BIOLOGICAL EVALUATION OF A NOVEL POLYMERIC BIOMATERIAL AS A POTENTIAL BONE SUBSTITUTE.

Abstract: Biodegradable polymers are a therapeutic alternative for the rehabilitation of bone defects. In a previous work (SAIO 2022), we evaluated tissue response to compact implants made of polylactic acid (PLA) reinforced with calcium phosphate (β-TCP) at a concentration of 2.5%. At this concentration, histological studies performed 30 days post-implantation showed new bone formation of woven bone mainly rather than lamellar bone, which is able to withstand forces. OBJECTIVE: To evaluate tissue response to PLA/β-TCP using a higher concentration of β-TCP (5%) 30 days post-implantation. METHODS: Compact rectangular shaped implants of PLA/5% β-TCP (n=10) were characterized physically and chemically (SEM-EDS) and implanted in the hematopoietic bone marrow of the tibia of male Wistar rats (n=10). The animals were euthanized 30 days post-implantation and radiographic, histologic, and histomorphometric studies were performed (area of new bone formation and % of osseointegration). RESULTS: The physical-chemical characterization of the biomaterial showed the presence of particles inside the matrix of the polymer (SEM), and the microchemical analysis (EDS) revealed the presence of Ca-P in the particles and C-O in the matrix. Histological studies showed new bone formation of lamellar and woven bone in contact with the surface of the biomaterial, with no associated inflammatory response. As shown by the histomorphometric analysis, the area of bone tissue was 0.052 ± 0.011 mm2 and the percentage of osseointegration was 50 ± 0.07%. Some sectors of the surface of the polymer exhibited areas of biodegradation with scant penetration into the core of the biomaterial and multinucleated giant cells. CONCLUSION: The compact polymeric biomaterial studied here did not generate complete new bone formation of lamellar bone 30 days post-implantation, indicating that tissue response is not dependent on β-TCP concentration. Longer experimental times are necessary to further evaluate replacement of woven bone with lamellar bone and biomaterial degradation. The biodegradation observed only at the surface of the material and the scant penetration of tissues into the core of the implant underscore the need to modify the design and use a three-dimensional structure that is less compact and thus favors biodegradation and new bone formation.