Versatile up-converted emission microcrystals assisted photocuring for dental restorations

Conventional photocuring of dental restoration systems still remains challenge of limited curing depth due to light scattering in dental resin. It's essential to develop a versatile method based on upconversion nanoparticles assisted photocuring for overcoming the defect of low bottom layer hardness in deeper curing depth. In this study, we present a strategy that uses a pulse modulated 980 nm laser to induce photocuring in dental resin which contains up-converted emission microcrystals. Hardness of top layer of the dental resin cured by this strategy is comparable with that cured by blue light emitting diodes (LEDs). Moreover, the bottom/top percentage of hardness is obtained to be 68%, which is significantly higher than that cured by blue LEDs (46.3%). By using pulse modulated 980 nm laser, the peak curing temperature of dental resin is found to be 46.1 °C, which is lower than that cured by blue LEDs (50.5 °C) and much lower than that cured by continued 980 nm laser (128°C). Meanwhile, we demonstrated that this up-converted curing method can be applied in five different kinds of dental materials. This result highlighted that the upconversion microcrystals allow the activation of dental resins with a great potential in broadening the application range of dental restorations.