2007 Volume 50 Issue 2 Pages 162-173
Ceramics systems have become popular due to the demand for esthetic, durable restorative materials, and also due to improvements in materials, fabricating techniques, and bonding systems. However, there are deficiencies in their physical properties. The purpose of this study was to evaluate the effect of the coping system on ceramic by measuring the mechanical properties, adaptation of inlays and observation of the coping margins. The precious-metal coping material, Captek™ (Leach & Dillon, USA, Captek) was used for the experiment. Vintage Halo®(Shofu: Vintage Halo) and IPS Empress I® (Ivoclar-Vivadent: IPS Empress I) -fused-to-coping materials were prepared according to the manufacturers' instructions. The flexure strength was determined by using the Instron universal testing machine (cross head speed: 1mm/min, n=5). Fracture toughness (KIC) was calculated by the Indentation microfracture technique using Niihara's formula (n= 5). These ceramics-fused-to-coping materials were observed by SEM. The cement thickness of IPS Empress I with and without coping at MOD inlays was also measured. The flexure strength (MPa) of the ceramics with coping showed significantly higher values (Vintage Halo 149.6±13.0, IPS Empress I 200.0±24.5) than the ceramics without coping (82.9±3.0, 151.4±5.7, p<0.05). In the fracture toughness (MNm-3/2), IPS Empress I with coping showed significantly greater strengths (1.57±0.06) than those without coping (1.39±0.05, p<0.05). But Vintage Halo without coping showed significantly greater strengths (1.14±0.12) than those with coping (0.90±0.08, p<0.05). The interfaces of IPS Empress I and Vintage Halo-fused-to-coping materials showed no gaps. From the results of flexure strength, fracture toughness, and observation of the coping margin, the physical properties of IPS Empress I with coping definitely improved. Flexure strength of Vintage Halo definitely improved, and Vintage Halo and IPS Empress I showed good bonding interfaces between ceramics and Captek by SEM observation. But in the fracture toughness, Vintage Halo without coping showed significantly greater strengths than those with coping. This seems to be influenced by the mismatch of thermal expansion coefficient between Captek and Vintage Halo. Regarding cement thickness of IPS Empress I with coping and without coping, the width of the cement layer of ceramics with coping was generally wider than that of those without coping. This was caused by coping Captek transformation or exfoliation from refractory die material. Further consideration is necessary regarding the application of coping system on ceramic inlays.
