Evaluation of Pain Following the Use of Different Single-file Glide Path Systems: A Randomized Clinical Trial.

INTRODUCTION: This study aimed to evaluate postoperative pain intensity following glide-path preparation using the ProGlider (PG) and WaveOne Gold Glider (WOGG) systems in asymptomatic teeth with necrotic pulp and periapical lesions. METHODS: In this randomized clinical trial (ClinicalTrials.gov ID: NCT05955742) maxillary and mandibular molars with asymptomatic apical periodontitis of 78 patients (age, 18-65 years) were included. The patients were randomly divided into 3 groups: control (n = 26), PG (n = 26), and WOGG (n = 26). All the systems were used according to the manufacturer's instructions, and all the root canal treatments were completed by a single operator within 2 sessions. Postoperative pain was assessed using a numerical rating scale at 6, 12, 18, 24, 48, and 72 hours. Analgesics administered and abscess formation were also recorded. Statistical analyses were performed using the Mann-Whitney U, Bonferroni Dunn, Friedman, Chi-square, and Fisher exact tests. RESULTS: The postoperative pain at 12 and 18 hours was lower in the WOGG group than in the other groups (P < .05). The postoperative pain scores at 6 and 24 hours were higher among women than among men (P < .05). The highest postoperative pain scores were observed at 6 hours (P < .05). CONCLUSIONS: The WOGG glide-path file system was associated with less postoperative pain than the other systems. Abscess formation and analgesic use were higher in the PG group than in the other groups. Postoperative pain was greater in women than in men.

[Comparison of dentinal microcracks caused by new generation of single reciprocating files after root canal preparation].

PURPOSE: To compare the incidence of dentinal microcracks after root canal preparation by new generation of nickel-titanium instrument WaveOne Gold, Reciproc Blue with previous WaveOne and Reciproc. METHODS: Ninety extracted single-rooted mandibular premolars were randomly divided into 6 groups(n=15). The root canals were instrumented by using Hand K files, WaveOne, Reciproc, WaveOne Gold and Reciproc Blue. Fifteen teeth were left unprepared and served as negative controls. The root canals were all prepared to 25#. The roots were then sectioned at 3 mm, 6 mm and 9 mm from the apical orifice using a hard tissue slicer. The slices were observed under stereoscopic microscope at ×25 magnification. SPSS 17.0 software package was used for statistical analysis. RESULTS: No dentinal microcrack was found in the hand K files group and negative control group. The reciprocating single files WaveOne, WaveOne Gold, Reciproc and Reciproc Blue all produced dentinal microcracks after root canal preparation. The WaveOne generated the most dentinal microcracks than the hand K files(P＜0.05), and the microcracks were mainly concentrated in the middle part of the root. The number of dentinal microcracks caused by Reciproc and Reciproc Blue was the same, with no significant difference(P＞0.05). CONCLUSIONS: The new generation of reciprocating files of WaveOne Gold and Reciproc Blue may not increase the incidence of dentinal microcracks after root canal preparation.

Effect of EDDY and manual dynamic activation techniques on postoperative pain in non-surgical retreatment: a randomized controlled trial.

BACKGROUND: During non-surgical retreatment process, the products such as dentin debris, root canal fillings, irrigation solutions, microorganisms and remaining pulp tissues can extrude to the apical area and can cause the postoperative pain and flare-up. Thus, the aim of this study was to evaluatethe effect of EDDY and manual dynamic activation (MDA) techniques on postoperative pain (PP) associated with retreatment. METHODS: Ninety patients scheduled for retreatment were treated at a single visit. Non-vital mandibular premolar teeth diagnosed with asymptomatic apical periodontitis were included in this study. The patients were divided into two groups (n = 45) on the basis of the need for additional irrigation activation procedures (EDDY and MDA). The patients' post-treatment pain levels were asked to rate the intensity of their pain on a 10-point numerical rating scale (NRS) at the 12th, 24th, 48th, and 72nd h and 7 days.The data were analyzed using the chi-square and Wilcoxon signed-rank test was used for within-group comparisons and Mann Whitney U test was used to compare the groups by time period. RESULTS: The difference in postoperative pain intensity between two groups was statistically significant at 12, 24, 48, and 72 h (p < 0.05). There was no significant difference at 7 days. Moreover, no statistically significant difference was found between the two groups in terms of gender and analgesic medication intake (p > 0.05). Pain intensity after the treatment was lesser in the MDA groupthanin the EDDY group at 12, 24, 48, and 72 h. CONCLUSION: This study could lead us to conclude that the two activation systems can be used during endodontic retreatment with no difference at PP 7 days later. However, a comparison of the groups indicated that the EDDY resulted in significantly more PP at 12, 24, 48, and 72 h. Trial registration ClinicalTrials.gov Identifier: NCT04726670.

Evaluation of irrigant extrusion following the use of different root canal irrigation techniques: A systematic review and meta-analysis.

This systematic review investigates whether different irrigation techniques have different effects on irrigant extrusion from mature tooth apices. Articles published between January 2000 and January 2022 were searched in six electronic databases (MEDLINE, Embase, Google Scholar, Web of Science, Scopus and Cochrane) using appropriate keywords. Overall, 2265 articles were screened by their titles and abstracts. Fifty-six full-text articles were selected based on the inclusion criteria. Of them, 17 in vitro studies were included in the systematic review and meta-analysis. The meta-analysis was conducted using the random-effects inverse variance method. The results showed that the negative pressure technique caused a lesser amount (p = 0.00) and frequency (p = 0.00) of extrusion than the open-ended needle irrigation. Sonic and ultrasonic activation caused less amount of extrusion than both open-ended (p = 0.00 or p = 0.01) and closed-ended needle (p = 0.00) irrigation.

Micro-computed tomographic evaluation of endodontic ledge position in relation to canal curvatures.

BACKGROUND: Endodontic ledge (EL) formation is the most common complication of endodontic treatment. Although various etiological factors have been identified, canal curvature is the most significant variable correlated with EL formation. The aim of this micro-computed tomographic (micro-CT) study was to evaluate EL position in the mesial canals of the lower molars in relation to the degree of canal curvature. METHODS: Forty intact mandibular first molars with independent mesial canals with 20°-40° primary mesio-distal curvature, 10°-30° buccal-lingual canal curvature and 4 < r ≤ 8 mm main curvature radius were selected. Working length was measured with a K-File #10 and a high resolution pre-operative micro-CT analysis was performed. Ledges were created at the point of maximum canal curvature using stainless steel K-Files #30-35, alternating irrigation with 5% NaOCl and 10% EDTA. A post-operative high-resolution micro-CT analysis was then completed. Pre- and post-operative images were analyzed. The angle (α) formed between the vector passing through the geometric center of the EL and the center of the original canal lumen and the line joining the centers of the mesio-buccal and mesio-lingual canal orifices was calculated, and a descriptive statistical analysis was achieved. The α angle values were analyzed in relation to canal curvature using Kruskal-Wallis and post hoc Dunn's tests. The level of significance was set at P < 0.05. RESULTS: The α angles appeared inversely proportional to canal curvatures in the buccal-lingual and mesio-distal projections. The mean α angle was 36.4° (standard deviation 10.64; 95% confidence interval 34.1-40.9). CONCLUSION: Within the limitations of this study, endodontic ledges develop in the opposite direction to the three-dimensional canal curvature and their position is influenced by the degree of curvature. Clinically, the α angle values may be related to the recommended direction to manage endodontic ledges.

EDTA Combined with C-Pilot Files and Microultrasound for Root Canal Calcification: Dredging Effect and Safety Analysis.

Objective: This paper discussed the dredging effect and safety of ethylenediaminetetraacetic acid (EDTA) combined with C-pilot files and microultrasound (mUS) on root canal calcification. Methods: From October 2021 to January 2022, 132 patients with calcified root canals treated in our hospital were selected as the research subjects. Among them, 64 cases who received EDTA combined with C-pilot Files and mUS plus ultrasonic instruments to dredge calcified root canals were regarded as the research group (RG), and another 68 cases given ultrasonic instruments plus C-pilot files were regarded as the control group (CG). The root canal dredging time was recorded, and the dredging success rate and total success rate of different tooth positions and calcification sites were compared between groups. The clinical efficacy was assessed 6 months after treatment. Pain severity was evaluated by the Pain Intensity Numerical Rating Scale (PI-NRS) before (T0), during (T1), and after treatment (T2). Finally, the incidence of adverse reactions within one week after treatment was counted. Results: RG was observed with statistically higher success rates of root canal dredging in different tooth positions and calcified sites than CG (P < 0.05). Besides, the total effective rate of treatment was 92.19% in RG, which was also higher compared with CG, while the root canal dredging time in RG was shorter than that in CG (P < 0.05). Increased NRS scores were found in both groups at T1, and the score in RG was significantly lower compared with that in CG. At T2, both groups showed a lower PI-NRS score than T1 but higher than T0, and the score at T2 was also lower in RG as compared to CG (P < 0.05). Moreover, the reduced incidence of adverse reactions were observed in RG compared with CG (P < 0.05). Conclusions: EDTA combined with C-pilot files and mUS can effectively improve the dredging success rate of root canals obstructed by calcification, shorten the dredging time, and improve patient comfort, which is an effective method for clinical dredging of calcification obstructed root canals.

Comparative Evaluation of Potential Dentinal Microcracks Related to Instrumentation alongside Bypassed Broken Instruments: An In Vitro Study.

AIM AND OBJECTIVE: To investigate the occurrence of microcracks in the canals containing broken instruments in the middle and apical thirds after instrumentation with various systems. MATERIALS AND METHODS: One-hundred and fifty mature mandibular premolars with single straight canal were collected and stored in distilled water. Samples were checked out from any preexisting deformation or cracks, and then standardized in length. Thirty teeth were never instrumented (NI) as a control group, 60 teeth have received a broken instrument in the middle third, and 60 ones at the apical third. Teeth were placed in resin blocks with simulation of periodontal ligaments. After bypassing the instruments, samples were divided into four groups n = 30; first group was prepared manually MN until 25/0.02, while the other three groups were prepared until 25/0.04 using three different rotary systems; Race RC-2Shape TS-Hyflex CM HCM. Roots were cut transversely at levels of broken instruments and examined under 40× microscopic magnification. RESULTS: All the rotary groups produced microcracks. No significant difference of the partial cracks was observed among all groups at the middle and apical levels p >0.05. TS produced more complete cracks compared to each of NI, MN, RC at middle level and NI, MN at apical level; p <0.05. No significant differences of microcracks incidence were observed between two middle and apical levels among the five groups. CONCLUSION: Dentinal microcracks could be obviously resulted after rotary instrumentation alongside broken instruments, while manual shaping was less likely to cause microcracks. CLINICAL SIGNIFICANCE: Manual files were less likely to induce microcracks alongside broken instruments in comparison with rotary files which could be considered much safer.

The frequency of sodium hypochlorite extrusion during root canal treatment: an observational clinical study.

BACKGROUND: To determine the frequency of sodium hypochlorite (NaOCl) extrusion and evaluate the outcome of the injury. METHODS: A total of 1123 teeth indicated root canal treatment were included. An open-ended needle was used during/after the instrumentation. Acute burning pain during irrigation was considered as NaOCl extrusion. Negative aspiration was applied for patients with extrusion, and appropriate treatment was planned due to the symptoms. The number of patients who experienced extrusion and symptoms were recorded. Analysis of variance (ANOVA), at P < 0.05, was used to compare the data groups. RESULTS: NaOCl extrusion rate was found at 0.89%, and the injury with swelling that differential diagnosis of NaOCl accident caused by extrusion rate was 0.18%. The most common findings besides acute pain, as a sign of extrusion (n = 10), were accompanying apical bleeding (n = 6) and swelling (n = 2). According to the number of visits, a significant correlation was found between the symptoms (P = 0.010). No serious injury such as a neurological sign, tissue necrosis or trismus occurred in any patient. CONCLUSIONS: Demographic characteristics of the patients and preoperative condition of teeth were not related to NaOCl extrusion. The increasing number of visits may affect the probability of an accident. Negative aspiration immediately may be crucial in preventing severe injuries.

[Study on the influence of passive ultrasonic irrigation on debris cleaning ability and root canal shape].

PURPOSE: To evaluate the safety and effectiveness of passive ultrasonic irrigation(PUI) in curved root canals, and debris cleaning ability and the amount of root canal transportation of passive ultrasonic irrigation(PUI) in curved root canals. METHODS: A total of 36 mesially curved root canals of mandibular molars with a curvature above 25° were selected. The root canals were prepared with XP-endo Shaper root canal file. The samples were divided into A1 group (curved length＞3 mm, syringe irrigation), B1 group(curved length＞3 mm, PUI+K file), C1 group(curved length＞3 mm, PUI+irrisafe), A2 group (curved length＜3 mm, syringe irrigation), B2 group (curved length＜3 mm, PUI+K file), and C2 group (curved length＜3 mm, PUI+ irrisafe) (n=6). Micro-CT scans were performed on all samples before and after irrigation, and the volume increase in the root canal after irrigation and the transportation of the root canal were calculated. SPSS 22.0 software package was used to analyze the data. RESULTS: In the apical area of the root canal with a curved length greater than 3 mm, the root canal volume increase in the PUI+irrisafe group was significantly greater than that of the PUI+K file and syringe irrigation (P＜0.05), and at 5 mm section, the transportation of the root canal formed by PUI+irrisafe was significantly lower than that of the PUI+K file (P＜0.05), but there was no significant difference from syringe irrigation (P＞0.05); in root canals with a curved length less than 3 mm, root canal volume increment of the file group was significantly greater than that of syringe irrigation (P＜0.05), but there was no significant difference between the root canal transportation and syringe irrigation(P＜0.05). CONCLUSIONS: In root canals with larger curved length, passive ultrasonic irrigation combined with a pre-curved file can obtain a better cleaning effect, while in root canals with smaller curved length, both K file and pre-curved file with passive ultrasonic irrigation are safe and effective.

Instrumentation kinematics does not affect bacterial reduction, post-operative pain, and flare-ups: A randomized clinical trial.

AIM: This randomized clinical trial aimed to assess the effect of instrumentation kinematics (reciprocation or continuous rotation) on bacterial reduction, post-operative pain, and incidence of flare-ups after root canal treatment of single-rooted mandibular premolars with asymptomatic apical periodontitis. METHODOLOGY: Sixty-six patients were included in this prospective, parallel, randomized clinical trial. Patients were randomly allocated into two groups (N = 33) according to the kinematics of the shaping instrument: WaveOne Gold (WO) used in reciprocation or One Shape (OS) used in continuous rotation. Under complete asepsis, bacterial samples were taken before (S1) and after (S2) a standard cleaning and shaping protocol. Evaluation of bacterial reduction was done by both culture technique and quantitative real-time polymerase chain reaction (qPCR) analysis. Post-operative pain was evaluated using the visual analogue scale (VAS) after 24, 48, and 72 h following treatment, while flare-ups were recorded as a binary outcome (Yes/No). Independent and paired t-tests were used for inter- and intra-group comparisons for bacterial count data, respectively. For post-operative pain score, inter-group comparisons were analyzed using the Mann-Whitney U-test while intra-group comparisons were analyzed using Friedman test followed by pairwise comparisons utilizing the Wilcoxon signed rank test with Bonferroni correction. The significance level was set at p ≤ .05 within all tests. RESULTS: All the allocated participants received the intervention and were analysed. The comparison between culture and qPCR methods showed that qPCR analysis demonstrated significantly higher pre-instrumentation baseline bacterial count (p < .05). The percentage of bacterial reduction, detected by either method, significantly decreased after instrumentation using either rotation or reciprocation kinematics (p < .05). However, the difference between the WOG or OS files was statistically non-significant (p > .05). The intra-group comparisons showed a significant reduction in post-operative pain with time (p < .05) for both groups. However, the inter-group comparison demonstrated that the difference in post-operative pain after the use of either WOG or OS was statistically non-significant (p > .05). The incidence of flare-ups between both groups was also not-significant (p = 1). CONCLUSIONS: Shaping kinematics, either rotation or reciprocation motions, had no impact on bacterial reduction and the incidence of post-operative pain and flare-ups after root canal preparation of single-rooted premolars with asymptomatic apical periodontitis.

Dentinal microcracks and cemental tears related to chemo-mechanical root canal instrumentation: a micro-CT Cadaver Study.

BACKGROUND: The prevalence of radicular defects after root canal instrumentation is unresolved. This study used micro-CT to assess the relationship between the formation of radicular defects and chemo-mechanical instrumentation in a cadaver model. METHODS: Maxillary and mandibular molars (n = 24) were sectioned from cadaver specimens as a tissue block containing the teeth, alveolar bone and attached mucogingival tissues. After a baseline micro-CT scan (13.45 µm), the specimens were distributed into 3 groups (n = 8 molars): Reciproc® , ProTaper Next™ and Mtwo® . Micro-CT scans of each specimen were obtained after access, glide path and preparation with each instrument. The pre-operative and final post-operative micro-CT cross-sectional images of the roots were screened by two blinded examiners to identify any pre-existing and new radicular defects. Pre-existing and new radicular defects were examined histologically. RESULTS: Overall, 16 pre-existing radicular defects were identified in 12 of the 24 molars (50%). Most of these were cemental tears (87.5%), and not true dentinal microcracks. New dentinal microcracks were observed in the post-operative micro-CT scans of only 3 canals (3.9%; 3/77). However, only one of these defects was found to be present histologically. CONCLUSIONS: Within the limitations of the study, chemo-mechanical instrumentation did not routinely promote the formation of radicular defects.

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

BACKGROUND: 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. OBJECTIVES: 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). MATERIAL AND METHODS: 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). RESULTS: 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. CONCLUSIONS: Root canal instrumentation with the 2S, EFX1 and NN systems did not result in the formation of new dentinal microcracks.

Factors influencing incidents of complications while using nickel-titanium rotary instruments for root canal treatment.

BACKGROUND: To investigate the complications associated with the use of nickel titanium rotary instruments (NiTi-RIs) for root canal treatments (RCTs), in Saudi Arabia dental practice, and to explore the influencing factors. METHODS: After obtaining an ethical approval, two pilot studies were conducted to formulate the final questionnaire. The sample size was measured taking into consideration 60% expected response rates and confidence level of 99.9%. The questionnaire was emailed to 600 general dentists (GDs) randomly selected from the dental register and all of the endodontists (175). The email's introduction clarified objectives of the study and guaranteed that all of the collected information would remain confidential. A reminder was sent after 10 weeks. The data were collected and analyzed using the chi-squared test at a 0.05 significance level. RESULTS: With a 51% overall response rate, 71.9% off the respondents used NiTi-RIs. The majority (83.1%) experienced complications while using NiTi-RIs; with the instruments' fracture being significantly the most common complication (52.7%) (p < 0.001). The majority (87.7%) experienced NiTi-RIs' fracture at least once; with more endodontists (94.3%) than GDs (83.3%) (p < 0.001). The greater the number of weekly performed RCTs and participants' experiences, the more NiTi-RIs fractures and the greater the number of fracture incidents (p < 0.001). While 60% of those who performed 1-3 RCTs per week experienced NiTi-RIs fractures, 100% of those who performed more than 12 RCTs per week did so. The highest percentage of those who experienced more than 10 fractured NiTi-RIs (60%) was within the group who performed more than 12 RCTs per week. Although fracture incidents decreased with a smaller number of reuses, there was no significant correlation between the number of fractured instruments and NiTi-RIs discard strategy (p ≥ 0.05). CONCLUSION: Fracture incidence was the most common complication while using NiTi-RIs, regardless of the clinicians' experiences and skills. While the single use may reduce NiTi-RIs fractures, to some extent, the greater number of RCTs performed per week was the most influential factor.

[Complications occurred in root canal mechanical preparation: the reason, prevention and management].

Root canal preparation is one of the important procedures in root canal treatment as well as one of the key factors to the success of root canal treatment. It consists root canal cleaning and shaping, and further provides a favourable condition for root canal obturation. Because of the complexity and irregularity of root canal system, complications may occur during the root canal mechanical preparation, such as root canal ledges, transportations, perforations, instruments separating and flare ups. Understanding the reason and management of root canal mechanical preparation complications is helpful to prevent its occurrence and to reduce the unfavourable prognosis as well. This article discusses and systematically analyzes the reason, prevention and management of the complications in root canal mechanical preparation, in order to enhance the awareness of clinicians on these complications.

Quantitative evaluation of debris extruded apically using reciprocating versus continuous rotation single file with rotary and hand glide path file

Chemomechanical root canal preparation (CMRCP) is an important step in root canal treatment. However, one of its negative consequences is apical extrusion of debris of the root canal system contributing to treatment failure and flare-ups. Glide path preparation (GPP) is the initial phase of CMRCP and is crucial for assessing root canal anatomy and establishing unobstructed access to the apical part of the canal. Materials and methods: Forty human mandibular permanent central and lateral incisors were selected; the debris collection apparatus was prepared and the teeth were then divided into four groups: Group 1: Rotary glide path preparation with ProGlider followed by instrumentation with Wave One files. Group 2: Rotary glide path preparation with ProGlider followed by instrumentation with One Shape files. Group 3: Hand glide path preparation with K-file followed by instrumentation with Wave One files. Group 4: Hand glide path preparation with K-file followed by instrumentation with One Shape files. The collected debris was weighed in an analytical digital balance and the collected data were statistically analyzed. Results: No significant difference was present between groups with the same method of glide path preparation or between Wave One and One Shape files. Rotary glide path preparation produced less debris than hand preparation (p≤0.05). Conclusions: Extrusion of debris was observed in all test groups. Rotary glide path preparation could be preferred in clinical practice as it is associated with less debris extrusion than the manual method.

Comparison of microcomputed tomography, cone beam tomography, stereomicroscopy, and scanning electron microscopy techniques for detection of microcracks on root dentin and effect of different apical sizes on microcrack formation.

The aim of the study was to compare different imaging methods in the diagnosis of microcracks on root dentin and to evaluate the frequency of dentinal microcracks observed after root canal preparation using the ProTaper Universal (PTU) system of different sizes. A total of 30 mandibular molars' mesial roots were scanned with microcomputed tomography (micro-CT) and cone beam computed tomography (CBCT) imaging methods before instrumentation. Root canal instrumentation was performed up to PTU F2 and F4 files. After instrumentation stages, the roots were scanned again with micro-CT and then with CBCT in same parameters. All roots were sectioned horizontally at 2, 4, 6, 8, and 10 mm from the apices of the specimens. The sections were imaged under a stereomicroscope. Finally, imaging of the sections was done by scanning electron microscopy (SEM). Statistical data analysis of instrumentation steps was performed using Friedman and Wilcoxon tests, and the data of imaging methods were analyzed using Kruskal-Wallis and Mann-Whitney U tests (p = .05). Instrumentation with the PTU system up to F2 and F4 files significantly increased the number of microcracks compared with preoperative samples according to micro-CT imaging (p < .05). For detecting microcracks on the root dentin, there were no statistically significant differences between micro-CT (43.9%) and stereomicroscopy (45.8%) (p < .05). SEM showed significantly higher percentage of microcracks (88.3%) (p > .05). No microcrack was observed using the CBCT method. There were no statistically differences between micro-CT and stereomicroscopy. SEM showed more dentinal microcracks while no microcrack was observed with CBCT.

Force and vibration generated in apical direction by three endodontic files of different kinematics during simulated canal preparation: An in vitro analytical study.

During root canal shaping, pain could result from the high level of force or vibration generated. This could be related to file kinematics or geometry. In the present study, a comparison is made between forces and vibrations generated by endodontic files having three different kinematics. Square pillar resin blocks were used as simulated root canals to study forces and vibrations generated by the file having reciprocating motion (WaveOne Gold), transline motion (Self-Adjusting File), and rotary motion (2Shape). The forces and vibrations were measured using the dynamometer and accelerometer, respectively. Recorded time domain signals were processed in MATLAB to calculate the root mean square value. A one-way analysis of variance and Tukey's test for post hoc comparison at 95% confidence interval were applied over the root mean square data of different files. From a statistical analysis of the file systems, the null hypotheses could not be accepted (P < 0.05) as 95% of the confidence interval. Differences between the means were statistically significant. The root mean square values of force and vibration for WaveOne Gold significantly exceeded those of Self-Adjusting File, 2Shape1, and 2Shape2 while the root mean square values of vibration for 2Shape1 and 2Shape2 were significantly less than the Self-Adjusting File; however, the root mean square value of force for the 2Shape2 was significantly more than for the Self-Adjusting File. Under the present experimental conditions, significant differences in the root mean square values of force and vibration of the three endodontic files of different kinematics have been observed. The WaveOne Gold file system generated higher apical force and vibration than the transline and rotary file system.

Effect of Root Canal Preparation Techniques on Crack Formation in Root Dentin.

INTRODUCTION: The aim of this study was to assess the frequency of root crack formation caused by the use of manual instrumentation, 2 rotary systems, and 1 reciprocating system using light-emitting diode transillumination. METHODS: One hundred fifty mandibular premolars were randomly divided into 5 groups (n = 30): control 1, no intervention; control 2, instrumented with hand files; group 3, instrumented with ProTaper Universal rotary files (Dentsply Maillefer, Ballaigues, Switzerland); group 4, instrumented with OneShape rotary files (Micro-Mega, Besancon, France); and group 5: instrumented with the WaveOne reciprocal system (Dentsply Maillefer, Ballaigues, Switzerland). After root canal preparations, the roots were sectioned at 3, 6, and 9 mm from the apex with water irrigation. The slices were inspected under a stereomicroscope with light-emitting diode transillumination from the buccal, lingual, mesial, and distal directions at ×40 magnification to determine the presence/absence of cracks (dentinal defects). The chi-square test was used to analyze the data. RESULTS: There was a significant difference among the groups in crack frequency (P < .05). The 2 single systems had significantly higher cracks than the other 3 groups. At 3 mm from the apex, there were significantly more cracks in groups 4 and 5 than in groups 1, 2, and 3 (P < .05). At 6 mm from the apex, no significant difference was noted (P > .05). At 9 mm from the apex, the frequency of cracks in group 3 was significantly higher (P < .05). CONCLUSIONS: According to the results, using rotary instrumentation can result in some dentinal defects, and single-file systems, regardless of motion type, can cause significantly higher crack formation in the apical third of root canals.

Effect of Reciproc blue, XP-endo shaper, and WaveOne gold instruments on dentinal microcrack formation: A micro-computed tomographic evaluation.

The purpose of this study was to evaluate and compare the effect of Reciproc Blue (RPCB), XP-endo Shaper (XPS), and WaveOne Gold (WOG) single-files on dentinal microcrack formation using micro-computed tomography (micro-CT). Twenty-four mesial roots (24 mesio-buccal and 24 mesio-lingual canals) of mandibular molar teeth were prepared using RPCB, XPS, and WOG files (n = 8/each group). The samples were scanned with micro-CT in the pre- and post-preparation. Then, before preparation and after preparation cross-sectional images of the teeth were evaluated to detect the presence of microcracks. For each group, the number of microcracks was calculated as a percentage rate. The data were statistically analyzed using McNemar at 5% significance level (p < .05). Dentinal microcracks were observed in 25.99% (2,103 of 7,813), 31.99% (2,482 of 7,758), and 36.66% (2,836 of 7,731) of cross-sectional images of the XPS, WOG, and RPCB groups, respectively. In all the groups, all the dentinal microcracks seen in the post-treatment cross-sectional images were present in the corresponding pre-treatment images. Within the limitations of this study, the XPS, WOG, and RPCB files did not cause new dentinal microcrack formation or propagation of existing dentinal microcracks.

Evaluation of XP-endo Shaper, Reciproc Blue, and ProTaper Universal NiTi Systems on Dentinal Microcrack Formation Using Micro-Computed Tomography.

INTRODUCTION: The purpose of the present study was to evaluate the frequency of dentinal microcracks observed after root canal preparation with XP-endo Shaper (XP), Reciproc Blue (RB), and ProTaper Universal (PTU) instruments using micro-computed tomographic (µCT) analysis. METHODS: Thirty extracted mandibular first and second molars with mesial roots having 2 separate canals with an angle between 10°and 20° were randomly assigned to 3 experimental groups (n = 10) according to the different nickel-titanium systems used for root canal preparation: XP, RB, and PTU. The specimens were scanned using µCT imaging before and after root canal preparation. Then, preoperative and postoperative cross-sectional images of the teeth were evaluated to identify the presence of dentinal defects. For each group, the number of microcracks was determined as a percentage rate. The McNemar test was used to determine significant differences before and after instrumentation. The level of significance was set at P ≤ .05. RESULTS: No new dentinal microcracks were observed in the XP and RB groups. The PTU system significantly increased the percentage rate of microcracks compared with preoperative specimens (P < .05). CONCLUSIONS: Root canal preparations with XP and RB systems might not induce the formation of new dentinal microcracks on the mesial roots of mandibular molars. Further assessments are suggested for the examination of the morphology of microcracks after the use of these instruments.