The Research Of Fabricating Zirconia All-ceramic Restorations By Stereolithography Technique

Purpose:To construct a stereolithography system and prepare ceramic slurry suitable for it.To improve the mechanical properties of three-dimensional printed ceramic specimens by optimizing processing parameters.Observe the cytotoxicity of them and evaluate the dimension accuracy and clinical adaptation of 3D printed crowns so as to provide experimental basis for further clinical applicationMethods:1.Design and construct a stereolithography system.Ceramic slurry was prepared and its viscosity and curing character were measured.2.The orthogonal experimental design method was used to optimize the processing parameters.The density and flexural strength of ceramic specimens were measured,and the optimum processing parameters were determined.3.Ceramic specimens were fabricated and its cytotoxicity was evaluated by CCK8 method.4.The dimensional accuracy and clinical adaptation of crowns fabricated by two stereolithography systems(groupl:CSL 150;group 2:CeraFab 7500)were measured respectively.CAD/CAM milling system(X-MILL 500)were set as control groupResults:1.A stereolithography system was successfully constructed,which including a computer numerical control system,a process control software system,an ultraviolet laser and X-Y scanning mirror,etc.The prepared zirconia ceramic slurry has a solid-phase ratio of 50vol%.The viscosity was 4500mPa·s and the curing character can be represented as Cd=54.82 ln(E/102.86).2.The optimum processing parameters are:laser power of 0.45W,hatching space of 25 μm and scanning speed of 750mm/s.The density and flexural strength of the ceramics printed with this set of parameter reached 98.42%and 978.05MPa.3.CCK8 test results showed that ceramic specimens fabricated by stereolithography technique had no obvious cytotoxicity.4 Group2 showed the best dimension accuracy(40.8±10.6μm),followed by group 1(64.5±5.9μm)and the control group(71.7±13.3μm).Group1 and the control group showed no significant difference,whereas group2 and group 1,control group exhibited statistically significant differences.The control group showed significantly better adaptation on marginal(61.90±8.96μm),corner(60.07±6.32μm),occlusal(27.61 ±5.44μm)area but inferior adaptation on axial area(131.22±4.72μm)than group1(marginal:109.33±26.79μm,corner:97.64±29.37μm,occlusal 149.12±45.75μm,axial:70.64±14.97μm)and group2(marginal:92.55±31.80μm,corner:114.51±29.81μm,occlusal:209.95±32.05μm,axial:54.82±9.13μm).While significant differences can only be found in on the axial and occlusal area between group 1 and group 2Conclusions:It is feasible to apply this stereolithography system and ceramic slurry in fabricating dental all-ceramic restorations.The flexural strength,cytotoxicity and clinical adaptation of the crowns fabricated by the stereolithography system can meet the clinical requirements.However this kind of technique still lacks of dimensional stability,which need further research and improvement.