| Due to its excellent mechanical properties,good biocompatibility,and aesthetic resemblance to natural teeth,3 mol%yttria-stabilized tetragonal zirconia polycrystalline(3Y-TZP)ceramics have been the preferred material in the field of dental restoration.However,the excessive white color and lack of translucency make it difficult to match natural teeth,which does not meet the growing aesthetic demands in all-ceramic restorations.To address this issue,5 mol%partially yttria-stabilized zirconia ceramics(5Y-PSZ),also known as highly translucent zirconia ceramics,have been introduced to the market.At the same time,conventional ceramic processing methods are not only wasteful but also unable to produce individualized dental ceramic parts with complex structures.In contrast,stereolithography(SLA)offers high printing accuracy and surface quality and has great potential for application in the field of dental restoration by building parts layer by layer.Therefore,this study aimed to explore the optimal design of slurry preparation,light-curing performance,and debinding procedures based on SLA technology.Furthermore,this study aimed to provide an in-depth analysis of the effects of sintering temperature and solid loading on the microstructure and macroscopic properties of5Y-PSZ ceramics.Ultimately,the feasibility of using high-strength and highly translucent 5Y-PSZ ceramics in the dental prosthetic field was verified.The specific contents are as follows:(1)Slurry preparation and light-curing performance testing.The effects of the dispersant type and addition,solid loading on the rheological properties of the light-cured ceramic slurry for SLA technique were investigated.The results indicated that KOS110 had the best dispersion effect,and the optimal addition amount was 2 wt.%.The maximum solid loading was 52 vol.%,and the cure depth of the 52 vol.%slurry was 49μm at 7000 mm/s under a laser power of 100m W and a scanning pitch of 20μm.(2)The effects of sintering temperature on the microstructure and macroscopic properties of highly translucent zirconia ceramics were investigated.Based on thermogravimetric analysis,the debinding process parameters,including heating rate and holding time,were optimized,and followed by densification treatment at 1450℃、1500℃and 1550℃for 2 h,respectively.The results showed that all samples were a two-phase coexistence system of tetragonal and cubic zirconia.As sintering temperature increased,the content of cubic phase increased,and grain growth became more obvious.The large grain area was enriched with yttrium element and cubic phase,but this did not affect its hardness and fracture toughness.The sample achieved optimum translucency at 1500°C with a value of 0.43±0.01.Meanwhile,the density and flexural strength reached their maximum at 1550°C with 5.95±0.02 g/cm~3 and 685.65±69.04MPa,respectively.At this point,the fracture mode of the samples changed from predominant intergranular fracture to trans-intergranular mixed fracture mode.(3)Based on the determination of the maximum solid loading of 52 vol.%and the optimum sintering temperature of 1550°C,the effects of four solid loading(40 vol.%,44 vol.%,48 vol.%and 52 vol.%)on the light-curing molding,microstructure and macroscopic properties of the highly translucent zirconia ceramics were further explored.The results showed that when the laser power was increased from 100 m W to 120 m W,the cure depth of the 52 vol.%slurry increased from 49μm to 51μm.However,the increase in solid loading led to a decrease in the cure depth,critical energy,and penetration depth.Despite narrower pore size distribution widths were observed in the green bodies with high solid loading,the strength increased and then decreased with increasing solid loading and achieved a maximum strength of 35.09±2.02 MPa at 44 vol.%.After sintering at 1550°C,all ceramic samples exhibited similar grain size,hardness,phase composition and content,but the 52 vol.%samples showed the highest flexural strength and contrast ratio with values of 745.85±75.32 MPa and 0.40±0.01,respectively.The findings obtained from this study will serve as a valuable reference for future research and application of SLA technique in the production of highly translucent zirconia ceramics for dental use. |
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