*2.4. Scanning Electron Microscopy (SEM) Analysis*

The modes of failure were classified as follows: (1) adhesive (clean break at the bond), (2) cohesive (full break in the base material or tooth), and (3) mixed (combination of adhesive and cohesive failure modes). A precision low-speed Techcut 4tm saw (ALLIED High-Tech Product, Inc., Compton, CA, USA) was used to slice the roots along the long axis under constant water irrigation. A stereomicroscope at 50× magnification and a scanning electron microscope (SEM) (FEI QUANTA 250 FEG, Thermo Fisher Scientific, Waltham, MA, USA) were used to examine the sectioned root canals, and displaced posts were examined using a stereomicroscope at the same magnification [42].
