Dentinal Microcrack Formation Research Articles

Comparative Evaluation of ProTaper Gold, TruNatomy, and XP-endo Shaper Instruments on Dentinal Microcrack Formation: Scanning Electron Microscope Study

Comparative Evaluation of ProTaper Gold, TruNatomy, and XP-endo Shaper Instruments on Dentinal Microcrack Formation: Scanning Electron Microscope Study

Comparative evaluation of hand and rotary file systems on dentinal microcrack formation during pulpectomy procedure in primary teeth: an in vitro study.

Pulpectomy can be used for the management of deep dentinal carious lesions in primary teeth which can be restored. Mechanical preparation of root canals can be performed using hand or NiTi rotary files. However, this may cause dentinal stress and consequently dentinal microcracks. Hence, the aim was comparative evaluation of hand and rotary file systems on dentinal microcrack formation during pulpectomy procedure in primary teeth. 60 extracted primary molar teeth were selected comprising of 80 root canals. Simple random sampling was used to divide root canals into four groups (n = 20): Group A-Hedstrom file, Group B-Pro AF Baby Gold rotary, Group C-ProTaper Next rotary, and Group D-unprepared group. Assessment was conducted on presence or absence of microcracks using Chi square test (p < 0.05). The total number of microcracks in Group A: one (5%), Group B: four (20%), Group C: nine (45%) and Group D: zero (0%) which was statistically significant (p = 0.002). At cervical third, the number of microcracks seen with Group A: one (5%), Group B: zero (0%), Group C: five (25%) and Group D: zero (0%) (p = 0.005). At the middle third, the number of microcracks seen in Group A: zero (0%), Group B: four (20%), Group C: four (20%) and Group D: zero (0%) (p = 0.029). The study concluded that dentinal microcracks are formed with both hand and rotary file systems in primary teeth. ProTaper Next showed significantly higher number of microcracks, followed by ProAF Baby Gold and H files.

Formation of dentinal microcracks after root canal preparation with four kinds of mechanical nickel-titanium files.

This study aimed to compare the differences among four kinds of mechanical Ni-Ti files including T-Flex, Reciproc Blue (RB), ProTaper Gold (PTG), and ProTaper Universal (PTU) in dentinal microcrack generation after root canal preparation in vitro by using micro-computed tomography (micro-CT) analysis. A total of 32 freshly extracted double-root-canal premolars with an angle not exceeding 10° were selected and established as root canal preparation models in vitro. Then, the specimens were randomly assigned to four experimental groups (n=8) according to the different Ni-Ti systems used for root canal preparation: group T-Flex, group RB, group PTG, and group PTU. The voxel size of the micro-CT was set at 17.18 μm. Pre- and post-operative cross-sectional images of roots (n=56 940) were scanned and analyzed to identify the presence of dentinal microcracks. The results of each group were expressed by the quantity and percentage of sectional images with microcracks. McNemar test was used to determine whether a significant difference existed in the existence of dentinal microcracks before and after instrumentation. The level of significance was set at P<0.05. Overall, 11.04% of the images presented dentinal defects (n=6 288). Dentinal microcracks were observed in 9.82%, 10.79%, 12.27%, and 11.25% of the post-instrumentation images from groups T-Flex, RB, PTG, and PTU, respectively. However, all these dentinal microcracks were already present in the corresponding pre-operative images. No new microcrack of premolars were generated after the root canal preparation utilizing the aforementioned systems. Denti-nal microcracks already existed in advance in extracted teeth before root canal preparation. Root canal preparation using the T-Flex, RB, PTG, and PTU systems did not induce the formation of new dentinal microcracks on the straight root canals of premolars.

An in vitro evaluation of dentinal microcrack formation during root canal preparations by three different nickel–titanium systems: ProTaper Gold, HyFlex CM, and Silk

Aim: This study aimed to compare the frequency of dentinal microcracks after root canal shaping with three different nickel–titanium (NiTi) systems, namely, ProTaper Gold (PG), HyFlex CM (HCM), and Silk. Methods: One hundred mandibular premolars with a single canal were chosen for this study. All specimens were decoronated and divided into four groups of 25 each. Teeth were mounted in the acrylic block with simulated periodontal ligaments. Group I served as a negative control Group, in which no treatment was performed. Biomechanical preparation was done in the Group II, using the Protaper gold file system. Group III, using the Hyflex CM file system and Group IV, using the Silk file system. Specimens were horizontally sectioned at 3, 6, and 9 mm from the apex using the low-speed diamond disc under water cooling. The slices were then viewed under a stereomicroscope at ×25 to determine the presence of cracks. The absence or presence of cracks was recorded, and the data were analyzed with a Chi-square test. The significance level was set at P &lt; 0.05. Results: Coronal section showed lesser crack formation in all three groups after biomechanical preparation. More number of dentinal microcracks were seen in the apical sections, followed by the middle and the coronal sections in Group II (PG), followed by Group IV (Silk), and Group III (HCM), respectively. Group II showed more microcracks at all three levels of the root canals when compared with Groups III and IV. Intergroup analysis showed no statistically significant difference in microcrack formation. Conclusion: Within the limitation of this in vitro study, it can be concluded that NiTi instruments may cause cracks on the root surface. HCM and Silk files tend to produce a less number of cracks as compared to PG instruments.

Effects of ultrasonics and trephine burs on dentinal microcrack formation during broken instrument removal procedures: A micro-CT analysis.

The objective of this study was to compare the effects of ultrasonic and trephine burs on microcrack formation during the removal of broken instruments, utilising micro-computed tomography (Micro-CT). Twenty-five extracted human mandibular molars were used for this study. The hand files were fractured into the mesiobuccal canal, except in the control group. In the ultrasonic group (n = 10), ultrasonic tips were used to retrieve the instrument, while in the trephine group (n = 10), trephine burs (Meitrac, Meisinger) and an extractor device were utilised. For the control group (n = 5), only staging platform was prepared. After the removal procedures, micro-CT images were obtained from the specimens. The chi-squared test was used to analyse the data, and significance was considered to be p < 0.05. Overall, 15 736 cross sections were analysed. No significant differences were found between control and experimental groups. Removal of broken instruments with trephine burs caused significantly more dentinal microcracks compared with ultrasonics (p = 0.016).

Comparative Evaluation of TruNatomy, XP Endoshaper and Hand K File Systems on Dentinal Microcrack Formation and Vertical Root Fracture Resistance – An In Vitro Study

Background Vertical root fracture VRF accounts for 11 of failures in endodontically treated teeth. Microcracks can occur during instrumentation of root canal system with NiTi rotary files as it exerts forces increasing strain on dentinal wall which may progress to VRF. Newer file systems have been developed to reduce the risk of microcrack formation.Aim The aim of the present study was to evaluate the effect of TruNatomy XP Endoshaper and Hand K files on dentin microcrack formation and vertical root fracture resistance of root canals.Methods One hundred twenty-five extracted teeth were used in the study with 40 samples each in the experimental groups and five samples in the control group. Following instrumentation Group TRN-Trunatomy Group XPS ndash XP Endoshaper Group HF ndash Hand K File 50 of the samples were subjected to stereomicroscopic study for dentinal microcrack evaluation. The remaining samples were obturated and were subjected to Universal testing machine for vertical root fracture resistance assessment. Kruskal Wallis and Post hoc Bonferroni tests were used for statistical analysis.Results Statistically significant difference was observed between XP Endoshaper and other groups in terms of dentinal microcrack formation and vertical root fracture resistance. Significantly higher value was observed for Hand K file and TruNatomy against XP Endoshaper File p lt0.05.Conclusion TruNatomy serves as a file system causing least dentinal damage comparable to Hand K file system while XP Endoshaper caused more cracks.

Formation and Effect of Dentinal Microcracks After Root Canal Treatment

Many potential causes of root fracture have been put forth over the decades, such as theories that the fracture might begin with dentinal microcracks (DM) brought on by dentinal dehydration, post-insertion corrosion, spreader form, or strong movements utilized while filling processes. In the recent times, scientists have found that a sizable proportion of preexisting dentinal defects on the roots to be present. These problems are though too likely to be brought on by high extraction pressures and/or the way the teeth were stored. The limits of the standard methodologies are undoubtedly vulnerable to systematic analytical inaccuracies, making them far from an optimal experimental model, according to scientific rationale underlying this ambiguous scenario. It has also been shown that dentin moisture affects the biomechanical response of radicular dentin to root canal preparation, specimen storage circumstances are another issue with investigations on dentinal microcracks development. Instrumenting with manual, reciprocating, or rotary NiTi tools does not produce remnant microstrain accumulation in hydrated roots.

Stereomicroscopic Evaluation of Dentinal Microcracks After Instrumentation of Curved Canal with Rotary Files in Two Motions

Objective: This study aimed to examine the effects of three distinct file systems with two motion types—rotary and reciprocation—on the development of dentinal microcracks after root canal preparation using a stereomicroscope. Methods: Sixty mandibular molars with a curvature of 30° were decoronated and divided into three groups (Vortex Blue, Mtwo, and ProTaper Next) and two subgroups (rotary and reciprocating motions). The samples were then instrumented with the files, dyed with 1% methylene blue dye, and sectioned horizontally at 3, 6, and 9 mm from the root apex. The dentinal microcracks were inspected using a stereomicroscope at 40× magnification. One-way analysis of variance and post hoc Tukey tests were used to perform statistical analysis. Results: Crack formation was statistically significant at the 6-mm and 9-mm levels from the root apex in both motions (p &lt; 0.05). Among all the file system, Vortex Blue caused the highest dentinal microcracks in both motions at 6 mm from the root apex. Conclusion: The reciprocating motion resulted in fewer dentinal microcracks than the rotary motion. All file systems caused significant dentinal microcracks at the curvature of the root canal during both motions. Dentinal microcrack formation was not significant at the root apex.

Evaluation of Dentinal Microcracks following Diode Laser- and Ultrasonic-Activated Removal of Bioceramic Material during Root Canal Retreatment.

This study is aimed at evaluating the use of microcomputed tomography (micro-CT) analysis and the dentinal microcrack formation following retreatment of bioceramic sealer employing adjunct laser-activated irrigation and ultrasonic-activated irrigation. Thirty sound human single-canal teeth (n = 30) obturated using the single-cone technique with bioceramic sealer were retreated using nickel-titanium (NiTi) rotary files. The sample was randomly divided into three equal groups: group 1, the control group, was not subjected to further treatment; group 2 underwent ultrasonic activation of irrigants; group 3 underwent active irrigation with a diode laser (980 nm wavelength). Using micro-CT, the teeth were scanned before and after retreatment protocols. Two calibrated experienced observers viewed the cross-sectional images and calculated the number of dentinal defects. The presence of any crack or craze line on the external root surface or internal canal wall was counted. Data were analyzed using Friedman's two-way analysis of variance and Fisher's exact test. Statistical significance was set at p < 0.05. A significant increase occurred in the number of cracks post retreatment protocols, specifically in the coronal and middle canal thirds, compared to pre- and postinstrumentation (p = 0.0001). However, ultrasonic- or laser-activated irrigation did not result in a significant increase in the number of cracks (p = 0.345). NiTi rotary root canal retreatment was associated with a significant increase in dentinal microcracks. However, employing ultrasonic- or laser-activated irrigation as adjunct retreatment techniques did not reveal a significant increase in dentinal microcracks within the roots.

Radicular dentinal microcracks during biomechanical root canal preparation using four minimally invasive endodontic files.

The aim of the study was to compare the dentinal microcrack formation on human mandibular molars using 4 different minimally invasive file systems at 3, 6 and 9 mm from apex using a stereomicroscope. 125 mesial roots of mandibular molars were randomly divided into 5 groups and instrumented (n=25). Group 1: Control Group (CG), Group 2: Self Adjusting File (SAF), Group 3: XP-Endoshaper (XP), Group 4: TRUShape (TS), Group 5: V Taper 2H (VT). After instrumentation was completed, the roots were sectioned at 3 mm, 6 mm, and 9 mm from apex using a slow-speed circular saw. Digital images were captured using a 24× stereomicroscope by using a digital camera. Two operators independently checked each specimen for the presence of dentinal defects. Statistical comparison between the file systems was done using Chi-square (p<0.05). There was no statistically significant difference in the frequency of microcracks between the groups of file systems (X2=4.509, p>0.05). VT file system exhibited higher microcracks (25%) but was not statistically significantly higher than XP (12%), TRUShape (12%), and SAF (4%) endodontic file systems. Within the limitations of this study, it can be concluded that all the file systems used in our research are minimally invasive files and produced few dentinal microcracks. VT files produced maximum while SAF produced the least number of micro-cracks.

Dentinal Microcrack Formation by Different Rotary Endodontic File Systems: An In-vitro Study

Introduction: During endodontic treatment, biomechanical preparation of the root canals constitutes one of the prime steps to enable bacterial eradication, irrigant percolation and three dimensional obturation of the canal space. Currently used rotary endodontic instruments generate stresses in the dentinal walls as microcracks and craze lines which can eventually precipitate vertical root fractures. This endangers the prognosis of an endodontically treated tooth or can even lead to tooth extractions. Aim: To compare dentinal micro-crack formation during biomechanical preparation by different Nickel-Titanium rotary endodontic instruments, Reciprocating single file system and Self-Adjusting File (SAF) using a stereomicroscope. Materials and Methods: The study was a randomised controlled trial conducted for a total duration of two months. A total of eighty extracted human mandibular molars with intact mesial roots were selected. Endodontic access was achieved. Hyflex CM file (Coltene), One Shape file (Micromega), Twisted File (TF; SybronEndo, Orange, CA), One endo file (Nano endo), ProTaper Next file (Dentsply Maillefer), Reciproc file (VDW) and SAFs were used to prepare the samples, leaving ten teeth unprepared which served as control. Sectioning of the prepared samples were carried out perpendicular to their long axes at 9, 6 and 3 mm. Under 40X magnification of a stereomicroscope, digital images of each section were recorded with the aid of a digital camera. Examination of each specimen was carried out by two operators to verify the presence of dentinal defects/microcracks. The statistical analysis was done by Chi-square test. Results: Except the control group, all the remaining groups recorded the presence of dentinal defects. The incidence of cracks was highest in One Endo (40%) followed by One Shape, Twisted (30%), Protaper Next (23.33%), Reciproc (10%), Hyflex (6.6%), SAF (3.3%) and control (0%). A significant difference was found for the cracks in coronal section between the file systems (p=0.0001). Conclusion: Usage of nickel titanium rotary instruments leads to the formation of microcracks or craze lines in root dentine. Instruments which have Matellurgical (M) wire or Controlled Memory (CM) wire in their metallurgy result in fewer formations of micro-cracks. When compared to multiple rotary files system, a reciprocating file led to the induction of lesser number of radicular cracks. SAF creates minimal cracks as compared to other file systems.

Comparative evaluation of the effect of hand file, different nickel-titanium retreatment files, and self-adjusting file system on the incidence of dentinal microcrack formation during the removal of root canal filling material: An in vitro stereomicroscopic study

Aim: The aim of the study is to evaluate the effect of hand files, rotary nickel-titanium files, and self-adjusting file (SAF) on the incidence of crack formation during retreatment. Materials and Methods: Eighty extracted human mandibular molar teeth with intact mesial roots were selected. They were divided into 8 groups of 10 teeth each; Group 1: Control, Group 2: Obturated control, Group 3: Hand files, Group 4: ProTaper Universal Retreatment, Group 5: Twisted File Adaptive, Group 6: Reciproc Blue, Group 7: XP-endo Finisher R, Group 8: SAF system. All teeth had the coronal portions and distal roots removed by a diamond-coated disc with water cooling, leaving roots approximately 13 mm in length. Except for Group 1, all canals were similarly instrumented and obturated at an apical size of 40.02. Retreatment was performed in each group according to manufacturer's recommendations except for Groups 1 and 2. The roots were sectioned horizontally at 3, 6, and 9 mm from the apex with a low-speed saw. Stereomicroscopic evaluation of the sections was done to assess the presence or absence of defects. Results: The groups that were not retreated (Groups 1 and 2) showed no defects. Hand files showed the least number of defects followed by the SAF. Reciproc Blue showed the most dentinal defects. Conclusion: All NiTi instruments tend to induce various degrees of dentinal damage during retreatment procedures. The SAF and hand instrumentation presented satisfactory results with minimal dentinal microcracks.

Micro-computed tomography assessment of dentinal microcracks after the preparation of curved root canals with rotary and reciprocal systems.

Root canal preparation with nickel-titanium (NiTi) instruments may lead to the formation of microcracks in the root canal wall. Vertical root fractures may initiate from dentinal cracks, and eventually necessitate tooth extraction. This study aimed to assess the effect of the instrumentation of curved root canals of mandibular molars with the 2Shape (2S) sequential rotary, EdgeFile® X1 (EFX1) reciprocating and NeoNiTi (NN) rotational single-file systems on the formation of dentinal microcracks with the use of micro-computed tomography (micro-CT). Thirty curved mandibular molar root canals were instrumented with the 2S, EFX1 and NN systems (10 in each group). The teeth underwent micro-CT before and after instrumentation. Next, the pre-instrumentation and post-instrumentation cross-sectional images were evaluated and compared for the detection of dentinal microcracks. The number of microcracks in each group was calculated and reported as percentage. The data was analyzed using the McNemar's test with the IBM SPSS Statistics for Windows software, v. 25.0 (α = 0.05). Out of the 29,280 cross-sectional images evaluated in this study, 11.5% showed dentinal microcracks (n = 3,362). On the post-instrumentation images, the frequency percentage of microcracks was 12.0% (n = 585) in the 2S group, 8.8% (n = 402) in the EFX1 group and 13.3% (n = 694) in the NN group. All of the microcracks detected on the post-instrumentation images were also present on the preinstrumentation images and no new microcracks were formed after root canal instrumentation with the aforementioned systems. Root canal instrumentation with the 2S, EFX1 and NN systems did not result in the formation of new dentinal microcracks.

Effectiveness of different fiber post removal techniques and their influence on dentinal microcrack formation

ObjectivesThe aim of this study was to evaluate the effectiveness of different fiber post removal techniques and to correlate dentinal loss with microcrack formation.Materials and methodsForty-five extracted single-rooted teeth were root canal treated and fiber posts were adhesively luted. Specimens were divided into three groups (n = 15) according to the removal technique: long-shaft round bur (EndoTracer #08, Komet, Lemgo, Germany), SonicFlex Endo (KaVo, Biberach, Germany), DT Post Removal Kit (VDW, Munich, Germany). Roots were scanned before post cementation and after post removal using micro-computed tomography. Dentin loss, residual luting material, working time, and the induction of microcracks were assessed. Statistical analysis was performed by using multiple contrast tests (max-t tests, α = 0.05). Correlations between parameters dentin loss/new microcracks and dentin loss/residual material were calculated using Kendall’s tau.ResultsPost removal with SonicFlex Endo resulted in the highest amount of removed dentin with significant differences to the round bur and the DT Post Removal Kit. No technique was found to completely remove the post and luting material. All techniques induced microcracks with the DT Post Removal Kit presenting the highest number of new defects. No correlation between dentin loss and new microcracks was observed. Deviations from the original root canal occurred in all groups, but no perforation was observed.ConclusionsAll techniques resulted in dentin loss, residual luting material, and the formation of microcracks. However, no correlation between dentin loss and the induction of microcracks was observed.Clinical relevanceAs all techniques resulted in microcrack formation and dentin loss, this study emphasizes the risk of iatrogenic damage due to post removal procedures.

A review on the effect of using rotary hyflex electrical discharge machining endodontic files on the formation of dentinal microcracks in straight root canals

Endodontic therapy is based on cleaning and shaping the canal system till the apex with total obturation of the canal. However, it is not always straightforward. Endodontics specialists face many complicated cases as sever curved canals, calcified canals and canals with previously initiated therapy which require to deal with. dental professionals pay attention to create new methods or to improve the already developed equipment and procedures to facilitate their work. Rotary endodontics files are in the center of attention. nowadays, recent files with extraordinary properties have been revolutionized. The standard Nickel Titanium rotary endodontic files are not always preferred. It cannot serve well in the aforementioned complex cases due to its larger tapers and unique shape memory property. Moreover, these files have led to several dentinal microcracks formation during canal preparation using the flaring instruments. Microcracks are evaluated through the accurately presented sliced images using Micro-Computer Tomography (micro-CT) done before and after root canal preparation. This has led to the invention of new generations of rotary endodontics files, with unique properties improving its behavior during the instrumentation, including Controlled Memory (CM) files and Electrical discharge Machine (EDM) files, opening the door for a new era in the field of endodontics dentistry. The present study aims to review HyFlex EDM files, including their properties, clinical dental usage, and the role of micro-CT in analyzing dentinal micro cracks formed with HyFlex EDM files.

Comparative Evaluation of Dentinal Microcrack Formation before and after Root Canal Preparation Using Rotary, Reciprocating, and Adaptive Instruments at Different Working Lengths—A Micro–computed Tomographic Study

IntroductionThis study aimed to compare root dentinal microcrack formation after root canal shaping using rotary, reciprocating, and adaptive instruments at different working lengths using micro–computed tomographic imaging. MethodsOne hundred eighty extracted mature mandibular molar mesial roots with 2 separate canals were selected. The mesial roots were resected at the cementoenamel junction and randomly divided into 4 groups (n = 45) based on the nickel-titanium file system used: ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland), ProTaper Gold (Dentsply Maillefer), Twisted File Adaptive (SybronEndo, Orange, CA), and Reciproc Blue (VDW, Munich, Germany). Each of the 4 groups were then subdivided into 3 groups (n = 15) depending on the working length used for root canal preparation (ie, instrumentation 1 mm short, flush, and 1 mm beyond the major apical foramen). The roots were imaged with micro–computed tomographic scanning before and after root canal preparation. The cross-sectional images generated were screened to detect the presence of new microcracks. ResultsThe ProTaper Universal system significantly increased the number of postinstrumentation microcracks at all working lengths (P ≤ .05). No significant increase (P > .05) in postinstrumentation microcracks was observed in the ProTaper Gold, Twisted File Adaptive, or Reciproc Blue groups. ConclusionsRotary instrumentation induced a higher number of dentinal microcracks compared with reciprocating and adaptive instruments. Instrumentation at different working lengths did not significantly influence the formation of dentinal microcracks.

Micro-computed tomographic assessment of dentinal microcrack formation in straight and curved root canals in extracted teeth prepared with hand, rotary and reciprocating instruments.

To compare microcrack formation in roots of extracted teeth after the shaping of straight and curved root canals with hand, rotary and reciprocating files using micro-computed tomographic (micro-CT) analysis. Thirty straight mandibular incisors and 30 severely curved mesial roots of mandibular molars were randomly divided into 6 experimental groups (n=10) according to the systems used for the root canal preparation and the root canal curvature: ProTaper Universal for Hand Use (Dentsply Sirona, Ballaigues, Switzerland), HyFlex EDM (Coltene-Whaledent, Altstätten, Switzerland) and Reciproc Blue (VDW, Munich, Germany) files used in mandibular incisors (straight canals) and mesial roots of mandibular molars (curved canals). The roots were imaged with micro-CT scanning at an isotropic resolution of 14μm before and after root canal preparation, and the cross-sectional images generated were assessed to detect microcracks. All dentinal defects identified after root canal preparation were already present before instrumentation, and no new microcracks were detected. Dentinal microcracks were present in 19% (ProTaper Universal for Hand Use), 11% (Hyflex EDM) and 23% (Reciproc Blue) of the cross-sections when the instrumentation was performed in mandibular incisors. Instrumentation of mandibular molars revealed microcracks in 15% (ProTaper Universal for Hand Use), 16% (Hyflex EDM) and 17% (Reciproc Blue) of the cross-sections. Preparation of straight and curved root canals with ProTaper Universal for Hand Use, HyFlex EDM and Reciproc Blue systems did not produce microcracks in extracted teeth when evaluated with micro-CT.

Influence of retreatment in the formation of dentinal microcracks in mandibular molars filled with a calcium silicate based sealer

Introduction: In endodontically treated teeth, dentinal defects such as microcracks can progress to a vertical root fracture and lead to tooth loss. Objective: The present study aimed to evaluate, by micro-computed tomography analysis, the formation of dentinal microcracks during filling removal in endodontic retreatment of root canals filled with gutta-percha and Total Fill BC bioceramic sealer. Methods: Twenty mesial roots of mandibular molars were instrumented and obturated with gutta-percha and Total Fill BC sealer and then the filling material was removed with rotary Protaper Retreatment files. The specimens were scanned before instrumentation, after filling and after retreatment. The transversal images obtained after filling were compared with the images obtained after removal of the filling material. A descriptive statistical analysis was performed. Results: Among the 24.444 cross-sections analyzed, 5.67% presented some type of dentinal defect, with 0.51% in the initial images, 2.58% in the post-filling images and 2.58% in the post-retreatment images. All the dentinal defects identified in the images obtained after the retreatment were already present in the corresponding images after the filling. New dentinal microcracks were not observed after removal of the filling material. Conclusion: Retreatment of mesial roots of mandibular molars filled with a silicate-based root canal filling material do not influence the formation of dentinal microcracks.

Stereomicroscopic Evaluation of Microcrack Formation in Dentin by ProTaper Next, Revo S, and WaveOne Gold File System.

Background:During the biomechanical preparation of the root canal by rotary file systems, stress is generated within the canal, which leads to dentinal microcrack formation. Such defects are evaluated only under the microscope.Aim:The present study aimed to evaluate dentinal microcrack formation after instrumentation with ProTaper Next (M-wire), Revo S (conventional NiTi), and WaveOne Gold (Gold-wire) file systems under the stereomicroscope.Materials and Methods:Forty single-rooted teeth free from any defect were selected and divided into four groups (Control, PTN, RS, and WOG). Experimental groups were instrumented with file system used in the study, and the control group were left unprepared. Samples were further decoronated and sectioned at 3 mm, 6 mm, and 9 mm from the apex perpendicular to the long axis and examined under a stereomicroscope at ×25 for different types of microcracks (no fracture, complete fracture, partial fracture, and other fracture).Statistical Analysis Used:Data analysis was done by the Chi-square test using the SPSS version 17.0 software. A two-sided (α = 2) P < 0.05 (P < 0.05) was considered statistically significant.Results:The null hypothesis was rejected. There was a statistically significant difference between the groups. All file systems created microcracks in the root dentin. WOG group showed an incidence of 66.7% for no fracture, PTN group had 40% for other fracture, and RS group had 60% for complete fracture.Conclusion:Single file system WOG with gold wire technology proves to be the best choice for canal preparation among the tested groups in terms of least dentinal crack formation.

Micro–computed Tomographic Evaluation of Dentinal Microcracks after Preparation of Curved Root Canals with ProTaper Gold, WaveOne Gold, and ProTaper Next Instruments

IntroductionThe aim of this study was to evaluate the influence of rotary (ProTaper Next [PTN; Dentsply Maillefer, Ballaigues, Switzerland] and ProTaper Gold [PTG, Dentsply Maillefer]) and reciprocating (WaveOne Gold [WOG, Dentsply Maillefer]) systems in dentinal microcrack generation after the preparation of curved root canals using micro–computed tomographic analysis. MethodsTwenty-four human mandibular molars with curved roots were scanned in a micro–computed tomographic device using an isotropic resolution of 6.78 μm and randomly assigned into 1 of 3 experimental groups (n = 8) according to the root canal instrumentation system used (PTN, PTG, or WOG). Then, the root canals were prepared up to PTN X2, PTG F2, and WOG Primary instruments in the PTN, PTG, and WOG groups, respectively. After canal preparation, each specimen was scanned again. Pre- and postoperative cross-sectional images of the roots (N = 35,304) were analyzed to identify the presence of dentinal microcracks. ResultsOverall, 26% of the images presented dentinal defects (n = 9188). Dentinal microcracks were observed in 24.6%, 26%, and 27.4% of the postinstrumentation images from the PTN, PTG, and WOG groups, respectively. However, all of these dentinal microcracks were already present in the corresponding preoperative images. No new microcracks were generated after the preparation of curved root canals of mandibular molars using the aforementioned systems. ConclusionsRoot canal instrumentation with PTN, PTG, and WOG systems did not induce the formation of new dentinal microcracks.