Abstract

Objective.
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.
Methods.
Two dental zirconia materials with different yttria content were assessed (<4 and >5mol%). Both discs (n = 45) and crown-shaped specimens (n = 30) of the two materials were pretreated with either air-abrasion or hot-etching with KHF₂ and compared with untreated controls with regards to surface roughness, crystallography, wettability, cement adhesion and fracture strength.
Results and Significance.
Air-abrasion improves adhesion and strength of zirconia with moderate yttria content (<4 mol%). Acid etching with heated KHF₂ showed the best effect on strength and cement retention on zirconia with higher yttria content (>5 mol%). Application of KHF₂ 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.
Conclusion
Pre-cementation procedures affected the load at fracture and cement retention in dental zirconias. Air-abrasion resulted in the highest strength for zirconia with moderate yttria content(<4 mol%/3Y). Acid etching with heated KHF₂ seemed to have the best effect on strength and cement retention on zirconias with higher yttria content (>5 mol%/5Y). The application was, however, complicated. Air abrasion with Al₂O₃ should be used with caution for pre-treating zirconia with higher yttria content (>5 mol%), as it has possible negative effects on strength. Pre-cementation procedures need to be adjusted for the different dental zirconia materials to optimize both strength and retention.

Reference
Pre-cementation procedures’ effect on dental zirconias with different yttria content
Øilo M, Haugli K, Rønold HJ, Ulsund AH, Ruud A, Kvam K
Dent Mater (2021). https://doi.org/10.1016/j.dental.2021.07.001