To evaluate the outcome of initial endodontic treatments performed by undergraduate students in a Greek dental school and to determine the factors that may impact the treatment outcome. Methods: From a randomly selected sample of 677 non-surgical endodontic treatments performed between 2012 and 2015, follow-up appointments were scheduled with patients whose dental records matched the inclusion criteria. After clinical and radiographic examination, the treatment outcome was classified as 'success' (healed/healing) or 'failure' (uncertain/unsatisfactory healing). The statistical analysis of the data was performed using generalized estimating equations. Intra-examiner and inter-examiner agreements were checked with the intraclass correlation coefficient and with Cohen's kappa. The statistical significance level was set at P<0.05. Results: A total of 244 teeth (349 roots) were included for further analysis, and the mean follow-up period was 2.8 years. Overall, the success rate for the treated roots was 72.8%. Μultivariate analysis revealed four decisive factors as having a positive impact on the outcome, namely, the absence of voids within the root fillings (P<0.001), the absence of pre-operative periapical lesions (P=0.001), the extension of the root filling material by 0-2 mm from the radiographic apex (P<0.001) and the root type (anterior roots: P=0.015 and premolar roots: P=0.011). The association of gender, arch, pulp status and type of coronal restoration with the outcome was not statistically significant (P>0.05). Moreover, when the outcome according to pre-operative periapical status and the technical variables of root fillings (apical extension and density) was investigated, roots without periapical lesion, with a root filling material extended 0-2 mm within the apex and without voids revealed the highest success rate (94.5%). Conclusion: The success rate of non-surgical endodontic treatments performed in a Greek dental school was in the range of those reported in other studies. The pre-operative periapical status, technical variables of root fillings (apical extension and density) and root type were regarded as significant prognostic factors of the outcome.

Radiographic technical quality of root canal fillings performed by undergraduate students and the related factors on the treatment outcome: A 2-to 5-year follow-up.

Objective: This study investigated the flow of an endodontic irrigant in a single-rooted tooth with internal root resorption (IRR). Methods: A simulation of a prepared central incisor with internal root resorption was created and irrigation with a 30-G needle was performed. The fluid pattern of the irrigant was evaluated using a Computational Fluid Dynamics model. In addition, the effects of the needle-insertion depth in the root canal and the size of root resorption on the fluid flow and the wall shear stress (WSS) values were assessed. The IRR was placed immediately below the canal orifice. Results: Inadequate irrigant washout was observed inside the resorption cavity when the needle was positioned 1 mm from the working length while placing the needle slightly above the resorption cavity resulted in significant irrigant circulation inside the resorption cavity. Moreover, when the needle was placed slightly above the defect, the calculated WSS values in the resorption cavity walls were significantly higher (approximately 20 times higher in every case). In cases where the needle was placed 1 mm from the working length, the average and maximum WWS values were between 3 Pa and 51 Pa, while in cases where the needle was placed coronal to the IRR, the values were between 55 Pa and 528 Pa. The radius of the resorption cavity did not affect the irrigant flow patterns. Conclusion: During the endodontic treatment of cases with internal root resorption, complementary irrigations with the needle tip placed slightly above the resorption cavity should be followed to better debride the root canal.