The influence of Y-TZP surface treatment on topography and ceramic/resin cement interfacial fracture toughness

Abstract

Objective: Consider the efficacy of glass infiltration etching (SIE) treatment as a procedure to modify the zirconia surface resulting in higher interfacial fracture toughness.

Methods: Y-TZP was subjected to 5 different surface treatments conditions consisting of no treatment (G1), SIE followed by hydrofluoric acid treatment (G2), heat treated at 750°C (G3), hydrofluoric acid treated (G4) and airborne-particle abrasion with alumina particles (G5). The effect of surface treatment on roughness was evaluated by Atomic Force Microscopy providing three different parameters: R_a, R_sk and surface area variation. The ceramic/resin cement interface was analyzed by Fracture Mechanics K_I test with failure mode determined by fractographic analysis. Weibull's analysis was also performed to evaluate the structural integrity of the adhesion zone.

Results: G2 and G4 specimens showed very similar, and high R_a values but different surface area variation (33% for G2 and 13% for G4) and they presented the highest fracture toughness (K_IC). Weibull's analysis showed G2 (SIE) tendency to exhibit higher K_IC values than the other groups but with more data scatter and a higher early failure probability than G4 specimens.

Significance: Selective glass infiltration etching surface treatment was effective in modifying the zirconia surface roughness, increasing the bonding area and hence the mechanical imbrications at the zirconia/resin cement interface resulting in higher fracture toughness (K_IC) values with higher K_IC values obtained when failure probability above 20% was expected (Weibull's distribution) among all the experimental groups.

Keywords: AFM; Dental ceramics; Failure analysis; Fractography; Interfacial fracture toughness; Resin cement; Surface roughness; Surface treatment; XRD; Y-TZP.