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Biomedical subjects

F Lutz

Publications and source records attributed to F Lutz.

At least 127 records · Page 7Linked to original sources
PubMed1992

[Composite inlays: clinical and scanning electron microscopic research after a 1-year functional period].

24 composite inlays placed and documented for post-graduate education purposes in 1990 were reassessed clinically and by means of SEM. The clinical examination after 1 year of clinical service gave excellent results. The quantitative SEM evaluation of the marginal adaptation in the replicable areas revealed 6.6% of marginal gaps at the tooth/cement- and 27.1% at the cement/inlay-interface. To be able to compare these findings to the initial situation, additional five inlays were placed and examined in the SEM immediately after placement. This group exhibited next to gap-free margins. The results were selectively analyzed according to fabrication technique, type and localization of the restorations. No significant difference was found among molars and premolars. On the other hand, higher percentages of marginal gaps at the cement/inlay interface were observed with multi-surfaced, indirect lab-made inlays.

Composite Resins↗
PubMed1992

[Marginal adaptation of adhesive inlays after removal of unpolymerized composite cement].

The removal of polymerized excess resin cement around adhesive inlays is very time consuming and often tooth-destructive. In this study we evaluated, if brushing away of the unset resin cement produced any marginal imperfections. It was found that this procedure caused underfilled margins especially in the occlusal portion of the inlay margins. For this reason the use of this method to remove excess resin cement is not recommended.

Cementation↗
PubMed1992

[Substance ablation with a superpulsed CO2 laser].

In this study a new, superpulsed CO2-laser was evaluated to remove enamel, dentin and several dental restorative materials. In the first part of the experiment, superpulsed mode was compared with pulsed and continuous wave using semiquantitative test methods. It was found that only superpulse was suitable for the purpose. In the following second part of the experiment, temperature rise, crater depth and crater diameter were quantitated for the superpulsed mode in a range of parameters defined in the first experimental part. It is concluded that superpulsed CO2-laser basically has the potential for a mechanical drill substitute, provided that the output power is limited to about 1 W and short pulses of 0.2-0.3 s duration are applied. In the present form the system is not adapted to clinical use. Cooling of the substrate and flexible beam delivery must be developed.

Dental Amalgam↗
PubMed1992

Clinical evaluation of a new pressed glass ceramic inlay material over 1.5 years.

Ten IPS/Empress pressed glass ceramic inlays were cemented in box-shaped, non-beveled, Class II, posterior cavities. They were evaluated clinically according to modified US Public Health Service criteria after 1.5 years in vivo. In addition, quantitative marginal analysis was performed immediately after placement of the inlays and at the 1.5-year recall. Clinical evaluation revealed that the inlays performed well after 1.5 years; all inlays received scores of Alfa or Beta for all criteria evaluated. Scanning electron microscopic examination indicated that the excellent initial marginal adaptation decreased significantly over 1.5 years.

Adhesiveness↗
PubMed1992

[The optimization of dentin bonding in mixed Class-V cavities].

A new functional bonding agent was tested in the placement of mixed class V in vitro restorations. Variable insertion procedures of the composite material were also evaluated. One of the procedures was the direct filling technique, the other were direct immediate composite inlays, cemented with light, chemically or dual cured composite cements. The quantitative SEM marginal analysis results showed a significant superiority (p less than 0.05) of the adhesive inlay restorative procedure over the direct filling technique. Dye penetration confirmed these findings. Among the inlay groups, postcuring and the curing method of the composite cement were crucial for the success.

Dental Bonding↗
PubMed1991

Relationship of primary structure to functional properties of the cytotoxin protein from Pseudomonas aeruginosa.

Deletion mutants of plasmid pSN3 carrying the Pseudomonas aeruginosa cytotoxin gene were prepared and expression in Escherichia coli of proteins with different molecular weights has been proved by Western blot. In addition, through PCR amplification of the cytotoxin gene and ligation into the vector, a single nucleotide change leading to an amino acid exchange from histidine to arginine has been constructed. The activities of the mutants were tested by binding of 125I-cytotoxin to rabbit erythrocyte ghosts and swelling of human granulocytes, showing that the cytotoxin activity is dependent on at least three different domains. Amino acids 12-20 from the C-terminus might be very important for proteolytic activation of protoxin to toxin.

Animals↗
PubMed1991

Quality and durability of marginal adaptation in bonded composite restorations.

Excellent marginal adaptation extends the longevity of restorations. Unfortunately, polymerization shrinkage of composite restorations adversely affects this quality requirement. The residual stress within the cured resin compromises the material's properties, causes marginal openings, and flexes cavity walls. In this study, the wall-to-wall contraction in MOD cavities was measured for different placement techniques. In addition, the restoration margins were quantitated before and after thermo-cycling and mechanical stressing. Factors which enhanced adaptation also optimized marginal quality and reduced the amount of residual stress. The latter was expressed by intercuspal narrowing after the restoration was completed. Both quality and stress resistance of the marginal adaptation were inversely correlated to the intercuspal narrowing caused by the polymerization contraction of bonded and excellently adapted resin restorations. The most effective factors which optimized marginal quality included: guidance of the shrinkage vectors; reducing the ratio of bonded to free, unbonded restoration surfaces; and minimizing the mass of in situ-cured composite. The latter principle was followed best in the adhesive inlay technique. In medium-sized adhesive MOD composite inlays, the volume loss induced by the polymerization contraction of the composite cement was non-destructively compensated for by an inward flexing of each cavity wall of approximately 10 microM.

Composite Resins↗
PubMed1991

Marginal adaptation of Class V restorations using different restorative techniques.

This in vitro study compares the marginal adaptation of Class V restorations with margins located half in enamel and half in dentine, which were placed using different restorative techniques. Five operative procedures were evaluated both in saucer-shaped erosion lesions and in box-shaped cavities with bevels in enamel. The five procedures included a composite inlay technique using both the chemically and the light curing versions of a resin based composite cement, a bulk placement technique using a chemically curing composite resin, an incremental technique and an incremental technique combined with a built-up base, using a light curing composite resin. A combination of Gluma/Clearfil served as the dentinal adhesive. The micromorphology of the tooth/restoration interface was analysed before and after thermal cycling; the marginal seal was analysed after thermal cycling only. In the conventional cavities, the restorations showed less leakage, and micromorphologically a better, but statistically insignificant superior marginal adaptation. The inlay technique rendered the best marginal quality in both enamel and dentine before and after thermal cycling. Due to the unique curing characteristics of the chemically cured composite resin and cement resulting in a significantly reduced rigid contraction, the inlays cemented with the chemically curing cement and the restorations placed with the chemically curing composite resin were superior to their light cured counterparts. The built-up base yielding a reduction of the composite mass did not enhance marginal adaptation because of the partial replacement of the strong adhesion to dentine mediated by the Gluma/Clearfil combination by the weaker bond promoted by the etched glass ionomer cement.

Acid Etching, Dental↗
PubMed1991

Induction of vascular injury by Pseudomonas aeruginosa cytotoxin in rabbit lungs is associated with the generation of different leukotrienes and hydroxyeicosatetraenoic acids.

Pseudomonas aeruginosa cytotoxin, a transmembrane pore-forming protein, causes an increase in pulmonary microvascular permeability with subsequent lung edema formation, possibly related to the induction of arachidonic acid (AA) lipoxygenase products. To investigate this, isolated rabbit lungs were perfused with cytotoxin-containing buffer (6.5 and 13 micrograms of toxin/ml). A severalfold increase in the capillary filtration coefficient was induced, both preceded and accompanied by a marked time- (15-60 min) and dose-dependent release of cysteinyl leukotrienes (LT), LTB4, and 5-, 12-, and 15-hydroxyeicosatetraenoic acids (HETEs) into the lung perfusate. In the bronchoalveolar lavage fluid, corresponding AA-derived products were detected; the total sum of HETEs surpassed that of cysteinyl LTs in this compartment. The lipoxygenase inhibitors AA861 (10 microM) and nordihydroguaiaretic acid (100 microM) and EGTA (5 mM) suppressed the intravascular and alveolar liberation of all 5-lipoxygenase-derived AA metabolites, paralleled by a marked reduction and retardation of microvascular permeability increase (AA861). It thus seems that Pseudomonas cytotoxin induces generation of LTs and HETEs in rabbit lungs that may contribute to the development of pulmonary microvascular injury evoked by this bacterial agent.

Animals↗
PubMed1991

Isolation and characterization of a transposon-induced cytotoxin-deficient mutant of Pseudomonas aeruginosa.

In order to provide a better system for investigating the role of cytotoxin in pathogenesis, we mutated wild-type Pseudomonas aeruginosa PA158 by introducing a transposon. The resulting pool of mutants was screened for cytotoxin-deficient strains. One mutant strain, PA114F5, was compared with PA158. Except for cytotoxin production and antibiotic resistance (specified by the transposon), the two strains appear isogenic. This mutant strain should be useful in further clarifying the role of cytotoxin in pathogenesis.

Cytotoxins↗
PubMed1991

Cariogenicity of Milchschnitte (Ferrero GmbH) and apple in program-fed rats.

The cariogenicity of Ferrero Milchschnitte and apple was tested in rats using a frequency-controlled feeding machine. Twelve litters of Osborne-Mendel rats orally infected with Streptococcus sobrinus OMZ-176 and Actinomyces viscosus Ny-1 were used. Four treatment groups were tested: (1) cooked starch/sucrose 1:1 as positive control; (2) Ferrero Milchschnitte; (3) apple; (4) gastric intubation only as negative control. Groups 1-3 were additionally fed by gastric intubation with essential nutrients. Rats on Milchschnitte and apple had less fissure and smooth-surface caries than rats on a starch/sucrose diet, but significantly more than the negative controls. The Milchschnitte group exhibited less plaque extent than the positive and the negative control. The apple group showed a higher plaque extent and massively extended erosions on molar surfaces. The CFU means of S. sobrinus were decreasing from treatment 1-4. Although differences between treatments were not significant, they were associated by concomitantly decreasing caries incidence. The test foods were also assessed using intraoral plaque-pH telemetry in 6 human volunteers. Both Milchschnitte and apple were acidogenic in human telemetry. They can therefore not be regarded as safe for teeth.

Animal Feed↗
PubMed1991

[The service life of Cerec abrasive disks].

The aim of this study was to evaluate the efficiency of Cerec CAD-CAM grinding discs coated with a standard (StD) and experimental (FeD) diamond pattern using 126 microns and 91 microns diamond grain sizes on each coating. The four types of grinding discs (StD126/91, FeD126/91) were used to mill the same standard mod inlays from blocoff+ (10 x 12 x 15 mm) of feldspathic porcelain (Vita) vs. Dicor MGC glass ceramic (Dentsply). The millings were performed on 12 Cerec units (Siemens) simultaneously for each combination of type of disc and type of material. Using porcelain, the discs milled the following median numbers of inlays: StD126: 6.3, StD91: 3.5 (p less than 0.01) and FeD126: 9.5, FeD91: 8.4. The milling efficiency of FeD91 was significantly (p less than 0.001) higher than that of StD126. Damaging effects on inlay margins were observed; degree 0: StD126 = 35% and FeD126 = 25%; degree 2: StD126 = 10% and FeD126 = 25%. Using Dicor MGC glass ceramic the median number of milled inlays was generally low (StD126: 4.0, StD91: 1.0, FeD126: 3.0, FeD91: 2.0). Damaging degree 3 occurred as follows; StD126 = 2.1%; FeD126 = 4.3%; FeD91 = 0.8%. Concluding from the observed milling efficiency and damaging effects, the standard disc StD126 was judged to offer the best compromise for milling both glass ceramic and porcelain material.

Carbon↗
PubMed1991

[Effects of post-curing on the wear resistance of composite materials].

The effects of different postcuring methods on the wear resistance of three different composite materials was evaluated using a clinically correlated in vitro test. While postcuring did not significantly affect the wear resistance of the occlusal contact surfaces in two of the materials tested, wear decreased significantly in the third material after heat postcuring. The effects of postcuring on wear resistance seem to be of a complex nature. Thus it is recommended not to use postcuring techniques indiscriminately.

Composite Resins↗