Objectives: The aim of this study was to evaluate the mechanical properties and curing efficiency of two indirect composite resins under different testing conditions.
Methods: The materials tested were: Ceramage (CE, Shofu) and Signum (SI, Heraeus Kulzer). Cylindrical specimens (n:4, d:1.12mm, l:18mm) were prepared according to the manufacturers and stored dry for 24 h. A Sm-Co magnet was attached to end of every specimen generating torque (M:1.12x10-2Nm/A) at the center of a Helmholtz coil. Four different testing conditions were applied: 21oC dry, 21o wet, 37o wet and 50o wet and the materials were tested under shear and flexural stresses, both under static and dynamic conditions. The materials were also subjected to creep testing at three different stresses for 3h with a recovery time of 50h. Shear and flexural moduli, loss tangent and permanent creep deformation were calculated. The amount of remaining C=C bonds (%RDB) was measured for each material 24h after curing employing ATR-FTIR spectroscopy. Statistical analysis was performed with t-test and two-way ANOVA (á:0.05).
Results: Statistically significant differences were found both in the mechanical properties and the curing efficiency of the materials. CE possessed higher shear and flexural modulus than SI (15.79 GPa and 5.66 GPa vs 7.04 GPa and 2.24GPa respectively). Both materials were affected by the presence of water and temperature. SI exhibited higher creep recovery than CE, showing less permanent deformation. CE showed the highest %RDB (63.6% vs 38.6% for SI).
Conclusions: Both indirect composites were affected by the testing conditions in the same way, although they differed significantly in their properties. Their mechanical properties depend on other factors than curing efficiency.