Influence of different luting concepts on long term retentive strength of zirconia crowns

To evaluate the retentive strength of a resin cement in combination with a conventional adhesive (Variolink II/Syntac Classic), two resin cements with self-etching adhesives (Panavia F 2.0/ED Primer, Multilink/Multilink Primer A/B), two self-adhering cements (RelyX Unicem Aplicap, Maxcem), and a resin-modified glass-ionomer cement (FujiCem) after cementation of zirconium-oxide ceramic crowns (LAVA) on extracted human teeth.

160 extracted teeth (n=20) were prepared in a standardized manner (10 degrees, h=3 mm). The crowns' inner surfaces were air-abraded/sandblasted (Rocatec Pre). Additional pretreatment was carried out with Multilink (metal primer or Monobond S). With RelyX Unicem Aplicap, an additional group that also received Rocatec Plus pretreatment was examined. Immediately after thermocycling (x5000, 5/55 degrees C), 50% of the luted ceramic crowns (n=10) were pulled off along the path of insertion (Zwick 1425); the remaining samples (n = 10) were tested after 1 year of water storage. Statistical analysis was performed using the Wilcoxon Mann-Whitney U-test and Bonferroni adjustment at the 5% level of significance.

The retentive strength values (N/mm2) after 1 year of water storage were (Min/Q1/Median/Q3/Max): Variolink II/Syntac: 1.0/1.9/2.5/3.3/5.2, Panavia F 2.0: 1.5/1.8/2.1/3.6/5,4, Multilink/Metallprimer: 2.9/4.6/5.3/9.4/11,7, Multilink/Monobond S: 4.1/4.8/5.4/7.7/12.6, RelyX Unicem Aplicap: 3.9/6.3/7.5/9.0/10.7, RelyX Unicem Aplicap/Rocatec Plus: 4.4/5.8/7.2/9.4/11.9, Maxcem: 0.9/2.2/3.0/3.3/4.5, FujiCem: 1.6/2.7/4.3/5.4/6.7. RelyX Unicem Aplicap and Multilink showed the highest median retentive strength values. Long-term water storage did not affect the retentive strength.