Nano-hydroxyapatite Mineralized Silk Fibroin Porous Scaffold For Tooth Extraction Site Preservation

Purpose: Tooth extraction initiates the alveolar bone resorption and remodeling,leading to a significant reduction in the height and width of alveolar ridge.The loss of bone mass may generate difficulties in restoring the aesthetics and function of the extracted site through oral implantation therapy.Therefore,the current trend in tooth extraction site research is focused toward alveolar ridge preservation technology which is defined as a technique to decrease alveolar ridge resorption after tooth extraction and increase the generation of new bone in the extraction socket.At present,artificial biomaterials used for site preservation have immunogenicity and poor osteo-conduction in vivo.The aim of this study was to construct a composite material that combines low immunogenicity and good osteogenic properties—nano-hydroxyapatite mineralized silk fibroin scaffold for alveolar ridge preservation.Methods: Silk fibroin was extracted from Bombyx mori silkworm cocoons,then,the silk fibroin porous scaffold(SF)was prepared by freezedrying method and the nano-hydroxyapatite mineralized silk fibroin scaffold(MSF)was obtained by hydrothermal mineralization.The scanning electron microscope(SEM),Fourier transform infrared spectrometer(FTIR),X-ray diffractometer(XRD),and contact angle tester were used to analyze the micromorphology,chemical composition,crystal phase,and hydrophilic nature of the MSF scaffold.Mouse embryo osteoblast precursor cells(MC3T3-E1)were seeded on MSF scaffolds to detect the biocompatibility and osteogenic property of MSF scaffolds,Furthermore,prepared grafts(SF or MSF scaffold)were implanted into the alveolar bone defect of Sprague Dawley rats and newly formed bone tissue was analyzed by micro-CT and histological.Results: SEM,FTIR,and XRD showed that nano-hydroxyapatite crystals were uniformly distributed on the surface of SF scaffold.The MSF hydrophilicity measured by water contact angle and swelling ratio was superior to plain SF scaffold.In addition,MC3T3-E1 adhered,grown,and proliferated normally on MSF scaffolds,and showed good osteogenic differentiation potential.Furthermore,the bone mineral density(BMD)and bone volume fraction(BV/TV)of the new formed bone of the MSF group were higher than those of the SF and control groups,and the reduction rate of alveolar bone were lower in MSF group,indicating that the MSF grafts induced more bone formation and reduced the height of alveolar bone resorption after tooth extraction.Conclusion: The MSF scaffold partially simulated the structure and composition of natural bone matrix.It promoted osteogenic differentiation of MC3T3-E1 cells in vitro,and also promoted new bone regeneration in tooth extraction sockets in vivo,indicating it is a biomaterial with great potential for tooth extraction site preservation.