Characterization of synthetic apatites for bioceramic implants.

Hydroxyapatite has been studied as a substance suitable for surgical substitution of bones and teeth with emphasis on its biocompatibility. The present work tries to identify the characteristics of this material either from the chemico-physical-structural point of view, or from the technological one, evaluating the best performance. By X-ray, i.r., thermal, chemical and SEM analyses, the relationship of different phenomena involved in the sintering was evaluated. Technological tests demonstrated the stability and the workability characteristics. In particular, the influence of CO2 was studied, in connection with the most suitable technique for hydroxyapatite (HAP) sintering, considering the eventual aims and requirements for industrial production.

[X-ray diffraction analysis of collagen fibers processed with glutaraldehyde and glycerol]. / Analisi diffrattometrica di fibre collagene trattate con glutaraldeide e glicerolo.

Rat tail tendon collagen fixed with glutaraldehyde and treated with glycerol has been studied by X-ray diffraction technique. The evaluation of the distribution of the areas at higher and less density of molecular packing in the collagen fibrils has been carried out through the analysis of the intensity distribution of the low angle X-ray diffraction maxima. The results show that this treatment usually employed in the freeze-etching technique induces a modification of the degree of order in specific regions inside the axial period D.

[Mechanical properties of the human basilar artery]. / Proprieta' meccaniche dell'arteria basilare umana.

The mechanical properties of the wall of human basilar artery have been determined by tension tests. The degree of orientation of collagen fibers inside the deformed arterial wall has been evaluated by the analysis of the mechanical results and by the X-ray diffraction pattern. The results show that the wall of the muscular arteries can be considered a "composite material" which mechanical properties, at high stress, are due mainly to the collagen fibers orientation.

[Role of the orientation of the collagen fibers on the mechanical properties of the carotid wall]. / Studio del ruolo esercitato dall'orientamento delle fibre collagene sulle proprieta' meccaniche della parete carotidea.

Mechanical test was applied to several carotid walls air-dried under different degree of deformation along the circumferential direction. The stress-strain curves show an increase of the elastic modulus as a function of the deformation. X-ray diffraction studies were applied to determine the degree of collagen orientation in the deformed samples. The carotid wall, in agreement with the "composite materials theory", shows that the collagen is the most responsible factor of the mechanical properties of the tissue.

[Collagen fiber orientation in the tunica media of the aorta as a function of intraluminal pressure]. / Orientamento delle fibre collagene nella tonaca media dell'arteria aorta in funzione della pressione intraluminare.

X-ray diffraction investigation and hystological analysis have been carried out on segments of pig's aortic media layer under different values of distending pressure. The roentgenografic study shows that collagen fibers aligne themselves along the circumferential direction of the vessel as a function of the intraluminal pressure and are completely oriented at systolic pressure. Hystological analysis reveales that the smooth cells orientation, as a function of intraluminal pressure, is very close to that of collagen fibers.

[Roentgenographic study of the structural organization of the collagen fibers in the tunica media of the aorta]. / Studio roentgenografico della organizzazione strutturale delle fibre collagene nella tonaca media dell'arteria aorta.

X-ray diffraction tecnique was used to investigate the distribution and orientation of collagen fibers in media layer of pig aortic wall as a function of mechanical deformation. Hyistological analyses were carried out to study the behavior of smooth cells when mechanical deformation is applied to media layer. The results show a close relationship between collagen fibers and smooth cells orientation.

[Distribution and orientation of the collagen fibers in the tunica media of muscular arteries]. / Distribuzione ed orientamento delle fibre collagene nella tonaca media delle arterie muscolari.

X-ray diffraction tecniques were used to study the distribution and orientation of collagen fibers in media layer of human muscular arteries as a function of mechanical deformation. The close relationship between collagen fibers and smooth cells orientation was shown by X-ray diffraction and histological analyses.