Assessment of Push Out Bond Strength and Cement Thickness for Oval Root Canals Restored with Different Post Techniques

Objectives: The aim of the present study was to evaluate the push out bond strength of fiber posts to oval shaped root canals using different post techniques and correlation of bond strength values to different cement thicknesses at different post level in different post techniques.
Methods: A total of thirty-two recently extracted human mandibular first premolars with oval root canals were selected and stored in normal saline solution. The teeth were horizontally sectioned 2 mm coronal to the cementoenamel junction with a double-faced diamond disk in a slow-speed handpiece with copious coolant. Root canal treatment was done for all teeth using a standardized technique. The teeth were then randomly divided into four equal groups (n=8) according to the post and core system used: Group I: Single circular post technique, Group II: Relined post technique, Group III: Double circular post technique, Group IV: Oval post technique. For each sample, the roots were cut horizontally, perpendicular to the long axis of the root using low speed diamond saw under water coolant to obtain three 2 mm ± 0.1 thick root specimens representing cervical, middle and apical third of the root. The resin cement thickness around each specimen obtained after slicing were measured using scanning electron microscope (SEM) at eight standardized points around the circumference of the slice; between the canal wall and the fiber post perimeter. Each root slice was subjected to compressive loading at a crosshead speed of 1 mm/min via a computer controlled Universal testing machine to record the maximum failure load in Newton. The push out bond strength was calculated by dividing the recorded peak load by the surface area of each slice.
Results: As regards to the mean push out bond strength values for the post techniques, there was a statistically significant difference between mean push out bond strength of different post techniques where oval post technique showed the statistically significant highest mean push out bond strength. Relined technique showed statistically significant lower mean value followed by double circular technique. Single circular technique showed the statistically significantly lowest