Evaluation of Er,Cr:YSGG laser technique for fiber post removal of endodontically treated teeth using micro-computed tomography.

Various clinical techniques such as removal kits, ultrasonic tips, burs, and drills, have been used for fiber post removal in endodontically treated teeth. In most clinical cases, the dental practitioners prefer to use ultrasonic tips, despite the heat generation and the formation of microcracks induced in the radicular dentin. The purpose of this study was to investigate the effectiveness of using erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser (2780 nm) as an alternative fiber post removal technique and to compare it to an ultrasonic method using micro-computed tomography (micro-CT). The operating parameters of the X-ray tube were set to 50 kVp and 300 mA. This approach allowed the generation of 2D lateral projections that were then used to reconstruct the 3D volume in DICOM format. Fiber posts were removed from 20 endodontically treated single-rooted premolars (n = 10) using an ultrasonic vibrator with diamond-coated ultrasonic tip (control method), or Er,Cr:YSGG laser irradiation protocol; average power 2.5 W, repetition rate 20 Hz, pulse duration 140 µs, 40% air and 20% water, and close-contact mode. The number of sections with newly formed microcracks, the loss of dentinal tissue, the amount of the residual resin cement, and the removal time were evaluated for both methods. The data were analyzed using paired t-test, Wilcoxon signed-rank and Mann-Whitney U tests at level of significance a = .05. In the laser-treated group the parameters regarding microcracks formation (21 ± 16) and removal time (4.7 ± 1.1 min) were advantageous compared to the ultrasonic-treated group (42 ± 27 and 9.2 ± 1.0 min, respectively), indicating that Er,Cr:YSGG laser could be an alternative fiber post removal technique.

Examination of Irrigant Flow on a Tooth With Internal Root Resorption by Using a Computational Fluid Dynamics Model.

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.

Factors Affecting the Outcome of Non-Surgical Endodontic Treatments Performed by Undergraduate Students in a Greek Dental School.

OBJECTIVE: 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.

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: To evaluate radiographically the quality of root canal fillings performed by undergraduate students between 2012 and 2015, and to investigate the impact of their quality in correlation with root type, preoperative periapical status, and type of restorative treatment on the treatment outcome. METHODS: Six hundred seventy-seven non-surgical root canal treatments were performed by undergraduate students from the Aristotle University of Thessaloniki at the endodontic department clinics between 2012 and 2015. Two hundred forty-four teeth (349 roots) fulfilled the criteria and were clinically and radiographically re-examined between 2016 and 2017, and the outcome was classified as "success" or "failure." Root canal fillings were radiographically evaluated in terms of apical extension and density. The root filling was classified as acceptable when both parameters were rated as acceptable. Statistical analysis was performed using generalized estimating equations. Pairwise comparisons were performed by the sequential Bonferroni method. Intra-examiner and inter-examiner agreements were checked by the intraclass correlation coefficient and Cohen's kappa. The statistical significance level was set at P<0.05. RESULTS: The percentage of the roots with acceptable root canal fillings was 40.4%. The molar roots demonstrated the lowest rate (30.7%) compared with the anterior (53%, P<0.05) and premolar teeth (43%, P>0.05). The results of the correlation of the quality of the root canal fillings with the root type, preoperative periapical status, type of coronal restoration, and the treatment outcome showed that the unacceptable quality of root canal filling in relation to root or presence of periapical lesion or crown revealed the lowest success rates (47.2%, 40.3%, and 52.3%, respectively). In contrast, results showed that roots with canal fillings of acceptable quality demonstrated success rates close to 90%, regardless of the other variables. CONCLUSION: Within the limitations of the present study, the percentage of radiographically acceptable root canal fillings performed in the undergraduate clinic of the Department of Endodontology at Aristotle University of Thessaloniki was low (40.4%). Results showed that there was a strong association of higher success rates with root fillings of acceptable quality.