An HA/PEEK scaffold with modified crystallinity via 3D-bioprinting for multiple applications in hard tissue engineering.

Hard tissues, especially teeth and bones, are highly mineralized and the large-scale defect or total loss of them is irreversible. There is still no ideal strategy for the reconstruction of various hard tissue defects that can achieve the balance between biological and mechanical properties. Polyether ether ketone (PEEK) has the potential to substitute for natural hard tissue in defect areas but is limited by its biological inertness. The addition of hydroxyapatite (HA) can significantly improve the osteogenic properties and osteointegration of PEEK materials. But the mechanical properties of HA/PEEK scaffolds are far from satisfaction making scaffolds easy to fracture. We put forward a strategy to balance the mechanical and biological properties of HA/PEEK scaffolds via the regulation of the inner crystallinity and HA mixing ratio and we systematically evaluated the modified HA/PEEK scaffolds through material characterization,in vitroandin vivoexperiments. And we found that the 20%HA/PEEK scaffolds with low crystallinity achieved the required strength and elasticity, and exhibited the characteristics of promoting the proliferation, migration and osteogenic differentiation of bone marrow mesenchymal stem cells. The results of the implantation of beagles' teeth, mandible and rib showed that the 20%HA/PEEK scaffold with low crystallinity could well withstand the local complex force in the defect area and combine well with natural bone tissue, which made it a candidate for a practical versatile hard tissue engineering scaffold.

Retrospective study on the merits of bone grafts and the influence of implant protrusion length after osteotome sinus elevation surgery.

OBJECTIVES: This study aims to evaluate the endo-sinus bone remodeling of dental implants placed via osteotome sinus floor elevation (OSFE) after 6 months and using different implant protrusion lengths and bone grafts through cone beam computed tomography (CBCT). METHODS: Ninety-six patients with 124 implants were included and assigned into four groups. Group 1: implant protrusion length<4 mm with bone graft; group 2: implant protrusion length>4 mm with bone graft; group 3: implant protrusion length<4 mm without bone graft; group 4: implant protrusion length>4 mm without bone graft. Apical bone gain (ABG), cortical bone gain (CBG), bone density gain (BDG), and marginal bone loss (MBL) were observed and analyzed at baseline and 6 months after implant surgery. RESULTS: The CBG in grafted groups 1 and 2 was higher than that in non-grafted groups. The ABG and BDG were higher in non-grafted groups 3 and 4 than in grafted groups, and the levels in group 3 were higher than those in group 4. The CBG in grafted group 2 was higher than that in group 1. No significant difference was observed in MBL analysis. CONCLUSIONS: The BDG of IPL<4 mm implants was higher than IPL>4 mm implant when bone grafts were not applied. No relevance was observed between IPL and CBG. Bone grafts can accelerate endo-sinus bone remodeling by increasing CBG and dissipating the influence of IPL on BDG.

The immune reaction and degradation fate of scaffold in cartilage/bone tissue engineering.

Tissue engineering with scaffolds provides novel prospects for bone/cartilage damage healing. Previous studies mainly focus on the development of physical/chemical property of scaffold and their efficiency on tissue regeneration. The biocompatibility and biodegradation of scaffold have been questioned with their rapidly increased application, since the ultimate clinical application requires biological safety and efficiency of biomaterials. After scaffolds are implanted in living organisms, excessive inflammatory response and foreign body reaction may compromise tissue healing outcomes, or eventually lead to the failure of regeneration. Further, scaffolds degradation and degraded derivatives may elicit immunogenic reaction, cause environmental change, influence encapsulated drug/growth factor release and cellular activity. Hence, the understanding of the degradation characteristics of various biomaterials is required as well. Non-invasive monitoring the fate of scaffolds inside the body needs to be explored for temporally and longitudinally optical observation. The review mainly aims to provide a retrospective summary and discussion of the biocompatibility, immune response and fate of scaffold in cartilage/bone tissue engineering. The continuing development of sophisticated biocompatible and biomimetic scaffolds will eventually lead to clinical application which can improve the quality of patients' care and life.

The establishment of a chemically defined serum-free culture system for human dental pulp stem cells.

BACKGROUND: The concept of establishing a dental stem cell (DSC) bank for oral and maxillofacial regeneration has become of great interest but it remains at a primitive stage. The routine application of serum-containing conditions for human DSC (hDSC) culture is in great controversy considering that the animal-originated serum can cause serious ethical concerns and lead to increasingly irrelevant variables, errors, and poor repeatability of experiment results. Thus, this study aimed to establish a safe, stable and efficient hDSC serum-free culturing system for future DSC bank usage. METHODS: Dental pulp stem cells (DPSCs) from human permanent tooth pulp were isolated, expanded, passaged, and divided into two groups according to their culture conditions: group 1 was the serum-containing medium (SCM) group; and group 2 was the serum-free Essential 8 medium (E8) group. DPSCs were characterized first, followed by cell proliferation, pluripotency, and migration study in SCM and E8 medium. RESULTS: Human DPSCs (hDPSCs) in E8 medium demonstrated greater proliferation, pluripotency, migration ability and less apoptosis. hDPSCs could be successfully induced to the adipogenic, osteogenic, neurogenic, and chondrogenic lineages in E8 group. Real-time polymerase chain reaction indicated that the expression of PPAR-γ, RUNX2, OCN and MAP-2 was higher in E8 group.  CONCLUSIONS: Compared with serum-containing medium, E8 medium exhitibed higher ability in maintaining the cell proliferation, pluripotency, migration, and stability. This new serum-free culture environment might be applicable for hDSC culture in the future.