Effects of additional collagen in biphasic calcium phosphates: a study in a rabbit calvaria

Objectives Biphasic calcium phosphates (BCP) are synthetic biomaterials developed as an alternative to the autogenous bone grafts and xenografts. The aim of the present study was to assess the influence of the addition of collagen onto the BCP resorption rate and bone formation. Material and methods Eighteen male NWZ rabbits approximately 12 weeks of age were used. Critical size defects were randomly treated with bilayered BCP materials comprising 12% HA and 88% alpha-TCP with and without collagen or sham-operated, respectively. All defects were covered with a resorbable collagen membrane. Animals were euthanized after 3 and 12 weeks of healing and investigated by micro-CT, histologic, and histomorphometric analysis. Results Woven bone formation was observed from the original bone at 3-week healing in all samples. After 3 months, mainly lamellar new bone in the peripheral area was observed. In the central region, both woven and lamellar bone were seen. Samples containing collagen showed less residual biomaterial than without collagen at both healing periods. Both types of granules were in close contact with new bone, yielding a complete defect closure at 3 months of healing. However, new bone volume and area was similar for both biomaterials. Conclusions Within its limitations, the study results qualify collagen as a biocompatible carrier for BCPs. The presence of collagen indicated neither significant impact on the resorption of the BCPs nor on bone formation.