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

Introduction Alumina on alumina friction couple has proven its reliability in the field of total hip arthroplasty. However, loosening of the alumina socket has bee n 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 osteconducti ve properties of two types of bioactive glasses as a coating on alumina sub strates. Materials and methods Two types of coated implants (silicate glass coated alumina - AVSi, and pho sphate glass coated alumina - AVP) were evaluated in a rabbit cancellous bo ne model. Pure alumina implants (A) were used as negative controls and bulk glasses (silicate - VSi and original 45S5, and phosphate glasses -VP) as n egative controls. Sacrifices were performed at 3, 12 and 24 weeks. The inte rlace evaluation included histomorphometry using an image analyzer. Results 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 af ter 24 weeks of implantation, while it was never observed around pure alumi na implants after 3 weeks. Discussion Amongst the hypotheses that could explain this mineralization inhibitory pr ocess, the one involving an Al3+ glasses contamination from Al2O3 is the li keliest. The high temperature coating procedure could be responsible for al umina transformation into a more soluble phase.