Morphological and structural study of pseudowollastonite implants in bone

In vitro experiments show that pseudowollastonite (alpha-CaSiO3) is a highl y bioactive material that forms a hydroxyapatite surface layer on exposure to simulated body fluid and also to human parotid saliva. This finding is v ery significant, as it indicates that the pseudowollastonite can be physica lly and chemically integrated into the structure of living bone tissue, and therefore could be suitable for repair or replacement of living bone. The physical and chemical nature of the remodelled interface between the ps eudowollastonite implants and the surrounding bone has been studied after i n vivo implantation of 20 pseudowollastonite cylinders into rat tibias. The interfaces formed after 3, 6, 8 and 12 weeks of implantation were examined histologically using an optical microscope and also by analytical scanning electron microscopy. SEM and X-ray elemental analysis showed that the new bone was growing in di rect contact with the implants. Other examinations found that the bone was fully mineralized. The ionic exchange taking place at the implant interface with the body fluids was essential in the process of the implant integrati on through a dissolution-precipitation-transformation mechanism. The study found the interface biologically and chemically active over the 12-week imp lantation period. The rate of new bone formation decreased after the first 3 weeks and reached constant value over the following 9 weeks. The osteobla stic cells migrated towards the interface and colonized the surface at the contact areas with the cortical regions and also bone marrow.