Canal Instrumentation Research Articles

The effects of different root canal instrumentation techniques on dentinal microcracks formation: A narrative review

Introduction: The influence of intracanal instrumentation technique on microcrack formation is a debatable subject. This review aimed to review the effect of different root canal instrumentation techniques (hand, continuous rotary, reciprocal rotary, adaptive, and self-adjusting file techniques) on microcracks formation and evaluate whether the incidence of cracks formation differs between destructive and nondestructive evaluation methods.Materials and Methods: All in vitro studies comparing the influence of at least two different instrumentation techniques were searched for this narrative review in PubMed, Scopus, and Google Scholar databases. The search included articles that were published from 2016 to 2020. The search was carried out by six independent reviewers in this review.Results: A total of twenty-five (n = 25) articles met the eligibility criteria. Only six studies showed the absence of new cracks development in 320 human teeth according to the instrumentation technique while the majority of the studies (n = 19) illustrated the presence of new cracks development in 1696 teeth. The results of this review showed that nondestructive methods may be less likely to cause microcracks than destructive methods.Conclusions: The number of dentinal microcracks varies depending on the type of instrumentation techniques and evaluation methods used. Therefore, in destructive evaluation methods, root canal instrumentation with hand, reciprocating, rotary, adaptive, and self-adjusting systems resulted in the development of more new dentinal microcracks than nondestructive methods.

Determination of clinical efficiency of pediatric rotary file systems for root canal preparation in primary molars - A comparative study

Introduction: To meet the demand of pediatric endodontists, exclusive pediatric rotary file systems have been recently introduced by the manufactures. However, no study has been conducted to compare the clinical efficiency between pediatric rotary file systems. Aim: To determine the clinical efficiency (instrumentation time, obturation time, quality of obturation and postoperative pain) of two pediatric rotary file systems following the root canal preparation of primary molars. Materials and Methods: A total of 75 primary molars requiring pulpectomy were selected from children aged 4 to 7 years. These teeth were divided into three groups of 25 teeth each. In the first, second, and third groups, the cleaning and shaping of the root canals were carried out with Pedo-Flex pediatric rotary files (Group PF), Kedo-S pediatric rotary files (Group KS), and, manual nickel-titanium K-files (Group MF), respectively. Obturation was carried out with zinc oxide eugenol cement with an engine-driven Lentulo spiral. The instrumentation and obturation times were recorded. The quality of the root filling was radiographically assessed immediately after obturation. The postoperative pain was evaluated at time intervals of 6, 12, 24, 48, 72 h, and 1 week. Results and Discussion: The instrumentation and obturation times were significantly less with the use of pediatric rotary file systems compared to the manual file system. The quality of obturation was superior in the root canals instrumented with pediatric rotary file systems compared to manual files. There was decreased postoperative pain with the use of pediatric rotary file systems as compared to manual files. In all three groups, postoperative pain decreased over time. The optimally filled root canals showed a significant correlation with the absence of postoperative pain. Conclusions: The use of pediatric rotary file systems for root canal instrumentation of primary molars resulted in the superior quality of obturation in decreased instrumentation and obturating times with the least postoperative pain. The overfilled root canals were not associated with significant postoperative pain.

Dentinal microcracks induced by endodontic procedures: A scientometric and bibliometric analysis.

Background:Due to the large number of publications relating the occurrence of dental microcracks to endodontic procedures, this bibliometric study evaluated the scientific pattern and trends in literature and provided an overview of scientific production in this context.Aim:To analyze, quantify, and characterize the scientific production and trends of published articles evaluating dentinal microcracks formation after endodontic treatment procedures between 2010 and 2020 using bibliometric indicators.Materials and Methods:Published articles were found by the search in the Medline (PubMed) and Scopus database using the combination of the following keywords: Dentinal crack OR Dentinal Microcrack OR Crack formation OR Dentin Defect AND Endodontic treatment OR Root canal preparation OR Canal Preparation OR Root canal treatment OR endodontic procedures. The search was also conducted in the Journal of Endodontics and International Endodontic Journal. After inclusion and exclusion criteria application, data from all studies included were collected.Results:Among the 556 results after the search, 45 studies were included and analyzed in this bibliometry. No trend was observed in terms of the increasing number of articles over time. Most of them used an in vitro design, compared the effect of different endodontic techniques/systems for root canal instrumentation on dentinal microcracks formation, and were conducted in Turkey, Brazil, and India. Journal of Endodontics and International Endodontic Journal were the main journals with a higher number of articles published. Interestingly, studies conducted with some funding did not lead to higher citation numbers. Moreover, a relevant proportion of studies did not consider the inclusion of control groups, baseline evaluation, or statistical analysis. Micro-CT was the main technique used to evaluate microcrack presence.Conclusion:Microcrack formation after the use of different endodontic techniques/systems has been constantly evaluated in the literature. There is a pattern of methodologies used, which may explain the concentration of these studies in specific journals and countries.

Comparative evaluation of cutting efficiency, cyclic fatigue, corrosion resistance, and autoclave cycle effects of three different file systems: An in-vitro micro-CT and metallurgy analysis

Aim: To compare the cutting efficiency, cyclic fatigue, corrosion resistance, and autoclave cycle effects of ProTaper Gold, TruNatomy, and WaveOne Gold file systems. Materials and Methods: Thirty mesiobuccal roots of extracted maxillary first molars were randomly divided into three groups (10 specimens each) for testing cutting efficiency: Groups A, B, and C: ProTaper Gold, TruNatomy-Prime, and WaveOne Gold-Primary, respectively. Root canal instrumentation was carried out in each root accordingly. Specimens’ weights were measured and micro-computed tomography was used to scan the samples before and after root canal preparation. For cyclic-fatigue, corrosion-resistance, and autoclave-cycle-effects testing, 30 files were allocated into three groups at random, Groups A, B, and C: ProTaper Gold-F2, TruNatomy-Prime, and WaveOne Gold-Primary (10 specimens each). For cyclic-fatigue testing, the instruments were firmly held in a stainless steel block with an artificial canal without pressure. The time (s) was calculated until fracture. For the corrosion-resistance test, SEM surface-topographical analysis was carried out in response to 5.25% NaOCl, 2% CHX, and 17% EDTA. For evaluation of autoclave cycle effects, SEM surface-topographical analysis was carried out for 1, 5, and 10 autoclave cycles. Data were analyzed statistically using one-way analysis of variance followed by multiple comparisons with Bonferroni’s test at P<0.05. Results: TruNatomy was the most resistant to cyclic fatigue and ProTaper Gold the least. WaveOne Gold removed significantly more dentin and had the least corrosion resistance and highest autoclave cycle effects. Conclusion: TruNatomy can be considered as a better file system compared with WaveOne Gold and has comparable efficiency with that of ProTaper Gold.

Apical extrusion of debris with root canal instrumentation in primary teeth: A systematic review.

This study aimed to systematically review available literature of in vitro studies on apical extrusion of debris through rotary instrumentation in comparison to manual instrumentation in pediatric endodontics, and also to perform a comparison between various rotary instrumentation systems for assessment of debris extrusion. A comprehensive search was conducted on PubMed, Medline, Cochrane Library, Embase, Scopus, and Google Scholar without any language restriction and year of publication. A planned search strategy was made for PubMed and applied to other databases. After full-text reading, 7 articles were selected for quantitative synthesis. Modified CONSORT checklist of items for reporting in vitro studies of dental materials was used for quality assessment of included studies. Root canal preparation with rotary instrumentation led to lesser apical debris extrusion than manual instrumentation. Self-adjusting file system was associated with the least debris extrusion among all included studies, followed by ProTaper Next, Kedo-S, ProTaper, K3, Mtwo, Revo-S, and Wave One. More apical debris extrusion was seen with manual instrumentation than rotary instrumentation. Furtrhermore, variance in debris extrusion was seen with different rotary file systems.

An in vitro Investigation of the Sealing Ability of Biodentine and Mineral Trioxide Aggregate as Retrofilling Materials after the use of Various Irrigating Solutions.

Aim:The purpose of this study was to assess the sealing ability of Biodentine (BD) and mineral trioxide aggregate (MTA) as retrograde filling materials after irrigation with 17% ethylenediaminetetraacetic acid (EDTA) and QMix irrigating solutions.Materials and Methods:Decoronation of 48 permanent maxillary central incisors was done. Root canal instrumentation was carried out in the samples. The apical root was resected for about 3 mm and retrocavities were prepared. Teeth were allocated into two groups (n = 24). MTA was used in Group 1. BD was used in Group 2. Depending on irrigation, the groups were subdivided A, B, and C subgroups. Group A − 0.9% saline; Group B − 17% EDTA; and Group C − QMix were used. The resected root end was irrigated with 5 ml of all irrigating solutions for 1 min. After final irrigation, cavities were filled with retrofilling materials in each group. Nail enamel was applied to the surfaces of the roots apart from the resected end. Roots were placed in India ink for 72 h. Teeth were sectioned longitudinally and microleakage was determined with a stereomicroscope.Statistical Analysis:Analysis was done using the one-way analysis of variance, Independent t-test, and post hoc test.Results:Statistically significant difference in the degree of microleakage was observed between irrigating solutions and the retrofilling materials.Conclusion:BD exhibits a better sealing ability compared to MTA as a retro filling material following QMix irrigation.

Dentinal Defects Induced by Offset and Alternating Contact Endodontic Rotary Files: An In Vitro Study

Objective: Dentinal defects during root canal preparation could lead to treatment failure and tooth extraction. Many rotary files are manufactured with asymmetric cross sections or alternating cutting edges to minimize contact with the canal wall. Decreasing contacts may generate low stresses and, hence, fewer dental defects during root canal instrumentation. This study aimed to evaluate the incidence of dentinal defects induced by ProTaper Next, Wave One Gold (Dentsply Maillefer, Ballaigues, Switzerland), and iRace (FKG Dentaire SA, La Chaux-de-Fonds, Switzerland) in comparison to the symmetric file HyFlex CM (Coltene-Whaledent, Allstetten, Switzerland). Materials and Methods: Sixty extracted single-rooted premolars with round canals were selected for this study. All teeth were decoronated and divided into four experimental groups according to the tested file systems. In each group, 15 canals were prepared with the crown down technique using a speed and torque recommended by manufacturers. The root samples were then sectioned horizontally at 3, 6, and 9 mm from the apex and examined under a stereomicroscope to evaluate the presence or absence of dentinal defects. Data were statistically analyzed with SPSS software using a chi-square test. Results: Dentinal defects were observed at all canal levels following all methods of instrumentation. ProTaper Next showed the lowest values of dentinal defects, whereas Hyflex CM displayed the highest values. Conclusion: Files with few contacts with the canal wall decreased the number of dentinal defects compared to the HyFlex CM file, with a nonsignificant difference being observed.

Retrieving fragments: A case series on managing instrument separation

The advancements made in the field of endodontics are increasing every day. Introducing a broad spectrum of newer root canal instruments has been a boon to the endodontist. Nevertheless, inadequate knowledge about its correct usage has proved to be a bane in the real sense. With the availability of sufficient armamentarium, good management skills combined with an excellent clinical experience all together serve as the best possible combination in dealing with fractured instruments, which otherwise seem like a challenging task. The microbiological and biomechanical aspects are the deciding parameters during decision-making. Thus, the series of cases presented in this case report is about the successful retrieval of broken files from root canals using Masserann kits and ultrasonics.

Evaluation of centralization ability and canal transportation of root canals prepared with three commercially available pediatric rotary files.

The complex root canal anatomy of primary root canals is considered to be most challenging. The quality of the root canal preparation plays a significant role in the success of endodontic treatment. Now, there are very few root canal instruments that are capable of cleaning the canal three dimensionally. To evaluate the efficacy of root canal instruments, various technologies have been used; one of the most reliable strategies was cone-beam computed tomography (CBCT). The aim of this study is to compare the centralization ability and canal transportation of three commercially available pediatric rotary file systems using CBCT analysis. Thirty-three extracted human primary teeth with a minimum 7 mm root length were randomly divided into three groups (group I - Kedo-SG Blue, group II - Kedo-S Square, and group III - Pro AF Baby Gold). Biomechanical preparation was done according to the manufacturers instructions. Pre- and postinstrumentation CBCT images were taken for each group to evaluate the remaining dentin thickness thereby assessing the centering ability and the canal transportation ability of different file systems. Significant difference was noticed in canal transportation and centering ability between the three tested groups. Mesiodistal canal transportation was significant at all three levels, whereas buccolingual canal transportation was significant only at the apical third of the root. However, Kedo-SG Blue and Pro AF Baby Gold showed lesser canal transportation compared to Kedo-S Square rotary file system. Mesiodistal centering ability was significant at cervical and apical thirds of the root with Kedo-S Square rotary file system maintaining less canal centricity. All three file systems tested in the study were effective in removing the radicular dentin. However, Kedo-SG Blue and Pro AF Baby Gold rotary file systems showed comparatively less canal transportation and more centering ability than Kedo-S Square rotary file system.

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.

Comparison of three irrigation methods: SWEEPS, ultrasonic, and traditional irrigation, in smear layer and debris removal abilities in the root canal, beyond the fractured instrument.

Background. :This study compared the effectiveness of three irrigation methods in removing smear layer and debris in the presence of the fractured instrument. The three compared irrigation methods were conventional syringe irrigation, passive ultrasonic irrigation, and SWEEPS (Shock wave enhanced emission photoacoustic streaming) irrigation.Methods and materials: Sixty-three permanent mandibular molars with moderate curvature were included in this experimental study. Mesiobuccal root canals were prepared with Race files (FKG Dentaire. Switzerland) up to #25, 4%. A #30, 6% Race file was used to simulate file fracture 3 mm short of working length. The prepared samples, randomly divided into three groups, and final irrigation was separately done in each group. Group 1 conventional syringe irrigation (CSI) as the control group, Group 2 passive ultrasonic irrigation (PUI), and Group 3 Shock wave enhanced emission photoacoustic streaming or SWEEPS Irrigation (SI). Smear layer and debris removal beyond separated file scored with scanning electron microscope(SEM) images. Data were analyzed using the nonparametric tests to compare the smear layer and debris scores.Result: SWEEPS and passive ultrasonic irrigation significantly removed smear layer and debris, better than conventional syringe irrigation (p<0.001). The smear layer and debris removal efficiency between passive ultrasonic Irrigation and SWEEPS were not significantly different (p = 0.629).Conclusion: In the face of the irretrievably broken instrument in the root canal, passive ultrasonic irrigation and the SWEEPS method can enhance smear layer and debris removal compared to conventional syringe irrigation.

Centering Ability of Three Different Reciprocating Rotary Files Using Cone Beam Computed Tomography – In-vitro Study

Background: Centering ability of root canal files is considered to be an imperative factor during root canal instrumentation. Hence it is decided to evaluate and compare the centering ability of Reciprocating rotary files in teeth by means of cone beam computed tomography in vitro condition.&#x0D; Objectives:&#x0D; &#x0D; To evaluate the centering ability of the Reciproc file system in extracted mandibular molar.&#x0D; To evaluate the centering ability of the Reciproc Blue file system in extracted mandibular molar.&#x0D; To evaluate the centering ability of the WaveOne file system in extracted mandibular molar.&#x0D; To compare the above file systems with each other.&#x0D; &#x0D; Methodology: 30 Newly extracted mandibular molars will be considered in the study. Before access opening teeth will be exposed for a pre-instrumentation CBCT scan. After this scanning standard access cavity preparation will be done followed by checking canal patency using 10#K-file. Then teeth will be divided into three groups for root canal instrumentation. Group 1: Instrumentation by using Reciproc file, Group 2: Instrumentation by using Reciproc Blue file, Group 3: Instrumentation by using WaveOne file. For evaluation of centering ability, the equation introduced by Gambill (1996) i.e., (m1 – m2) ÷ (d1 – d2) or (d1 – d2) ÷ (m1 – m2) and (b1-b2) ÷ (l1-l2) or (l1-l2) ÷ (b1-b2) will be used after post instrumentation CBCT scanning. &#x0D; Expected Results: The Reciproc Blue file system is expected to give better results in canal centering ability.&#x0D; Conclusion: Centering ability is considered to be important factor in biomechanical preparation, as it can retain the instruments in centre which is crucial to offer a precise extension, without weakening of the root structure. Different files are used to evaluate and compare the centering ability of instrument by CBCT.

Comparison of canal transportation and centering ability of three different endodontic rotary systems (an invitro study).

Background and objectives: one of the most important steps for root canal treatment is biomechanical preparation, which is the key stage of endodontic treatment with a predictive success factor if performed properly to prevent canal transportation. The aim of the present study is to compare the canal transportation and centering ability of Rotary ProTaper next, two Shape and Pro Taper gold systems in simulated root canals to find better instrumentation technique for maintaining root canal geometry. Methods: Thirty simulated curved canals of 35° curvature manufactured in clear resin blocks were randomly assigned to 3 groups (n = 10) according to the system used for canal instrumentation: ProTaper next, two Shape and Pro Taper gold systems groups, Centering ability was evaluated; Pre‐and postoperative images of the canals were taken at a stan‐ dardized position by a digital camera with a resolution of 25 mega pixel. An assessment of the shape of the canal was determined using Microsoft office Visio program version 11. Results: The result showed that Protaper Gold produce less transportation and remained better center in the canal than ProTaper Next and 2 shape. The difference in transportation between the ProTaper Gold and ProTaper Next systems was not statistically significant differences (P &gt; 0.05) while between ProTaper Gold and 2 shape and between ProTaper Next and 2 shape were significant differences (P &lt; 0.05). Conclusion: Protaper Gold produce less transportation of the canal than ProTaper Next and 2 shape.

SEM Evaluation of Various Intracanal Irrigation Devices on Smear Layer Removal: A Comparative Study

The present study aimed at assessing the effectiveness of different intracanal irrigation devices on the removal of the smear layer. The recently extracted 80 lower premolars having single canal were chosen for this in vitro study. A round diamond bur was used to gain endodontic access and the root canal was entered with a #15 K-file until the tip was just seen at the apical foramen. Manual instrumentation of root canals of all teeth was done using the step-back method. The samples were later divided randomly into four groups. Later, each sample was exposed to final irrigation by using four different irrigation systems, group 1: conventional needle irrigation, group 2: irrigation with ultrasonic activation, group 3: irrigation with EndoVac system activation, group 4: irrigation with EndoActivator. The samples were next mounted and visualized under scanning electron microscope (SEM) for the absence or presence of the smear layer. Irrigation with EndoVac system activation showed the presence of least smear layer (2.40 ± 0.32), followed next by EndoActivator (3.24 ± 0.46) and ultrasonic activation (4.96 ± 0.54) and conventional needle irrigation (5.20 ± 0.10). No statistically significant difference was found in the apical and coronal thirds of the root canal in removal of the smear layer on an intragroup comparison. However, a statistically significant (p < 0.001) difference was seen between the groups at the apical and coronal thirds on an intergroup comparison. This study demonstrated the EndoVac system group to be efficient in removal of the smear layer when compared to the EndoActivator system, ultrasonic activation, and conventional needle irrigation group. The definitive objective of endodontic therapy is to transform the affected teeth to a healthy and functional state. The irrigants can reach the working length when delivered by an effective irrigation delivery system. This type of delivery system should deliver adequate volume of irrigants all the way up to the working length and have sufficient flow and be efficient at debridement of complete canal system.

Confidence Level and Experience of Undergraduate Students toward Root Canal Preparation using Rotary versus Manual Root Canal Instrumentation: Preliminary Study

Background: The assessment of experience, difficulties encountered, and comparison of root canal preparation using manual versus rotary technique among undergraduate students is needed. Objectives: The aim of this study was to evaluate the perception of undergraduate dental students' first-time experience using Nickel–Titanium rotary instruments for root canal treatment. Materials and Methods: A descriptive cross-sectional study among 26 final year undergraduate dental students of batch 15 (2014–2015) from the University of Medical Sciences and Technology, Sudan. A self-administered questionnaire composed of two parts; in the first part the questions were relating to the students' confidence levels and experience of clinical root canal treatment using both rotary and manual instruments, while the second part focused on the comparison between rotary and manual instrumentation; difficulties encountered, complications, and preferences. The Chi-square test was used for comparison between different variables with the level of statistical significance set at P ≤ 0.05. Results: The majority (80.8%) had a satisfactory first-time experience when using rotary instruments in the root canal treatment of their patients. When using rotary, 26.7% of students experienced separated instruments, and 30% experienced over-preparation. However, the most common complications arising with the use of a manual instrument was ledge formation (23.4%). The most common canal in which separation of instruments occurred was the mesiobuccal canal of molar teeth with percentages of 72.7% for rotary and 52.9% for manual. The most commonly separated rotary file was S1 Protaper (77.8%). Conclusion: The majority of the undergraduate students had a satisfactory experience when using rotary instruments for root canal treatment. A high prevalence of complications was associated with the use of either rotary or manual technique. The most common complication was the separation of the instrument in the mesiobuccal canal of molar teeth.

Evaluation of Remaining Dentin Thickness After Manual and Evaluation of Remaining Dentin Thickness After Manual and Rotary Instrumentation In Primary Molars Using Cone Beam Rotary Instrumentation In Primary Molars Using Cone Beam Computed Tomography. (An In-Vitro Study)

Aim: To compare the radicular dentin thickness before and after instrumentation by manual stainless-steel (K-files) versus rotary files (AF™ Baby File) at coronal, middle, and apical thirds using Cone Beam Computed Tomography (CBCT). Materials and Methods: Forty roots of extracted mandibular primary molars were collected, and randomly and equally divided into 2 groups. Manual Group was prepared by K-files, and Rotary Group was prepared by rotary AF™ Baby File system. Samples were decapitated and stabilized in epoxy resin blocks. Samples were subjected to CBCT scan before and after instrumentation for radicular dentin thickness evaluation at 3 measuring points; apical, middle, and coronal. Results: An average amount of dentin removed was found to be significantly higher in Manual Group compared to Rotary Group in the 3 measuring points (P &lt;0.005). Conclusion: Rotary files can be considered more preferable than manual files in terms of preservation of radicular dentin thickness after root canal instrumentation, therefore rotary files can be a suitable substitute for conventional SS manual files

Effectiveness of XP-Endo Finisher and Passive Ultrasonic Irrigation in the Removal of the Smear Layer Using two Different Chelating Agents.

Statement of the Problem: The smear layer may harbor microorganisms and necrotic pulp tissue, jeopardizing irrigant penetration. Recently, Dual Rinse®, a weak chelating agent, has been introduced to the market. However, its chelating capacity in the final irrigation protocol with different activation systems has not yet been deeply analyzed.Purpose: The aim of this ex vivo study was to evaluate the effectiveness of passive ultrasonic irrigation (PUI) and XP-endo Finisher (XP) on smear layer removal in combination with two chelating agents, ethylenediaminetetraacetic acid (EDTA) and etidronic acid (HEDP).Materials and Method: This in vitro, experimental study evaluated fifty-two single-rooted human teeth were standardized to 16 mm in length. Root canal instrumentation was performed by the ProTaper Gold system up to the F4 file. The apical end of the samples was sealed with wax to simulate a closed system. Teeth from group 1 (n=24) were irrigated with 3% sodium hypochlorite (NaOCl) and 17% EDTA, while teeth from group 2 (n=24) were irrigated with 3% NaOCl mixed 9% HEDP. Both groups were divided into two subgroups (n=12) depending on the activation system used: XP (group XP-EDTA and XP-HEDP) or PUI (group PUI-EDTA and PUI-HEDP). The specimens were evaluated by scanning electron microscopy at 3, 5 and 8mm from the apex. Statistical analysis was performed using ANOVA and Bonferroni tests considering p> 0.05 as significant.Results: PUI-EDTA was the most effective at removing the smear layer, with a statistically significant difference from XP-EDTA (p< 0.042) and group XP-HEDP (p< 0.003). There were no statistically significant differences among the other groups.Conclusion: Under the conditions of this ex vivo study, no activation system was able to completely remove the smear layer from the root canal walls. However, the combination of NaOCl with ultrasonically activated EDTA obtained better results than the other treatments.

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

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. 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. 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. Within the limitations of the study, chemo-mechanical instrumentation did not routinely promote the formation of radicular defects.

Longitudinal craze line propagation in human root dentin after instrumentation with NiTi rotary files of different instrument tapers after long-term chewing simulation

ObjectivesThe aim of this study was to investigate whether file design and taper significantly influence microcrack initiation during machine preparation.Materials and methodsSixty extracted teeth with straight single canals were selected. The teeth were randomly assigned to four groups based on their root canal anatomy and the corresponding NiTi rotary file system (I, Mtwo; II, ProTaper Universal; III, F6 SkyTaper; control, no preparation and filling). The root canals of the experimental groups were filled using the single-cone technique. The tested teeth were all subjected to a mechanical chewing simulation with flat lead loading over a period of 3 years (corresponding to 150,000 cycles). The teeth were checked for dentinal defects (accumulative crack growth in length) under the digital microscope (Keyence VHX-5000) at time 0 (baseline prior to chewing simulation) and after 3, 6, 12, 24, and 36 months of loading. The cumulative crack increase was statistically analyzed using the Kruskal–Wallis test, Jonckheere–Terpstra test, and the Wilcoxon rank-sum test. The significance was set at p < 0.05.ResultsIn contrast to preparation with greater-tapered instruments, ProTaper Universal (group II) and F6 SkyTaper (group III) instrumentation with the smaller tapered Mtwo files (group I) showed less accumulative propagation of craze lines (p < 0.05) at all time points.ConclusionInstruments with greater taper for root canal instrumentation should be used with care to avoid negative long-term effects in the form of propagation of dentinal defects over time. A positive cutting-edge angle and a smaller taper have a positive effect on a lower craze line development.Clinical relevanceInstruments with a positive cutting-edge angle and a smaller taper are beneficial for the long-term preservation of dentinal tooth structure.

Comparison of Canal Transportation and Centering Ability of One-G, EdgeGlidePath, and Neolix: A MicroComputed Tomography Study of Curved Root Canals

Aims A glide path is created prior to root canal instrumentation by nickel-titanium (NiTi) rotary files to increase the efficiency and safety of cleaning and shaping. This study aimed to assess root canal transportation in use of different glide path files in curved canals. Materials and Methods 30 sound mesiobuccal root canals of mandibular molars with 20° to 40° curvature were selected and randomly assigned to 3 groups of EdgeGlidePath (EGP, EdgeEndo), One-G (Micro-Mega), and Neolix (Neoniti). The specimens were scanned before and after glide path creation by microcomputed tomography (micro-CT). The pre- and postoperative micro-CT scans were superimposed, and the degree of canal transportation and centering ratio were measured at 1, 3, 5, and 7 mm distances from the apical foramen. Statistical Analysis. The data were analyzed by two-way and one-way ANOVA. Results The effects of distance from the apical foramen and instrument type and the interaction effect of the two were not significant on the centering ability of the files or canal transportation. Conclusion EdgeGlidePath, One-G, and Neolix files fabricated from the conventional NiTi alloy or heat-treated M-Wire alloy showed similar performance regarding centering ability and canal transportation in glide path preparation in curved canals.