Preparation and Properties of Dental Composite Resin Cured under Near Infrared Irradiation Preparation and properties of dental composite resin cured under near infrared irradiation

A composite resin (CR) with photo-polymerization is widely used for dental filling material. Current CR has a restriction on the photo-polymerization depth because of the scattering of irradiated blue visible (VIS) light. Rare earth doped Y2O3 particles (Y2O3:RE) are known to emit blue VIS light under near infrared (NIR) excitation by an upconversion process. The particles can act as both filler to reinforce and illuminator to cure the resin by emitting blue VIS light under the irradiation of the NIR light, which propagates more deeply due to its longer wavelength. In this study, CR with Y2O3:RE was prepared. The Young's modulus of CR with Y2O3 was comparable with that of commercial CR, however, the hardness was lower than that of commercial CR. CR with Y2O3:RE was successfully cured with NIR irradiation. Then, the feasibility of Y2O3:RE as the NIR polymerization initiator using its upconversion emission for CR was suggested.