Mechanical characterization of resin cements used for luting fiber posts by nanoindentation.

Objectives: To evaluate the mechanical behavior of resin cements used for luting fiber post. The influence of the curing mode is analysed.

Methods: Nanoindentation techniques have been applied to determine hardness and Young's modulus of disc-shaped specimens of three types of cements: chemical- , photo- and dual-cured, provided by Ivoclar-Vivadent. Results obtained have been compared with measurements performed inside the post-cement-dentin system. Mechanical properties are evaluated together with scanning electron micrographs showing the post-cement and dentin-cement interfaces.

Results And Significance: Differences have been detected between mechanical measurements performed inside the post-cement-dentin system and those carried out in laboratory disc-shaped specimens. The close presence of post and dentin boundaries has a lot of influence on the cement behavior. The nanoindentation measurements indicate that the photo-cured cement exhibits a high hardness and stiffness, but with a more marked tendency to brittle failure. The chemically cured cement is the material with higher ability to bear deformation without damage, although its hardness and elastic modulus are significantly lower. Dual-cured cements present the best combination of properties.