Retention of zirconia crowns to Ti-base abutments: effect of luting protocol, abutment treatment and autoclave sterilization

Purpose: To evaluate the influence of resin cement type, surface pretreatment and autoclave sterilization on the retention of Y-TZP crowns to Ti-base abutments. Methods: Y-TZP crowns were designed and milled to fit Ti-base abutments. Crowns were cemented using either a conventional resin cement (conventional) with a universal adhesive or a self-adhesive resin cement (self-adhesive), both following no surface pretreatment (No) or Ti-base abutment sandblasting (SB) (n=20/group). Half of the cemented samples were subjected to in-office autoclave sterilization. Pullout testing was performed in a universal testing machine at a speed of 1 mm/min until crown displacement. Data were statistically evaluated through a linear mixed model following post hoc comparisons by LSD test. Results: Pullout data as a function of cement type demonstrated higher retention for conventional relative to self-adhesive cement (p<0.001). Ti-base sandblasting (SB) favored crown retentiveness over No pretreatment (p<0.001). Sterilized crowns exhibited higher pullout values than non-sterile (p=0.036). All the two- and three-factor interaction analyses corroborated with the superior adhesive strength of conventional compared to self-adhesive cement (all, p<0 .011), as well as, SB relative to No pretreatment (all, p<0.024). While autoclave sterilization maximized bond strength when self-adhesive cement (data collapsed over surface pretreatment, p<0.050) and No pretreatment were evaluated (data collapsed over surface pretreatment. p<0.013), no significant difference was observed for conventional resin cement (p=0.280) and SB (p=0.878) groups. Conclusions: Conventional resin cement and/or Ti-base sandblasting increased Y-TZP crown retentiveness, with no significant influence of autoclave sterilization. Autoclaving increased retentiveness when self-adhesive cement andlor no Ti-base pretreatment were used.