Figure 1.

The basic principle of invisible orthodontic aligners. (A) Comparison between the traditional plaster casting method and the 3D printing technique to obtain dental models. While plaster casting requires splitting teeth and manual adjusting for each step and multiple cast models at different stages, the 3D printing technique affords mass model manufacture for each step, and dental models for all steps are printed individually yet at one batch. (B) The overall procedures to produce clear aligners using 3D-printed models, mainly involving data acquiring, treatment planning, 3D printing of personalized dental models, thermoforming and post processing.