LAUSR

Abstract 3Y-TZP ceramics are commonly used in restorative dentistry for fixed partial dentures, implants, abutments and root posts. The stress-induced transformation-toughening mechanism leads to improved mechanical properties advocating 3Y-TZP to be ground or sandblasted for better clinical performance. Such invasive mechanical treatments facilitate the additional surface strengthening as a result of the residual compressive stresses, but the exact origin is not completely understood. This study evaluated the effect of continuous impacting between 3Y-TZP root posts during 500 -h-long shaking on the extent of (sub)surface microstructural changes affecting the fracture strength. With an increase of the shaking time the surface roughness decreased, where the grains were flattened and partially spalled. The observed 6-micrometre-thick altered subsurface region containing compressive residual stresses contributed to a systematic increase in the forces of fracture within the sample population; however, only for those containing the surface type of critical flaws that were in the form of mould imprints.