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Biomedical subjects

F Lutz

Publications and source records attributed to F Lutz.

At least 163 records · Page 9Linked to original sources
PubMed1990

[The wear on enamel, amalgam and their enamel antagonists in a computer-controlled mastication simulator].

In a long-term in-vitro test the wear of enamel fossae, amalgam restorations and their opposing enamel cusps in the occlusal contact area was evaluated, qualitatively and quantitatively. The wear of enamel cusps differed from the wear of enamel fossae. The amalgam restorations wore down more rapidly than enamel fossae, but they were less destructive against their opposing enamel cusps. The wear of all tested materials was not linear. The results will serve as reference data for future long-term in-vitro tests of posterior restorative materials.

Computer Simulation↗
PubMed1990

[Cremation and the environmental mercury burden].

The dental status of 130 deceased Zurich people was evaluated from radiographs of their maxillary and mandibular dentitions taken during their autopsies. A mean mass of mercury of 2.49 +/- 0.37 g was calculated per dentate deceased based on the analysis of 134 extracted premolars and molars with amalgam restorations. The mercury contamination due to cremation in 1988 in Switzerland was calculated to vary between 45.8 and 79.0 kg, based on both the data from the sample analyzed and the fact that 55.5% of Swiss funerals were cremations, the average age of death was 73 and that 70% of the people of that age retained some of their teeth. Mercury contamination by cremation, therefore comprised only 0.61 to 1.53% of the total mercury contamination produced by all waste incineration methods. The minimal contribution to the mercury contamination due to cremation can thus not be used as an argument to ban the use of dental amalgams.

Air Pollutants↗
PubMed1990

[In vitro evaluation of two composite material for posterior restorations].

In this in vitro study the wear resistance and abrasiveness against opposing enamel cusps, marginal adaptation and radiopacity of two experimental composite resin materials were tested. The results indicated that in particular the fine particles hybrid showed low wear. The radiopacity of both materials tested was just acceptable. Marginal adaptation was insufficient in both cases, the reason being most probably the low viscous bonding agent and the polymerization shrinkage. Therefore both test materials are not suitable for use as direct posterior composite fillings.

Composite Resins↗
PubMed1990

[In-vitro test results of the evaluation of dental restoration systems. Correlation with in-vivo results].

The wear of amalgam- and composite-inlay MODs after loading in a new in vitro test was compared with clinical results quantitatively and qualitatively. The quantitative evaluation showed a high correlation between in vivo and in vitro data for both filling materials. The qualitative wear patterns were also very similar. It was concluded, that the results from the new in vitro test are clinically relevant.

Corrosion↗
PubMed1990

[Optimization of the powder application in the Cerec method with environment-friendly propellant systems].

This study compared the thickness of powder layers sprayed on Cerec inlay cavity preparations before taking the "optical impression". 6 different powder propellant methods were evaluated. 60 MOD inlay cavities were prepared in vitro in extracted human molars and mounted in phantom-head jaws. 10 clinicians powdered 1 cavity each for each of the 6 methods. The powdered teeth were embedded in acrylic and the preparations sectioned parallel to the cavity floor, mesio-distally and bucco-lingually. The powder layer thickness on the proximo-lateral walls (PLW), cavity floors (CF) and occlusal margins (OM) were measured using a light microscope. The means and SD are: [Table; see text] This study showed that propane-butane propellants were as effective as the fluoridated hydrocarbons. A wet system (5) was good despite the transient surface cooling (-43 degrees C) effect. However, the air-flow system (6) produced acceptable powder layers as well, avoiding any chemical contamination of the room air.

Aerosol Propellants↗
PubMed1990

[The cleaning effect of different root canal instruments. A semiquantitative comparative study].

The efficacy of various root canal cleaning instruments was evaluated in this in vitro study. 60 freshly extracted teeth were divided into 6 groups of 10 teeth each. The root canals of the teeth were cleaned with hand-instruments, sonic instruments (Sonic Air 3000 and Endostar 5), mechanical instruments (Canalfinder System), and ultrasonic instruments (Cavi-Endo with or without integrated rinsing) according to the manufacturer's instructions. The canals were then examined in a SEM at 60 selected points to assess the presence or absence of smear layer, dentin chips, and cellular remnants. The smoothness of the canal walls was also evaluated. Similar amounts of tissue remnants were scored by the SEM method. None of the instruments tested were able to produce debris-free specimens. The Cavi-Endo, Endostar 5, Sonic Air 3000, and the hand-instruments yielded similar scores. However, the Endostar 5 cleaned the canals quicker and with fewer problems than the other instruments. The efficacy of the integrated rinsing in the Cavi-Endo must be questioned. The smear layer was somewhat reduced by the Cavi-Endo, using a syringe and needle, but without the integrated spray. The Canalfinder System produced poorer cleaning scores but they were not significantly different from the other instruments' scores.

Dental Pulp Cavity↗
PubMed1990

[An in vitro test procedure for evaluating dental restoration systems. 1. A computer-controlled mastication simulator].

This article describes the development and testing of a computer-controlled chewing simulator which is able to simulate the wear mechanisms and temperature changes that can occur in the mouth. It was further evaluated if the opposing cusps used in this chewing simulator should be metallic or if natural enamel was preferential. The results indicated that the machine fulfilled the parameters concerning chewing motion and thermal changes reported in the literature. Furthermore it was shown that natural enamel cusps must be used as the opposing dentition. The chewing simulator will form a part of an in-vitro test, which will allow the evaluation of dental restorative systems under clinically relevant conditions.

Computer Simulation↗
PubMed1989

Pseudomonas aeruginosa cytotoxin: the influence of sphingomyelin on binding and cation permeability increase in mammalian erythrocytes.

A cytotoxic protein isolated from Pseudomonas aeruginosa damages the plasma membranes of many mammalian cells by forming pores. We studied binding of the 125I-cytotoxin and the resulting increase of cation permeability in erythrocytes of various mammalian species. The sensitivity of red blood cells was inversely related to the relative sphingomyelin content in their external surface. Thus, erythrocytes with a sphingomyelin to phosphatidylcholine ratio below 1 (dog, rat, rabbit and man) were sensitive, whereas red blood cells with a ratio above 1 (pig, cattle and sheep) were not attacked even with 100-fold higher cytotoxin concentrations. At 37 degrees C 6.8 +/- 1.2 x 10(3) molecules of 125I-cytotoxin were bound per rabbit erythrocyte (KD = 59 nM), whereas no binding occurred to cattle cells. Cleavage of sphingomyelin by sphingomyelinase C from Bacillus cereus (EC 3.1.4.12) triggered a dose-dependent enhancement in binding and permeability increase, particularly in red blood cells with a high proportion of sphingomyelin. The KDs for all animal species investigated were 53-60 nM. Pretreatment with mainly phosphatidylcholine-hydrolyzing phospholipases D from Streptomyces chromofuscus and cabbage (EC 3.1.4.4) or phospholipase C from Bacillus cereus (EC 3.1.4.3) did not influence the cytotoxin effect. The negative correlation between susceptibility and the proportion of sphingomyelin in plasma membranes suggests a binding site close to sphingomyelin.

Animals↗
PubMed1989

Human root caries: histopathology of initial lesions in cementum and dentin.

The histopathology of human root caries was examined in extracted teeth by different optical methods. The present part of the study details the sequential stages of initial caries in both cementum and peripheral dentin. Significant differences are shown between the mechanisms operating on the various dental hard tissues during development of caries. Histologically distinguishable reaction patterns depended on both the degree of the cariogenic challenge and the respective structural features of cementum and peripheral dentin. Earliest lesions, histologically visible as small clefts traversing cementum and extending into peripheral dentin, were clinically not detectable. Cementum was stepwise destroyed until peripheral dentin became exposed. The exposed peripheral dentin was sclerosed and tubule-free. Demineralization of dentin preceded the degradation of the organic matrix. Frequently, a hypermineralized layer occurred in both cementum and exposed dentin. Its localization was not identical with the anatomical surface. Initial penetration of bacteria into peripheral dentin occurred along small clefts. Breakdown of the organic matrix was the final step in the destructive phase of the carious process.

Aged↗
PubMed1989

Pseudomonas aeruginosa cytotoxin: periplasmic localization and inhibition of macrophages.

Pseudomonas aeruginosa cytotoxin has been isolated previously from cell autolysates. Both purified cytotoxin and periplasmic contents (osmotic shock fluid) cross-reacted on Western immunoblots with antibodies specific for cytotoxin. In addition, both preparations caused a significant reduction in antibody-mediated phagocytosis of P. aeruginosa M2 by mouse macrophage cell line P388D1. Phagocytosis was restored in each case on preincubation of cytotoxin or periplasmic contents with anti-cytotoxin serum. Both cytotoxin and periplasmic contents caused depolarization of the P388D1 cell membrane, as demonstrated with a polarization-sensitive fluorescent probe. Similar correlations were not observed for other P. aeruginosa cell fractions or for osmotic shock fluid from Escherichia coli C600. These data indicate that P. aeruginosa cytotoxin is localized in the periplasm and has the potential to inhibit macrophage-mediated phagocytosis, possibly by perturbing ion gradients across the macrophage plasma membrane.

Animals↗