The purpose of this study was to evaluate the influence of fabrication methods of lithium disilicate reinforced glass-ceramic crown on marginal and internal fit. Lithium disilicate reinforced glass-ceramic crowns were fabricated using ingots for heat press forming and blocks for CAD/CAM milling manufactured by Hass and Ivoclar/Vivadent. Dentiform of maxillary central incisor was prepared with a 6°taper and 1 mm deep chamfer margin and duplicated with silicone. Then the polyurethane resin was poured at silicone mold to produce working model. Marginal and internal fit were measured by the silicone replica technique. Each silicon replica was cut into labio-lingual and mesio-distal sections and the thickness of the light body silicon was measured. Fourteen reference points were determined and measured using a microscope. As a result of calculating and comparing the average value of 14 points in all groups, the measured value was within 120 µm, the clinically acceptable range suggested by previous literatures. In all groups, the marginal fit was smaller than the internal fit. At the margin area, significant differences were identified only between the ECM group and the EPM group, and there was no statistically significant difference between the remaining groups. At the deep chamfer area, the ECM and ABM group produced by the CAD system had excellent compatibility. In the axial wall and incisal area, ECM was superior to both EPC and EPM. Also, both ABM and APC groups were statistically significantly superior than APM.

The purpose of this study was to evaluate the influence of fabrication methods of lithium disilicate reinforced glass-ceramic crown on marginal and internal fit. Lithium disilicate reinforced glass-ceramic crowns were fabricated using ingots for heat press forming and blocks for CAD/CAM milling manufactured by Hass and Ivoclar/Vivadent. Dentiform of maxillary central incisor was prepared with a 6°taper and 1 mm deep chamfer margin and duplicated with silicone. Then the polyurethane resin was poured at silicone mold to produce working model. Marginal and internal fit were measured by the silicone replica technique. Each silicon replica was cut into labio-lingual and mesio-distal sections and the thickness of the light body silicon was measured. Fourteen reference points were determined and measured using a microscope. As a result of calculating and comparing the average value of 14 points in all groups, the measured value was within 120 µm, the clinically acceptable range suggested by previous literatures. In all groups, the marginal fit was smaller than the internal fit. At the margin area, significant differences were identified only between the ECM group and the EPM group, and there was no statistically significant difference between the remaining groups. At the deep chamfer area, the ECM and ABM group produced by the CAD system had excellent compatibility. In the axial wall and incisal area, ECM was superior to both EPC and EPM. Also, both ABM and APC groups were statistically significantly superior than APM.

The purpose of this study was to evaluate the effect of the reaction between investment material and zirconia on the strength of zirconia in the application of heat-pressing method. Sixty specimens were cut (24 mm×4 mm×0.5 mm) into plates from Zirtooth ™ Multi O-9814 block (∅98×14T, HASS, Gangwondo, Korea) and sintered at 1450℃. Specimens were divided into 6 subgroups according to the depending on the investement material; (a) UN group (Control), (b) PH group (Prime vest HS), (c) CP group (Calibra-press), (d) BV group (BC-Vest), (e) MH group (Microstar-HS), (f) F1 group (Formula 1). Five investment materials were buried according to the procedure recommended by the manufacturer and left at room temperature for 30 minutes. The investment mold was dried and maintained at an elevated temperature of 850℃ for 50 minutes. Then, Amber Lisi-POZ LT (HASS) was placed in a thermoformed electric furnace (Programat EP3000/G2, Ivoclar Vivadent, Schaan, Liechtenstein) together with the mold, heated to 915℃ at an elevation temperature of 45℃/min, and moored for 15 minutes. The specimens were loaded to fracture in a universal testing machine and the fracture surface was examined by a field-emission scanning electron microscopy (FE-SEM). The surface of the zirconia specimen with the investment material was analyzed by energy dispersive X-ray spectroscopy (EDS). The 3-point flexural strength test showed the highest value (1265.5 MPa) in the UN group and the lowest value (756.1 MPa) in the F1 group. As a result of EDS analysis, the largest amount of Si was detected in the F1 group, and the most interfacial changes occurred as a result of FE-SEM analysis. It was concluded that when the zirconia is buried with the investment material and the heat press molding is performed, the state of the interface is changed due to the investment material at the bonding interface while the strength is lowered.

The purpose of this study was to evaluate the effect of the reaction between investment material and zirconia on the strength of zirconia in the application of heat-pressing method. Sixty specimens were cut (24 mm×4 mm×0.5 mm) into plates from Zirtooth ™ Multi O-9814 block (∅98×14T, HASS, Gangwondo, Korea) and sintered at 1450℃. Specimens were divided into 6 subgroups according to the depending on the investement material; (a) UN group (Control), (b) PH group (Prime vest HS), (c) CP group (Calibra-press), (d) BV group (BC-Vest), (e) MH group (Microstar-HS), (f) F1 group (Formula 1). Five investment materials were buried according to the procedure recommended by the manufacturer and left at room temperature for 30 minutes. The investment mold was dried and maintained at an elevated temperature of 850℃ for 50 minutes. Then, Amber Lisi-POZ LT (HASS) was placed in a thermoformed electric furnace (Programat EP3000/G2, Ivoclar Vivadent, Schaan, Liechtenstein) together with the mold, heated to 915℃ at an elevation temperature of 45℃/min, and moored for 15 minutes. The specimens were loaded to fracture in a universal testing machine and the fracture surface was examined by a field-emission scanning electron microscopy (FE-SEM). The surface of the zirconia specimen with the investment material was analyzed by energy dispersive X-ray spectroscopy (EDS). The 3-point flexural strength test showed the highest value (1265.5 MPa) in the UN group and the lowest value (756.1 MPa) in the F1 group. As a result of EDS analysis, the largest amount of Si was detected in the F1 group, and the most interfacial changes occurred as a result of FE-SEM analysis. It was concluded that when the zirconia is buried with the investment material and the heat press molding is performed, the state of the interface is changed due to the investment material at the bonding interface while the strength is lowered.

No abstract available.
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