Abstract:
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Tetragonal polycrystalline zirconia stabilized with 3% mol of yttria (3Y-TZP) is a popular
biocompatible ceramic which has the highest mechanical properties of any single oxide
ceramic. Its application in recent years to dental restorations and implants has raised
concerns about to its resistance to low temperature degradation (LTD), because in
orthopedics it has been shown that femoral heads used in hip-joint arthroplasty may be
vulnerable to LTD. Femoral heads explanted after several years in vivo have been
thoroughly studied and now there is overwhelming evidence that low temperature
degradation is an important issue in vivo for 3Y-TZP, at least in this application. Some
recent publications devoted to dental zirconia have already underlined the need to
remember that zirconia is susceptible to suffer LTD if exact processing conditions are not
followed. Despite this, the problem of LTD in dental zirconia seems to be underemphasized
so far. In the present work, a strategy is presented to increase resistance to LTD with the
purpose to increase the long-term reliability of dental implants. A new method is proposed
which is based in small changes in the standard processing steps for 3Y-TZP that
significantly enhance the resistance to LTD while maintaining its good mechanical
properties. This has been demonstrated by producing specimens under usual
manufacturing practice in dental labs but introducing a tetravalent Cerium ion by infiltrating
with a cerium salt solution in either water or ethanol in the pre-sintering stage and finally
sintering at different temperatures. The developed methodology has been assessed by
studying the resistance to LTD and the mechanical characterization after each processing
condition. |