A. Merolli

Evaluation of different preparations of plasma-spray hydroxyapatite coating on titanium alloy and duplex stainless steel in the rabbit

Many variables are involved in hydroxyapatite coating of metals by plasma-spray techniques. The authors have investigated the biological response to some of the most relevant variables in a controlled in vivo trial. The bone response in the rabbit towards hydroxyapatite coated cylinders was studied keeping the following variables fixed: (a) crystallinity of coating (greater than 90% and between 70% and 60%); (b) thickness of coating (50 and 100 μm); (c) metallic substrate (titanium alloy and duplex stainless stell). Analysis of the results highlights the importance of defining the crystallinity of the coating to forecast its in vivo behaviour: highly crystalline coating is more stable in time but can give rise to fragmented bulky particles; a less crystalline coating is subject to slow degradation in the long term but facilitates its substitution by newly formed bone. Furthermore, it has been found that no relevant differences can be ascribed to a variation in coating thickness between 50 and 100 μm. It has, also, been observed that there are no differences when duplex stainless steel is used instead of titanium alloy as metallic substrate, confirming that bone responds primarily to the coating.

Comparison in in-vivo response between a bioactive glass and a non-bioactive glass

AbstractThe authors report on the in-vivo comparison, in the rabbit, between the response to a bioactive glass and the response to a non-bioactive glass. Implants have been performed in muscle and bone. Two different glasses were investigated, namely B01 and I02. B01 is a glass designed to be degradable and resorbable and has a percentual molar composition of:

Response to polyetherimide based composite materials implanted in muscle and in bone

SiO_2 49.6; P_2 O_5 2.7\% ;s + MgO + Na_2 O + K_2 O + Al_2 O_3

Bone response to polymers based on poly-lactic acid and having different degradation times

47.7% with a 1 : 1 CaO/Na2O ratio. I02 is a sodium-calcium-silicate non-resorbable glass lacking P2O5 and has a percentual molar composition of:

A more detailed mechanism to explain the “bands of Fontana” in peripheral nerves

SiO_2 70.7\% ; CaO + MgO + Na_2 O + K_2 O + Al_2 O_3

Plantar pressure distribution in patients with neuropathic diabetic foot

29.3%. In-vivo tests were planned as: (a) intramuscular implants of glass cylinders in the rectus femoris and retrievals took place at 2, 16 and 43 weeks; (b) intraosseus implants of glass cylinders in the distal femural canal and retrievals took place at 8 and 43 weeks. Histology and light microscopy analysis followed. Bioactive degradable glass elicits a favorable response both in muscle and bone; a gradual degradation process leads to disruption and partial resorption of the material and a tight apposition is promoted with the newly formed bone. The non-bioactive sodium-calcium-silicate glass (named I02) may elicit, like the bioactive degradable B01, a favorable response which is characterized by the absence of inflammatory or other adverse reactions; anyway it does not change its structure at an optical microscopic level and it does not promote any tight apposition with bone. ©2000 Kluwer Academic Publishers