The Research Of Polymer Infiltrated Zirconia Ceramic Network Dental Materials

Objectives:To manufacture polymer-infiltrated zirconia ceramic network（PICN）dental materials,observe the structure and evaluate the mechanical behaviors and biocompatibility of them.To determine and identify the effects of ceramic network density and sintering temperature on the mechanical properties of the polymer-infiltrated zirconia ceramic network（PICN）dental materials.And explore the possibility of its clinical application and provide experimental basis for its clinical application in the future.Methods:Dense zirconia ceramic and three group zirconia ceramic networks with four varying amounts of polyethylene glycol（PEG）were prepared by the dry press and cold isostatic press methods.And each group specimens were sintered at three different temperatures（1100°C,1200°C and 1300°C）,respectively.Then PICNs based on these porous ceramics were prepared,as well as a pure polymer.Each group has 10specimens.The porosity of the porous ceramics was measured by Archimedes method.Both porous ceramics and PICN samples were gold-coated for scanning electron microscope（SEM;SU3500,Japan）observation of the morphologies.After the specimen preparation,flexural strength and elastic modulus values were measured via the three-point bending test,and the fracture toughness was determined by the single-edge notch beam（SENB）method.The Vickers hardness was tested by an indentation-strength system,a scanning electron microscope（SEM）was employed to observe the microstructure and the fracture surface and MTT assay was conducted to detect the cytotoxicity of materials.Statistical analyses were performed using SPSS for Windows,release 22.0（SPSS Inc.,Chicago,IL,USA）.Results:All the specimens were prepared successfully.Experimental group specimens were polymer-infiltrated zirconia ceramic network（PICN）dental materials with four varying ceramic network density sintered at three different temperatures（1100°C,1200°C and1300°C）.And control group specimens were zirconia ceramic networks with four varying porosities sintered at three different temperatures,dense zirconia ceramics sintered at three different temperatures and pure polymer.The porosity of the porous ceramics sintered at each temperature was 8%,15%,26%and42%,respectively.Accordingly,the porous ceramics density was 92%,85%,74%,58%.SEM observations indicated that the materials were made from irregular shaped ceramic phases,resulting in irregular pores that were connected to each other and the dominant ceramic network structure and the reinforcing polymer network structure are merged fully with one another.Depending on the density of the porous ceramic the flexural strength of 1100°C PICNs ranged from 58 to 96.23MPa,the elastic modulus from 14.56to38.8GPa,the fracture toughness ranged between 0.83 and 1.40 MPam^1/2 and the hardness between0.39 and 4.90 GPa.The flexural strength of 1100°C porous zirconia ceramic networks ranged from 23.88to46.34MPa,the elastic modulus from 1.57to26.14 GPa,the fracture toughness ranged between 0.51and1.15 MPam^1/2 and the hardness between0.29 and1.65 GPa.The dense ceramic materials of 1100°C have flexural strength,elastic modulus,fracture toughness,and hardness values of 252.59MPa,86.42GPa,3.76 MPam^1/2 and 5.89GPa,respectively.The flexural strength of 1200°C PICNs ranged from 94.28 to 178.12MPa,the elastic modulus from 29.67 to 77.48 GPa,the fracture toughness ranged between 1.47 and 2.97 MPam^1/2 and the hardness between0.97 and 9.83 GPa.The flexural strength of 1200°C porous zirconia ceramic networks ranged from 59.37to130.89MPa,the elastic modulus from 10.55to37.37 GPa,the fracture toughness ranged between 0.69and2.18 MPam^1/2 and the hardness between0.59and3.92 GPa.The dense ceramic materials of 1200°C have flexural strength,elastic modulus,fracture toughness,and hardness values of 538.55MPa,155.22GPa,7.48 MPam^1/2 and 12.26GPa,respectively.The flexural strength of1300°C PICNs ranged from 106.81 to 211.77MPa,the elastic modulus from 40.24 to100.52 GPa,the fracture toughness ranged between 1.36 and 2.48MPam^1/2 and the hardness between 1.97 and 10.79 GPa.The flexural strength of 1300°C porous zirconia ceramic networks ranged from 68.42to139.11MPa,the elastic modulus from13.95to56.83 GPa,the fracture toughness ranged between 0.64and2.04 MPam^1/2 and the hardness between0.88and4.81 GPa.The dense ceramic materials of 1300°C have flexural strength,elastic modulus,fracture toughness,and hardness values of576.15MPa,186.79GPa,5.50 MPam^1/2 and 13.14GPa,respectively.Also,the pure polymer materials have flexural strength,elastic modulus,fracture toughness,and hardness values of 97.08MPa,3.09GPa,1.08 MPam^1/2 and 0.23GPa,respectively.Except for the flexural strength values obtained for 1300°C PICN 85%and 74%（P=0.112）and the fracture toughness for 1300°C PICN92%and PICN85%（P=0.161）,significant differences in other groups were observed（p<0.05）.SEM observations indicated that crack in the dense ceramic was long and smooth,and crack in the PICNs show obvious branching and deflection,crack growth was hindered by the polymer network.MTT assay was performed to evaluate the cytotoxicity of PICN,Ceramic and Polymer materials.The cells in PICN,Ceramic and Polymer materials grow well with high growth density.These cells are spreading larger with a fusiform morphology than that on cover slips without any abnormality.Also,at every point time（3,5,7d）,the OD value at 492 nm of PICN,Ceramic and Polymer materials were much higher than that of cover slips（P<0.05）.Furthermore,the PICN OD values range between that of dense ceramic and polymer,no significant difference was observed between PICN,Ceramic and Polymer materials（P>0.05）,grading 0 in toxicity.Conclusion:This polymer-infiltrated ceramic material is a successful step toward the goal of developing a material with similar mechanical behavior to that of natural human enamel and dentin.These materials also have good biocompatibility and could be used in dental restorations.The density and sintering temperature greatly affect the mechanical properties of the PICN materials.When Ceramic density was between 74%and 85%and sintering temperature range from 1200°C to 1300°C,excellent performance of the PICN materials will be achieved.