RESUMEN
STATEMENT OF PROBLEM: Rapid sintering protocols are available for the fabrication of zirconia restorations, but whether rapid sintering influences color or translucency is unclear. PURPOSE: The purpose of this in vitro study was to investigate the effect of different rapid sintering protocols on the color and translucency of cubic and tetragonal zirconias. MATERIAL AND METHODS: Sixty disk-shaped specimens of 1-mm-thick cubic (DD CubeX2) and tetragonal (DD Bio ZX2) zirconia were investigated. Specimens of each type of zirconia were divided into three groups: conventional, speed, and superspeed sintering protocols. The conventional group of each zirconia type served as the control for calculating color differences. Translucency for each group was assessed by the translucency parameter and contrast ratio. Two-way analysis of variance was used for statistical analysis of the data (α=.05). RESULTS: The translucency of cubic and tetragonal zirconia decreased after speed and superspeed sintering (P<.001). Superspeed sintering resulted in a greater color change than speed sintering (P<.001). CONCLUSIONS: Rapid sintering protocols produced a significant effect on the color and translucency of cubic and tetragonal zirconias.
Asunto(s)
Cerámica , Circonio , Materiales Dentales , Propiedades de SuperficieRESUMEN
PURPOSE: To evaluate the fracture mechanics of cemented versus fused CAD-on veneers on customized zirconia implant abutments. MATERIALS AND METHODS: Forty-five identical customized CAD/CAM zirconia implant abutments (0.5 mm thick) were prepared and seated on short titanium implant abutments (Ti base). A second scan was made to fabricate 45 CAD-on veneers (IPS Empress CAD, A2). Fifteen CAD-on veneers were cemented on the zirconia abutments (Panavia F2.0). Another 15 were fused to the zirconia abutments using low-fusing glass, while manually layered veneers served as control (n = 15). The restorations were subjected to artificial aging (3.2 million cycles between 5 and 10 kg in a water bath at 37°C) before being axially loaded to failure. Fractured specimens were examined using scanning electron microscopy to detect fracture origin, location, and size of critical crack. Stress at failure was calculated using fractography principles (alpha = 0.05). RESULTS: Cemented CAD-on restorations demonstrated significantly higher (F = 72, p < 0.001) fracture load compared to fused CAD-on and manually layered restorations. Fractographic analysis of fractured specimens indicated that cemented CAD-on veneers failed due to radial cracks originating from the veneer/resin interface. Branching of the critical crack was observed in the bulk of the veneer. Fused CAD-on veneers demonstrated cohesive fracture originating at the thickest part of the veneer ceramic, while manually layered veneers failed due to interfacial fracture at the zirconia/veneer interface. CONCLUSIONS: Within the limitations of this study, cemented CAD-on veneers on customized zirconia implant abutments demonstrated higher fracture than fused and manually layered veneers.