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Biomedical subjects

A Ravaglioli

Publications and source records attributed to A Ravaglioli.

8 recordsLinked to original sources
PubMed1992

Interface between hydroxyapatite and mandibular human bone tissue.

Samples from intraosseous dental implants, removed from patients for mechanical failures, were examined to analyse the interaction between hydroxyapatite as plasma sprayed coating on titanium supports and human bone. The implantation time varied up to 8 years. No failures had arisen from problems at the interface between the hydroxyapatite coating and bone. The number of samples examined and the implantation times give good statistical conclusions. Histological and microchemical studies showed the good performance and compatibility of this sprayed hydroxyapatite. We present evidence from the best samples which show close bonding with the surrounding bone tissue. New bone is seen all around the coated implant. The composition of the calcium phosphate deposited on the hydroxyapatite and cellular approach were determined, and demonstrate the efficiency of the interaction between this plasma sprayed hydroxyapatite and the bone.

Adhesiveness↗
PubMed1990

In vitro observations of iron-doped bioactive glasses.

Several in vitro tests are necessary to evaluate the biological compatibility of materials used to manufacture implants for humans or animals. These tests will indicate whether these materials can be tolerated when implanted in vivo. Since ceramic materials are suitable for coating layers, it was decided to study their performance by adding certain oxides as doping agents. This paper describes their influence in vivo in some preliminary tests and in vitro for iron trioxide only. This work attempts to ascertain the range of doping to maintain the bioactivity characteristics and in particular the influence of iron trioxide as a doping agent in the bioactive glass. To do so the adhesion of baby hamster kidney cells to bioactive glasses doped with different concentrations (2 and 4 wt%) of this compound was quantified. The base glass without iron oxide was used as a control as 0 wt% doping. In a second phase, a coating of fibronectin, a glycoprotein that plays an important role in cell binding and spreading on substrates, was quantified on the same surfaces. It was shown that the cell avidity for the surfaces of the materials increases with increased doping of iron oxide. The values are significantly higher than those observed for the base glass. Fibronectin adsorption quantification showed a similar trend, with values of adsorption similar for the doped samples and higher than that of the non-doped glass. It was demonstrated that iron trioxide induces an increase in cell adhesion capability with bioactive glass surfaces and the capability of adhesion of the fibronectin to act as a substrate on the same surfaces.

Adsorption↗
PubMed1990

Comparative analyses among interfaces of some ceramic materials and bone in sheep.

Aim of this work is the evaluation of "in situ" implants in an animal model to study the interfaces that some ceramic materials for dental bone defects develop with bone and to check which material is more osteoconductive. In a sheep's jaw, eight holes were drilled and filled with six ceramic materials in granular shape. Two bilateral holes were left empty as reference. The ceramic materials were: porous tricalcium phosphate (TCP), porous hydroxylapatite (HA) and four bioactive glasses. The glasses differ for doping agents that affect the velocity of biodegradation in the living body. Monthly radiographs were taken and the X-ray pictures analyzed by means of a Video Display Computer in order to quantify the optical density changes occurred in the holes. After 4 months implantation, the segments of the jaw containing the materials were fixed in paraformaldehyde, embedded in methylmethacrylate and sectioned. The results obtained under the microradiograph, the SEM and the X-ray microprobe showed a good bone repair only with TCP granules. A great degradation was seen in HA granules and particularly in glasses. The degradation modified the structure and the composition of the glass granules, but it was not followed by a consequent bone deposition.

Animals↗
PubMed1988

Mineralization and calcium fixation within a porous apatitic ceramic material after implantation in the femur of rabbits.

Cylinders (0.8 cm long, 1.0 cm of diameter and with an axial hole), constituted, after firing, of a ceramic mixture of hydroxylapatite (HA) and beta-tricalciumphosphate (beta-TCP) in a 10:1 ratio, were implanted into mid-diaphyseal defects of one femur of 20 rabbits and stabilized with intramedullary rods. The implantation sites were checked radiographically every month, and after 3 months (3 animals) and 6 months (17 animals) the rabbits were sacrificed and the implants with the surrounding tissue were embedded in methylmethacrylate, cut to thick sections and analyzed by scanning electron microscopy (SEM). Porosimetric and x-rays diffraction analyses were carried out before and after implantation of the cylinders, and the state of mineralization at the bone-implant interface was determined by EDAX microprobe analysis. Bony callus formation started at 1 month at the osteotomy sites, as judged by radiography, but after 3 months a not-mineralized zone had still been demonstrated between bone and the implants. At 6 months, 13 implants showed themselves firmly fixed in their implantations beds, while 4 implants were only incorporated at their proximal ends. In bone contact zones, an enrichment of Ca2+ was displayed by microanalytical techniques in the outer zone of the implanted samples which may be explained by an apparent additional phase transformation of HA into TCP, thanks to the change of the Ca/P ratio, that takes place in vivo.

Animals↗
PubMed1988

Interpretation of difficulties in the initial adhesion of bio-active glasses to bone.

The authors propose a model to explain the initial difficulties in achieving adhesion between bio-active glasses and bone. It is explained that in vitro tests involve biophysical situations which are different, and in many cases very different, from those which take place in in vivo implantation. The model suggests procedures which could be applied to bio-active glasses after the manufacturing process in order to improve their initial adhesion to bone.

Animals↗
PubMed1988

Structural modifications and biological compatibility of doped bio-active glasses.

The Raman laser and infrared spectra of doped bio-active glasses of the 45S5 type are presented and discussed. The spectroscopic results show that the doping agents cause the destruction of the basic glass structure and the consequent formation of SiO4(4-) units in the glass network. When the doped glasses have been immersed in a physiological solution (199 medium), a film of calcite forms on the glass surface and this modification is related to the type of doping agent used, decisive for close linking between metal supports and the glass. The presence of doping agents does not prevent the normal growth of the bone onto the surface of doped bioactive glasses. Histological tests show that tissue response to very fine powders of doped glasses increases up to 15 days more or less according to the structural modifications revealed by spectroscopic measurements.

Animals↗