RESUMEN
Objective:To evaluate the reliability of flexural strength and subcritical crack growth(SCG)of WL and HT zirconia ce-ramics under cyclic loading.Methods:Bar-shaped speciments of WL(n =30)and HT(n =30)were fabricated and loaded in three-point bending and cyclically fatigued.The flexural strength and the number of cycles to fracture were obtained from three-point flexural test and cyclic fatigue test respectively.Data were examined using Weibull statistics.Pairs law was used to analysize the subcritical crack growth(SCG),the behavior of which was described in terms of crack velocity as a function of maximum stress intensity factor (KImax ).Results:The Weibull module(m)of WL and HT was 10.64 and 12.04,the stress corrosion cracking susceptive indexes(n) 23.71 and 32.87,the SCG 90% and 76.7%,the KImax 49.6% and 50.9% of its maximum stress intensity factor(KIC ),respectively. Conclusion:WL and HT produce pronounced SCG.The minimum fatigue crack growth rate of HT is lower than that of WL(νHT <νWL ).
RESUMEN
Objective:To evaluate the effects of surface modification with different concentration silica sol through sol-gel processing on bond strength between dental zirconia ceramic and resin cement. Methods:Silica coating was prepared by colloidal silica sol with concentrations of 20%,30%,40% on dental Zirconia ceramic. 32 discs zirconia ceramic specimens were fabricated and randomly divided into four groups respectively after polishing and sandblasting.The ceramic surfaces of different groups were received different treatments:(1)silane couple agent;(2)20% silica coating and silane couple agent;(3)30%silica coating and silane couple agent;(4) 40% silica coating and silane couple agent. Each ceramic block was bonded to light curing composite resin. All samples were stored in distilled water at 37 degrees for 24 h before a shear bond test to measure the bond strength of the resin cement to the ceramic surface. Scanning electrical microscopy (SEM) and energy depressive spectrum (EDS) were used to analyze the silica coating. Results:Contents of surface silicon increased after modification with silica coating prepared by sol-gel method. Bond strengths of groups with silica coating were significantly higher(P