Tensile Bond Strength of Different Luting Agents at the Cement-Restoration-Interface

Objectives: The aim of this study was to evaluate the tensile bond strength at the cement-restoration interface of different luting agents bonded to different restoration materials by using a newly developed testing procedure.

Methods: Disc-shaped specimens made from Y-TZP zirconia, glass ceramic and non-precious metal were used as restoration materials. A cylinder with smaller diameter was cemented onto each disc-shaped specimen. The five luting agents (Clearfil SA Cement CSA and Panavia F2.0 PF, Kuraray, Japan; RelyX Unicem RX, 3M ESPE, Germany; Maxcem Elite ME, KerrHawe, Switzerland, iCem iC, Heraeus Kulzer, Germany) were used according to the manufacturers´ instructions. The cemented specimens (n=6 for each restoration-cement-combination) were stored for 23 days in distilled water (37°C). A universal testing machine (Z010, software: TestXpertII V3.0, Zwick/Roell, Germany) was used for testing and results were statistically analyzed (ANOVA, α=0.05, univariate, bifactorial, SPSS 19.0).

Results: Debonding of samples during storage was noticed (CSA:0, PF:1, RX:2, ME:7, iC:3). In these cases, tensile bond strength was considered to be 0 MPa. Regarding the restoration material, no significant influence on tensile bond strength could be detected. For ME and iC, tensile bond strength was significantly lower than for RX and PF. For RX and PF, tensile bond strength was significantly lower than for CSA. There was no significant difference between ME and iC nor between RX and PF. CSA showed the highest values for tensile bond strength.

Conclusions: The newly developed procedure for tensile bond strength testing offers the major benefit of a real tensile test without a component of shear bond strength. The testing procedure is specially designed for luting agents, as the functionality of anorganic cements is based on friction, which is not provided by this specimen-geometry. For such cements, a newly developed procedure for shear bond strength testing could be applied.