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Biomedical subjects

G Pichler

Publications and source records attributed to G Pichler.

32 records · Page 2Linked to original sources
PubMed1998

Serial lumbar tapping to prevent posthaemorrhagic hydrocephalus after intracranial haemorrhage in preterm infants.

Posthaemorrhagic ventricular dilation following intraventricular haemorrhage is a serious problem with high morbidity in preterm babies. No consensus exists as to the treatment of intraventricular haemorrhage and as to the treatment or prophylaxis of posthaemorrhagic ventricular dilation. Serial lumbar tapping was already in use to treat existing or being in the offing ventricular dilation. In the present study we evaluated the incidence of posthaemorrhagic hydrocephalus when lumbar tapping was initiated early, i. e. immediately before ventricular dilation had started. Between January 1989 and December 1996 37 preterm infants suffering from intraventricular haemorrhage grade III or grade III plus periventricular haemorrhage were enrolled in this study. Lumbar tapping was started as soon as possible: median (25. percentile-75. percentile) two (0-4) days after onset of haemorrhage. A median of 11 (8-17) punctures was performed in each patient. The outcome was as follows: 6 patients (16.2%) showed complete remission, 24 (64.9%) developed ventriculomegaly and 7 (18.9%) developed posthaemorrhagic hydrocephalus with subsequent need of shunt implantation. With the low incidence of shunt implantations in our study we suggest to reconsider the effectiveness of SLP performed immediately after onset of haemorrhage.

Cerebral Hemorrhage↗
PubMed1998

The effect of the photopolymerization method on the quality of composite resin samples.

An optimal degree of conversion and minimal polymerization shrinkage are generally antagonistic goals, as increased monomer conversion invariably leads to elevated polymerization shrinkage values. However, both parameters are indispensable for an optimal resin composite restoration. A number of approaches have been used to reduce the stress on the restoration cavity wall interface, such as dentine bonding agents to counteract polymerization shrinkage, stress-absorbing lining materials and low-intensity curing lights to control the flow capacity of the material during polymerization. However, the configuration of the cavity and cohesive fractures of the material and surrounding tooth tissues are still a problem in day-to-day clinical practice. A new photopolymerization light source, pulsed laser, ensures a higher degree of conversion and lower polymerization shrinkage, and differentiates this technique from standard polymerization methods and continuous-wave argon laser polymerization. The coherence and monochromacity of pulsed laser light set at 468 nm and the far greater intensity of laser nanopulses produce a saturation effect in the depths of the composite, thus resulting in higher monomer conversion. The total amount of energy illuminating the sample surface, which is only one-fifth of that of conventional methods, and the cooling and relaxation of the material between nanopulses may be responsible for the reduced net polymerization shrinkage.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1998

[Kinetic therapy of severe meconium aspiration syndrome].

Recent studies showed the possible positive effect of body position changes during mechanical ventilation of severe lung diseases in adult patients. In neonatology kinetic therapy is still rarely used, therefore we present this case report. A full term newborn suffering from severe MAS and peripartal asphyxia was transferred to our NICU to perform extracorporeal lung support, if necessary. After application of a natural porcine surfactant and start of inhalative nitric oxide therapy (10 ppm) a clinical stabilisation was possible. Because of hypercapnia, high frequency oscillation ventilation was introduced later on. The PaCO2 values decreased quickly. A few days later severe pulmonary secretion problems occurred, which led to atelectasis and barotrauma due to local hyperinflation. After several different ventilation strategies had failed to improve the situation, kinetic therapy in combination with conventional mechanical ventilation was started. Under this therapy-concept it was possible to reventilate the atelectatic lung areas, and quickly an improvement of oxygenation was seen. Weaning from the respirator was possible within one week. In conclusion, we think that an important progress in therapy was due to kinetic therapy.

Adult↗
PubMed1997

Pulsed blue laser curing of hybrid composite resins.

Clinical performance of light-curing composite restorations is greatly influenced by the quality of the curing-light. Currently used photopolymerization units have some important drawbacks, such as decreasing light output with time and distance, which results in a relatively low degree of conversion and shallow depth of cure, particularly of darker shades. Experiments with continuous argon laser polymerization showed overheating of the composite sample, as well as increased shrinkage of the material. In this study a pulsed laser, set at 468 nm (the maximum of the camphorquinone absorption coefficient), with 20-ns pulse duration, repetition rate of 10 Hz and energy of 10 mJ per pulse, was used as a light source. The aim of the study was to evaluate the effect of polymerization of light and dark shades of three different hybrid composites cured by pulsed laser at the surface and at 3.0 mm depth. The degree of conversion was measured by Fourier transform infrared spectroscopy (FTIR). Applying pulsed blue laser, significantly better results were obtained for both shades compared to standard polymerization values. Very weak dependence of the degree of conversion, between the surface measurements and those at 3.0 mm, were observed in the case of pulsed laser polymerization due to the piercing nanopulses and the monochromatic light at 468 nm.

Dental Cements↗
PubMed1995

Polymerization of composites using pulsed laser.

The quality of visible-light-cured composites depends on the capability of the light source to properly polymerize the material within a specified exposure time. In this study, the degree of conversion of different composite materials (hybrid and microfilled) of light and dark shades was compared after illumination by a standard curing unit and pulsed laser (lambda=468) respectively. The degree of conversion was measured by Fourier transform infrared spectroscopy. Results obtained by the analysis of the pulsed laser-induced polymerization were significantly higher for all the materials and shades observed. All values of the degree of conversion were lower for dark shades of all types of composites, regardless of the photopolymerization technique used. Besides the surface, better polymerization was recorded also at depths of 1.0, 2.0 and 3.0 mm, respectively. These values varied from 59.7%+/-2.14 to 84.5%+/-0.33 for pulsed laser (including all depths) caused by the saturation effect induced by high power laser pulses and from 42.7%+/-1.48 to 74.7%+/-0.99 for standard polymerization.

Acrylic Resins↗
PubMed1991

Indium light source for curing composite resins.

There is an existing problem of cumulative hazardous effect of violet and near ultra-violet light which is produced by standard polymerisation units. Another restrict is shallow depth of cure, particularly of darker composite shades in premolar and molar region. Searching for better light source we used indium resonance lines from several indium high pressure lamps and tested curing effect on three different composite resins. The overall results are better with the lamp in which two strong resonance lines of indium are present, rather than with a lamp with just one strong resonance line. The improvements in lamp design are necessary to overcome conventional polymerisation lamps.

Composite Resins↗
PubMed1990

Zinc and sodium high pressure lamps for curing composite resins.

Polymerisation characteristics of conventional units for curing composite resins are insufficient considering handling feasibilities particularly in the premolar and molar region. There is also hazardous ocular effect of near ultra-violet part of visible spectra. Sodium high pressure lamp technology has been applied to develop a new high pressure zinc lamp, which is for the first time used for curing composite materials. The results of polymerisation measurements show that future improvements over the usual halogen light sources are possible. Zinc lamp was also compared with the high pressure sodium lamp filled with mercury or cadmium.

Cadmium↗
PubMed1977

Cytological analysis of X-ray-induced aberrations in spermatocytes I and the somatic ganglia of male Drosophila melanogaster.

The correlation between damage induced in somatic cells and that induced in germinal cells of the same genetic pool of individuals is important in establishing the possibility of extrapolation of this damage to the offspring. We have used Drosophila melanogaster to compare cytologically the frequency of aberrations induced in the cells of somatic ganglia and in the spermatocytes I of males irradiated with 625 R X-rays. The spermatocytes were more sensitive than the gangliar cells to radiation: the aberrations induced in the spermatocytes I were three times more frequent than those induced in the ganglia. The distribution of the aberrations was, however, similar. The most important variable element lies in our observing no symmetrical exchanges in the spermatocytes. This result seems to us to be related to the fact that in the males of D. melanogaster there is no crossing-over.

Animals↗