Esthetic Improvements and In Vitro Testing of In-Ceram Alumina and Spinell Ceramic

The original In-Ceram material (In-Ceram Alumina), composed of sintered aluminum oxide subsequently infused with a glass, features interesting mechanical properties. In-Ceram Spinell was marketed more recently to improve the esthetic potential. This study compared the flexural strength of various combinations of sintered alumina and spinel infiltrated with the associated glasses. In addition, the influence of vacuum during the infusion process was investigated using density measurements. The characteristic strength (load at which 63% of the specimens had failed) was 530 MPa for the original material, 5 23.7 MPa when the same material was infiltrated under vacuum, 481.4 MPa when sintered alumina was infused under vacuum with the glass originally marketed for the spinel, and 283.1 MPa for the sintered spinel infiltrated under vacuum with the associated glass. A significant increase in density was observed when the infiltration firing of sintered alumina was peformed under vacuum. Furthermore, the in vivo evaluation of specific esthetic parameters inherent to differenty types of cores was made and revealed the realtive opacity of alumina; spinel was found to have the ability to blend in with the underlying substrate. Both materials demonstrated a general lack of fluorescence.