{Reference Type}: Journal Article
{Title}: Application of near-infrared-to-blue upconversion luminescence for the polymerization of resin cements through zirconia discs.
{Author}: Chou YC;Chuang SF;Lin JC;Li CL;Liu BY;Lee CL;
{Journal}: Dent Mater
{Volume}: 40
{Issue}: 8
{Year}: 2024 Aug 7
{Factor}: 5.687
{DOI}: 10.1016/j.dental.2024.06.005
{Abstract}: <B>OBJECTIVE: </B>To investigate a near-infrared-to-blue luminescence upconversion curing method for polymerizing resin cements under zirconia discs.<BR><B>METHODS: </B>Lava zirconia discs of different thicknesses (0.5-2.0 mm) were manufactured. First, the transmittances of the NIR and two blue lights (BLs) (LED and halogen lights) through these discs were measured. Second, NaYF4:Yb3+/Tm3+ upconversion phosphor (UP) powder was milled into 0.5-μm particle sizes. A light-curable resin cement VariolinkII base was chosen as the control (UP0), and an experimental cement (UP5) was prepared by adding 5 % UPs. These two cements were examined using multiphoton excitation microscopy for particle distribution. UP5 and UP0 were polymerized with or without zirconia shielding then subjected to a microhardness test. A multifold analysis was performed to examine the effects of zirconia thickness, curing protocols (pure BL or combined BL and NIR curing), and cement type.<BR><B>RESULTS: </B>The transmittance of NIR was superior to that of BL through zirconia discs of all thicknesses. UP particles were homogeneously distributed in UP5 and emitted blue luminescence under 980-nm NIR excitation. UP5 showed higher microhardness values than UP0 under any curing protocol or zirconia shielding condition. The combination of 20-s BL and 40-s NIR curing yielded the highest microhardness in uncovered UP5. However, combining 40-s BL and 20-s NIR curing surpassed the other groups when the zirconia discs were thicker than 0.5 mm.<BR><B>CONCLUSIONS: </B>NIR exhibits higher transmission through zirconia than BL. UP particles work as strengthen fillers and photosensitizers in cements. NIR upconversion curing could be a new strategy for polymerizing resin cements under thick zirconia restorations.