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Fracture toughness and hardness of a Y-TZP dental ceramic after mechanical surface treatments.

Traini TGherlone EParabita SFCaputi SPiattelli A.


Department of Dentistry, Vita Salute University, San Raffaele Hospital, via Olgettina 58, 20132, Milano, Italy, This email address is being protected from spambots. You need JavaScript enabled to view it. .



The aim of the investigation was to evaluate the effects of surface mechanical treatments of all-Y-TZP restorations. In order to do that, surface roughness (Rs), fractal dimension (Df), fracture toughness (Ft), Vickers hardness (Hv), crack length (Cl), and opening (Co) were determined.


Y-TZP bar-shaped specimens (n=30) were subdivided into three groups: as received by milling center (M), after coarse polishing (CP), and after fine polishing (FP). The specimens were examined under both confocal laser and electron scanning microscopes. One-way ANOVA and post hoc tests were used to analyze the data (α=0.05).


The FP group showed a significantly lesser amount of Rs (P<0.05). The Df analysis confirmed the significantly lesser amount of surface complexity within the FP group (P<0.05). The Hv values were not significantly different among the groups. The Ft was significantly lesser within the FP group (P<0.05). At the same time, both Cl and Co were significantly higher within the FP group (P<0.05). Likewise, the FP treatment showed a significant decrease in roughness and surface complexity associated to a decrease of fracture toughness with a significant microcrack increase.


The present study suggests that the fine polishing procedure in all-YTZP restorations produces surface embrittlement.


Because of the surface embrittlement, mechanical surface polishing of all-zirconia restorations should be avoided.

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