Bond Strength of CAD/CAM-Fabricated, Temporary Single-Tooth Crowns on Titanium Abutments

Objectives: Temporary single-tooth restorations on implants are required in various scenarios. Polymer-based CAD/CAM composites can be used in the CAD/CAM process to fabricate such restorations. Standardized production conditions lead to improved material properties, but present challenges for cementation.
Methods: In the present study, 430 temporary single crowns were digitally fabricated on titanium abutments made of CAD/CAM PMMA. The bond strength in MPa was investigated for five different luting materials in combination with four different pretreatments of the inner surface of the restoration. In addition, two different storage scenarios of the test specimens were investigated for each combination of luting material and pre-treatment. The test specimens were debonded in a universal testing machine using a combined shear-tensile test. The fracture behavior was then investigated.
Results: In the majority of the test series, the pre-treatment of the restoration showed a statistically highly significant influence on the bond strength (p < 0.001). In general, the highest bond strengths were achieved with pre-treatment using sandblasting with 50 µm aluminum oxide + Monobond + Heliobond. In addition, the influence of the choice of luting material was statistically highly significant in all cases (p < 0.001).
The use of thermocycling led to a decrease in bond strength for the materials Speed Cem Plus, Premier Implant Cement and Temp-Bond NE for all four pre-treatment methods. For the materials Harvard Implant semi-permanent and TempoCem ID, thermocycling led to an increase but also to a decrease in bond strength, depending on the pre-treatment method.
Conclusions: While the data obtained can only be transferred to a clinical scenario to a limited extent, they do provide an initial point of reference for the selection of pre-treatment and luting material. The selection should be based on the required wearing time of the temporary restoration.