Effect of multistep processing technique on the formation of micro-defects and residual stresses in zirconia dental restorations.

摘要: Purpose The clinical failures of zirconia dental restorations are often caused by extrinsic artifacts introduced processing. The aim this study was to investigate the micro-defects and residual stresses generated during multistep process restorations. Materials Methods Thermal spray granulated 3Y-TZP powders were dry pressed two tools exhibiting distinctly different Young's moduli, cold isostatic (CIP-ed), pressure-less fully sintered. green bodies a stiff tool treated with procedures: direct milling (green milling) followed sintering; half-sintering (raw or without sintering grinding. sintered crowns clinically adjusted using both diamond bur SiC bur, respectively. Phase composition microstructure pressed, milled, ground surfaces studied XRD SEM. Results Tetragonal phase main all detected specimens. Excessive raw grinding confirmed strained T (111) peak, monoclinic phase, obviously changed I(002)t/I(200)t ratio. would form compressive stress layer, while it too shallow inhibit crack propagation even for Large voids high-coordination numbers common packing micro-defects. Once formed, they barely healed CIP-ing sintering. A pressing be useful reducing surface voids. Milling removed voids, but no help interior ones. Raw more serious chippings, most originating from existing than due its brittle failure less recommended production. Grinding dense grain refinement much severe micro-defects, especially when adjustment applied compared bur. Conclusions Micro-defects accumulated through entire production chain determine final restorations. Several procedural improvements offered expected reduce processing