2.7. Aging
The aging of the samples to stimulate clinical conditions was conducted in a thermocycling machine (SD Mechnotronik THE 1100, Feldkirchen-Westerham, Germany). The samples were placed in a 10 × 10 open specimen basket and subjected to 5000 cycles in a water bath at (5 to 55 °C) for 30 s/cycle and a 5 s transfer time.