Tamer Taşdemir

This study aimed to compare the removability of two bioceramic root canal sealers (Well-Root ST and EndoSeal MTA) with a resin-based sealer (AH Plus) during retreatment in oval-shaped canals. Thirty-six extracted human mandibular premolars with single oval canals were selected. After instrumentation with ProTaper Next, the root canals were obturated using cold lateral condensation with the test sealers and gutta percha cones ( n = 12 per group). Retreatment was performed using ProTaper Universal Retreatment files without solvent. The time to reach working length (TWL) and total retreatment time (TRT) were recorded. Residual filling material was evaluated using stereomicroscopy and scanning electron microscopy (SEM). Data were analyzed using One-way ANOVA and Kruskal-Wallis tests, with the significance level set at ( p < 0.05). EndoSeal MTA showed the shortest TWL and TRT, similar to AH Plus, but significantly shorter than Well-Root ST ( p < 0.05). No significant differences in residual filling material were found among the sealer groups ( p > 0.05), although Well-Root ST and AH Plus revealed significantly lower residue levels in the middle third compared to other regions ( p < 0.05). SEM analysis revealed significantly more debris and smear layer in the Well-Root ST group, especially in the coronal and middle thirds ( p < 0.001). None of the sealers allowed complete removal of filling material. While EndoSeal MTA was removed in a time comparable to AH Plus, Well-Root ST required significantly longer retreatment time and left more debris. No sealer permitted complete removal, highlighting the challenge of retreating oval canals obturated with bioceramic sealers.

PurposeThe purpose of this ex vivo study was to investigate the effects of 5 distinct irrigant activation systems on bacterial colonization within dentinal tubules utilizing confocal laser scanning microscopy (CLSM).Materials and MethodsSixty extracted human mandibular premolars with single canals were prepared using resiprocal instruments. The teeth were embedded in acrylic resin blocks and the root canals were inoculated with Enterococcus faecalis. Root canals were irrigated using five different irrigant activation methods: standard needle irrigation, IrriFlex, EDDY, Endoactivator, and passive ultrasonic irrigation (PUI). Horizontal sections, 1 ± 0.1 mm in thickness, were obtained at distances of 2, 5 and 8 mm from the apical end of the teeth. Sections were visualized using a CLSM. The penetration depth of dead bacteria was measured to evaluate the antimicrobial efficacy of the irrigant activation systems. Statistical analysis was performed using Kruskal-Wallis and Mann-Whitney U tests with Bonferroni correction.ResultsPUI showed significantly greater penetration depth of dead bacteria in both the coronal and apical thirds compared to the other experimental groups (p<0.05).ConclusionAlthough a statistically significant reduction in bacteria was observed in all experimental groups compared to the control, the canal disinfection was not complete in any of the groups. According to our results, standard needle irrigation had the lowest disinfection efficiency, while PUI demonstrated the highest among the evaluated activation methods.

This study aimed to examine the amount of apically extruded debris and time during retreatment with five current file systems, which exhibit various kinematic movements. One hundred upper central incisors were shaped with manual files and filled using the thermoplastic injection method. The root canal fillings in each group (n = 20) were removed using the Genius (GN), ProTaper Next (PTN), Reciproc (RCP) Blue, Tango‐Endo (TE) and Twisted File Adaptive (TFA) file systems. The apically extruded debris was collected in preweighed Eppendorf tubes. Time to reach working length and total time were also recorded. The PTN, RCP Blue and TFA instruments caused significantly less apically extruded debris and shorter total retreatment time than the GN and TE file systems (p < 0.05). The time to reach the working length was the shortest in the PTN group compared to the other groups (p < 0.05). All file systems extruded debris while removing the root canal filling.

The purpose of the present study was to investigate the effect of the different irrigant combinations used in final irrigation on the push-out bond strength of root canal sealers that have different compositions. In total 60 dentinal slices in 1 mm thickness were collected from 15 extracted mandibular premolar teeth; 4 slices from each tooth. 3 canal-like artificial cavities were opened on each dentinal slice. Samples were divided into 4 experimental groups, each of which consisted of 15 samples. In group 1, samples were immersed in 5.25% NaOCl and 17% EDTA solutions respectively; in group 2, immersed in 5.25% NaOCl and 2% CHX solutions respectively; in group 3, immersed in 5.25% NaOCl, 17% EDTA and 2% CHX solutions respectively; and in group 4 immersed in distilled water. After drying with absorbent papers, each cavity in dentinal slice sample was filled with different sealer (Endoseal MTA, Tech Biosealer Endo or AH Plus). Two days later, the push-out bond examination was performed. AH Plus showed higher push-out bond strength value in two combinations (group 2 and 3) in which final irrigants contained CHX (p<0.001). Dentinal push-out bond strengths of root canal sealers from Endoseal MTA and Tech BioSealer Endo were not affected by final irrigant (p=0.965). Using CHX after NaOCl in final irrigant increases push-out strength of epoxy resinbased sealer but, did not create any difference in dentinal push-out bond strength of calcium silicate-based sealers.

To compare the antimicrobial effects of two different irrigation solutions activated with erbium, chromium-doped yttrium, scandium, gallium and garnet (Er,Cr:YSGG) laser or an ultrasonic system and a photodynamic therapy (PDT) on Enterococcus faecalis (E. faecalis). The root canals of 72 single-rooted human permanent incisors were prepared with ProTaper Universal rotary instruments and incubated with E. faecalis (ATCC 29212) for 4 weeks. Then the teeth were randomly divided into seven experimental groups with 10 specimens for canal disinfection procedures. Group I, standard needle irrigation (SNI) with 2.5% sodium hypochlorite (NaOCl); group II, SNI with 2% chlorhexidine gluconate (CHX); group III, laser-activated irrigation (LAI) by Er,Cr:YSGG of NaOCl; group IV, LAI of CHX; and group V, passive ultrasonic irrigation (PUI) of NaOCl; group VI, PUI of CHX; group VII, PDT. The remaining two teeth were used as the control group. After the disinfection procedures were completed, the root canals were filled with phosphate-buffered saline and bacterial samples were taken with sterile paper cones. The cultivation was performed on Mueller-Hinton agar (MHA) plates. The live bacteria were calculated by counting the colonies on these plaques. The statistical analysis was performed using Kruskal-Wallis H test and Miller's multiple comparison technique. Both LAI and PUI of NaOCl and PUI of CHX were more successful than the PDT on root canal disinfection (p < 0.05). Within the limitation of the present study, the activation of NaOCl solution by Er,Cr:YSGG laser or an ultrasonic system can be useful in the elimination of the E. faecalis from the canal. The PUI of CHX also has similar results. Photodynamic therapy showed a lower performance compared to these methods. The activation of the sodium hypochlorite with Er,Cr:YSGG laser or PUI may be useful for removal of the E. faecalis biofilm layer in the root canal.

The aim of this study was to compare the neurotoxicity of various root canal sealers on rat sciatic nerve by electrophysiologic and histopathologic analyses. A total of 40 male rats were randomly divided into five groups: Control, AH Plus, GuttaFlow, Sealapex and Smartpastebio. Sciatic nerves of the rats were uncovered using the surgical procedures, and the prepared sealers were then applied on nerves with a polyethylene tube vehicle for 15 days. Nerve potentials were recorded at initial exposure, 5, 30 and 120 min (early phase), and 15 days (late phase) by an electrophysiologic analysis system for all groups. The obtained measurements were then used to calculate the nerve conduction velocities (NCV). Subsequently, all rats were sacrificed, and their sciatic nerves were removed for histopathologic analysis. Statistical analysis was performed using the Kruskal-Wallis and Mann-Whitney U tests for intergroup variables and the Friedman and Wilcoxon test for intragroup variables. Statistical significance was set at P < 0.05. There was no significant difference between early and late phase results in the control group. This group showed little or no lasting damage to nerve tissue. All sealers decreased the NCV in the early phase time periods, but this decrease was only statistically significant in the AH Plus group at 120-min time period (P < 0.0125). During the late phase, the AH Plus and GuttaFlow groups almost reached initial NCV values, and it was lower than the initial values in the Sealapex and Smartpastebio groups. However, this decrease was not statistically significant. When intergroup comparisons were performed, statistically significant differences occurred at 30 min in the Sealapex group and 120 min in the AH Plus group compared with the control group (P < 0.0125). All sealers induced neurotoxicity as a result of degenerative and inflammatory responses of nerve tissue in histologic analysis. Histologic analysis revealed Sealapex and GuttaFlow to be the most and least neurotoxic, respectively. All tested root canal sealers exhibited a variable degree of neurotoxicity depending on their chemical compositions. Apical extrusion of endodontic filling materials may cause undesired consequences, such as inflammation and severe neurotoxic damage; therefore, extrusion factor plays an important role during the root canal treatment.