抄録
In order to evaluate the strength of castable glass ceramic (DICORTM) crowns and bridges, compressive strength tests were performed on the crowns of maxillary central incisors and the three unit maxillary anterior fixed partial dentures.
The crowns were made under the three conditions as follows: I. 4 times firing of DICOR shading porcelain, II. 4 times firing without applying DICOR shading porcelain, III. without firing of the shading.
Loads were applied at 4 points of the crowns as follows: A. center of the lingual surface, B. linguoincisal edge, C. linguogingival ridge, D. distal edge.
The bridges were loaded at the center of the pontics.
Every specimen was loaded from the direction of 45° from the tooth axis by using an Instron testing machine at a crosshead speed of 0.5 mm/min. The load at fracture and the type of failure were recorded.
The results obtained were as follows:
1. Mean values of the fracture loads of crowns were, 135.3kg at loading point A, 34.0kg at B, 60.7kg at C, and 31.8 kg at D.
2. Mean value of the fracture load of bridges was 50.0kg.
3. The application of shading porcelain or the firing procedure of the shading had no influence on the strength of the crown. Shading porcelain fused firmly to the crowns.
4. The DICOR crown had high stability of strength. And it was suggested that the DICOR bridge in this study could be adequate to withstand normal occlusal loads.
