Rotating fatigue and flexural strength of direct and indirect resin-composite restorative materials

To evaluate the flexural strength and rotating fatigue resistance of direct and indirect resin composite restorative materials.

Filtek Z100 and Filtek Z250 (3M ESPE) are direct resin composite restorative materials, and Sinfony (3M ESPE) and Neco (Heraeus Kulzer) are indirect composites. Bar specimens (2 x 2 x 25 mm; n=10) of these materials were used to determine the flexural strength (Fs) by means of 3-point bending tests according to ISO 4049. The same size specimens (n=20) were used to prepare hour-glass shaped specimens. Rotating fatigue resistance (RFR) was determined in a rotating-bending cantilever test with the stress located at the constriction of the hour glass. The rotating fatigue resistance tests were conducted according to the staircase approach (104 cycles, 1.0 Hz) and the mean RFR was calculated using logistic regression analysis.

Fs ranged between 100.0 and 141.9 MPa and the RFR 51.6 to 89.6 MPa. After 10,000 cycles the strength of the materials decreased between 35 and 48%. RFR of Filtek Z100, Filtek Z250, and Neco (77.4 - 89.6 MPa) were significantly higher than Sinfony (51.6 MPa).