Objectives: The ability of a restorative material to withstand fracture is of crucial importance especially in stress bearing area. The study aim therefore to analyse the fracture toughness of a large number of dental restorative materials categories.
Materials and Methods: The fracture toughness (KIC) of 69 restorative materials belonging to 10 materials categories – Micro-hybrid, Nanofilled, Microfilled, Packable, Ormocer-based and Flowable resin-based Composites (RBC), Compomers and Flowable Compomers as well as Glass Ionomer Cements (GIC) and Resin-modified GIC was measured by means of the single-edge notched-beam method after storing the samples (n=8) for 24h in distilled water. Data were analyzed with the one-way ANOVA followed by the Tukey's test and partial eta-squared statistics (p < 0.05).
Results: Large variations between the tested materials within a material category were found. The lowest KIC was reached in the GIC-group, followed by the microfilled-RBCs, resin-modified GIC and flowable compomers, which do not differ significantly among each other as a material group. The ormocer-based, packable and micro-hybrid RBCs performed statistically similar, reaching the highest KIC values. Between the two categories of flowables – composites and compomers – no differences were measured.
Material Type | KIC [MPa√m] |
GIC | 0.45a(0.12) |
Microfilled-RBCs | 1.02b(.22) |
Resin-modified-GIC | 1.12bc(0.33) |
Flowable compomers | 1.29bcd(.37) |
Flowable-RBCs | 1.41cde(.32) |
Compomers | 1.44cde(.46) |
Nano-RBCs | 1.46cde(.28) |
Ormocer-based Composites | 1.55def(.27) |
Packable-RBCs | 1.77ef (.41) |
Hybrid-RBCs | 1.84f (.45) |
Conclusions: The correlation between KIC and filler volume (0.34) and weight (0.40) was low. KIC increased with the volume fraction of fillers until a critical value of 57%, following with a plateau, with constant values until ca. 65% volume fraction, decreasing slightly above this value. Due to very large variability of KIC within a material type, the selection of a suitable restorative material should not been done with respect to a specific material category, especially in stressed bearing areas, but by considering the individual measured material properties.