Evaluation of Fluorescent Orthodontic Adhesives Containing Y₂O₃:Eu³⁺ Particles

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Orthodontic adhesives are usually colorless and transparent for aesthetic purposes. However, making such adhesives fluorescent is one of the most effective solutions to make them visible to ensure safe and complete removal after orthodontic treatments. Trivalent europium ions were doped into yttrium oxides by a homogeneous precipitation method. The particles were synthesized via a homogeneous precipitation method and had a narrow size distribution (200–300 nm) and showed sharp crystallinity independent of the starting concentration of Eu³⁺. The strongest emission and absorption peaks were identified at 611 nm and 396 nm, respectively. In this study, 8 mol% was confirmed to be the optimum doping concentration. The emission intensity of phosphor containing PMMA adhesives was appreciably weak even when the concentration of phosphors was 10 wt%. It may be attributed to the clustering of the particles or a multiphonon relaxation process owing to organic groups in the polymer. We conclude that the crystalline Y₂O₃:Eu³⁺ particles could be applicable for the development of fluorescent orthodontic adhesives.