Wear and 3D Micro-Morphological Studies on CAD/CAM Milled Dental Zirconia for Post-Fabrication Dental Processes

Abstract

The post-fabrication processes on CAD/CAM milled dental Zirconia result in surface roughening, micro-cracking, a decline in surface texture, and loss of strength. Also, the hydrothermal stresses formed due to water, blood, and synovial fluid infiltration into the crack space initiate crack propagation. The present work makes an effort to study the effect of surface morphology due to the post-processing of Yttrium-stabilized tetragonal Zirconia (Y-TZP) after CAD/CAM milling by studying the height, spatial, functional parameters (volume & Stratified surfaces), and 3-D surface roughness parameters in detail. Five groups based on post-processing combinations currently used in clinical conditions were selected for the study. Group 1(G1-S) involved the milling of pre-sintered blocks followed by sintering. Group 2(G2-S+P) consisted of sintering followed by the polishing process. Group 3(G3-S+P+S.B) consisted of sintering, polishing, and sandblasting with Aluminium Oxide (Al2O3) with a particle size of 110µm. Group4 (G4- S+S.B) involved sintering followed by sandblasting. Group5 (G5-S+S.B+P) consisted of sintering, sandblasting, and polishing. The surfaces were evaluated using a 3-D surface profilometer before and after wear. Before wear, the G4 process group responded with the highest surface roughness value, (Average roughness) Sa=1.378±0.409μm, and it was within the limit, which supported osseointegration. Valleys were predominant in almost all the groups, except G4. Also, the peak and core parameters for G3 &G4 were higher and will be of interest for further bone-implant contact (BIC) studies. The groups with sandblasting fabrication processes (G3, G4) exhibited relatively higher 3-D roughness parameters when compared to the groups with fabrication processes (G1, G2, G5). After wear, there was a considerable decline in the material peak. The research revealed that the methods with sandblasting could be suitable for osseointegration, BIC, and in-vivo performance for crown applications. Also, sandblasting followed by polishing (G5) was found to be optimal. Dentists will be able to determine the right clinical adjustments for their chairside CAD/CAM dentistry using 3-D surface roughness morphological analyses. It will also aid researchers in conducting in-depth studies on the issues related to oral cavity.