[Intra-individual comparison of alpha- and beta-TCP ceramics in an animal experiment]

In the quest for bioinert adaptable alloplastic materials, TCP ceramics have gained a new application in craniofacial bone substitutes. Therefore, a histomorphological, intraindividual, comparative study was conducted on seven adult Goettingen miniature pigs (GMP) to analyze the difference of the degradation and remodelling processes of alpha-TCP and beta-TCP in critical size defects of the proximal tibiae. In addition, primary insertion of dental implants followed to study osseous integration. The critical size defects, which were created in the proximal tibiae in GMPs, were filled on the left side with beta-TCP and on the right side with alpha-TCP. Two GMPs were used as control group. After 4-68 weeks of investigation, the GMPs were sacrificed by narcosis. The histological investigation showed that these ceramics have an osteoconductive effect. It was noted that ossification proceeds centripetally. It could be demonstrated that the degradation of the materials follows a hydrolytical process and that the intratrabecular integrated ceramic remnants follow a dynamic remodelling process. Within 68 weeks after implantation, 90% of the TCP granulae were degraded. Macrophages were found in the marrow space, containing microparticles of TCP, especially after alpha-TCP implantation. In conclusion, defined degradation of these ceramics allows early functional bone regeneration with an additional undisturbed biofunctional unisotrop orientation of new trabeculae. Furthermore, dental implants should be inserted 5-6 months after TCP implantation.