Preparation Of Invisible Orthodontics Materials

At present,the invisible orthodontic appliance in hospitals is mainly the imported material which is expensive.Domestic materials are less effective than imported materials.And invisible orthodontic materials lack of relevant properties indiex.Based on the analysis of commercial materials,this paper has formulated the basic properties indiex of invisible orthodontic materials.Polyurethane(TPU)and poly(ethylene terephthalateco-1,4-cylclohexylenedimethylene terephthalate)(PETG)were selected as the matrix material,and melted blending technology was used to prepare invisible orthodontic materials.Systematic studies of key properties of orthodontic materials:stress relaxation.The main conclusions are as follows:(1)Stress relaxation test with the imported appliances Bilon,Erkodur and domestic appliances 3D AID,the laboratory-made material,and the 8h stress relaxation rate are 4.3%,8.4%,5.8%,9.6%.The stress relaxation rate of the laboratory-made material is close to that of commercial appliances.(2)The basic properties indiex of invisible orthodontic materials:transmittance>80%,haze<20,8 h stress relaxation rate<10%,flexural stress:20 MPa-25 MPa,flexural modulus:1800 MPa-2400 MPa,tensile strength:50 MPa-65 MPa,tensile modulus:1500 MPa-2000 MPa,impact strength>20 kJ/m2,water absorption rate<3%.(3)Polycarbonate(PC)can reduce the stress relaxation of PETG and increase the mechanical strength of PETG without affecting the transparency of PETG.When blends content 30%PC,its 8 h stress relaxation rate is 9.6%,its flexural stress is 25 MPa,its flexural modulus is 2287 MPa,its tensile strength is 50 MPa,its tensile modulus is 1500 MPa,and its impact strength is 24 kJ/m2,its water absorption rate is 1.5%,its hemolysis rate is 1.4%.Modified PETG/PC blends with different hardness polyurethane,the impact strength of the blends increased,but the stress relaxation rate of the blends increased too.(4)PETG/PC blends material was injected into film,with diameter of 120 mm and thickness of 1 mm.It was formed on a vacuum thermoforming machine,and the comprehensive properties of this invisible orthodontic appliance is similar to that of the imported appliance.