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Context: Cleaning and shaping of the canals damages the root dentin which becomes a gateway to dentinal cracks and thereby causes failure of the treatment. Aim: The aim of this study was to assess and compare dentinal crack formation caused by three different nickel-titanium (NiTi) rotary file systems in primary anterior teeth. Settings and Design: The present in vitro study is an experimental, comparative study. Materials and Methods: One hundred fifty extracted primary anterior teeth were included in this study. The teeth were randomly divided into five groups. Group 1: Pedoflex rotary file system, Group 2: Prime Pedo™ rotary file system, Group 3: Kedo-S2 rotary file system, Group 4: K-files, and Group 5: no instrumentation. Roots were sectioned and viewed under a stereomicroscope for the presence of any cracks. Statistical Analysis Used: The data were analyzed using the Chi-square test and Kruskal-Wallis test. Results: In the coronal, middle, and apical thirds, Group 2 showed a maximum number of crack formations in the middle third (57%), followed by Group 3 (43.3%) and Group 1 (36.7%). Groups 4 and 5 showed no crack formation in all the root sections. The middle third showed a maximum number of crack formations compared to the coronal and apical thirds. Conclusions: Rotary systems render various benefits with an acceptable success in comparison to conventional hand instrumentation. Within the limitation of this study, it was found that Pedoflex rotary file system was the best with the least number of crack formations.

Background and Objectives: The aim of this study was to see the incidence of cracks in root dentin after coronal flaring using various rotary instruments such as Gates Glidden (GG) drills, ProTaper Universal SX, OneFlare, and HyFlex EDM. Materials and Methods: Seventy freshly extracted premolar teeth with single canal were collected. All the teeth were randomly divided into five groups of fourteen each (n = 14), of which one group served as the control and the rest of the four groups were instrumented with GG drills, ProTaper Universal SX, OneFlare, and HyFlex EDM, respectively. Results: The GG drills resulted in a higher rate of crack formation in root dentin (P < 0.05) than the ProTaper Universal SX, OneFlare, and HyFlex EDM instruments (P > 0.05). Conclusion: The use of GG drills resulted in more crack formation. However, the results for the ProTaper Universal SX, OneFlare, and HyFlex EDM flaring instruments were less in terms of crack formation.

Objectives: This study was aimed to evaluate the cause-effect relationship between canal preparation with ProTaper Next (PTN) and ProTaper Gold (PTG) using optimum torque reverse (OTR) motion or continuous rotation and dentinal crack formation. Materials and Methods: Fifty distobuccal roots of human maxillary first molars were divided into five groups; Group I: PTG Full rotation, Group II: PTG in OTR, Group III: PTN Full rotation, Group IV: PTN in OTR, Group V: unprepared (control group). After mechanical preparation, the distobuccal roots were sectioned horizontally at 3, 6, and 9 mm from the apex. Images were captured using a stereomicroscope at 25X to determine the presence or absence of dentinal cracks. Friedman test was used to compare between root sections followed by Wilcoxon signed-rank test for pairwise comparison. Kruskal-Wallis test was used to compare between tested rotary systems followed by pairwise comparison with Dunn Bonferroni correction (α = 0.05). Results: Crack development was significantly higher in PTG using OTR motion 36.7% followed by PTN using OTR 33.3%, while the control group showed no cracks. PTG and PTN with full rotation showed crack development with 23.3% and 13.3%, respectively. Conclusions: The type of motion kinematics used during mechanical preparation have an impact on dentinal crack formation. Nickel-titanium instruments with larger taper tend to induce more cracks.

Background This study used micro-computed tomography (µCT) to assess the post space preparation systems [Rebilda (VOCO), RelyX (3M)] and preparations of varying lengths to create root dentin cracks. Methods Forty extracted maxillary first premolars with two roots were randomly divided into four groups. Teeth were decoronated to a length of 18 mm. Following root canal treatment, first µCT scans were performed. Post spaces were prepared with Rebilda post drills at 1/2 of the working length (WL) in Group 1 and at 2/3 of the WL in Group 2, while post spaces were prepared with RelyX post drills at 1/2 of the WL in Group 3 and at 2/3 of the WL in Group 4. After post space preparation, second µCT scans were performed. Dentinal cracks were detected by comparing the first and second µCT scan images, which were classified as “newly formed cracks”, “advanced cracks” and “completed cracks”. The chi-square test was used to compare among the groups, with a p-value of < 0.05 considered statistically significant. Results No statistically significant differences were observed between the groups for completed and advanced cracks ( P  > 0.05). In terms of newly formed cracks, the Rebilda-2/3 group showed more cracks than the RelyX-1/2 group, and the RelyX-2/3 group had more cracks than the RelyX-1/2 group ( P  < 0.05). Conclusion Completed and advanced cracks were observed in all groups, while no newly formed cracks were detected in the RelyX-1/2 group. The type of post drill and the preparation length are crucial factors in preventing the development of root dentinal cracks. Preparing 1/2 of the canal length may be a safer preparation length, and the RelyX drill may pose less risk of inducing root dentinal cracks.

Aim: To compare dentinal cracks incidences after root canal preparation using Hand K-files; Rotary files: Protaper NEXT (PTN), Hyflex Controlled Memory (CM); and Reciprocating files: Wave One and Wave One Gold files. Materials and Methods: Hundred extracted human mandibular first premolars with straight root canals were taken postextraction and were allocated randomly into five groups (n = 20 teeth per group). The canals were instrumented using Hand K-files, Protaper Next (PTN), Hyflex CM, Wave One, and Wave One Gold systems. Group 1-Control group comprised of canals prepared by Hand files. Further, the roots were sectioned at three levels: 3, 6, and 9 mm horizontally from the apex using a saw at a low-speed saw and under water cooling. These slices were examined under a stereomicroscope at 25× magnification and the presence of any dentinal cracks was noted. The frequency of cracks was presented in number and percentage. Intergroup comparison of crack frequency was performed using analysis of variance. Results: No cracks were observed in the control group. In all the other groups, dentinal cracks were observed. The rotary files PTN and Hyflex CM files produced significantly fewer dentinal cracks than the reciprocating Wave One and Wave One Gold files (P < 0.05). The reciprocating files significantly produced more cracks apically than the rotary files (P < 0.05). Analyses were performed on SPSS software (windows version 22.0). Conclusion: Instrumentation with file systems can cause crack formation in the dentinal wall of the root canal. Determination of which files to choose for root canal preparation is technique sensitive and each instrument type has own benefits. However, care should be taken while biomechanical preparation to avoid dentinal cracks formation.

Context: Neoendo Flex and Mani Silk are recently launched nickel–titanium (NiTi) rotary files. Dentinal cracks and file separation remain a critical problem in the endodontic domain. Aim: The aim was to evaluate and compare the incidence of dentinal crack formation after root canal preparation with Neoendo flex and Mani silk files. Materials and Methods: Thirty-six extracted single-rooted premolars with straight, single root canals were selected for the study. The specimens were randomly assigned to three groups, with 12 samples in each group. The root canal preparation for the three groups was done with hand K-file, Mani Silk, and Neoendo Flex files, respectively, following which the specimens were horizontally sectioned at 3, 6, and 9 mm from the apex. Sectioned samples were viewed under a stereomicroscope to determine the presence or absence of dentinal cracks. The data were analyzed using one-way ANOVA and Chi-square test. Results: Hand K-files and Mani Silk files produced a lesser number of cracks than Neoendo Flex files; however, the difference was not statistically significant among the three file groups at 3 mm and 6 mm (P > 0.05). A statistically significant difference between the groups was seen at 9 mm, where Mani Silk files produced fewer cracks than K files and Neoendo Flex files (P = 0.007). Overall, Neoendo Flex significantly produced more cracks than Mani Silk and hand K-files (P = 0.0029). Conclusions: Both hand K files and NiTi rotary instruments may cause dentinal cracks. Neoendo Flex files tend to produce more dentinal cracks than Mani silk and K-file.

To compare three various methods in the diagnosis of dentinal cracks formed in the apical third after root resection.One hundred extracted human maxillary central incisors were selected. The root canals were prepared with step-back technique. Then 3mm from the apical end of all roots was cut perpendicular to the long axis of the tooth. The apical end of each root was evaluated to make sure there were no cracks. Fifty specimens were randomly chosen and connected to an apparatus especially designed for application of force (50-60N) by a universal testing machine for crack formation. The cracked (no=50) and non-cracked (no=50) specimens were examined by three methods of fiber optic transillumination, methylene blue staining and combination of the two. Sensitivity and specificity of the methods were evaluated. The most suitable method for detecting cracks was determined using Youden index. To compare agreement between studied methods with the gold standard, kappa statistics and odds ratio of McNemar were utilized.The sensitivity of transillumination, staining and the combination method were 82.0, 50.0 and 90.0%, respectively. The staining technique had the lowest sensitivity and the highest specificity. Both transillumination and the combination method had Youden index of 0.56, but the combination method diagnosed truly cracked samples more than the other techniques.The efficacy of transillumination in identification of apical root-end cracks undetectable by unaided vision was similar to the combination method. However, the efficacy of 2% methylene blue without transillumination was significantly lower than the other two methodologies.

Objectives This study aims to assess the effectiveness of an intracanal composite anchorage to replace conventionally cemented titanium or bonded glass fibre posts. Materials and methods Post space preparation was performed up to depths of 6 mm (groups 1 and 2) and 3 mm (group 3) in root filled mandibular premolars. In group 1, titanium posts were cemented with zinc phosphate cement. Glass fibre posts were adhesively cemented in group 2 using a dual-cure composite resin. In group 3, intracanal anchorage was solely performed with a dual-cure composite. All teeth were restored with standardised direct composite crowns without a ferrule. After thermo-mechanical loading, static load was applied until failure. Fracture patterns were assessed, and a microscopic analysis was performed to analyse the occurrence of additional cracks. Results Group 2 revealed a significantly higher median fracture value (408 N) than groups 1 and 3, while no difference was detected between group 1 (290 N) and group 3 (234 N) ( p  = .1417). In group 3, the more favourable fracture patterns were observed. However, the majority of teeth within this fracture category revealed additional minor cracks of the root. Conclusions Within the limitations of this study, adhesive intracanal anchorage to a depth of 3 mm with resin composite only has the same fracture resistance as titanium posts conventionally cemented to a depth of 6 mm. Even teeth with repairable main fractures exhibited additional dentinal cracks on the root. Clinical relevance Additional dentinal root cracks in the teeth with repairable main fractures may considerably impair their longevity.

Aim: The aim is to assess and compare the microcrack formation in radicular dentin after obturating the root canals with cold lateral condensation (CLC), warm vertical condensation (WVC), and injectable gutta-percha (IGP) techniques using micro-computed tomography (CT). Materials and Methods: Human extracted mandibular premolar teeth (n = 60) were haphazardly assigned based on the obturation technique into three experimental groups (n = 20 each). Root canals are cleaned and shaped with M Two rotary files and 3% sodium hypochlorite irrigant. Cross-sectional images were taken with Micro-CT to record the baseline defects present on root samples. After root canal obturation either with CLC or WVC or injectable obturation techniques, micro-CT images were captured again to analyze the increase in the number and type of dentinal defects. Statistical analysis of data was performed using the Mann–Whitney U test and the Mcnemar test at 5% significance level. Results: An increase in the number of radicular micro-cracks was identified in samples obturated with lateral condensation technique (1.66%). No change in the percentage of micro-cracks was recorded after obturation with warm vertical or injectable guttapercha (IGP) techniques (P > 0.05). The three obturation techniques were not statistically different in the occurrence of micro-cracks after obturation. Conclusion: The three obturating techniques tested showed no significant increase in radicular dentin defects' occurrence or propagation.

The aim of this study was to compare the dentinal defects caused by Reciproc, TF Adaptive and ProTaper Next NiTi rotary file systems during the retreatment procedure. A total of 150 mandibular incisors with straight and single root canals were included in the present study. All the root canals were prepared up to an apical diameter 0.40 mm using stainless steel files. Thirty teeth were randomly stored as the negative control group. A total of 120 specimens were obturated with gutta-percha and AH Plus sealer using vertical compaction technique. Thirty specimens with root canal filling were randomly separated for the only-filled group. Then the teeth were randomly divided into 3 groups; Reciproc, TF Adaptive and ProTaper Next. The retreatment procedure was performed with these NiTi files. Then 150 specimens were cut perpendicular to tooth axis at 3-, 6-, and 9-mm distances from the apex, and examined to determine the presence of any cracks at ×25 under a stereomicroscope. Chi-squared test was used at 5% significance level. All the tested NiTi file systems were found to cause significantly more dentinal defects compared to unprepared and only-filled groups (P<0.05). No statistically significant differences were found between the groups in terms of dentinal defects (P>0.05). No correlation was found between the slice levels and the dentinal defect distribution (P>0.05). Within the limitations of present study, all the tested NiTi file systems were found to cause significantly more dentinal defects compared to unprepared and only-filled groups.