title: Fracture toughness and hardness of a Y-TZP dental ceramic after mechanical surface treatments.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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).
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  The present study suggests that the fine polishing procedure in all-YTZP restorations produces surface embrittlement.
  
  
  CONCLUSIONS
  Because of the surface embrittlement, mechanical surface polishing of all-zirconia restorations should be avoided.
authors.affiliation: Department of Dentistry, Vita Salute University, San Raffaele Hospital, via Olgettina 58, 20132, Milano, Italy, t.traini@unich.it.
authors.forename: Tonino
authors.initials: T
authors.lastname: Traini
authors.forename: Enrico
authors.initials: E
authors.lastname: Gherlone
authors.forename: Stefano Ferrari
authors.initials: SF
authors.lastname: Parabita
authors.forename: Sergio
authors.initials: S
authors.lastname: Caputi
authors.forename: Adriano
authors.initials: A
authors.lastname: Piattelli
mesh_terms: D002516:Ceramics; D003764:Dental Materials; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D013499:Surface Properties
chemical_list: D003764:Dental Materials