Bond strength of three luting agents to zirconia ceramic - Influence of surface treatment and thermocycling

Objective: this in vitro study aimed to evaluate the influence of different surface treatments,3 luting agents and thermocycling on microtensile bond strength (μtbs) to zirconia ceramic. material and methods: a total of 18 blocks (5×5×4 mm) were fabricated from zirconia ceramic (ice zirkonia) and duplicated into composite blocks (alphadent). ceramic blocks were divided into 3 groups (n=6) according to the following surface treatments: airborne-particle abrasion (aa),silica-coating,(sc) (cojet) and silica coating followed by silane application (scsi) (espe sil). each group was divided into 3 subgroups (n=2) according to the 3 luting agents used. resin-modified glass-ionomer cement (rmgic,ketac cem plus),self-adhesive resin cement (un,relyx unicem) and adhesive resin cement (ml,multilink automix) were used for bonding composite and zirconia blocks. each bonding assembly was cut into microbars (10 mm long and 1±0.1 mm2). seven specimens of each subgroup were stored in water bath at 37°c for 1 week. the other 7 specimens were stored in water bath at 37°c for 30 days then thermocycled (tc) for 7,500 cycles. μtbs values were recorded for each specimen using a universal testing machine. statistical analyses were performed using a 3-way anova model followed by serial 1-way anovas. comparison of means was performed with tukey's hsd test at (α=0.05). results: μtbs ranged from 16.8 to 31.8 mpa after 1 week and from 7.3 to 16.4 mpa after 30 days of storage in water and thermocycling. artificial aging significantly decreased μtbs (p<0.05). considering surface treatment,scsi significantly increased μtbs (p<0.05) compared to sc and aa. resin cements (un and ml) demonstrated significantly higher μtbs (p<0.05) compared to rmgic cement. conclusions: silica coating followed by silane application together with adhesive resin cements significantly increased μtbs,while thermocycling significantly decreased μtbs.