One of the most commonly tested mechanical
properties of dental restorative materials is flexural
strength (FS), which is considered important for
characterizing brittle materials. This type of test
generates complex stresses that combine tensile,
compressive, and shear stresses when specimens are
loaded.29 Several studies examined FS of a number
of commercial nanocomposites comparing hybrid and
microfilled composites.11,13,22,28-36 Direct comparison
showed that the FS of nanocomposites was equiva lent to or even higher than other composites
tested11,13,22,29,31,37 with values ranging from 103 to
192 MPa.38-40 Mitra and others,22 who developed
nanocomposite materials in 2003, reported FS values
ranging from 153 to 177 MPa. These values were
significantly higher than a number of tested hybrid
composites, comparable to that of one hybrid material and significantly higher than the microfilled
composite (Table 2). Similarly, Pontes and others29
reported significantly higher FS of a nanocomposite
compared with a hybrid. On the other hand, several
investigators reported FS values of several nano composites comparable to or significantly lower than
a number of hybrid materials but significantly
higher than microfilled composites.11,31,36,40-42