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Biomedical subjects

L Niemi

Publications and source records attributed to L Niemi.

18 recordsLinked to original sources
PubMed1992

Reaction of bone to HA, carbonate-HA, hydroxyapatite + calcium orthophosphate and to hydroxyapatite + calcium ortho- and pyrophosphate.

Slip cast conical implants of HA, carbonate-HA, calcium orthophosphate/hydroxyapatite and hydroxyapatite/calcium pyrophosphate/calcium orthophosphate with weight ratios 75/25 and 50/30/20 were implanted in rabbit tibia. The bone-implant interfaces were evaluated histologically, by means of SEM/EDX analysis and by push-out test. Thirty-six implanted samples were investigated after 2, 8, and 24 weeks. The triphasic calcium phosphate showed a moderate disintegration. This material showed 2 weeks after implantation a bonding between new bone and implant could be seen in parts of the operation site by SEM. Eight weeks after implantation an intimate relationship between the bone tissue and all specimens of each material was found. After 24 weeks the Ca/P ratio in the bone had reached the Ca/P ratio of mature bone determined by SEM/EDX analysis.

Animals↗
PubMed1992

Is there need for change of health examinations for sea pilots?

Sea pilots must be capable of carrying out their work in all situations. Thus, they must not have any disease or defect, that could impair their job performance. By periodic medical examinations attempts are made to ensure their working capacity. In most countries these examinations are carried out by a general practitioner and they include only few if any objective laboratory tests. The aim of the present investigation was to study the effectiveness of the periodic medical examinations to find out in the population of pilots examined persons with health risks, especially risks for cardiovascular diseases. All the pilots examined were over 45 years old (n = 135, response rate 88%). Self-evaluation of health was carried out by a questionnaire. Blood analyses were made and chest X-ray as well as exercise-ECC were taken. The most common subjective symptoms concerned musculoskeletal and gastrointestinal systems; sleep disturbances were also quite common. The three most frequent diseases diagnosed earlier by a doctor were musculoskeletal and gastrointestinal diseases, and arterial hypertension. About 24% of pilots had a lower physical working capacity than predicted. The body mass index indicated at least 11% overweight in half of the cases. At exercise-ECG four pilots appeared to have an ischaemic heart disease and additionally eleven pilots had abnormal ECG. Over 80% of pilots had a serum cholesterol value higher than 5 mmol/l, and serum triglyceride values exceeded the normal value of 2.0 mmol/l in every fourth case. Serum glutamyl transaminase was pathological in over 20% of the cases, and serum glucose level in 8%. The findings by routine physical examinations were very few consisting of stiffness in musculoskeletal system, two cases of elevated blood pressure, two heart murmurs, varicose veins etc. In two cases an inguinal hernia was suspected. The current periodic health examinations does not seem to effectively prevent a person with possible health defect from working as a sea pilot. More objective tests must be included in these examinations and more attention should be paid to prevention of overweight, effective treatment of musculoskeletal symptoms, improving physical working capacity and helping pilots to manage their psychic stress.

Body Mass Index↗
PubMed1990

The influence of ageing on the release of hydrocortisone from o/w creams.

The influence of ageing on the release of hydrocortisone from o/w creams containing ionic and nonionic emulgators and different amounts of water was investigated over a period of 48 weeks. The influence of ageing was dependent on the type of emulgator and the amount of water in the cream. Up to 12 weeks of storage, ageing affected the creams containing ionic emulgators by retarding the release of hydrocortisone; after that, hydrocortisone release was enhanced and the release profile also changed. For the creams containing 60% water, the effects of ageing differed slightly from the creams containing 40% or 80% water. These findings can be explained by particle growth and agglomeration but changes in the microstructure of the creams may also be important. Creams containing nonionic emulgators were only slightly affected by ageing.

Animals↗
PubMed1989

Effect of water content and type of emulgator on the release of hydrocortisone from o/w creams.

The release of hydrocortisone was determined in vitro from o/w-creams containing an anionic (sodium lauryl sulphate), a cationic (cetrimide) or a nonionic (cetomacrogol 1000) surfactant as emulgator and different amounts of water. The solubility of hydrocortisone in water-emulgator systems and the solubilizing capacity of these emulgators for hydrocortisone were also determined. The release of hydrocortisone from creams containing emulgators increased in the same order as the solubilizing capacity of these emulgators for hydrocortisone, which indicates how important the concentration of dissolved hydrocortisone in the cream is for release. The effect of water content on the release of hydrocortisone was also dependent on the emulgator used. With a nonionic emulgator, release was enhanced slightly as the water content in the cream increased. In the case of ionic emulgators, release of hydrocortisone was retarded as the amounts of water in the cream increased up to 60% water content; above this, the release was enhanced, probably owing to changes in the liquid crystalline microstructure of the cream.

Emulsions↗
PubMed1989

Influence of ageing on hydrocortisone particles in o/w creams.

The influence of ageing on hydrocortisone crystal growth and particle location in nine o/w-creams was examined microscopically over a period of 48 weeks. The creams consisted of ionic or non-ionic surfactants as emulgators, contained different amounts of water, and had a hydrocortisone concentration of 1%. In the dispersed state, the hydrocortisone particles were found to migrate to the liquid paraffin-water interface, in some cases covering the whole oil droplet in the cream. During storage the hydrocortisone particles also grew slightly larger. These enlarged hydrocortisone particles tended to lie parallel to each other. The location of hydrocortisone particles at the liquid paraffin-water interface can be discussed in terms of attainment of the minimum free energy state.

Chemistry, Pharmaceutical↗
PubMed1986

An electrochemical and multispectroscopic study of corrosion of Ag-Pd-Cu-Au alloys.

Corrosion of a multi-phase Ag-Pd-Cu-Au-based commercial dental casting alloy and a Cu-Pd-rich and Ag-rich single-phase alloy was studied by open-circuit potential measurements, atomic absorption spectrometry, and electron spectroscopy. The alloys were immersed in an artificial saliva solution for 24 hr while the open-circuit potentials of the alloys were measured. The potentials were found to stabilize at certain levels after a steep rise during the first hours of the experiment. Cu was found to dissolve considerably from the Cu-Pd-rich alloy, with simultaneous enrichment of Pd in the surface layer of the alloy. Ag dissolved slightly from the Ag-rich alloy, but both Cu and Ag were found to dissolve from the multi-phase alloy. Neither Pd nor Au dissolved from any of the alloys studied.

Chemical Phenomena↗
PubMed1986

Tarnishing in vivo of Ag-Pd-Cu-Zn alloys.

Pre-polished specimens of four Ag-Pd-Cu-Zn alloys have been tested for tarnishing while embedded in full acrylic dentures for from six to eight months in vivo. The results have been compared with those from previous immersion tests using 2% Na2S solutions. In both types of tests, a multiphase alloy consisting of a Pd-Cu-Zn-rich compound in a Ag-rich matrix displayed less corrosion and tarnish resistance than did alloys with compositions similar to the Pd-Cu-Zn-rich compound or the Ag-rich matrix. It is suggested that the presence of local microgalvanic cells due to chemical inhomogeneities caused the observed susceptibility to tarnishing. Sulfur was detected by a microprobe in the tarnish layer developed in the oral cavity. The discoloration on this multiphase alloy covered the interdendritic areas with short distances between the chemical inhomogeneities. This microstructural location was somewhat different from the many dark spots created predominantly on Ag-rich areas during in vitro testing. This difference is most likely due to dissimilar conditions with regard to sulfide ion concentrations, the presence of protein films, and the length of exposure time.

Aged↗
PubMed1984

The structure of a commercial dental Ag-Pd-Cu-Au casting alloy.

The structure of a commercial dental Ag-Pd-Cu-Au casting alloy has been studied by microprobe and X-ray diffraction analyses after various heat treatments. The composition of phases in equilibrium was established. After being annealed at 400 degrees C, 500 degrees C, and 600 degrees C for seven wk, the alloy consisted of three phases: a Cu- and Pd-rich fee phase (alpha 1) with alpha = 0.372nm, a Ag-rich matrix (alpha 2) with alpha = 0.399nm, and an ordered CsCl-type bcc PdCu phase with alpha = 0.296nm. The PdCu phase was not observed above 600 degrees C, and the proportion of the alpha 1 phase decreased sharply above 700 degrees C. After being annealed at 900 degrees C, the alloy matrix was partly decomposed at the Cu-enriched grain boundaries. The decomposed areas grew into the grain interior during subsequent precipitation hardening. No segregation of Au was detected after casting, and the element was evenly distributed throughout the alloy structure after all heat treatments.

Chemical Phenomena↗
PubMed1984

Tarnish and corrosion of a commercial dental Ag-Pd-Cu-Au casting alloy.

The correlation between microstructure, tarnish, and corrosion behavior of a commercial dental Ag-Pd-Cu-Au casting alloy after various heat treatments was studied. The attacked structural components were identified by comparing SEM micrographs with light optical micrographs taken after exposure of the alloy to a 2% Na2S solution and after dynamic polarization in de-aerated artificial saliva. The characteristic dynamic polarization curves for the alloy after the heat treatments were established. The results were verified by analogous testing of two experimental alloys with compositions similar to those of the analyzed components in the commercial alloy annealed at 600 degrees C for seven wk. The matrix of the commercial alloy was decomposed, according to the heat treatments, into varying proportions of a tarnish- and corrosion-resistant Cu- and Pd-rich component (A) and a nonresistant Ag-rich component (B). The presence of A considerably increased the tarnish rate of B, due to galvanic coupling. Age-hardening of the alloy increased the proportion of the tarnish- and corrosion-prone component B.

Chemical Phenomena↗
PubMed1975

Absence of echocardiographic abnormalities of the anterior mitral valve leaflet in rheumatoid arthritis.

Thirty-five consecutives patients with classic or definite rheumatoid arthritis underwent echocardiography to evaluate the motion of the anterior mitral valve leaflet. Adequate echocardiograms were obtained in 31 patients. All 31 patients showed normal valve motion and a normal EF slope. If meticulous technique was not observed, a falsely low value for the EF slope was obtained and a normal slope was found when the method was improved. This study shows that echocardiographic abnormalities of the anterior mitral valve leaflet rarely, if ever, occur in patients with rheumatoid arthritis, provided that careful attention to recording method is observed.

Adolescent↗
PubMedDate not supplied

The biocompatibility of a dental Ag-Pd-Cu-Au-based casting alloy and its structural components.

The biocompatibility of type III casting gold alloy, an Ag-Pd-Cu-Au-based dental casting alloy and its two main structural components, a CuPd-rich and an Ag-rich phase, was studied after subcutaneous implantation for 7 weeks in 20 guinea pigs. The Ag-Pd-Cu-Au alloy was surrounded by a capsule of immature collagen with fibroblasts and an increased vascular supply. The CuPd-rich component induced and maintained an acute inflammation with highly vascularized granulation tissue. The tissue reaction to the Ag-rich component and the Au-based alloy was slight. Ten of the guinea pigs were sensitized to PdCl2 prior to the implantation period, but this caused no enhanced tissue reaction, except for an increase in the number of mast cells around three of the alloys.

Animals↗
PubMedDate not supplied

In vitro cytotoxicity of Ag-Pd-Cu-based casting alloys.

The cytotoxicity and its correlation to alloy composition, structure, corrosion, as well as galvanic coupling was studied with 12 Ag-Pd-Cu-type alloys, one conventional type III gold alloy and pure Ag, Cu, and Pd. The agar overlay cell culture technique was used. Single phase binary CuPd alloys were only slightly cytotoxic below a Cu content of 30 wt%. The tested multiphase alloys were all toxic, but no correlation between toxicity and Cu content could be observed. Solid solution annealing increased the cytotoxicity of a multiphase alloy. Exposure of a single phase alloy to an artificial saliva for 1 week prior to the test decreased its cytotoxicity significantly. Galvanic coupling of the alloys through an outer copper wire decreased their cytotoxicity.

Biocompatible Materials↗