The Bone Tissue Responses to Prehydrated and Collagenated Cortico-Cancellous Porcine Bone Grafts: A Study in Rabbit Maxillary Defects

Background: Bone substitutes should have osteoconductive properties and be completely replaced with new bone with time. Adding collagen gel to prehydrated and collagenated porcine bone (PCPB) particles results in a sticky and moldable material which facilitates clinical handling. However, the possible influence of the gel on the bone tissue response is not known. Purpose: The objective of the study was to evaluate the bone tissue responses to PCPB graft with or without collagen gel and to evaluate the resorption/degradation properties of the biomaterials. Materials and Methods: Fourteen rabbits were used in the study. Bilateral bone defects, 5 x 8 x 3 mm, were created in the maxilla and filled with PCPB + collagen gel (test) or with PCPB only (control) and covered with a collagen membrane. Animals were killed after 2 (n = 3), 4 (n = 3), and 8 weeks (n = 8) for histological and morphometrical evaluations. Results: There were no differences between test and control defects. Both materials showed bone formation directly on the particles by typical osteoblastic seams. The bone area increased with time (2-8 weeks) for both sides, from 16.2% (control) and 19.2% (test) to 42.7 and 43.8%, respectively. The PCPB, whether mixed with collagen gel or not, was resorbed by osteoclasts as well as part of remodeling with the formation of osteons within the particles. Morphometry showed a decrease of PCPB area from 19.4% (control) and 23.8% (test) after 2 weeks to 3.7 and 9.3% after 8 weeks, respectively. Conclusions: Mixing collagen gel and PCPB to facilitate the clinical handling does not influence the bone tissue responses to the material, which exhibited osteoconductive properties and was resorbed with time.