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Biomedical subjects

M Bergman

Publications and source records attributed to M Bergman.

At least 91 records · Page 5Linked to original sources
PubMed1993

Polishing systems for dental ceramics.

The increasing use of ceramic crowns and inlays in posterior teeth has highlighted the clinical difficulties involved in achieving a good surface finish after corrective grinding. In the present work several polishing systems and techniques were compared, initially using only one dental ceramic, Vita Mark I. The two systems that produced the best results were then further used for the polishing of several different dental ceramics, mainly newer types. The initial surface roughness and the surface condition attained after various polishing stages were evaluated by using a surface roughness analyzer. In the initial test series the SofLex system and the Shofu Porcelain Laminate Polishing Kit produced the best results; they were therefore chosen for the second part of the investigation. In this the two polishing systems concerned produced a satisfactory surface finish in a clinically acceptable time for all the ceramics tested. The use of a diamond-containing polishing past did not improve the surface smoothness obtained with the SofLex system but gave a more varied result for the Shofu system.

Aluminum Oxide↗
PubMed1993

Femur fractures caused by gunshots: treatment by immediate reamed intramedullary nailing.

Fractures of the femur caused by gunshots are increasingly common. There is no standard treatment of these fractures since there are no clear guidelines relating these injuries to open fracture classification. We reviewed our experience with such fractures, which included 65 patients who had an immediate reamed intramedullary nail placed as treatment. The soft-tissue injury, vascular injury, missile velocity, and length of hospital stay were evaluated. We found that all patients healed with no infections. The overall morbidity and average hospital stay were decreased compared with studies advocating delayed intramedullary nailing and prolonged intravenous antibiotics. We recommend that patients with fractures of the femur caused by gunshots are candidates for immediate reamed intramedullary nailing providing that there is only mild to moderate soft-tissue contamination and no evidence of major devitalization.

Adolescent↗
PubMed1992

The human p50csk tyrosine kinase phosphorylates p56lck at Tyr-505 and down regulates its catalytic activity.

Protein tyrosine kinases participate in the transduction and modulation of signals that regulate proliferation and differentiation of cells. Excessive or deregulated protein tyrosine kinase activity can cause malignant transformation. The catalytic activity of the T cell protein tyrosine kinase p56lck is normally suppressed by phosphorylation of a carboxyl-terminal tyrosine, Tyr-505, by another cellular protein tyrosine kinase. Here we characterize a human cytosolic 50 kDa protein tyrosine kinase, p50csk, which specifically phosphorylates Tyr-505 of p56lck and a synthetic peptide containing this site. Phosphorylation of Tyr-505 suppressed the catalytic activity of p56lck. We suggest that p50csk negatively regulates p56lck, and perhaps other cellular src family kinases.

Amino Acid Sequence↗
PubMed1992

The c-src tyrosine kinase (CSK) gene, a potential antioncogene, localizes to human chromosome region 15q23----q25.

We have previously reported the cloning of a novel cytoplasmic tyrosine kinase, CSK. This tyrosine kinase has been shown to downregulate the tyrosine kinase activity of the c-src oncoprotein through tyrosine phosphorylation of the c-src carboxyl terminus. Cell transformation by src oncoproteins is caused by several oncogenic mechanisms, which interfere with this phosphorylation. The CSK gene could therefore potentially function as an antioncogene. We have here mapped the CSK gene to 15q23----q25 by in situ hybridization.

CSK Tyrosine-Protein Kinase↗
PubMed1992

Daily dose calculations from measurements of intra-oral mercury vapor.

Measurements of intra-oral mercury vapor from amalgam fillings are discussed. It was shown that the only quantity which it is possible to measure is the mercury release rate, and that the concentrations of mercury vapor in the oral cavity published in most earlier studies are the mercury concentrations in the measuring cell of the measuring apparatus and not the concentrations in the oral cavity. The consequences for the daily dose equations of the facts that the mercury source is present inside the oral cavity and that the amount of mercury released during a certain time is limited are discussed. It was found that most daily dose equations used have a questionable mercury distribution on inspiration, expiration, and swallowing. Re-calculations of almost all the available daily dose data showed a mean daily dose value of about 1.3 micrograms Hg/day (range, 0.3-2.2 micrograms Hg/day). The mean swallowed amount of mercury from intra-oral mercury vapor was calculated as being in the order of 10 micrograms Hg/day (range, 2.4-17 micrograms Hg/day), resulting in an estimated absorption of about 1 microgram Hg/day from the gastro-intestinal tract.

Air Pollution, Indoor↗
PubMed1992

A clinical examination of ceramic (Cerec) inlays.

Two hundred and five Cerec ceramic inlays placed by 8 dentists in 72 patients were examined independently by 3 calibrated evaluators 12-24 months after insertion, using the criteria of the California Dental Association (CDA) and also certain periodontal variables. Proximal dental plaque and bleeding on probing were not seen more often on Cerec surfaces than on control homologous surfaces. Ten patients reported postoperative sensitivity after treatment with Cerec inlays. Excellent CDA ratings for Color and Surface were obtained in 57% and 26%, respectively, and for Anatomic Form and Margin Integrity in 55% and 83%, respectively. Obvious differences were seen among the participating dentists with regard to the clinical quality of Cerec inlays. At present, the long-term performance of the Cerec technique cannot be predicted.

Adolescent↗
PubMed1992

Piezoelectricity in dental materials, a conceivable cause of postrestorative sensitivity.

With the increased use of tooth-colored posterior inlays reports of postrestorative sensitivity have also increased. One of the symptoms the patients complain of is a sharp pain when the inlays are loaded through chewing and biting. Many explanations for the causes of dissimilar types of postrestorative sensitivity have been offered, but one conceivable explanation that has not hitherto been studied is the direct piezoelectric effect in dental materials. Direct piezoelectric effect means that when certain anisotropic crystals are mechanically loaded, a charge is generated on the surface. The aim of the present study was to examine whether this physical phenomenon occurs in certain materials intended for dental use. Specimens of four different dental ceramics and one indirect composite resin for inlays were mechanically loaded with various forces, and the current was directly recorded. Currents of up to 0.9 microA with a pulse duraton of 0.4 msec were extracted, and it cannot be excluded that the piezoelectric phenomenon and related properties may cause postrestorative sensitivity. This has to be taken into consideration when posterior inlays of the types concerned are used.

Acrylic Resins↗
PubMed1992

Frequency selectivity as a potential measure of noise damage susceptibility.

The notched-noise procedure of Patterson (1974, Journal of the Accoustical Society of America, 55, 802-809; 1976, Journal of the Acoustical Society of America, 59, 640-654) was employed in revealing changes in auditory frequency selectivity (FS) in noise-exposed industrial workers in manufacturing plants in which noise levels in the working environment exceeded 90 dB(A). With 4 kHz as the test frequency, both threshold and FS measures were applied to three groups of non-exposed young adults (total N = 61) for reference values and to workers in three different factories, some ('noise-exposed') working in noise levels over 90 dB(A) (total N = 222). In another study involving 185 workers only the FS test was repeated after a work session, and the results are reported on 31 who worked in high noise levels. Pre-work-shift data showed that when thresholds were better than 30-dB HL most FS values were 10 dB or more, while subjects with hearing threshold levels beyond that showed reduced FS. Two post-work-shift studies of 144 ears of the noise-exposed workers showed significant deleterious changes in both thresholds and FS but the relationships were different in the two studies. The findings indicate that the notched-noise test is sensitive to noise-induced auditory damage, even after a single work-shift. Attractive features of the procedure are that it reduces the need for a quiet test environment and that it can be more resistant to testee manipulation or threshold 'learning' effects, often seen in industrial audiometric testing.

Acoustics↗
PubMed1992

The castability of unalloyed titanium in three different casting machines.

The general demand for a variety of fine detail work made of titanium has resulted in the development of equipment/systems for the casting of this metal. Dental casting machines suitable for the casting of titanium are now also available. The aim of the present study was therefore to evaluate the possibility of precision casting of dental crown restorations of unalloyed titanium. The three kinds of casting equipment currently used in Sweden were tested by evaluating the crown edge diameter of 10 titanium crowns processed by each one of the titanium casting machines. The results revealed that clinically acceptable margins can be obtained but also that further improvements in processing have to be achieved before titanium casting can be considered as uncomplicated as the casting of traditional dental gold alloys.

Crowns↗
PubMed1992

Base plate wax, dimensional stability and sorption of active components following treatment with disinfectant solutions.

The influence of seven disinfectants on the dimensional stability of a base plate wax, Tenax, was studied. Two methods for treatment were tested - immersion for one hour and spraying respectively. After spraying no significant influence on the wax could be established and after immersion four of the seven disinfectants, including Cidex and K-644, likewise had no significant influence on the dimensional stability. The wax specimens did not show any significant weight increase (less than one per cent) after immersion for four days but in four disinfectant solutions the surface properties of the wax specimens had changed showing that active components of the disinfectants were absorbed into or adsorbed on the wax surface.

Absorption↗
PubMed1992

Intraocular pressure level in glaucomatous and nonglaucomatous eyes after complicated cataract surgery and implantation of an AC-IOL.

The effects of a semiflexible, one-piece, open-loop anterior-chamber intraocular lens (AC-IOL) implanted after intracapsular or extracapsular cataract extraction complicated by posterior-capsular or zonular rupture on intraocular pressure (IOP) level and the control of previous glaucoma were studied in 48 eyes with primary implantation and in 10 eyes with secondary implantation. Fifty-four percent of the eyes with primary implantation had exfoliation syndrome; anterior vitrectomy was performed in 60.4%. An immediate pressure rise (IOP greater than or equal to 30 mm Hg) was observed in 29.3% of the eyes. The long-term IOP level (median follow up, 21.5 months) was less than or equal to 20 mm Hg in 83.7% and between 21 and 29 mm Hg in the remaining 16.3%. In three of the nine glaucomatous eyes, the medication had to be increased; in the remaining six, the IOP could be controlled with the previous or reduced medication or with none at all. In three out of the 49 (6.1%) nonglaucomatous eyes, glaucoma medication was started during the follow up. All of these eyes had exfoliation syndrome and two of the fellow eyes had similar IOPs and were receiving similar medication. The results indicate that the semiflexible, open-loop AC-IOL has little effect on IOP and seems to be a safe alternative, even in glaucomatous eyes, if a posterior chamber lens cannot be used.

Adult↗
PubMed1991

The effect of dietary vitamin E and beta-carotene on oxidation processes in the rat testis.

The effects of dietary vitamin E and beta-carotene were studied on enzymes involved in arachidonic acid metabolism and other related enzymes in the rat testis. Groups of rats were fed various soybean oil-based semi purified diets. Group 1 was fed a vitamin E-supplemented diet (+E - beta); Group 2 was fed a beta-carotene-supplemented diet (-E + beta); Group 3, the control group (-E - beta) was fed a vitamin E-deficient diet; and Group 4, the standard diet group (S), was fed vitamin E plus beta-carotene-standard diet. Soybean oxidized oil was added to the three diet groups - (+E - beta), (- E + beta) and (- E - beta), whereas the diet of S group contained non-oxidized oil. After 8 weeks rats were killed, blood and testis samples were collected for biochemical determinations. Vitamin E deficiency caused significant increase in testis thiobarbituric acid value and activities of testis NADPH oxidase, testis 15-lipoxygenase and in plasma pyruvate kinase. In contrast, significant decreases were observed in activity of testis prostaglandin synthetase, compared with antioxidant-supplemented diet groups. We also found a significant increase in 15-lipoxygenase activity in (- E + beta) diet group, compared with (- E - beta) diet group. Fatty acid analysis of testis parenchyma indicated decrease in palmitate (16:0) and arachidonate (20:4(n - 6)), and increase in oleate (18:1(n-6)) linoleate (18:2(n - 6)) and linolenate (18:3(n - 3)), when compared (-E - beta) diet group with vitamin E-supplemented diet groups. The results suggest that dietary vitamin E has a role in both enzymatic and non-enzymatic peroxidation of polyunsaturated fatty acids in the testis.

Animals↗
PubMed1991

Corrosion and strength of dental low-gold brazing materials.

Previous studies have shown the clinical feasibility of using three alternatives to dental casting gold alloys Type 3. In the present study brazed specimens of these alternatives were evaluated using a corrosion test and a tensile test according to a proposed ISO Standard (ISO/DIS 9333). Brazed specimens of a high-gold alloy were used as a reference. Furthermore, the microstructure of the brazed joints and the fracture surface characteristics were monitored. The present study revealed that none of the specimens exhibited any visual sign of chemical attack after suspension in the test solution for 7 days. The tensile strength testing resulted in stresses at fracture point that met the requirements of the proposed ISO Standard. All fractures were of the ductile type. Cohesive failures were seen in all specimens except in the reference alloy (JS C) specimens. No clear relationship between fracture surface appearance and tensile strength was found. Distinct demarcation lines between brazing and parent materials were seen. Based on the present results there seems to be no reason to reject the use of brazed constructions made of the alternative alloys Midas, Rajah, and Albacast.

Corrosion↗
PubMed1991

The effect of the three columns of the spine on the instantaneous axis of rotation in flexion and extension.

Instrumentation designed for stabilization and correction of spinal deformities must limit the amount of motion in flexion and extension. In flexion or extension, the vertebral bodies move about a specific point called the instantaneous axis of rotation. The ability of the implant to limit this motion is a function of its relation to the axis of rotation of the spine. The goal of this study was threefold: 1) to define the instantaneous axis of rotation of the spine in flexion and extension; 2) to study the effect of the loss of the three columns of the spine on the location of the instantaneous axis of rotation; and 3) to determine how the above parameters relate to the choice of anterior or posterior instrumentation. Ten human cadaver spines were subjected to compressive loads in flexion and extension. The columns of the spine were then destroyed in sequence at L3. The instantaneous axis of rotation for each vertebral body was found by the method of Reuleaux, and the effect of the compromise of the columns on the location of the instantaneous axis of rotation was noted. Understanding the exact location of the instantaneous axis of rotation after a specific injury would allow the clinician to objectively choose the best surgical approach and the appropriate instrumentation.

Humans↗
PubMed1991

cyl encodes a putative cytoplasmic tyrosine kinase lacking the conserved tyrosine autophosphorylation site (Y416src).

We have isolated a cDNA encoding a novel tyrosine kinase family member, named cyl (consensus tyrosine-lacking kinase), from the K562 human leukemia cell line. The deduced cyl protein lacks signal and transmembrane sequences but contains features of known cytoplasmic tyrosine kinases, including amino-terminal SH3 and SH2 domains. However, having very short amino and carboxy termini, cyl does not seem to belong to any of the previously characterized subfamilies of cytoplasmic tyrosine kinases. Furthermore, cyl lacks the highly conserved tyrosine autophosphorylation site (Y416src) in the tyrosine kinase catalytic domain. The cyl gene is located on human chromosome 15. It is expressed ubiquitously as two independently regulated mRNA species of 2.6 and 3.4 kb in human leukemia cell lines and fetal tissues.

Adrenal Glands↗
PubMed1990

Appearance and origin of snRNP antigens in chick erythrocyte nuclei reactivated in heterokaryons.

Fusion of terminally differentiated chick erythrocytes (CE) with transcriptionally active rat myoblasts results in heterokaryons in which the CE nuclei undergo reactivation of RNA synthesis and splicing. In order to analyze the transport and assembly of small nuclear ribonucleoprotein (snRNP) particles and larger molecular complexes engaged in RNA processing, we have examined CE nuclei in heterokaryons for the presence of four U snRNP-related nuclear antigens (Sm, 70,000 Mr, F78 and M3G-cap) and for one antigen (La), associated with RNA polymerase III transcripts. Inactive erythrocyte nuclei showed low levels of Sm and F78 antigens, but the other antigens were undetectable. Immediately after fusion, the fluorescence of the pre-existing chicken Sm antigen was detected in the CEn, and then the intensity of the signal increased rapidly during reactivation. The other antigens appeared more slowly, reaching full intensity at different time points after fusion. Blocking of chick transcription did not block the appearance of Sm, 70,000 Mr, cap and La antigens but did effectively inhibit the appearance of the F78 antigen. It has previously been demonstrated that the structure recognized by this monoclonal antibody is physically associated with functional splicing complexes. Blocking of translation in heterokaryons abolished uptake of snRNPs into the chicken nuclei. Taken together, the results indicate that rat snRNP complexes were imported into the chick nuclei after assembly in the cytoplasm. For all the studied antigens, except F78, this translocation was independent of chick RNA synthesis. The appearance of the F78 antigen was totally dependent on expression of chicken genes.

Animals↗