Comparative evaluation of mechanical characteristics of nanofiller containing resin composites

Purpose: To determine basic mechanical characteristics of six commercially available nanofiller containing resin composites compared to a microhybrid and a microfilled reference material. The tested hypothesis was that there are no differences in mechanical properties between the materials. Methods: Durafill VS (DUR) and Filtek Z250 (Z250) were used as microfilled and microhybrid references. The nanofiller containing products were: Filtek Supreme XT (FIL), Grandio (GRA), Kalore (KAL), MI Flow (MIF), Tetric EvoCeram (TET), and Venus Diamond (VED). The following material characteristics were determined after 24 hours water storage (n=6): Flexural strength and modulus (FM), yield stress (0.02%), tensile strength and modulus (TM), diametral tensile strength, Knoop hardness (KHN), and fracture toughness (KIC). Results: The microfilled composite DUR consistently showed the lowest values for each property investigated. The group of nanofiller containing products could be subdivided into two groups: the nanohybrid products GRA and VED and the nanofilled FIL with higher values, on the one hand, and the flowable MIF, and the prepolymer containing composites KAL and TET, on the other. The mechanical performance of the microhybrid reference material Z250 was overall slightly better or in line with the nanohybrid and nanofilled materials. Stringent linear relationships were found between KHN and the moduli FM and TM, respectively (r> 0.95). Linear relations between the other material values investigated were moderate to high.