Papers by Author: Il Seok Park

Abstract: Hertzian cyclic fatigue properties of the glass-infiltrated alumina and spinel were evaluated using a WC sphere of radius of 3.18 mm in exact in vitro environment (artificial saliva) at contact loads from 200 N to 1000 N to investigate indentation damage and strength degradation. At 200 N, no strength degradation was observed up to 106 contact cycles. As the load increased from 200 N to 1000 N, the reduction in strength was found when the transition from ring to radial cracking occurred. The degree of strength degradation after critical cycling was more pronounced probably owing to the chemical reaction of the artificial saliva with the glass phase along the radial cracks introduced during the large numbers of contact cycles.

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: 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.