Effect of the surface finish on the mechanical properties and cellular adhesion in (Ce,Y)-TZP/Al2O3 ceramic composites for denture implants

Ceramic composites based on (Ce, Y)-TZP/Al2O3 system have great potential for applications as dental implants due to their unusually great balance between good mechanical properties and resistance to hydrothermal degradation. Surface roughness plays an important role in controlling these properties, but few studies have investigated the relationship between cytocompatibility and surface roughness, at levels considered moderate and low, comparable to titanium implants. In this work, bending strength, hydrothermal degradation and bio-logical evaluation of a ceramic composite based on (Ce,Y)-TZP/Al2O3 system were investigated as a function of surface roughness. Compacted samples were sintered at 1500 degrees C -2h and then submitted to different surface treatments: Group 1 composed of samples with smooth surfaces, Group 2 and Group 3 composed of rough surfaces (grinded with 15 mu m or 45 mu m diamond sandpaper, respectively. Samples were characterized by X-ray diffraction, scanning electron microscopy, contact angle and optical profilometry and then subjected to hydro-thermal degradation tests in autoclave (134 degrees C -2 bar) using artificial saliva. The Piston-on-three-balls (P-3B) testing was used to determine flexural strength. To assess indirect cytotoxicity, samples were immersed in the culture medium for NIH-3T3 cells for 72 h. Furthermore, cell adhesion and proliferation were investigated using MG63 cells (human osteosarcoma) after 3, 7, 14, and 21 days of culture. Cytotoxicity, adhesion, and cell pro-liferation were examined by the Methyl Tetrazolium salt (MTS) and Alizarin Red, using a confocal laser mi-croscope. The results indicated that the materials have high resistance to degradation. Furthermore, the (Ce,Y)-TZP/Al2O3 composites are not cytotoxic. The flexural strength of the composites was 913 +/- 103 MPa in samples presenting original (smooth) surface, however, a reduction in the order of 17% was observed in samples con-taining rough surfaces. The rougher samples show the best cellular adhesion and proliferation, leading to the formation of a mineralized matrix after 21 days. These results clearly suggest that the new (Ce,Y)-TZP/Al2O3 brand is strong and highly biocompatible and warrants further study.