Ex vi̇vo evaluati̇on of root fracture resi̇stance of teeth wi̇th external cervi̇cal root resorpti̇on repai̇red wi̇th di̇fferent endodonti̇c cements

This study was aimed to assess the fracture resistance of upper human incisor teeth which restored with three different endodontic repair materials after external cervical root resorption was created under ex vivo conditions. A total of 96 extracted permanent human upper incisor teeth which had same morphologically and structurally properties were used in this study. After performing the standardised root canal treatment procedures, all teeth were randomly divided into a negative control group, a positive control group and 8 experimental groups (n=12 per each group). The teeth without any resorption cavities were served as a negative control group. The teeth with the resorption cavities which were not restored were used as a positive control group. The remaining 72 teeth were randomly divided into three groups according to the endodontic materials applied for the resorption repair procedures. Each group were then divided into two subgroups according to incubation periods (24-h and 7-day) of the materials after repair procedures. Except the negative control group, the standardised resorption cavities with a diameter and a depth of 1.8 mm were performed on buccocervical regions of the roots by using a size 1.8 round bur. Cavities were then restored with Biodentine, NeoMTA or Glass ionomer cements. After resorption treatment procedures, the specimens were incubated in sheep blood agar medium at 37°C for two different time periods in an incubator. The force was applied to the lingual surface of the cingulum at an angle of 135° to the long axis of the roots until fracture occurred by an Instron universal testing device. The forces necessary to fracture for each specimen were recorded in Newtons and analysed statistically by using One-way ANOVA and post hoc Tukey HSD and Student's t-tests (p=0.05). According to the results, even though there are no statistically significant differences, both the 24-h and 7-day Glass ionomer cement groups slightly increased the fracture resistance of the teeth when compared to the positive control group (p>0.05). The mean fracture resistance of teeth restored with NeoMTA and Biodentine incubated for both 24-h and 7-day groups were significantly higher than the Glass ionomer cement groups (p<0.05). There were no significantly difference between 24-h and 7-day subgroups of NeoMTA and Biodentine materials (p>0.05). After the application of the fracture resistance test, a crown-root fracture or a horizontal root fracture were detected when the specimens were observed for the fracture type. The crown-root fracture (%70.83) was more frequently one in all test groups. Within all limitations of this ex vivo study, it was found that the external cervical root resorption significantly decreased the fracture resistance of all teeth. Restoring the external cervical root resorption with glass ionomer cement did not increase the force required fracture of the roots compared the control groups while NeoMTA and Biodentine increased significantly. Keywords: Biodentine; External cervical resorption; Fracture resistance; Glass ionomer cements; NeoMTA