Osteogenesis And Mechanical Study Of Concentrated Growth Factor Combined With Mineralized Collagen In Repairing Mandibular Defects

Objective: Mineralized collagen(MC)is a new and effective bone tissue engineering scaffold material,which has been widely studied and applied due to its good biocompatibility,osteoconductivity,osteoinductivity and biodegradability.In order to speed up the new bone formation of MC,this study used concentrated growth factor(CGF)and MC in combination to repair rabbit mandibular defects,and observed and compared conditions and biomechanical properties of the new bone formation after MC/CGF and simple MC materials were implanted into rabbit mandibular defects at different periods,and provide theoretical and experimental basis for the application of new bone graft materials in oral clinics.Methods: 1.Material: MC bone meal is provided by Beijing Allgens Medical Technology Co.,Ltd.2.Preparation of CGF: Take 9ml of venous blood and centrifuge to obtain CGF gel.3.The surface morphology of the material: after the mixture of CGF and MC is freezedried,the surface morphology of MC and MC/CGF is observed with a scanning electron microscope.4.Establishment of animal model and materials implantation: 81 New Zealand big-eared rabbits were randomly grouped,and circular bone defects with a diameter of 8mm and a depth of 4mm were prepared on both mandibles of the experimental rabbits,and MC/CGF was implanted on the right side and MC was implanted on the left side.They were sacrificed at 8,16,and 24 weeks after operation and samples were taken.5.General observation: Observe the bone growth in the defect area of the experimental rabbits in each group after the operation,and whether there is obvious inflammation.6.Use X-ray film and Micro-CT scan to analyze the new bone formation and material degradation,and the Micro-CT reconstruction results bone volume(BV),bone volume to total volume(BV/TV),bone trabecular thickness(Tb.Th),trabecular bone number(Tb.N),trabecular bone separation(Tb.Sp),residual material volume(RMV),residual material volume percentage(RMVF)and other parameters are analyzed and evaluated.7.Make hard tissue sections,use HE and Masson staining to detect the formation of new bone in the defect area.Make paraffin sections and use immunohistochemical staining to detect the expression level of OCN and BMP2.8.Use a universal mechanical testing machine to detect the compressive strength and elastic modulus of the new bone.9.Use SPSS 22.0 software for statistical analysis of experimental data.Results: 1.The surface morphology of the material: the surface of the material is rough and porous.The surface of MC/CGF is looser.2.General observation: the experimental rabbits eat and move normally for 7 days after operation.There is no obvious inflammation in the operation area.Bone meal particles are still visible at 8 weeks after operation.At 16 weeks,the boundary between new bone and surrounding bone is unclear.At 24 weeks the new bone in the MC/CGF group had no boundary with the surrounding bone tissue,and the bone was mature.3.Both X-ray film and Micro-CT showed that at each time point,the new bone formation of the MC/CGF group was better than that of the MC group,the difference was statistically significant,and the material degradation of the MC/CGF group was significantly more than that of the MC group.The 3D reconstruction of Micro-CT display the BV,BV/TV,Th.Tb,Th.N,Th.sp,RMV and RMVF of MC/CGF group were better than those of the MC group(p<0.05).4.HE and Masson staining results show that the maturity and continuity of new bone in the MC/CGF group are better than those in the MC group.5.Immunohistochemical staining showed that the expression of OCN increased gradually at 8,16,and 24 weeks,and the difference between the two group was statistically significant(p<0.05).The expression of BMP2 was the highest at 8 weeks,and gradually decreased with time.The difference was not statistically significant at 24 weeks.6.The results of biomechanical testing showed that the compressive strength and elastic modulus of the MC/CGF group were higher than those of the MC group.Conclusion: The new bone formation and biomechanical properties of the MC/CGF group were better than those of the MC group.The application of CGF promotes new bone formation of MC,and provides new ideas for the application of new bone tissue engineering scaffold materials to oral clinics.