In vivo behaviour of a custom-made 3D synthetic bone substitute

Objectives: To evaluate the in vivo behaviour of a custom-made 3D synthetic bone substitute used as scaffold for sinus augmentation procedures in an animal model. Bone substitute was a calcium phosphate ceramic fabricated by the direct rapid prototyping technique dispense-plotting. Methods: Scaffolds were first analyzed for geometrical and chemical properties using a helium pycnometer, a semi-quantitative X-ray diffraction measurements, and a scanning electron microscopy. Then, six sheep underwent sinus augmentation with the scaffolds. Animals were sacrificed after healing periods of 45 and 90 days, and block sections obtained from grafted sites were subjected to micro-CT, morphological, and morphometric analyses. Results: A complete integration of the scaffold inserted in the sinuses was recorded from specimens obtained after a 45 days healing period, with abundant deposition of newly formed bone tissue within the biomaterial pores. In particular, histological analysis revealed initial foci of bone remodeling were mainly localized at the periphery of the implanted area after 45 days, while continuous bridges of mature lamellar bone were recorded in 90 days healing specimens. In addition, the process of bone generation remained active throughout the 90 days period after sinus augmentation, increasing significantly either in the central or in the peripheral portion of grafted area. Moreover, morphometric analysis allowed to measure total vascular area, indicating a more active blood vessels remodeling at the peripheral fields and its increasing after 90 days from sinus augmentation. Conclusions: This study showed how a technique allowing to control porosity, pore design and external shape of ceramic bone substitute may be valuable for producing synthetic bone grafts with good clinical performance. Moreover, the hypothesis that bone regeneration proceeds from periphery to center of the sinus cavity was confirmed. These results may represent a validation of safety and biocompatibility of this innovative custom-made synthetic bone substitute for oro-maxillo-facial surgical procedures.