Zirconium oxide–ceramic relationship is not yet well known. Core–veneer interface is one of the weakest aspect of these restorations so that ceramic chipping or cracking are possible.
6 Different factors may influence veneer cracking as differences in thermal expansion coefficients between core and ceramic, firing shrinkage of ceramic, flaws on veneering and poor wetting by veneering on core. Special ceramics are nowadays developed for zirconia in order to minimize this unfavorable aspect, but more evaluation of zirconia core– veneer bond must be performed. After veneering control and finishing, luting of restoration can be performed.
Surface treatment seems to be unnecessary to obtain good adhesion. At the present time Zr-ceramic restorations should be luted with resin cement without surface treatment or, at least, with trebochemical treatment.
Ageing of zirconia rod can have detrimental effects on its mechanical properties. Mechanical stresses and wetness exposure are critical to accelerate this process.
Nowadays effects of ageing on zirconium oxide used for oral rehabilitation are not yet well known. By an in vitro simulation resulted that, although ageing reduce mechanical features of Zirconia, resistance values decrease into clinical acceptable values.
By using CAD/CAM technology, it is now possible to obtain zirconium oxide implant abutments. Replacing missing teeth with an implant-supported FPD requires functional and aesthetic evaluation by the clinician. In order to achieve a good outcome for an implant-supported FPD, many aspects need to be considered. A natural-looking emergence must be obtained in order to harmonize restoration and natural teeth. Intrasulcular abutment design is critical to reduce the risk of metallic blue shimmer through thin soft tissue. The use of ceramic abutments reduces this risk, allowing for optimal adaptation between the margins of the restoration and the soft tissue.
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