Pre-cementation procedures' effect on dental zirconias with different yttria content.

• Pre-cementation procedures can affect both cement retention and crown strength. • Zirconia materials with different amounts of yttria-stabilizer benefit from different pre-cementation procedures. • Disc-shaped specimens are not suitable to assess all aspects of pre-treatment procedures for prosthetic restorations. Several pre-cementation procedures have been advocated to enhance adhesion between zirconia and resin-based cement. There is, however, limited documentation on how these pre-treatments affect the strength of zirconia crowns as most tests are performed on discs or bars. The aim was to assess the effect of pre-cementation procedures on fracture mode, fracture strength and cement retention on zirconia. Two dental zirconia materials with different yttria content were assessed (<4 and>5 mol%). Both discs (n = 45) and crown-shaped specimens (n = 30) of the two materials were pretreated with either air-abrasion or hot-etching with KHF 2 and compared with untreated controls with regards to surface roughness, crystallography, wettability, cement adhesion and fracture strength. Air-abrasion improves adhesion and strength of zirconia with moderate yttria content (<4 mol%). Acid etching with heated KHF 2 showed the best effect on strength and cement retention on zirconia with higher yttria content (>5 mol%). Application of KHF 2 was, however, complicated on crown-shaped specimens. Pre-treatment and cementation protocols should be optimized for different dental zirconias to improve both strength and retention. [ABSTRACT FROM AUTHOR]