Observations of the bone activity adjacent to unloaded dental implants coated with Polyactive or HA

In addition to bone-bonding biomaterials such as calcium phosphate ceramics and Bioglass/glass ceramics, an elastomeric poly(ethylene oxide) poly(butylene terephthalate) (PEO/PBT) segmented block co-polymer (Polyactive) was recently introduced. In contrast to ceramic biomaterials, Polyactive is a flexible material. In a previous three-dimensional finite element analysis study, it was stated that application of a flexible Polyactive coating simulates the function of the periodontal ligament. The topic of this investigation was to compare the bone-bonding capacity of Polyactive-coated titanium implants with hydroxylapatite (HA) coated implants. The implants were inserted bilaterally in the edentulous part of the mandibular bone of 12 goats. After 3 weeks, the implants were in close contact with the cortical bone, but no cortical bone reaction or remodelling was observed. After 9 weeks, an extensive bone reaction was seen around the HA and Polyactive-coated implants and contact was frequently encountered between newly formed bone and the implants. Within the surface of the Polyactive coating, a considerable amount of calcification was present. After 25 weeks, cortical remodelling was still apparent. A striking finding was the apparent association between osteon formation and calcification within the surface of the Polyactive layer. Back-scatter analysis of the non-decalcified Polyactive bone interface showed the presence of a calcium phosphate layer in the implant material that apparently formed a continuity with the mineral matrix of bone, suggesting bone-bonding. In general, it was observed that the bone reactions to HA and Polyactive were comparable. A swelling of the coating, just beneath the cortical layer (champagne-cork effect) was often seen.(ABSTRACT TRUNCATED AT 250 WORDS)