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Biomedical subjects

K Ekstrand

Publications and source records attributed to K Ekstrand.

At least 19 recordsLinked to original sources
PubMed1999

In vitro cytotoxicity of fibre-polymethyl methacrylate composite used in dentures.

The aim of this study was to determine the in vitro cytotoxicity of fibre-polymethyl methacrylate (PMMA) composite used in denture bases. Both heat-cured and autopolymerized PMMA were tested as the matrix of the fibre composite or as a plain denture polymer. The fibres tested included unsized E-glass and silica fibres, silica fibres which were sized with a silane coupling agent only, as well as commercially epoxy-silane or methacrylate-chrome complex sized E-glass fibres. The indirect contact cytotoxicity test by agar diffusion was carried out according to the international standard ISO 10993-5 after storing the test specimens in water for 24 h. PVC plastic was used as a positive control and polyethylene plastic was used as a negative control. Within the limitations of the agar diffusion test, it can be concluded that neither the unreinforced PMMA nor the fibre composite made from PMMA and fibres was cytotoxic.

Animals↗
PubMed1999

A polarized light and scanning electron microscopic study of human fissure and lingual enamel of unerupted mandibular third molars.

Using histological and ultrastructural techniques the aims of this study were to investigate whether the mineralization pattern and surface microanatomy of the caries-susceptible fissure enamel were different from those on the caries-inactive lingual surface. The material consisted of 31 unerupted third mandibular molars. The specimens were initially grouped into four categories: (1) without, (2) with initial, (3) with almost completed and (4) with completed root formation. One ground section with fissure-like morphology was selected from each tooth. Using water as a medium the observed birefringence was negative along the lingual and fissure transverses in specimens with almost completed and with completed root formation, while the observed birefringence was positive at different distances in the enamel in sections representing less maturation stages. Qualitative imbibition studies revealed hypomineralized enamel in the lower part of the fissures in specimens representing almost and completed root formation. Imbibed in quinoline, parts of the hypomineralized enamel behaved like a molecular sieve due to the presence of micropores, indicating that the structural arrangement is different from that in the enamel adjacent to this areas. After division of the sections into a lingual and a buccal part, SEM features were described from lower and upper parts of the buccal fissure wall and on lingual enamel in the area corresponding to the bottom part of the fissure. The surface microanatomy varied greatly. Negative developmental irregularities such as fissures and holes were associated with the immature enamel, while matured enamel - particularly fissures - housed many positive developmental irregularities such as enamel caps and protrusions. The crystal size in the mature specimens appeared smaller and more uniform than the crystals from the immature specimens. Apart from the occurrence of hypomineralized enamel in fissures and numerous positive developmental irregularities on the fissure surface, no major differences between fissure and lingual enamel were noticed, neither with respect to mineralization pattern during final stages of tooth development nor to the degree of surface porosity prior to tooth emergence.

Crystallography↗
PubMed1997

The influence of x-ray energy on lung dose uniformity in total-body irradiation.

PURPOSE: In this study we examine the influence of x-ray energy on the uniformity of the dose within the lung in total-body irradiation treatments in which partial transmission blocks are used to control the lung dose. METHODS AND MATERIALS: A solid water phantom with a cork insert to simulate a lung was irradiated by x-rays with energies of either 6, 10, or 18 MV. The source to phantom distance was 3.9 meters. The cork insert was either 10 cm wide or 6 cm wide. Partial transmission blocks with transmission factors of 50% were placed anterior to the cork insert. The blocks were either 8 or 4 cm in width. Kodak XV-2 film was placed in the midline of the phantom to record the dose. Midplane dose profiles were measured with a densitometer. RESULTS: For the 10 cm wide cork insert the uniformity of the dose over 80% of the block width varied from 6.6% for the 6 MV x-rays to 12.2% for the 18 MV x-rays. For the 6 cm wide cork insert the uniformity was comparable for all three x-ray energies, but for 18 MV the central dose increased by 9.4% compared to the 10 cm wide insert. CONCLUSION: Many factors must be considered in optimizing the dose for total-body irradiation. This study suggests that for AP/PA techniques lung dose uniformity is superior with 6 MV irradiation. The blanket recommendation that the highest x-ray energy be used in TBI is not valid for all situations.

Lung↗
PubMed1997

Submaximal early exercise test compared to clinical findings for evaluation of short- and long-term prognosis after the first myocardial infarction. Result from the MONICA Projects in Augsburg and Toulouse.

Clinical and ergometric data were derived from 1098 consecutive exercise tests in patients with a first acute myocardial infarction between 1974-1983. In 1992 a follow-up was performed in order to analyse the importance of a submaximal early exercise test, in combination with clinical data, for the prediction of short- and long-term prognosis of cardiovascular death. The relative value of 20 clinical variables, including medical history, markers of infarction size, medication etc., and 28 variables at exercise test were studied. Univariate, multivariate and survival analysis, for estimation of prognosis and independent prediction of cardiovascular death was used. Independent clinical risk factors for cardiovascular death were (1) Within 1 year: relative heart volume (ml.m-2 body surface area) on chest X-ray. (2) Long-term mortality: maximum heart rate and relative heart volume, diabetes, age and digitalis medication. Independent exercise risk factors were: (1) Within 1 year: heart rate, ventricular arrhythmia and ST depression > or = 1 mm before exercise, diastolic blood pressure at maximum exercise and target heart rate. (2) Long-term mortality: angina pectoris and/or ST depression > or = 1 mm at maximum exercise. In subgroups of patients with clinical risk factors, mortality risk increased if there were signs of angina pectoris and/or ST depression > or = 1 mm during exercise. The risk increased 100% in diabetics, 91% with age > 70 years, 58% with relative heart volume > or = 500 ml.m-2 body surface area, 42% with heart rate > or = 100 at admission, and 34% with digitalis medication. No increase was found in the subgroup of patients without clinical risk factors. Thus, submaximal early exercise stress testing provides important information for short- and long-term prognosis in patients after the first acute myocardial infarction compared to clinical evaluation alone.

Adult↗
PubMed1996

Cardiovascular risk factors in commercial flight aircrew officers compared with those in the general population.

Cardiovascular disease is the most common reason for loss of license among commercial flight pilots. This study was done to explore cardiovascular risk factors among aircrew officers. The study group consisted of 113 male commercial flight aircrew officers (aviators), aged thirty-five to forty-four years (mean: 38.8 years) who participated in the compulsory health screening. Men investigated at the Health Screening Centre, Malmö, were used as the reference group. Group 1, for ECG, (n 771), aged thirty-eight to forty-four years (mean: 42.1). Group 2, for height, weight, body mass index (BMI) (weight kg/height m2), blood pressure, serum cholesterol (total), and smoking habits (n 5005), aged thirty-five to forty-four years (mean: 39.2). The aviators did not differ from the reference population in regard to height, weight, BMI, diastolic blood pressure, or smoking habits. However, the incidences of electrocardiographic left ventricular hypertrophy, increased systolic blood pressure, and the level of cholesterol were significantly higher in the aviators when compared with the controls. Aircrew members may primarily be selected by criteria that differ from the male population in general. Excessive environmental stress, ie, shift work, jet lag, fatigue, as well as dietary factors, may also contribute to anomalies in the group. The clinical consequences of these anomalies for the aviators should be further evaluated, for they are important both for the aviators and for flying safety.

Adult↗
PubMed1995

Evaluation of implant-supported carbon/graphite fiber-reinforced poly (methyl methacrylate) prostheses. A longitudinal multicenter study.

Carbon/graphite fiber-reinforced poly (methyl methacrylate) (CGFP) has been suggested as an alternative framework material for implant-supported fixed prostheses. The aim of this study was to evaluate CGFP prostheses clinically over time in patients treated with titanium implants of the Brånemark type and to study the handling of the material in the technical production. Twenty-five patients were fitted with 27 CGFP prostheses supported by 119 implants. Three implants, all in the upper jaw, were lost after loading. After a mean functioning time of 44 months (range 32-56), 19 prostheses (70%) were still in situ. In all, 5 prostheses fractured, of which 3 were exchanged whereas 2 could be repaired. The fractures were discovered early after loading and located close to the end abutment cylinders. During the follow-up period, the bone loss around the implants was about the same as earlier reported values for fixed prostheses with cast frameworks. It is concluded that a CGFP framework can be used to form the biocompatible superstructure of implant-supported prostheses with high precision at a low material cost and with good aesthetic results. The mechanical properties are so far not satisfactory but the method has the potential to be further developed and standardized.

Adult↗
PubMed1993

Denture adhesives: cytotoxicity, microbial contamination, and formaldehyde content.

Denture adhesives are extensively used to enhance retention of dentures. Denture adhesives and their leachable components are ingested, but reports on the biologic aspects of denture adhesives are scarce. This study investigated some biological properties of 19 commercially available denture adhesives. The adhesives were assessed by the agar overlay technique and analyzed for microbial contamination and formaldehyde content. In the agar overlay test, all of the materials caused severe cytotoxic effects. Sabouraud dextrose agar was used for cultivation of fungi and tryptone soya broth for cultivation of aerobes, including fungi. Most of the samples tested showed microbial growth. The formaldehyde test revealed the presence of substantial amounts in four products and minor amounts in two products.

Adhesives↗
PubMed1992

Informational feedback and self-esteem among male and female athletes.

The self-esteem of male and female competitive athletes was compared after each was provided either positive or negative (verbal) informational feedback on a nonathletic task, a series of single-solution anagrams. Subjects were 50 men and 50 women, aged 18 to 25 years, who were tested on the semantic differential to estimate athletes' self-esteem before and after receiving the informational feedback. Over-all, female athletes responded more strongly to both feedback conditions, with both groups being more influenced by negative rather than by positive feedback.

Achievement↗
PubMed1991

Markers for development of hypertension in commercial flight aviators.

In order to discover markers for the development of cardiovascular disease and hypertension, we studied systolic and diastolic blood pressure, ECG, and heart rate before, during and after exercise; body mass index (BMI); serum cholesterol; and smoking habits in 183 male aviators (mean age 41 years at commencement, and 55 at follow-up). Those developing cardiovascular disease had an overrepresentation of smokers but the disease could not be related to any other variable. By contrast we found the following independent markers for prediction of future hypertension in normotensive aviators: increased BMI, increased diastolic blood pressure at 50 W, low heart rate at maximal exercise and smoking. Of these markers high diastolic blood pressure and low heart rate during exercise are new. Subjects with initially elevated blood pressure who did not develop hypertension decreased their diastolic blood pressure after exercise in contrast to those developing hypertension.

Aerospace Medicine↗
PubMed1991

[Indications and use of fissure sealants in public dental health care in Denmark. A questionnaire-investigation].

During the past decade usage of the fissure sealant technique for occlusal caries prevention has been increasingly recommended. This study explores variations in indications and usage of this technique in Denmark. A questionnaire was sent to 205 chief dental officers in the Danish Public Child Dental Health Service (PDHS) covering 90% of Danish children and to municipalities, where dental health to children is provided by private practitioners. More than half of the respondents did not use firmly defined criteria for fissure sealant application. Oral hygiene and previous caries experience were most often stated as indications. Actual usage of the sealant technique differed significantly from the PDHS and private clinics. Thus, 33% of the chief dental officers in the PDHS said that sealants were routinely applied to 8- and 13-year-olds, 43% to 30-80% of the children, and 15% used sealants to less than 10% of 8- and 13-year-olds. In contrast, only 5% of the private clinics reported routinely use of sealing technique, 22% used application to 30-80% of the children, while more than one third of the private practitioners used sealants to less than 10% of the 8- and 13-year-olds. In spite of the significant difference in sealant usage between PDHS and private practitioners, it was not possible to see a corresponding difference neither in caries prevalence nor in occlusal filling incidence. Moreover, analysis of PDHS caries prevalence data revealed that PDHS variations could not be explained by variations of risk in terms of social classes and caries incidence.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Carbon/graphite fiber reinforced poly(methyl methacrylate): properties under dry and wet conditions.

The flexural properties of poly(methyl methacrylate) (PMMA) reinforced with carbon/graphite (C/G) fibers with three different surface treatments were investigated by transverse bend testing after dry and wet storage. The fibers used were (1) commercially available fibers, (2) cleaned fibers, and (3) cleaned and sized fibers. The coating agents of commercial unidirectional and braided C/G fibers as well as impurities on C/G fibers for medical uses were characterized by means of high-performance liquid chromatography (HPLC). The agar overlay technique was used to assess the cytotoxicity of leachable elements from different fibers and processed composites. Composites with both unidirectional and braided tubular C/G fibers were investigated after storage in water. Fracture stress and flexural modulus decreased when "commercial" fibers were used as reinforcing material. Composites with cleaned and sized fibers gave only minor differences in flexural properties after dry and wet storage. By means of SEM micrographs the adhesion behavior of unsized C/G fibers, epoxy sized fibers, cleaned fibers, and cleaned and sized fibers were assessed. After water storage a substantial part of the cleaned fibers adhered to the matrix material. The adhesion capacity of the other fibers was reduced since the water absorption caused separation of fiber and matrix.

Biocompatible Materials↗
PubMed1987

Polymers for healing caps on titanium implants.

Healing caps are used during the healing period after abutment connection on titanium implants of the Branemark type. These healing caps consist of a screw embedded in polyamide-6 (PA-6) which is considerably weakened during this healing period. The properties of PA-6 and poly(4-methyl-1-pentene) (PMP) were studied. Storage in water at 37 degrees C led to a marked reduction in the flexural modulus of PA-6, but only a minor decrease for PMP. PA-6 showed a marked increase in volume due to water uptake, whereas PMP showed no significant change in volume. The improved properties of PMP compared to PA-6 when used for healing caps were demonstrated. The results of an agar overlay cytotoxicity test indicated that both PMP and PA-6 were nontoxic under laboratory controlled conditions.

Adsorption↗
PubMed1987

Ability of edentulous human beings to adapt to changes in vertical dimension.

The ability of ten edentulous patients and one patient with a full upper removable denture and a full arch (16-26) lower fixed denture to adapt to sudden change of the interocclusal distance was tested. An upper acrylic bite splint was inserted which, on average, increased the vertical dimension of the face by approximately twice the mean interocclusal distance during relaxation. After this procedure all patients quickly acquired an unstrained new postural position of the mandible. Directly after insertion, when instructed to relax, all patients hit the lower surface of the splint. They seemed, however, to need only one such experience to adapt to the increased interocclusal distance. The second time they repeated the procedure none of them touched the splint. Instead a new postural position was established with a mean interocclusal distance of 3.3 mm. This fast re-programming of jaw muscle tonus and length is assumed to be a response to different peripheral receptor discharge converging to the cerebellum and other programming centres. The present study on edentulous patients shows that afferent discharge from periodontal receptors is not a necessary prerequisite. It also confirms that the old concept of consistency of the mandibular postural position (Thompson, 1946) is erroneous.

Adaptation, Physiological↗
PubMed1987

Etching patterns of Co-Cr alloys for bonded cast restorations.

Resin-bonded bridges may replace missing teeth and act as splints in periodontal treatment. The objective of this study was to investigate the etch pattern after electrolytic etching of selected Co-Cr alloys in hydrochloric acid and to assess the changes in alloy composition after different etching times. The alloys investigated were Vitallium, Wironit, Wironium, Nobilium Hard, and Niranium NN. Alloy specimens were electrolytically etched in a hydrochloric acid solution for 1, 2, 5, and 10 min. The etched specimens were examined in a light microscope and a scanning electron microscope (SEM). Different etching patterns were revealed in the various alloys. Microprobe analyses after the etching of Vitallium showed generally that Co was released and that Cr content increased at the surface.

Acid Etching, Dental↗