Denry I L, Rosenstiel S F
Ohio State University, College of Dentistry, Columbus 43210.
J Dent Res. 1993 Mar;72(3):572-6. doi: 10.1177/00220345930720030301.
Previous studies on the surface properties of Dicor castable glass-ceramic have shown the formation of a specific crystalline phase at the glass-ceramic/embedment interface. If this phase is not removed by grinding, it leads to an undesirable strength decrease. The aims of this study were: (1) to determine the nature of this surface layer, (2) to promote the formation of a different crystalline phase at the surface with the intention of improving the properties of the glass-ceramic, by modification of the composition of the Dicor ceramming embedment, and (3) to evaluate the fracture toughness and flexural strength of Dicor glass-ceramic after embedment modification. Modifications were made to the embedment by incorporation of 2.5 wt% of lithium fluoride and ceramming at various temperatures. X-ray diffraction was used to determine the crystalline nature of the surface layer. Fracture toughness was investigated by the indentation technique. The maximum bi-axial stresses were calculated after the samples were fractured in water on a ball-on-ring fixture at 0.5 mm/min. With the recommended embedment and ceramming cycle, the crystalline phase constituting the ceram layer was a calcium magnesium silicate CaMg(SiO3)2 (diopside). The crystalline composition of the ceram layer was successfully modified by addition of 2.5 wt% lithium fluoride to the embedment. This promoted the crystallization of mica in the ceram layer and increased the fracture toughness of the glass-ceramic when the ceramming temperature was 950 or 975 degrees C. The flexural strength was significantly increased when the ceramming temperature was 1000 degrees C.
先前关于Dicor可铸微晶玻璃表面性能的研究表明，在微晶玻璃/包埋体界面处形成了特定的晶相。如果该相未通过研磨去除，会导致强度意外降低。本研究的目的是：（1）确定该表面层的性质；（2）通过改变Dicor微晶化包埋体的成分，促进在表面形成不同的晶相，以改善微晶玻璃的性能；（3）评估包埋体改性后Dicor微晶玻璃的断裂韧性和抗弯强度。通过加入2.5 wt%的氟化锂并在不同温度下进行微晶化处理对包埋体进行改性。采用X射线衍射确定表面层的晶体性质。通过压痕技术研究断裂韧性。样品在水中以0.5 mm/min的速度在环-球夹具上断裂后，计算最大双轴应力。按照推荐的包埋体和微晶化工艺，构成微晶层的晶相为硅酸钙镁CaMg(SiO3)2（透辉石）。通过向包埋体中添加2.5 wt%的氟化锂，成功改变了微晶层的晶体组成。当微晶化温度为950或975℃时，这促进了微晶层中云母的结晶，并提高了微晶玻璃的断裂韧性。当微晶化温度为1000℃时，抗弯强度显著提高。
