Comparison of postoperative pain after the use of different nickel titanium instrumentation systems: a randomized clinical trial.

Purpose: Postoperative pain is a common complication in endodontics contributed by multiple etiological factors, which consist canal preparation instruments and kinematics. The aim of this randomized clinical trial compare the postoperative pain in terms of intensity and incidence after the use of different nickel titanium (NiTi) file systems. Patients and methods: In this randomized clinical trial (NCT03791762), a total of 150 patients were root canal treated by 2 experienced endodontists according to a standardised protocol. The subjects were randomly assigned to 1 of the 3 groups according to preparation instrument used: ProTaper Next (Dentsply Sirona, Ballaigues, Switzerland), Reciproc Blue (VDW, Munich, Germany) and WaveOne Gold (Dentsply Sirona). Following preparation the teeth underwent standardized root canal treatment procedures in a single visit. The patients were contacted to gather information about the incidence of pain and intensity at 6th, 12th, 18th, 24th, 48th, and 72nd hours postoperatively. The data were analysed using chi-square, one-way analysis of variance and post hoc Tukey tests and logistic regression analysis with 5% significance threshold. Results: No significant difference was found among preparation groups in relation to the intensity of postoperative pain. The incidence of postoperative pain was significantly linked with the preoperative pain presence with odds ratio values ranging between 2.06 and 4.08 irrespective of the preparation technique (P<0.05). Conclusion: The effects of reciprocating and the continuous rotary systems on the intensity and incidence of postoperative pain were found to be similar.

Metallurgical characterisation and torsional resistance of blue thermomechanically treated nickel titanium instruments after simulated ex vivo retreatment procedure.

To compare used and unused Reciproc Blue and Reciproc after retreatment, the instruments were used in the mesiobuccal canals of maxillary molars with curvature. The torsional resistances were tested and then unused instruments were subjected to XRD, DSC and microhardness tests. Student's t, ANOVA and Tukey's tests were performed (α-level 0.05). The torsional strength of used Reciproc Blue was not significantly different than unused ones (P > .05), while torsional strength of Reciproc decreased significantly (P < .05). DSC and XRD indicated that Reciproc Blue exhibited prominent transformation peaks corresponding austenite to R-phase. Microhardness of Reciproc was significantly higher (P < .05). A second reuse of Reciproc Blue for retreatment could be considered safe in terms of torsional strength. Blue treatment also decreased surface microhardness of the instrument and changed phase composition by increasing the R-phase.

Push-out bond strength of oval versus circular fiber posts irradiated by erbium-doped yttrium aluminum garnet laser.

STATEMENT OF PROBLEM: Fiber posts in conjunction with resin cements are widely used to provide retention in endodontically treated teeth. The bond strength of restorative materials to root canal dentin is an important issue for the long-term success of restorative procedures. The push-out test is widely used to measure the bonding between the post and radicular dentin. PURPOSE: The purpose of this in vitro study was to evaluate the effect of erbium-doped yttrium aluminum garnet (Er-YAG) laser treatment of dentinal walls on the bond strength of circular and oval fiber posts luted in oval root canals. MATERIAL AND METHODS: Forty mandibular premolar teeth were endodontically treated and restored with 2 different intracanal post systems. Push-out tests were performed and data were analyzed by using 2-way analysis of variance and post hoc Bonferroni tests. RESULTS: Laser pretreatment of dentinal walls resulted in higher push-out bond strength than that of the nonlasered groups (P<.05). Oval fiber posts showed significantly higher push-out bond strength values than those of circular fiber posts in the coronal region (P<.05). In the apical region, no statistically significant difference was noted among the groups regarding push-out bond strength (P>.05). CONCLUSIONS: The laser pretreatment with an oval ultrasonic tip of an oval fiber post system improved bonding to root canal dentin when compared with a circular post system with conventional preparation.

Effect of F-File on removal of the smear layer: a scanning electron microscope study.

The aim of this study was to evaluate the effectiveness of F-File with NaOCl on removal of the smear layer. A total of 48 single-rooted teeth were instrumented using crown-down technique with one of the irrigation agents: distilled water, 5.25% NaOCl, RC-Prep, Glyde, MTAD or F-File with NaOCl. The remaining smear layer was scored at cervical, middle and apical thirds of the roots with SEM. In all the canals of experimental groups the coronal sections were cleaner than the middle and apical sections except with distilled water (P<0.001). In the coronal third, intensive smear layer was observed in distilled water, NaOCl and F-File groups and less smear layer in MTAD (P<0.05) and least in RC-Prep and Glyde groups. In the middle third, RC-Prep and Glyde groups had less smear layer than the other groups (P<0.001). In the apical third, there was intensive smear layer in all specimens and statistical analyses showed no significant difference among the groups (P>0.05). The F-file failed to improve the effect of NaOCl in removing smear layer.

Effect of immediate and delayed post space preparation on the apical seal of root canals obturated with different sealers and techniques

During mechanical preparation of the post space, the root canal filling may be twisted or vibrated, depending on several factors associated with the preparation technique and quality of filling. OBJECTIVE: The purpose of this study was to investigate the effect of immediate and delayed post space preparation on the integrity of the apical seal. MATERIAL AND METHODS: Sixty-four extracted human incisors were biomechanically prepared using the step-back technique. Sixty roots were randomly assigned to 6 experimental groups of 10 teeth each and the remaining 4 roots served as positive and negative controls (n=2). The root canals in the different groups were obturated with cold lateral and warm vertical condensation of gutta-percha and one of two sealers (Sealapex and Diaket). Post space was prepared either individually or simultaneously. An insulated copper wire was cut into 10-cm-long pieces. In each canal, one piece was inserted to maintain contact with gutta-percha and extended to the outside as one of two working electrodes. A stainless steel wire with the same dimensions of those of the copper wire, used as the other working electrode, was immersed into the background electrolyte from the center of the bottle. The electrical current between standard and experimental electrodes in canals was measured over a period of 10 days applying a conductivity meter. The Kruskal-Wallis test (p=0.05) determined whether there was a significant difference in microleakage among the groups and the Mann-Whitney U test (p=0.01) was used for multiple comparison grouping variables. RESULTS: The results suggest that only the differences between the root canal filling techniques were statistically significant (p<0.01). There were no statistically significant difference in the sealers and the times of filling removal for post space preparation (p>0.01). CONCLUSION: The quality of the root canal filling is important for the integrity of the apical seal.