Papers by Author: Se Young Choi

Abstract: Aqueous-based alumina tape, prepared using acrylate emulsion binder, was employed to form 3-unit all-ceramic anterior fixed partial denture core structures. Formability, linear shrinkage, and strength of the tape were optimized by adjusting tape composition to a/(a+b+p)=0.84 and b/(b+p)=0.5. Marginal fitness of the core framework was acceptable for clinical applications when more than two points on lingual side of core structure were placed to touch a plate during sintering. The 3-unit all-ceramic anterior fixed partial denture utilized ceramic tape has functioned successfully for 3 years without any loss of structural integrity and esthetics.

Abstract: This study evaluated periodontal repair and biomaterial reaction following implantation of a newly fabricated calcium aluminate bony cement incorporating LiF-maleic acid on the regeneration of 1-wall intrabony defects in the beagle dogs. The surgical control group received a flap operation only, while the experimental group was treated with calcium aluminate bony cement incorporating LiF-maleic acid. The subjects were sacrificed 12 weeks after surgery and a comparative histologic analysis was done. In the experimental group, the grafted calcium aluminate cement was not absorbed and fibrous connective tissue was epithelized around the particles of the grafted bony cement. Because of certain favorable properties, such as its easy manipulation and its ability to maintain the morphology of the defect site by acting as a scaffold, the newly developed cement is suitable for us as a graft material, and could be used very effectively in alveolar augmentation. However, further study needs to be conducted before it can be used as a bone graft material for periodontal tissue regeneration.

Abstract: This present study was carried out to find out the effects of calcium aluminate cement(CaO·Al203, CAC), which has been developed with biocompatibility and mechanical properties, in biological environments. Two different particle sizes of CAC - 3.5 µm vs. 212-250 µm which is recommended in periodontal bone grafting procedures – were filled in 8mm calvarial defects in Sprague-Dawley rats. The specimens were examined histologically, especially the bone-cement interface and the response of surrounding tissues. The result of this study shows that when calvarial defects in white rats are filled with 212-250 µm calcium aluminate cement, the materials proved to be bio-compatible in growth and healing on the surrounding tissues. When further researches on direct bone adhesion and bone regeneration ability are fulfilled, CAC is expected to be applied to various fields of periodontology in the future.

Abstract: Aqueous alumina tapes were prepared by a doctor blade using polyvinyl pyrrolidone (PVP) as a binder and gelatin and polyvinyl alcohol (PVA) as additional binders to improve drying rate and mechanical properties of the tapes containing PVP. As binder was prepared by mixing 89.5 wt% of PVP, 10 wt% of PVA, and 0.5 wt% of gelatin, tape properties were optimized showing complete drying in 3h, tensile strength of 1 MPa, and high flexibility. Marginal gap of all-ceramic dental crowns prepared using the tapes was about 56 µm indicating the tape cast alumina dental crowns are clinically applicable.

Abstract: We have synthesized a Eu²⁺-activated Sr₂SiO₄yellow phosphor and investigated an attempt to develop white LEDs by combining it with a GaN blue LED chip. Two distinct emission bands from the GaN-based LED and the Sr₂SiO₄:Eu phosphor are clearly observed at 400 nm and at around 550 nm, respectively. These two emission bands combine to give a spectrum that appears white to the naked eye. Our results show that GaN (400 nm chip)-based Sr₂SiO₄:Eu exhibits a better luminous efficiency than that of the industrially available product InGaN (460 nm chip)-based YAG:Ce.