Thermal treatment influence on optical properties of 3D printed objects by vat photopolymerization

Color deviation of final parts for vat photopolymerization process is a typical problem of the technology due to the postcuring. Wide variety of postcuring units lead to different colors after ultraviolet (UV) exposure within the same UV dosage. To address this, a new approach for postprocessing which implies additional thermal treatment after UV postcuring was developed. This method allows to reduce yellowing of the printed part and make it brighter as well as to shorten color difference between parts postcured in various postcuring units. For example, color deviation (∆E) for Dental Bleach Pro resin changed after thermal treatment from 17.82 to 6.02 which is more than in 10 units. However thermal conditions must be carefully chosen. The color deviation origin is proposed and discussed and the influence of light intensity of UV curing units on color is considered. Simultaneous thermal and UV treatment effect on optical and mechanical properties is also discussed.