Objective: This study aimed to examine programmed death protein 1 (PD-1) and programmed death ligand 1 (PD-L1) expression on leukocytes from chronic apical periodontitis, and to determine the levels of cytokines in the apical periodontitis lesions.
Methods: Leukocytes from healthy gingival tissue (n=16) and chronic apical periodontitis (n=10) were evaluated using flow cytometry. The PD-1 and PDL-1 expressions were evaluated using flow cytometry. The cytokine levels were evaluated by enzyme-linked immunosorbent assay. Data were analyzed using one-way ANOVA. The statistical significance level was set at P<0.05.
Results: Results showed that the apical periodontitis lesions are more infiltrated by PD-1+ and PDL1+ lymphocytes than the control samples. In addition, the PDL-1 expression was detected on macrophages in the apical periodontitis lesions, and was significantly higher compared to leukocytes from healthy gingival tissue. The IFN-γ, TGF-β, IL-10, and TNF-α levels were significantly higher in the apical periodontitis lesions compared to control samples.
Conclusion: The PD-1, PD-L1, and CTLA-4 molecules are evident in apical periodontitis, and can be an important immune checkpoint in chronic periapical periodontitis.

Objective: This study aimed to investigate the relationship between final apical preparation size and smear layer removal in the apical third using conventional irrigation in mandibular bicuspids.
Methods: A total of 66 extracted human mandibular bicuspids with comparable root canal morphology were equally divided into five experimental groups and a control group (n=11). Based on their experimental group, samples were instrumented up to size 25, 30, 35, 40, or 45 with 0.04 taper using 2.5% sodium hypochlorite (NaOCl) as the irrigant. Final irrigation was performed with 17% EDTA followed by 2.5% NaOCl. The control group was instrumented up to size 45/.04, and was irrigated with distilled water. Samples were sectioned buccolingually, and they were qualitatively evaluated under scanning electron microscope for efficacy in smear layer removal. The Kruskal–Wallis and Mann–Whitney U tests were employed for statistical analysis.
Results: Statistical analysis revealed comparable removal of smear layer in the coronal and middle thirds of all experimental samples regardless of grouping. When using file size larger than 35, removal of smear layer in the apical third significantly improved (p<0.05). No significant difference was observed between 40/.04 and 45/.04.
Conclusion: Under the conditions of this study, using conventional irrigation, apical enlargement more than size 35/.04 is essential to enhance removal of smear layer at the apical third.

Objective: To compare the antimicrobial activity and tissue dissolution capacity of calcium hypochlorite (Ca(OCl)2) solution with sodium hypochlorite (NaOCl) solution at 0.5%, 1.0%, 2.5%, and 5.25% concentrations.
Methods: To determine the inhibition halos produced by the tested substances against Enterococcus faecalis, the agar diffusion method was employed. Additionally, the broth contact method was used to determine the time required for the inhibition of E. faecalis. Bovine pulp fragments were used to test the dissolution. Half of the pulps were freely deposited samples in cell culture wells, and the remaining samples were fixed on bovine dentine bases.
Results: For both Ca(OCl)2 and NaOCl solutions, the greatest inhibition zones were observed at 5.25% concentration. However, the most significant inhibition zone was measured with 5.25% Ca(OCl)2 solution (17.38 mm). Hypochlorite solutions at 2.5% and 5.25% concentrations required less time to inhibit E. faecalis than those at 0.5% and 1.0% concentrations (P<0.05). There was no difference in inhibition times between 2.5% and 5.25% hypochlorite solutions (P>0.05). The most effective hypochlorite solution concentrations were 5.25% and 2.5% for dissolving pulp fragments (P<0.05). Additionally, suspended pulp fragments were more susceptible to dissolution than fragments attached to dentine blocks (P<0.05), except for 0.5% Ca(OCl)2.
Conclusion: Ca(OCl)2 solutions showed antimicrobial activity against E. faecalis and can dissolve pulp tissues. Future studies are warranted to examine the suitability of Ca(OCl)2 in the chemico–mechanical preparation of the root canal system.

Objective: This ex vivo study aims to investigate the root filling quality of warm vertical technique, single-cone technique with GuttaFlow2, Endoseal MTA and EndoSequence BC sealer as a sealer in artificial internal resorption cavity.
Methods: For this study, 40 human single-root teeth were selected. After root preparation, the roots were horizontally sectioned 7 mm from the apex. The hemisphere cavities were created on both sides, and then they were re-approximated. According to filling methods and materials, the samples were randomly assigned to four experimental groups: I: warm vertical compaction technique (WVC), II: single-cone technique with GuttaFlow2 (GF), III: single-cone technique with Endoseal MTA sealer (EM), IV: single-cone technique with EndoSequence BC sealer (ES). Filled roots were radiographed in buccolingual and mesiodistal views to check the obturation, and stored in humid environment at the room temperature for 7 days. Each tooth was sectioned 7 mm from the root apex at the level of the previous cut, and it was then photographed under stereomicroscope. The photographs and radiographs of all samples were imported to an image-analysis software to calculate the percentage of sealer, gutta-percha, and voids. The results were statistically analyzed using one-way ANOVA and Kruskal–Wallis Dunn’s tests.
Results: In buccolingual view of radiographs, the WVC and EM groups showed significantly lower percentage of voids (P value<0.05) compared to that in the GF group. In mesiodistal view, the WVC and EM groups showed significantly lower percentage of voids (P value<0.05) compared to that in the GF and ES groups. In stereomicroscope evaluation, the WVC and EM groups showed significantly lower percentage of voids (P value<0.05) compared to that in the GF and ES groups. The differences observed between the WVC and EM groups (P value>0.05) or between the GF and ES groups (P value>0.05) were not significant.
Conclusion: WVC technique and single-cone technique with EM sealer are the optimum methods to fill artificial resorption cavities.

Objective: This study aims to evaluate the accuracy of three-dimensional root canal length measurements performed by dentists with different experience levels using a special software based on cone beam computed tomography (CBCT).
Methods: A CBCT scan of an artificial resin maxillary molar was used to train dentists (n=65) in using the software (3D Endo, DentsplySirona, Ballaigues, Switzerland) as part of a continuing education course. At the beginning, each participant completed a questionnaire on endodontic and CBCT experiences. After comprehensive instructions, each participant performed an entire three-dimensional treatment plan by tracing the root canal anatomy between the apical foramen and the center of the canal orifice and simulating a straight-line access. The final root canal length was indicated after the virtual rubber stop of a simulated instrument was adapted to the adjoining cusp. To evaluate the individual accuracy in terms of trueness and precision, differences between the three-dimensional planning and the actual root canal length (ARCL) were calculated, and statistically analyzed.
Results: Mean absolute differences between the measurements with the 3D Endo™ software (n=260) and the ARCL were 0.30±0.22 mm. All measurements were within a limit of ±1 mm. The accuracy of root canal length measurements was significantly influenced by the type of root canal (p<0.0001). The smallest deviations were observed for the palatal root canal (0.18±0.13 mm), followed by the mesiobuccal (0.26±0.22 mm), the distobuccal (0.32±0.17 mm), and the second mesiobuccal root canal (0.46±0.24 mm).
Conclusion: Within the limitations of this study, the 3D Endo software enables reproducible and accurate root canal length measurements as part of a three-dimensional endodontic treatment plan. However, measurements should always be clinically verified, as root canal morphology has a statistically significant influence.

Objective: This study investigated the influence of different irrigants and the use of orange oil solvent in the removal of filling materials during root canal retreatment.
Methods: Forty maxillary premolars were shaped using the ProTaper System up to file F3 (size 30, 0.09 taper) and filled by Tagger’s hybrid technique using the AH Plus. Samples were randomly assigned to four groups (n=10) according to the irrigating protocol during endodontic retreatment with the ProTaper Universal Retreatment System: G1, 2% chlorhexidine (CHX) gel; G2, 2% CHX gel with an orange oil solvent; G3, 5% sodium hypochlorite (NaOCl); and G4, 5% NaOCl with an orange oil solvent. Afterwards, the samples were longitudinally split into two halves, and the root wall images were prepared by scanning electron microscopy. Two pre-calibrated evaluators analyzed the images using a filling materials remnants score system. Data were statistically analyzed using the Kruskal–Wallis and Dunn’s tests (p<0.05).
Results: All samples had residual filling materials in the root canal walls after instrumentation. According to the presence of the filling material remnants in the total area of samples, the groups were ranked in the following order: G2=G4>G1=G3. No statistical differences were found when the CHX and NaOCl were used (p>0.05). Groups in which a solvent was used showed a less effective cleaning ability (p<0.05). The use of NaOCl with solvent presented the highest amounts of filling materials remnants in the critical apical area (p<0.05).
Conclusion: The use of orange oil with NaOCl or CHX does not improve the removal of residual root canal filling materials.

Objective: The aim of root canal obturation is to prevent leakage and inhibit microbial invasion. This study aimed to determine the effect of chlorhexidine (CHX) and dimethyl sulfoxide (DMSO) as final irrigants on microleakage of root filling immediately and after 18 months. The hypothesis was that either CHX or DMSO would not affect the immediate or long-term microleakage.
Methods: A total of 120 human third molar root canals were obturated with RealSeal SE or Topseal and gutta percha. Before obturation, the canals were irrigated with saline (control), 2% CHX or 5% DMSO. Microleakage of half of each groups (n=10) was measured after 3 days, and of the other half was measured after 18 months with fluid filtration method.
Results: In immediate measurements, RealSeal SE performed significantly better in CHX-irrigated group (p=0.035; Mann-Whitney test). For both sealers, DMSO had the lowest mean microleakage values, which were also statistically significantly lower than with CHX irrigation within sealers (p<0.009 for Topseal and p=0.04 for RealSeal SE; Mann-Whitney test). With RealSeal SE, the microleakage with CHX was significantly higher than that in controls (p=0.022; Mann-Whitney test).
Conclusion: Neither final irrigant showed statistically significant differences in the immediate microleakage within the two sealers. Irrigation with DMSO caused significantly less microleakage than CHX for both sealers after 18 months.

Apical periodontitis and vertical root fracture (VRF) might coexist in the same root, thus representing a diagnostic challenge in endodontics. Diagnosis should be based on detailed clinical examination and precise radiographic interpretation in addition to histological examination, if needed. The histological findings of the case presented showed the possible coexistence of a VRF in the coronal third of the root and signs of apical periodontitis caused by intracanal infection in the apical third of the same root. The presentation of this case underlines the importance of histological examination as a valid complementary diagnostic tool with clinical and radiographic examinations in reaching an accurate diagnosis once the root has been extracted.