The specimens were embedded in a chemically cured acrylic resin (Ortho-Jet Acrylic, Lang Dental MFG, Wheeling, IL, USA) in a custom-made mold. The mold was placed perpendicular to the tooth surface. Using a low-speed micro-saw, each embedded tooth specimen was cut into a slice of 2.0 ± 0.2 mm in thickness to obtain a specimen for the push-out bond strength test (Figure 1A ). A universal testing machine (Z020, Zwick Roell, Ulm, Germany) was used with a 500-N load cell at a crosshead speed of 0.5 mm/min to apply push-out force in the apico-coronal direction (Figure 1B ). The maximum failure load was recorded in newtons (N) and then converted to megapascals (MPa) by applying the following formula:
The adhesion area of the root canal filling was calculated using the following equation:
where r1 is the smaller radius of the root canal diameter (mm), r2 is the larger radius, h represents the thickness of the root section (mm), and π is the mathematical constant pi, approximated as 3.14.
The sample was observed under a stereomicroscope (MZ16FA, Leica, Wetzlar, Germany) at ×30 magnification to determine the failure mode. Failures were categorized as cohesive (dentin walls totally covered with sealer), adhesive (no sealer visible on dentin walls), or mixed (a combination of cohesive and adhesive failure).
The adhesion area of the root canal filling was calculated using the following equation:
where r1 is the smaller radius of the root canal diameter (mm), r2 is the larger radius, h represents the thickness of the root section (mm), and π is the mathematical constant pi, approximated as 3.14.
The sample was observed under a stereomicroscope (MZ16FA, Leica, Wetzlar, Germany) at ×30 magnification to determine the failure mode. Failures were categorized as cohesive (dentin walls totally covered with sealer), adhesive (no sealer visible on dentin walls), or mixed (a combination of cohesive and adhesive failure).
