The tendency to fracture of composites is a crucial factor to dentistry because contact-fatigue is one of the failure modes occurring often mainly in posterior restorations. The mechanical characterization is a key study to understand the nature of the dependency between the tribological behaviour and the mechanical properties. In the present work five commercially available composite restorative materials, used for posterior restorations, were tested concerning four fundamental aspects of the mechanical characterisation: Young's Modulus (determined by dynamical methods), Flexural Strength, Hertzian contact fatigue and Micro-hardness.