| Invisible orthodontics are becoming the preferred treatment for patients with malocclusion.Patients are affected by age factors,individual differences and other factors,the most suitable orthodontic power of each person’s teeth is different,orthodontists according to the patient’s own situation,choose the appropriate mechanical stiffness of dental sheets material to make appliances,which is the key to safe and efficient orthodontic treatment.At present,there is no dental sheets manufacturer at home and abroad that can produce a series of dental sheets of different stiffness.In this thesis,polyethylene terephthalate-1,4-cyclohexanedimethanol ester(PETG and PCTG)were selected as the substrate and polycarbonate(PC)was used as the reinforcing material,and orthodontic dental sheets with different mechanical rigidity were prepared by blending and lamination.The specific content and conclusions are as follows:1,Through the test and analysis of three kinds of imported dental sheets materials,Zendura Flx,Zendura and GT Flex,the performance standards for orthodontic dental sheets selection were determined:(1)Tensile strength 23～76MPa,tensile modulus 1000～2700 MPa;(2)Bending strength 16～31 MPa,bending modulus 1400～2800 MPa;(3)Tear strength> 140 N/mm;(4)8 h stress relaxation rate< 30%;(5)Light transmittance> 80%;(6)Water absorption< 1%;and(7)Good biocompatibility and non-cytotoxicity.2,PETG and PCTG as the substrate,PC as the reinforcement material,PETG/PC and PCTG/PC 0.8 mm blended orthodontic dental sheets with PC mass fraction of 10%～50% were prepared by blending,and it was found that:(1)The mechanical properties of both blended dental sheets increased with the increase of PC consumption,and when the PC dosage was 50 wt.%,the tensile modulus of PETG/PC and PCTG/PC sheets increased to 2288.2 MPa and1935.6 MPa,respectively,and the flexural modulus was 2659.7 MPa and 2622.7MPa,respectively.(2)The stress relaxation resistance of both dental sheets increased with the increase of PC consumption,and both can meet the use standards,when the PC dosage was 50 wt.%,the stress retention rate of PETG/PC and PCTG/PC dental sheets increased to 80.2% and 91.5%,respectively.(3)The light transmittance of the two dental sheets was above 80%,the haze of PETG/PC blended dental sheets was high,about 50%,and the haze of PCTG/PC dental sheets was low,about 1.3%.(4)The cytotoxicity and blood compatibility of the two kinds of dental sheets can meet the safety requirements of medical devices.3,Using PETG and PC as materials,a series of 0.8 mm PETG/PC laminated double-layer dental sheets with different thickness ratios were prepared by lamination,and it was found that:(1)The strength,modulus and stress retention efficiency of PETG/PC laminated double-layer dental sheets increased with the increase of PC layer thickness.When the PC thickness was0.4 mm,the tensile modulus reached 2495.0 MPa,the flexural modulus reached2728.6 MPa,and the stress retention rate reached 90.7%.(2)The optical properties of PETG/PC laminated double-layer dental sheets were greatly improved compared with PETG/PC blended dental sheets,with light transmittance higher than 89% and haze lower than 1.5%.(3)PETG/PC laminated double-layer dental sheets cytotoxicity and blood compatibility can meet the safety requirements of medical devices.4,Through comparison,it was found that:(1)PCTG/PC blended dental sheets had weak rigidity,high stress retention and good transparency.(2)PETG/PC laminated dental sheets had strong rigidity,high light transmittance and low haze.5,The orthodontist selected the oral information of patient to make a plaster tooth mold,according to the deformity of the patient’s teeth,the orthodontist chose PCTG/PC 80/20,60/40 blended dental sheets and PETG/PC0.4/0.4 laminated dental sheets as the appliance materials.Using the vacuum hot-pressing process,highly transparent invisible orthodontic appliances were prepared,and the appearance and performance of the appliances met the actual needs of the patient. |
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