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Biomedical subjects

R Martinetti

Publications and source records attributed to R Martinetti.

5 recordsLinked to original sources
PubMed1997

Resorption of composite polymer-hydroxyapatite membranes: a time-course study in rabbit.

The histological findings in rabbit, concerning the resorption of a new composite hydroxyapatite-polymer membrane used in guided tissue regeneration are reported. The polymer appeared to be completely resorbed in about 4-6 months, while the inorganic component, hydroxyapatite, appeared to begin to resorb after the tenth month. The integrity of the membrane appeared to be unchanged after a 10-month period. No inflammatory cell infiltrate was present. This new type of membrane appeared to be relatively well tolerated by the host, had no significant adverse soft and hard tissue reaction, appeared to be easy to handle and had good space-maintaining capabilities. More research is certainly needed before clinical use in man.

Absorption↗
PubMed1997

Net-shaped hydroxyapatite implants for release of agents modulating periodontal-like tissues.

Periodontal-like tissues and, in particular, alveolar bone- and root cementum-like material can theoretically be modulated by release of biochemical agents such as bisphosphonate (PCP), growth hormone (GH) and alkaline phosphatase (ALP) from the implant surface. The present research focused on porous ceramic hydroxyapatite (PCHA) implants. In the past the PCHA implants were machined on a lathe out of simple blocks of PCHA ceramic. This was a tedious and cumbersome method, often resulting in implants with undesirable characteristics: different porosities, cracks and fractures. Therefore a moulding technique was developed to sinter near-net-shaped PCHA implants at 2 different sintering temperatures: 1170 degrees C and 1280 degrees C, resulting in PCHA implants with porosities of 62.06% (PCHA type 1) and 40.74% (PCHA type 2), respectively. After 1 h incubation in a 10(-2) M solution of PCP, the total amounts adsorbed onto PCHA type 1 and type 2 were 114.9 +/- 2.1 micrograms and 46.1 +/- 1.5 micrograms, respectively. This was approximately 5 times higher than after incubation for 1 wk in a 10(-4) M solution of PCP. The total amounts of PCP released after the observation period of 75 d from PCHA type 1 and type 2 after incubation in the 10(-2) M solution were 103.1 +/- 1.8 micrograms and 42.8 +/- 1.5 micrograms, respectively. The total amounts released from type 1 and 2 after incubation in the 10(-4) M solution were 7.4 +/- 0.4 micrograms and 4.1 +/- 0.1 micrograms, respectively. After 2 wk of incubation in a liver/bone/kidney ALP solution the total amount of ALP adsorbed onto PCHA type 1 implants was 5039 +/- 412 mU/ml. The total amounts of ALP released were 4674 +/- 438 mU/ml and 53 +/- 20 mU/ml after 1 and 2 wk, respectively. The release of ALP was high at the beginning but slowed down thereafter. It was evident that despite the well-known high bonding affinity of PCP to HA the release of PCP occurred steadily, over a long period of time in vitro.

Adsorption↗
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↗
PubMedDate not supplied

[Necessity and validity of standard models for experimental preclinical evaluation of biomaterials. An example of biologic characterization of a hydroxyapatite-based implant material].

A large number of methods are now available for the preclinical screening of implantable materials concerning their biocompatibility and their ability to stimulate tissue formation. In vitro techniques represent a very useful tool, since this way we can realistically simulate the biological events which occur in vivo at the bone-implant interface. In the present study scanning electron microscopy and light microscopy observations were performed in order to assess the effect of an hydroxyapatite granulate on cell behaviour and morphology. Uptake of proteins to hydroxyapatite surface has been also investigated by comparing the amounts adsorbed after incubation with bovine serum albumin and bovine pancreaticamilase. According to our preliminary observation cells do not show signs of toxicity or inhibition of cell growth even after 14 days of co-culture with hydroxyapatite. Granules were covered by an uninterrupted cell layer by day seven. Even after two days micrographs show cells anchored and spread over the surface of the underlying granules, with a flattened and stellate shape. Such a morphology indicates a very high cellular activity, suggesting that the interaction with hydroxyapatite seriously increased metabolism. Measurements of protein adsorption on the hydroxyapatite surface show that changes in the size of particles affect the binding of proteins, while, in the case of granular hydroxyapatite, despite changes in size of granules, variations of protein adsorption were not observed, neither in relation to their different isoelectric point. Our preliminary results represent a good example of the opportunities presented by an experimental in vitro model.

Biocompatible Materials↗