On the possibility of estimating the fracture toughness of enamel.

Objectives: There are many works that have attempted to estimate the fracture toughness of enamel by indentation techniques using equations whose success in determining the actual value of fracture toughness, rely on a particular three-dimensional pattern consisting of cracks growing from the edges of the indentation. Recently, an alternative methodology based on an energetic approach has been developed to estimate the fracture toughness of coatings by depth sensing indentation that is not less affected by the cracks pattern generated. In this work, the energetic approach to indentation fracture toughness of bovine enamel is presented and compared with those toughness values obtained using the traditional expressions reported in the literature.

Microhardness of different resin cement shades inside the root canal.

Objectives: To compare microhardness along the root canal post space of two resin cements in different shades and a dual-cure resin core material.

Study Design: Root canals of 21 bovine incisors were prepared for post space. Translucent posts (X∘Post, Dentsply DeTrey) were luted using one the following resin luting agent: Calibra (Dentsply DeTrey) in Translucent, Medium and Opaque shades, RelyX Unicem (3M ESPE) in Translucent, A2 and A3 shades and the dual-cure resin core material Core∘X flow.

Mechanical characterization of sclerotic occlusal dentin by nanoindentation and nanoscratch.

Purpose: To evaluate the mechanical properties of occlusal wear lesions identified as sclerotic.

Methods: Nanoindentation and nanoscratch techniques have been applied to determine elastic modulus (E), hardness (H) and wear resistance of different types of sclerotic dentin. Nanoscratch testing was applied to evaluate the tribological behavior.

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.