[Osteoconductive properties of bioactive glasses in a bulk form and as a coating on alumina]

Alumina on alumina friction couple has proven its reliability in the field of total hip arthroplasty. However, loosening of the alumina socket has been responsible for most of the failures. An improvement of the bone/alumina interface could be achieved with the use of an osteconductive material as a coating on alumina. The aim of this study was to evaluate the osteconductive properties of two types of bioactive glasses as a coating on alumina substrates.

Two types of coated implants (silicate glass coated alumina - AVSi, and phosphate glass coated alumina - AVP) were evaluated in a rabbit cancellous bone model. Pure alumina implants (A) were used as negative controls and bulk glasses (silicate - VSi and original 45S5, and phosphate glasses -VP) as negative controls. Sacrifices were performed at 3, 12 and 24 weeks. The interface evaluation included histomorphometry using an image analyzer.

Silicate glasses demonstrated high osteoconductive properties. However, non mineralized osteoid tissue was the main tissue in contact with both coated implants and bulk phosphate glasses. This tissue covered over 70 p. 100 after 24 weeks of implantation, while it was never observed around pure alumina implants after 3 weeks.

Amongst the hypotheses that could explain this mineralization inhibitory process, the one involving an Al(3+) glasses contamination from Al(2) O(3) is the likeliest. The high temperature coating procedure could be responsible for alumina transformation into a more soluble phase.