Purpose: Adhesion to zirconia is still a challenge.There is no consensus concerning the most effective adhesion protocol for zirconia used in dentistry.This is important particularly for restorations where mechanical retention is deficient. The aim of this systematic review was to analyse the adhesion potential of resin cements to zirconia and to highlight the best surface conditioning method affecting the bond strength results to this substrate. Materials and Methods: A systematic review of the literature was conducted through the MEDLINE (PubMed) database between 11/01/2011and 11/01/2016.Original scientific papers on the adhesion to zirconia published were included. The following combination of MeSH terms was used: "dental cements"[Majr] AND "yttria stabilized tetragonal zirconia"[Supplementary Concept]. Two reviewers achieved screening and data abstraction. Results: The first search provided 69 papers. Then, after selecting only the last 5 years, we obtained 41articles.Titles and abstracts screening yielded 33 articles, out of which 30 were found potentially right to be included (after full text selection). The most documented surface treatments were: • Airborne particle abrasion, tribochemical treatment, surface coating, laser treatment, acid treatment and primer treatment, while the cements used belonged mostly to 4 families: MDP, Self-adhesive cements, 4-Meta and Bis-GMA. • Irrespective of the conditioning method used, the MDP-based cements showed significantly higher bond strength than other types of cements, but this values dropped after artificial aging, which means that the MDP cements still require a previous mechanical treatment to guarantee stability over time. Conclusion: Within the limitations of our study, it can be concluded that the combination of the tribochemical treatment and the use of MDP based cements is the most effective, durable and safest conditioning method considering the literature included in our work. Further works are still required with more standardisation and focus on the aging factor.
