Influence of sintering temperature on phase formation, microstructure and mechanical properties of the recycled ceramic body derived from cad/cam dental zirconia waste
Dental zirconia (ZrO2) debris derived from computer aided design and computer
aided manufacturing (CAD/CAM) waste was initially vibro-milled into nanosized ZrO2
powders prior to ceramic fabrication. The optimal pressureless sintering temperature for the
production of ZrO2 ceramics was suggested via analysis of phase formation, microstructure,
densification and mechanical properties results obtained from a combination of X-ray
diffraction (XRD), scanning electron microscopy (SEM), Archimedes principle, Vickers hardness
testing and three-point flexural strength techniques. The strength data was further analyzed
using the one-way ANOVA with Scheffe post hoc test (p = 0.05) and Weibull analysis.
Weibull modulus, characteristic strength and SEM characterizations were accomplished in
the fracture mode. In general, it was found that no phases other than tetragonal ZrO2
were observed in the samples sintered below 1100 C whilst a coexistence of both
monoclinic- and tetragonal-ZrO2 phases was found in the samples experienced higher
sintering temperatures. Larger average grain sizes were observed for the samples sintered
at higher temperature, whereas their porosities could be reduced resulting in an increasing of
the relative density. This work demonstrated that both of physical and mechanical properties
of the recycled ceramics derived from CAD/CAM dental ZrO2 waste could be significantly
tailored via the choice of sintering temperature at 1100 C which provides the most comparable
properties to the commercial dental ZrO2 pre-sintered block, showing the appropriation
for CAD/CAM machining.