercury, only 3% of the total mercury was found in the 105,000g supernatant and about 88% in a SDS-insoluble fraction. In this fraction the molar ratio between mercury and selenium was close to 1:1. This study supports results from previous animal studies and indicates that mercury in human kidney cortex could be deposited in forms with different solubility. It could be of importance to speciate different forms of mercury in tissues according to solubility and association to selenium when interpretations of mercury concentrations are made.

Adolescent↗

PubMed1993

Activity of antioxidative enzymes in erythrocytes and concentration of selenium in plasma related to mercury exposure.

The activity of catalase and glutathione peroxidase (GSH-Px) in erythrocytes and concentration of selenium in plasma and mercury in whole blood, plasma, and urine were analyzed in 36 individuals occupationally exposed to mercury vapor, in 14 individuals with skin hypersensitivity to inorganic mercury, and in 17 individuals with subjective symptoms alleged to result from dental amalgam fillings. The control group consisted of 39 individuals with amalgam fillings, but no occupational exposure to mercury. Selenium in plasma was determined by GFAAS with Zeeman background correction. After exclusion of individuals with reported intake of selenium supplement the median plasma selenium concentration in the group with occupational exposure to mercury was 1.24 mumol/L, in the allergy group 1.22 mumol/L, in the amalgam group 1.25 mumol/L, and in the control group 1.22 mumol/L. The activities of catalase and GSH-Px were similar in all groups. However, in females lower GSH-Px activity was found in the amalgam group compared with females in the control group. GSH-Px activity in smokers was slightly lower than in non-smokers. No correlations were found between concentration of selenium or mercury in plasma and activity of glutathione peroxidase or catalase in erythrocytes.

Adult↗