The Research Of Precision And Mechanical Properties Of Non-bracket Invisible Orthodontic System

The invisible orthodontic system,a new dental orthodontic technology,has been gradually accepted by patients and dentists because of its advantages.This system contains several materials including impression materials, gypsum materials and appliance materials. In this paper,several technologies have been used to test the main concerned properties of each material. And the result shows:The accuracy of3shapeD700scanner is close to the accuracy declared by the3shape company. The accuracy and precision of D700and TRIOS shows no significant difference.An up-to-3week-long term study on PVS dimensional change shows that a short time disinfection with glutaraldehyde has no significant influence on the dimensional stability.Research on the alginate impression’s dimensional change under different storage condition has proved that the alginate impression’s dimensional stability become worse when the impression is exposed to dry air longer than15min. It is necessary to put the imression into water condition after when the storing time is longer than15min.Long term research of gypsum models’dimentional change indicated that the gypsum models expand quickly in the first hour after model taking. In addition,the models’ expanding speed varies dramatically in the first hour. In summmary, the gypsum models will reach their max volume within one day.An experiment has been put out to test the influence of different pre-treatment on the appliance materials’ stress loose property.It was discovered that10thermal cyclings significantly fasten the lossing speed of appliance materials.Nevertheless, after20thermal cyclings, the loosing speed is slower than those with10thermal cyclings. This phenomenon may be attributed to the change in microstructure. Furthermore, storage under-4℃slightly improve the material’s stress loosing property.