Effect of Saliva on Bond Strength of Glass-Ionomer-Cement to Zirconia

Objectives: Several types of dental cement have been used for zirconia-based restorations, such as Resin-modified-glass-ionomer-cement (RMGIC) or Self-adhesive-resin-cement (SARC). After the try-in of restoration, the prosthetic surface might be contaminated by saliva or exudate. While salivary contamination is reportedly the main cause of decreased bond strength in resin cements, glass-ionomer-cement is considered to be less affected by saliva. The purpose of this study was to investigate the influence of salivary contamination on the bond strength to zirconia.
Methods: Three RMGICs, FujiCEM Evolve (FE, GC), RelyX Luting Plus Automix (RL, 3M ESPE), ZirCAD Cement (ZC, Ivoclar), two SARCs, G-CEM ONE EM (GO, GC) and MAXCEM Elite (ME, Kerr) were used. Yttria-stabilized-zirconia (Aadva Zr-Block, YSZ, GC) was prepared by sandblasting with aluminum oxide. The specimens were classified into three groups (n=8). Group1 was without salivary contamination and used as the control group. Group2 and 3 were applied with saliva, kept for 2minutes, and rinsed with water by three-way syringe. One was rinsed with water only (Group2), and the another was applied with phosphoric acid etchant gel and rinsed after 30seconds (Group3). The samples were cemented with tensile-bond-test-jig (sandblasted YSZ), stored (37°C water, 24hrs), tested (1mm/min.) and statistically analyzed (Kruskal-Wallis test, Dunn test, p<0.05).
Results: FE and RL were not affected by salivary contamination. On the other hand, the bond strength of GO and ME was reduced by salivary contamination, while it was improved by using a phosphoric acid etchant. Regardless of salivary contamination, there were pre-test failures in all test conditions in ZirCAD.
Conclusions: FE was not affected by salivary contamination while the bond strength of SARCs was reduced. This result suggests that FE was clinically superior and less troublesome.