Title Page
ABSTRACT
국문 초록
Contents
CHAPTER 1. INTRODUCTION (Background introduction) 28
1.1. Biocermic materials 29
1.2. Manufacturing process of ceramic object 32
1. Powder pressing process 32
2. Injection molding process 32
3. Computer numerical control process 33
1.3. Additive manufacturing for ceramic object 35
1. Extrusion-based AM techniques 35
2. Lithography-based AM techniques 36
CHAPTER 2. Macroporous hydroxyapatite scaffold comprised of microporous hollow filaments using UV-assisted 3D plotting 38
2.1. Introduction 39
2.2. Pilot test for hollow filament 3D plotting 44
2.2.1. Ceramic shell and core materials for pilot test 44
2.2.2. Extrusion of core-shell feedrod with pilot composition and extruding behavior of core and shell composites slurry 44
2.2.3. Optimization of extruding behavior for uniform core-shell structure. 45
2.2.4. Filament and scaffold from core-shell feedrod with similar extruding behavior 52
2.3. Experimental Procedure 56
2.3.1. Process parameters on the scaffolds 56
2.3.2. HA shell and CB core preparation 56
2.3.3. Custom-made UV-assisted 3D plotting machine 62
2.3.4. Optimization of extrusion behavior of the CB-core 62
2.3.4. HA scaffolds preparation using UV curing-assisted 3D plotting 66
2.3.5. Macro/micro-porous structure evaluation 66
2.3.6. Compressive strength tests 67
2.4. Results and Discussion 69
2.4.1. Macro and microstructures of green core-shelled filaments 69
2.4.4. Macroporous and microporous structures of scaffolds 75
2.4.5. Overall porosity, macroporosity, and microporosity of HA scaffolds 82
2.4.6. Compressive strengths of the HA scaffolds 85
2.4.8. Potential of the produced HA as bone scaffolds 89
2.4.9. Utility of present approach for advanced design of a scaffold 91
2.5. Conclusions 94
CHAPTER 3. 3D printing of ZnO/silica ceramic resin composite with antimicrobial effect 95
3.1. Introduction 96
3.2. Experimental Procedure 103
3.2.1. Starting materials 103
3.2.2. Characteristics of ZnO/SiO₂ filler 105
3.2.2. ZnO/SiO₂ ceramic resin composite preparation 113
3.2.3. Optimization of resin 3D printing condition 116
3.2.5. Evaluation of ZnO/SiO₂ filler distribution in the resin composites 118
3.2.6. Evaluation of mechanical properties of resin composites 119
3.2.7. Evaluation of antimicrobial effect 121
3.3. Results and discussion 124
3.3.1. Rheology behavior of resin composite 124
3.3.2. Photo-curing behavior analysis of resin composites 126
3.3.3. Optimization of process parameters - curing time 129
3.3.4. Optimization of process parameters - off time 133
3.3.4. Evaluation of quality of the printing - Curing width 137
3.3.5. Evaluation of filler content within printed sample by TGA 140
3.3.5. Indirect evaluation of filler-distribution - SEM-EDS analysis 142
3.3.6. Mechanical properties of resin composites 146
3.3.7. Antimicrobial effect of resin composites 152
3.3.8. 3D printing of provisional bridge using ZnO/SiO₂ ceramic resin composite 155
3.4. Conclusions 157
CHAPTER 4. Conclusions 159
REFERENCES 162
Table 1. Materials and composition of calcium phosphate (CaP) shell for pilot test of microporous hollow filament 47
Table 2. Materials and composition of core candidates for pilot test of microporous hollow filament 48
Table 3. Debinding and sintering schedule of core-shell ceramic filament and scaffold. 54
Table 4. Components of the HA shell and CB core. 59
Table 5. Compositions of the shell and core slurry. 60
Table 6. Dimension of filaments and CB cores (or channel) obtained for the designed, green, and sintered filaments. 72
Table 7. Dimension of scaffold with different filament pitch (2.0 and 1.5 mm) and pore-forming agent contents (50 and 60 Vol.%) 78
Table 8. Overall porosities, macroporosities, and microporosities of the macroporous HA scaffolds comprised of microporous hollow filaments produced... 84
Table 9. Compressive strengths and modulus of the macroporous HA scaffolds comprised of microporous hollow filaments produced using different filaments... 88
Table 10. Compressive strengths of porous HA scaffolds produced using various manufacturing techniques. 90
Table 11. Dental monomer and their characteristics 100
Table 12. constituents of ZnO/SiO₂ resin composites 104
Table 13. EDS analysis of ZnO/SiO₂ composite filler at the point from 1 to 6. 108
Table 14. Compositions of the resin composite 114
Table 15. Evaluation of photocuring behavior of ZnO/SiO₂ resin composite with 0, 5, and 10 vol.% [(1) heat flow - time curve by photocuring, (2) percent... 128
Table 16. Average curing depth with different ZnO/SiO₂ contents depending on irradiation time 131
Table 17. Average of dimension and area of printed sample of resin composites with different ZnO/SiO₂ contents 136
Table 18. Average of Vickers hardness values of resin composites 148
Table 19. Average flexural strength and modulus of resin composites with different filler contents. 149
Table 20. Average of the number of colonies on the agar plate depending on resin filler contents. 154
Figure 1. Definition of ceramics and various bioceramics 31
Figure 2. Traditional manufacturing processes for ceramic object (powder pressing injection molding, and CAD/CAM) and additive manufacturing techniques 34
Figure 3. Additive manufacturing for ceramic object (Extrusion-based AM techniques and lithography-based AM techniques) 37
Figure 4. Schematic diagram of the UV curing-assisted 3D plotting of core-shelled feedrod for the manufacturing of macroporous ceramic scaffolds comprised of... 43
Figure 5. Schematic of calcium phosphate (CaP) shell for pilot test of microporous hollow filament 47
Figure 6. Schematic of core candidates for pilot test of microporous hollow filament 48
Figure 7. Hollow filament structure of pilot test with core-shell feedrod consisted of ceramic shell and carbon black composite.3 49
Figure 8-1 and 2. (1) Liquid flow depending on Reynolds number (Re), Equation of required force for injection in a cylindrical syringe with needle using shear thinning... 50
Figure 9. Extruding behavior of ceramic shell and core composition with different carbon black weight. 51
Figure 10. Debinding and sintering graph of core-shell ceramic filament and scaffold. 54
Figure 11-1 and 2. filament and scaffold using core-shell feedrod with similar extruding behavior (11-1 → SEM analysis for hollow and micro structure / 11-2 →... 55
Figure 12. Process parameters on the scaffolds (filament pitch (2.0 - 1.5 mm) and pore-forming agents (50 and 60 Vol.%)) 58
Figure 13-1 and 2. Preparation of core-shell slurry and feedrod of co-extrusion 61
Figure 14. Custom-made UV-assisted 3D plotting machine 64
Figure 15. Optimization of extrusion behavior of the HA-shell and CB-core 65
Figure 16. Representative optical image of the extruded green filament showing the microstructures HA shells, obtained after freeze-drying to remove the camphene-... 71
Figure 17. Representative FE-SEM images of the microporous hollow HA filaments of green and sintering at 1250 °C for 3 h showing the hollow structure,... 73
Figure 18. Representative FE-SEM images of the microporous hollow HA filaments of green and sintering at 1250 °C for 2 h showing the hollow structure,... 74
Figure 19. Representative optical images of the macroporous HA scaffolds comprised of microporous hollow filaments with different filament pitch (2.0 and... 77
Figure 20. Representative Surface morphology of the HA scaffolds (filament pitch=1.5 mm and camphene-camphor content in the HA shell=60 vol%) 79
Figure 21. Representative μ-CT images of the macroporous HA scaffolds comprised of microporous hollow filaments with different filament pitch of 2.0 mm and 1.5 mm... 80
Figure 22. Representative FE-SEM images showing the side views of the macroporous HA scaffolds comprised of microporous hollow filaments with... 81
Figure 23. Overall porosities, macroporosities, and microporosities of the macroporous HA scaffolds comprised of microporous hollow filaments produced... 83
Figure 24. Representative compressive stress-strain curves and compressvie strength observed for the macroporous HA scaffolds comprised of microporous hollow... 87
Figure 25. (A) Optical images and (B) μ-CT images of the Scaffold with locally controlled macro-structures 92
Figure 26. (A) Optical images of the Free-standing structures comprised of microporous hollow filaments 93
Figure 27. Antimicrobial mechanism of zinc oxide 101
Figure 28. Schematic diagram of the antimicrobial resin composites with zinc oxide and silica complex filler for 3D printing of provisional crown and bridge 102
Figure 29. SEM images of ZnO/SiO₂ composite filler [point from 1 to 6] 108
Figure 30. XRD analysis of as received-ZnO/SiO₂ crystalline pattern and calcined ZnO/SiO₂ at 900 ˚C and 1400 ˚C for 3 hours 109
Figure 31. Particle size analysis of ZnO/SiO₂ composite filler using (1) Zeta-sizer (Dynamic light scattering) and (2) FE-SEM 110
Figure 32. Thermogravimetric analysis (TGA) of ZnO/SiO₂ composite filler 111
Figure 33. Characteristics of ZnO/SiO₂ filler - ROS generation using Nitroblue tetrazolium (NBT) (33-1) and absorbance spectrum of NBT solution was measured... 112
Figure 34. Preparation of resin and photocurable 3D printing 115
Figure 35. Printed disk specimens using resin composites with different ZnO/SiO₂ contents (all specimen polished by 5000 grit sandpaper and handpiece with felt buff) 123
Figure 36. Evaluation of rheology behavior of 10 Vol.% resin composite with different dispersant wt.% (i.e, 1 wt.%, 2 wt.%, 3 wt.% and 4 wt.%) 125
Figure 37. Evaluation of photocuring behavior of ZnO/SiO₂ resin composite with 0, 5, and 10 vol.% [(1) heat flow - time curve by photocuring, (2) percent... 127
Figure 38. (1) photocured one layer of squares with 5 x 5 mm (2) measured curing depth using resin composites with different ZnO/SiO₂ contents 130
Figure 39. Printed square with 30 x 30 x 2 mm at the curing time of 1.5 and 2.5 s of curing time of each layer 132
Figure 40. (1) Evaluation of rheology behavior of ZnO/SiO₂ resin composite with 0, 5, and 10 vol.% and (2) Off-time (delay after layer-formation) schematic 134
Figure 41. Printed squares with the 0, 30, 60, and 90 s off time using resin composites with 0, 5, 10 Vol.% ZnO/SiO₂ contents 135
Figure 42. Printed squares with optimized off time using resin composites with 0, 5, 10 Vol.% ZnO/SiO₂ contents 136
Figure 43. FE-SEM images of printed cylinders with range of 1.0 mm to 0.1 mm for evaluating curing width of ZnO/SiO₂ filler using resin composites with 0, 5 and 10... 138
Figure 44. Average length of printed cylinders with range of 1.0 μm to 0.6 μm for evaluating curing width change by incorporating ZnO/SiO₂ filler 139
Figure 45. Thermogravimetric analysis (TGA) of resin composites with 5 Vol.% and 10 Vol.% of ZnO/SiO₂ 141
Figure 46. EDS analysis of 5Vol.% images at 1000X, using 'analyzer function' at 1~5. 143
Figure 47. EDS analysis of 10 Vol.% images at 1000X, using 'analyzer function' at 1~5. 144
Figure 48. EDS analysis of polished surface of the printed specimen with 0, 5 and 10Vol.% of ZnO/SiO₂ 145
Figure 49. Vickers hardness (HV) of Representative indentation of resin composites with different ZnO/SiO₂ contents 148
Figure 50. Representative flexural load-displacement curve of resin composites biaxial flexural strength and modulus by biaxial flexural strength test 149
Figure 51. Representative fractured disk specimen by biaxial flexural strength test control / 5 Vol% / 10 Vol.% 151
Figure 52. Representative Colony forming unit (CFU) test of resin composite and the number of colonies on the agar plate depending on resin filler contents. 153
Figure 53. Average of the number of colonies on the agar plate depending on resin filler contents. 154
Figure 54. Printed Provisional bridge with antimicrobial effect using optimized 3D printing condition. 156