Investigation the effect of gutta-percha cone mediated ultrasonic activation on push-out bond strength and dentin tubul penetration of calcium-silicate and resin based sealers

The aim of this study was to investigate the effect of con-mediated ultrasonic activation on dentin tubule penetration and push-out bond strength of the newly developed calcium silicate based (NeoMTA Plus) and resin-based (AH Plus) root canal sealers. A total of 160 single-rooted human mandibular premolar teeth were used in the study. The crowns of the teeth were cut to a standardized length of 14mm. Chemomechanical preparation was performed using a rotary file system (Mtwo 40/.04) and 2.5% NaOCl irrigation. The final irrigation was performed using 2.5% NaOCl and 17% EDTA followed by flushing the canals with distilled water to terminate the solution's activity. Subsequently, the samples were randomly divided into two main groups and further divided into four subgroups (n=20) based on the type of filling material and obturation technique to be used. For group A samples, the root canal filling materials were mixed according to the manufacturer's instructions. In group B samples, 0.1% Rhodamine B dye was added to the root canal filling materials prepared for confocal microscope examination. Group A1: Silicate based paste Group A2: Silicate based paste / UA Group A3: Resin based paste Group A4: Resin based paste / UA Group B1: Silicate based paste Group B2: Silicate based paste / UA Group B3: Resin based paste Group B4: Resin based paste / UA After obturation, all samples were horizontally sectioned at 3, 7, and 11 mm from the apex. For Group A, push-out tests were performed using a universal testing machine. To apply vertical force to the filling materials, stainless steel pistons of three different diameters (0.5, 0.6, and 0.8 mm) corresponding to the apical, middle, and coronal portions, respectively, were used. The maximum force at which the displacement of the canal filling material occurred (F-max) was recorded in Newtons, and the push-out bond strength was calculated for each sample in megapascals (MPa). Subsequently, any defects or failures in the samples were examined under 40x magnification. For Group B, the samples were mounted on glass slides and imaged using a confocal laser scanning microscope at 10x magnification with a wavelength range of 560-600 nm. When the entire canal could not be examined in a single image, partial images were taken and then merged into a single image using Photoshop. The digital images were transferred to the ImageJ program to measure the total dentin tubule penetration area. The dentin tubule penetration area was measured in micrometers (μm) and converted to square millimeters (mm2) for statistical analysis. Based on the obtained data, there was no significant difference in bond strength between Ah Plus and NeoMTA Plus when considering ultrasonic activation, both with and without it. In the case of using the Ah Plus sealer, the only difference observed was a lower bond strength at the apical region, while ultrasonic activation did not significantly affect the bond strength. Statistically significant differences were not observed in the examined failure modes. The applied ultrasonic activation increased the penetration area and depth of the NeoMTA Plus sealer, while it decreased the penetration of the Ah Plus root canal filling material.