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Biomedical subjects

L Torrisi

Publications and source records attributed to L Torrisi.

At least 19 recordsLinked to original sources
PubMed1999

Pervasive developmental disorder and epilepsy due to maternally derived duplication of 15q11-q13.

Duplications of chromosome 15 have been reported in individuals with atypical autism, varying degrees of mental retardation, and epilepsy. The authors report the molecular analysis, neurophysiologic, and clinical evaluation of a 12-year-old boy with atypical autism and epilepsy due to a maternally derived 15q11-q13 duplication. Their findings suggest that this chromosomal region harbors genes for autism and possibly for partial epilepsy that may act in a dose-dependent manner.

Child↗
PubMed1999

[Comparison of different finishing methods for composites and compomers. Profilometric analysis].

BACKGROUND: Reconstructions with aesthetical materials neither finished nor polished can be extremely irregular and wrinkled. For this reason they represent an ideal basis for the growing of pigmentation which come from food remainings and the nestle of bacteria on the plaque. The finishing of aesthetical materials is a fundamental step in conservative dentistry. The finishing session regarding the aesthetical restorations should be considered and planned at the moment of their insertion in the prepared hollows. The finishing should not be considered an option, but the conclusion of all the conservative treatment. Purpose of the search is to examine and assess, through a technical equipment measuring the superficial wrinkledness of the materials, the action of 4 systems of finishing and polishing on two aesthetical materials widely used in the daily practice by dental surgeons: a compomer (Compoglass, Vivadent) and a composite (Spectrum, Dentsply). METHODS: For each of these two materials some little slabs model have been prepared, choosing the universal colour in the colorimetric scale. The two types of filling materials have been compared with 4 systems of finishing and polishing: Sof-Lex Pop-on (3M), Enhance system (Dentsply), Hawe Micro Disc (Howe Neos), Heawe Gommini Polisher (Heawe Neos). The total working time did not overcome 1 minute. The little slabs have been obtained, pressing the resin between two slides used in microscopy. In the hope to guarantee in the different samples, a uniform thickness, we have used a technical device. On each covering slide we have put a weight of 0.5 kg for 5 minutes. The thickness of the little slabs obtained was 2 mm. Thus, pressed between the two slides, the aesthetical material has been photopolymerized according to the time suggested by Manufacturing Industries. The sizes concerning the wrinkledness of samples subjected to different treatments have been carried out using a pointed profilometer with high sensitivity. (Tencor-P10). This instrument used in the National Laboratory of Catania, called INFN, is able to graphitize the wrinkledness of a surface "survbeying" it with a diamond ultramicrometric point. RESULTS: All tested systems gradually produce the upper layers of the materials less suitable to resist the assault of plaque bacteria as time passed. The 3M coarse and medium grain Disks are very abrasive and for this reason the surface of the materials is ill-shaped. Those disks with fine and extra fine grain, smooth the tracks left by previous disks. As they have been always used according to their decreasing granulometry, the disks are used only for removing small composite pieces in excess and to improve micromorphology of the restauration. The "Gommini" are less abrasive than Disks. In a few minutes and often with only one step they produce a much regular and polished fillings surface. CONCLUSIONS: The "Gommini" have a preference when the last photopolymerization has left a regular layer, with a very good micromorphology. Actually, "Gommini" do not remove much material, but they continue to smooth the outline of the reconstruction. Disks are not classified as being of first quality in the finishing of composites and compomers.

Composite Resins↗
PubMed1999

The NiTi superelastic alloy application to the dentistry field.

The main properties of NiTi alloys are presented, discussed and compared with respect to those of stainless steels. Special regard is given to the use of NiTi alloy as orthodontic wires and endodontic instruments. The superelastic properties of orthodontic wires and endodontic files are measured as a function of the applied stress, of the strain and of the temperature. Both biomedical devices are submitted to surface analysis to control the interface with the biological environment in which they will be immersed.

Biocompatible Materials↗
PubMed1997

Doppler-broadening of positron annihilation in a biological environment.

The aim of this study was to investigate the Doppler effect of the 511 keV gamma peak from positron annihilation in biological matter. The broadening of the annihilation peak is due to positron annihilation with electrons that have high momentum. In aqueous solutions annihilation depends on the temperature and it is linked positronium formation. Measurements in vivo, on human brain, were taken during the diagnosis of positron emission tomography (PET) on healthy patients by injecting them with the beta emitter of short lifetime 18F. The Doppler-broadening in biological tissues rich in water content decreased significantly compared to biological solutions and water.

Body Water↗
PubMed1997

Microfilters for biomedicine obtained by swift ion processing.

Swift ions with 50 MeV energy are used to irradiate bio-polymeric films. Lithium, carbon and oxygen beams, with fluencies ranging between 10(8) and 10(13) ions/cm2, are swept on large surfaces of hydrogenated and fluorated polymers. The electronic stopping power of the ion induces high rates of ionization, excitation and radical formation along the ion path with production of chain-scission and cross-linking processes which can be investigated by the molecular emission from the irradiated polymer. The radiation damage increases the chemical solubility of the material around the ion track up to distances of the order of 100 nm. A suitable chemical etching removes the damaged material leaving micrometric holes in the polymeric film. This process gives rise to micro-perforated films which can be used as microfilters, with sub-micrometric pore dimension, high selectivity and controllable porosity. Their use is very interesting for special applications in ultra- and microfiltration of biological liquids.

Biocompatible Materials↗
PubMed1996

Ion implantation and thermal nitridation of biocompatible titanium.

Nitrogen implantation and thermal nitridation processes are investigated to improve the wear resistance of titanium medical devices. Ion implantation uses 80 keV nitrogen ions and doses ranging between 1 x 10(17) and 5 x 10(17)/cm2 to modify the surface layers up to 140 nm depth. Stable surface layers are obtained at high ion doses by post-annealing at 550 degrees C for 30 min. Thermal processes are developed as a function of the time (20-90 min) and annealing temperature (950-1100 degrees C) in a dry nitrogen atmosphere. The amount of titanium nitride formed during the thermal process increases with the annealing temperature and time. Samples are analysed by Rutherford Backscattering Spectroscopy (RBS), Auger Electron Spectroscopy (AES) and Scanning Electron Microscopy (SEM). Ion implantation and thermal nitridation processes increase the surface hardness and wear resistance improving the mechanical properties of titanium used for movable devices for total joint replacements, such as the hip and knee protheses.

Alloys↗
PubMed1995

Improvements in bio-mechanical adhesion of screws used in medical field: first application in spinal surgery.

Metallic screws are becoming more and more useful to join bones or for prosthesis support in orthopaedic and dental surgery. High biocompatible materials such as titanium alloys and hydroxyapatite ceramics are making possible the realization of stable fixation devices utilizable in load-bearing applications. The mechanical and biological anchorage of metallic screws to the bone depends on many factors: mechanical screws-bone thread matching, use of cements between bone and screw, chemical-physical treatments of screw surface, use of screw coverage films based on osteointegrating ceramics or active bioglasses, use of porous coverage films to induce bone ingrowth into the pore, and so on. The first step of the research, the aim of the present paper, is the comparison among screws of different shapes and geometric characteristics in order to find the best macromechanical system versus the different load conditions. Static and dynamic tests are applied to the screws mounted on segments of pig spine, in order to measure the mechanical characteristics of the system under tension (pull-out), bending on the principal planes along the axis of the screw and fatigue loads. Physical analysis, obtained using energetic charged particles, such as SEM, RBS, and AES, are used to characterize the screw surface compositions and morphology.

Adhesiveness↗
PubMed1994

Fluoride concentration in ancient teeth measured by nuclear reaction.

Fluoride content in the enamel and dentine of ancient teeth has been measured using a nuclear analysis technique. Analysed teeth were found in a vast necropolis of Sicily (Italy) which is archeologically datable between the 13th and the 8th century B.C. Measurements gave high fluoride concentrations, of the order of 10 mg per gram of hydroxyapatite, comparable with the content of fluorotic teeth of patients living nowadays in regions rich in fluorinated drinking water. Results suggest that the dental caries process was probably unknown to the tribal population living in this geographical area.

Dental Caries↗
PubMed1994

Microfilters by laser processing of bio-polymers.

Thin films of bio-polymers, such as polymethylmetacrylate, polytetrafluoroethylene, polyethylene-terephthalate and polyimide, are efficiently etched in air by UV laser pulses. A different sharp laser fluence threshold for significant etching is measured for each polymer. The thresholds are correlated to the chemical structure and to the wavelength-dependent absorption coefficient of the irradiated polymer. The polymers, having low absorption coefficients, show thresholds of the order of some J/cm2, about one magnitude higher than polymers having high absorption coefficients. Measurements on the polymer etching rates, in terms of removed molecules per eV at the used 347 nm wavelength, and a discussion on the laser-polymer interaction are presented. An interesting application of the laser ablation process to bio-polymers, concerning the ability to realize microfilters for the bio-medical field by irradiating the polymer surface through a perforated metal mask, is discussed.

Absorption↗
PubMed1993

Micron-size particles emission from bioceramics induced by pulsed laser deposition.

Pulsed laser deposition of hydroxyapatite is applied to cover titanium medical prosthesis. Laser irradiation of ceramics by power-pulsed ruby laser produces high velocity micron-size particles emission with a narrow ejection plume directed normally to the target surface. Photoemitted particles are deposited on a metal surface at 400 degrees C to obtain a granular film, stoichiometric, polycrystalline, and very adherent to the substrate. Deposited films are highly biocompatible and may be used to induce osteointegration processes of the implanted prosthesis with the bone tissues. The comparison between laser and plasma spray depositions of bioceramics is discussed.

Ceramics↗
PubMed1990

Fluorine microanalysis in teeth.

Fluorine content in dental tissues has been measured by using nuclear reactions with high energy proton beams and detecting alpha particles and/or gamma rays emitted from fluorine nuclei. The sensitivity of the nuclear analysis reaches 0.1 mg/g and the depth distribution of fluorine atoms can be determined up to 5 mum. The depth resolution is about 0.3 mum with alpha particles and 0.1 mum with gamma rays. Distributions of fluorine both in surface enamel and in cross section of teeth were measured by using a proton probe 500 mum in diameter. A systematic increase in the fluorine concentration has been observed in the healthy incisors dental enamel (1-3 mg/g) with respect to the molar ones (0.5-1 mg/g). A comparison between the fluorine content in healthy teeth and in pathological ones was made.

Alpha Particles↗
PubMed1990

[Shape memory alloys for orthodontic use studied with electron beams].

Shape memory alloys, which have the ability to be deformed into a temporary shape and then returned to its original shape giving useful elastic forces, are used in orthodontics field as shaped archs and springs. Their characteristics offer high potentiality to produce new orthodontics devices and to use in implantology. Using different analysis techniques with focussed electron beams, Authors have investigated on the superficial topography, alloy structural composition and on the absorbed elements of superficial layers of Nitinol orthodontics archs. SEM analysis have shown a compact and finished surface. PIXE analysis has quantized the atomic alloy composition in 55% and 45% on nickel and titanium, respectively. Auger spectroscopy and ion sputtering technique have shown that in surface of new archs oxygen and carbon are present up to about 300 A depth.

Alloys↗
PubMed1990

Auger and pixe microanalysis of intrauterine devices (IUDs).

Auger Emission Spectroscopy (AES) and Particle Induced X-ray Emission (PIXE) analysis were employed in a study on the calcification and oxidation processes of the copper wires used in Intra-Uterine Device (IUDs) contraceptives. A strong copper release (approximately 50 micrograms/day) has been observed in the first year of IUDS application during the high device antifertility effect. The copper release is reduced with the IUD-use time, because of the calcification process on the surface by organic liquids. This effect produces a drastic reduction in the contraceptive efficiency, and a new IUDs replacement is needed after about 2 years of use. Auger, X-ray spectrometry and scanning electron microscopy (SEM) have been used to investigate the lifetime and efficiency of IUDS in order to understand the surface modification of copper wire during its permanence in the intrauterine environment.

Calcium↗
PubMed1989

[Boron in dental hard tissues studied by 11B(p,alpha)8Be nuclear reaction].

Boron's low atomic number and low concentration make its measurement in hard dental tissues difficult. Using nuclear reaction, the 11B(p,alpha)8Be*, enamel, dentine and radicular cement of 18 dental elements, ten healthy and eight decayed teeth, both permanent and deciduous were studied. The highest Boron concentrations were found in the two most superficial microns of the vestibular enamel in non-decayed incisors, particularly deciduous ones. Premolar and molar teeth showed lower Boron concentrations than frontal ones, decayed teeth revealed hardly any Boron. In confirmation of the prevailing exogenous contribution of this karyostatic trace element, on average, Boron concentrations were 2.5 times as high as dentine and 10 times as high as cement.

Boron↗
PubMed1989

[In vitro enamel fluoridation using an ultraviolet laser].

28 samples of human enamel have been studied in order to measure fluoride absorption after treatment with ultraviolet radiations. Samples treated with topical application only presented limited fluoride absorption in enamel surface (up to 0.5 microns deep). The absorption rate was higher, using an U.V. lamp. In samples treated with "excimer" laser, fluoride absorption was much higher in the surface layer and occurred also deeper (3 microns).

Absorption↗