Experimental Study On 3D Printed Porous Coating Of Titanium Alloy Surface Enhancing Osseointegration

Part ? Experimental study on the 3D printed porous coating of Titanium Alloy surface and its mechanical property testObject: To explore the possibility of using 3D printing technology to manufacturing porous coating of titanium alloy surface and its mechanical property.Method: After computer-aided design modeling,the files were import to 3D printer and the titanium alloy prostheses were printed;the prostheses were characterized by include pore size and porosity by SEM;the compressive strength and shear strength of titanium alloy prostheses were measured by electronic universal material testing machine.Result: Four groups of titanium alloy with different pore size and porosity porous coating were manufactured by 3D printing technology,and their pore parameter were group A 218.7?m 61.2%,group B 262?m 68.1%,group C 558?m 79.2%,group D 753?m 89.0%,which characterized by SEM.The compressive strength and shear strength of four groups were group A 78.02 MPa,44.28 MPa;group B 20.62 MPa,23.17MPa;group C 8.32 MPa,12.64MPa;group D 4.26 MPa,8.53 MPa.Conclusion: The porous coating of titanium alloy surface can be precisely manufactured by 3D printing technology which have good mechanical property.With the gradual increase of pore size,the compressive and shear properties of the prostheses showed a sharp decline,relatively the pore of 262?m 68.1% may be the best parameter for prosthesis,also could provide a reference for prosthesis design in the future.Part ? Experimental study on the effect of 3D printed porous coating of Titanium Alloy surface on the biological behavior of MG-63 cellObject: To study the compatible of the 3D printed porous coating of titanium alloy surface and the effect of different pore parameter on MG-63 cells.Method: MG-63 cells were cultured on the 3D printed porous coating of titanium alloy surface for 24 h,48h and 72 h,then the morphology of cells was observed by SEM;Cell count performed under fluorescence microscope after DAPI staining.Cell survival rate of each group were measured by CCK8 method;the expression of ALP and OCN was measured by ALP kit and Western blot.Result: The cells of group A and group B had better extension shape and protruded more pseudopodia than group C and group D at any point in time.Cells adhered on group A and group B was more than group C and group D after 24 h,which showed statistical difference;Cells adhered on group B was more than any other group after 48 h,which showed statistical difference,and there was no statistical difference between any two groups after 72 h.After being cultured for 24 h,the cell survival rate of group A was lower than any other group include the blank group,the difference was statistically significant;group B was lower than group C and group D,the difference was statistically significant,and there was no statistical difference between group B and blank group;group C was lower than group D,the difference was statistically significant,but there was no statistical difference between group C and blank group;the group D was higher than blank group,the difference was statistically significant.After being cultured for 48 h,the cell survival rate of group A was lower than any other group include the blank group,the difference was statistically significant;group B was higher than group A,but lower than blank group and group D,the difference showed statistically significant,while there was no statistical difference between group B and group C;group C was lower than blank group and group D,the difference was statistically significant;the group D was higher than blank group,and there was statistical difference between the two groups.After being cultured for 72 h,the cell survival rate of group A was lower than any other group include the blank group,the difference was statistically significant;group B was lower than blank group,group C and group D,the difference was statistically significant;group C was lower than blank group and group D,the difference was statistically significant;the group D was higher than blank group,and there was statistical difference between the two groups.At all of three point in time,the expression of ALP and OCN of the four group showed no statistical difference between any two groups.Conclusion: 3D printed porous coating of titanium alloy surface can significantly affect the biological behavior of MG-63 cells,relatively the smaller pores(218.7?m 61.2%,262?m 68.1%)are conducive to cell adhesion and differentiation,the bigger pores(753?m,89.0%)are conducive to cell proliferation;there may be error when cells are collected from the smaller porous coating,so given the low proliferation,whether considering it as the material toxicity or inhibition of proliferation or not,further study is needed.Part ? Experimental study on 3D printed porous coating of Titanium Alloy surface enhancing osseointegration and its machanismObject: To study the effect of 3D printed porous coating of titanium alloy surface with different pore parameters on enhancing osseointegration and the expression of osteogenic gene.Method:3 groups of titanium alloy with porous coating were manufactured by 3D printing technology,which have different pore parameter(group A 262?m 68.1%,group B 558?m 79.2%,group C 753?m 89.0%).27 New Zealand white rabbits were randomly divided into 3 groups,3 groups of prosthesis were implanted into the bilateral femoral medullary cavity of each group of rabbits,and 3 rabbits were sacrificed at the end of the fourth,eighth,twelfth week after operation.The X-ray and Micro-CT were taken to observe the general condition of the specimens,while bone volume fraction and tissue mineral density were measured by Micro-CT.Undecalcified hard tissue sections were made for Goldner's staining and observing under fluorescence microscope.Pull-out test was performed at certain point in time.q PCR was used to measure the expression of Runx2 and Osterix.Result: X-ray and Micro-CT showed no obvious bone formation of each group at 4th week after operation,with time went on,the new bone formation increased gradually,and peaked at 12 th week after operation,group A showed better property for bone formation than group B and group C.All the three groups showed that fluorescence was weak and the bands were all narrow at 4th week after operation,as time went on,the fluorescence intensity increased,the bands was wider,the distance between green fluorescence and yellow fluorescence became larger,which peaked at 12 th week after operation,the fluorescence of group A showed the best morphology.The Goldner's staining showed that all groups were mainly nuclear at 4th week after operation,as time went on,the osteoid increased gradually,and peaked at 12 th week after operation,group A showed more osteoid formation than group B and group C.BVF and TMD of each group showed no statistical difference between any two groups at 4th and 8th week after operation,but group A was larger than group B and group C at 12 th week after operation,meanwhile,there is no statistical difference between group B and group C.The expression of Runx2 and Osterix of gourp A was higher than group B and group C at 4th and 8th week after operation,the difference was statistically significant,while there is no statistical difference between group B and group C.The expression of Runx2 of gourp C was lower than group A and group B at 12 th after operation,the difference was statistically significant,and there is no statistical difference between group A and group B.The expression of Osterix showed no statistical difference between any two groups at 12 th after operation.The peak pull-out load showed no statistical difference between any two groups at 4th week after operation.The peak pull-out load of group A was larger than group B and group C at 8th week after operation,and there is no statistical difference between group B and group C.The peak pullout load showed statistical difference between any two groups,and the sequence from high to low is: group A,group B,group C.The expression of Runx2 and Osterix showed no statistical difference between any two groups at 4th and 8th week after operation,but there is statistical difference between any two groups at 12 th week after operation,and the sequence from high to low is: group A,group B,group C.Conclusion: 3D printed porous coating of titanium alloy surface can enhance osseointegration significantly;as time went on,the volume and velocity of bone formation increased gradually,while the pore size of 262?m and porosity of 68.1% is best for enhancing osseointegration;the change of pore parameter have greater impact on biomechanics compared to osteogenic effect.