Assessment of Incidence, Management and Contributory Factors of Root Canal Instrument Separation in an Endodontics Post- Graduate Program: A Retrospective Clinical Study.

BACKGROUND: The successful outcome of nonsurgical root canal treatment (NS-RCT) is largely dependent on the technical quality of the procedure. OBJECTIVE: To investigate the incidence of separated instruments in endodontic postgraduate clinics between January 2018 and December 2021, and to determine the potential contributory factors that increase the risk of instrument separation. MATERIALS AND METHODS: A retrospective observational study was conducted in the Department of Endodontics, Faculty of Dentistry, King Abdulaziz University, Jeddah, Saudi Arabia. Data was collected to determine the incidence of separated instruments and their associated variables. Seven variables were analyzed separately: nonsurgical initial or retreatment case, tooth type, tooth arch, tooth location, canal type, root curvature, level of fracture, and file type. RESULTS: A total of 3150 cases were treated, of which 108 cases had separated instruments. The overall incidence of instrument separation was 3.4% while 53.7% of separated instruments occurred in the mandibular molars, followed by 42.6% in the maxillary molars. The highest frequency of instrument separation was recorded in the mesiobuccal canal (35.2%). The level of separation was found to be statistically significant in relation to the management (P < .001). CONCLUSION: Nickel-titanium instruments tend to separate more inside the root canal system than stainless steel instruments. However, under the limitation of this study, the incidence of instrument separation is still quite low, even with postgraduate endodontic residents with limited experience.

Assessment of the Effect of Different Irrigation Protocols on the Penetration of Irrigation Solution into Simulated Lateral Canals (In Vitro Study).

OBJECTIVE: To compare the effectiveness of lateral canal irrigation penetration by conventional needle, passive ultrasonic, sonic endo activator, and Erbium laser (2780nm). METHODS: A total of 40 palatal roots of human maxillary first molars were collected and instrumented at a working length of 12 mm by an X1-X4 rotary Protaper Next system (Dentsply, Maillefer, Ballaigues, Switzerland) using the crown-down technique. Artificial lateral canals were made at 2, 4, and 6 mm from the apex on mesial and distal sides using an ISO rotary reamer (Dentsply, Maillefer, Ballaigues, Switzerland; #10 for mesial, #08 for distal). The samples were then cleared using methyl salicylate. A solution of black ink and normal saline was used as an irrigant for the root canal. The percentages of the penetration of the ink into the lateral canals were measured using a stereomicroscope (Q-Scope, Arnhem, The Netherlands) with the aid of program Image J. The Tukey test is used to assess the significant difference between intragroup and intergroup comparisons of different thirds, and the T-test is used to assess the significant difference between every two groups and for the mesial and distal sides of each group. The level of significance was set at 0.05. RESULTS: Results showed that none of the activation techniques used resulted in complete lateral canal penetrations; however, on both sides at all thirds, the Erbium laser (2780 nm) achieved the highest results with a highly significant statistical difference (p=0.05) with all other groups, and the least penetration was in the conventional needle group. CONCLUSION: The size of the lateral canal is a restricting factor for all activation methods; the best results can be achieved by laser. Conventional needles cannot be used alone to disinfect complex canal anatomy; however, passive ultrasonic and sonic endo activator activations can produce comparable results.

Comparative assessment of cleaning efficacy of two exclusive paediatric rotary files in root canals of primary teeth: An in vitro study.

BACKGROUND: Paediatric rotary file systems have recently been developed for primary teeth use. AIM: To study the cleaning efficacies of two paediatric rotary endodontic files, the Prime PedoTM, and the Kedo-SG BlueTM against the standard H files. DESIGN: This in vitro study included 54 freshly extracted primary molars, which were randomised into three groups (n = 18 each) and were prepared using either Kedo-SG BlueTM, Prime PedoTM or hand H files after injecting methylene blue dye into the canals. Pre- and post-operative cone beam computerised tomography (CBCT) was performed to assess change in root canal volumes. Methylene blue dye removal from canals was assessed using stereomicroscopy, and canal cleanliness was examined by scanning electron microscopy (SEM). RESULTS: Both Prime PedoTM and Kedo-SG BlueTM files reduced significantly less dentine when compared with conventional hand filing with Prime PedoTM removing the least amount of dentine. No significant difference was found in median SEM scores among the groups in the cervical, middle and apical thirds of the roots. Stereomicroscopic assessment of root canal cleanliness using dye removal technique shows a statistically significant difference existing between Kedo-SG BlueTM and hand H files groups. CONCLUSION: Prime PedoTM removed the least amount of dentine. Kedo-SG BlueTM performed significantly better than conventional hand filing with H files when the root canal cleanliness was assessed.

Assessment of the root surface temperature during the use of intracanal agitation systems: In vitro study.

This study aimed to evaluate the temperature changes that the different methods of agitation of irrigants promote on the external dental root surface. Nine extracted human lower premolars were standardized by cone-beam computed tomography and used. The root canal was instrumented with a Reciproc 40.06 file. Temperature measurement was performed using K-type thermocouple sensors attached to the middle, cervical, and apical thirds of the teeth. The teeth had their roots immersed in distilled water at 37ºC, which were distributed into 3 experimental groups according to the mechanical agitation methods to be studied. US Group (n=3), Irrisonic Ultrasonic Tip activated through ultrasound; EC Group (n=3), Easyclean Tip coupled to a contra-angle low-speed handpiece; XP Group (n=3), XP-endo Finisher file coupled to an endodontic electrical motor. Temperature measurements were performed simultaneously with agitation and irrigation of intracanal irrigants. Statistical analysis was performed using SPSS software with a significance level of 5%. For multiple comparisons, the Tukey test was used. The association between mechanical agitation methods and root third was statistically significant. Regarding the temperatures recorded on the external surface of the roots, the ultrasonic tip was significantly higher than the XP-endo Finisher file and the Easyclean tip, which did not differ from each other. Regarding the ultrasonic tip, the external temperature in the middle third (39.46ºC) of the root was significantly lower than in the cervical (40.41ºC) and apical third (40.53ºC). None of the agitation methods of irrigants studied presented heating above 47ºC, and their use is safe for periodontal tissues.

Quantitative Assessment of Dimensional Evaluation and Artefacts from Filling Materials with CBCT Using Standard Phantom Roots.

OBJECTIVE: To investigate the accuracy of dimensional evaluation and representation of artefacts generated by different gutta-percha (GP) cones with or without sealer with CBCT using a reproducible, standardised phantom root methodology. METHODS: The reproducible artificial phantom roots with six root canal sizes from #25 to #50 and 0.04 taper were aligned according to the jaw curvature in a stone model for dimensional measurements. Each root was scanned while empty and filled with four types of filling materials. The specimens were scanned using the CS 9300 3D (Carestream Dental, Rochester, NY, USA) (at two different resolutions), 3D Accuitomo (J Morita, Kyoto, Japan) and NewTom VGi (Verona, Italy) CBCT systems. The hyperdense and hypodense axial slice artefacts from root canal sizes #40, #45 and #50 were recorded. RESULTS: Dimensions were significantly smaller and more accurate with CS 9300/0.09 mm voxel size than with other protocols. The hypodense band was found mostly in the CS 9300 3D system with 0.18 mm voxel size, especially in the buccal-lingual (95%) and coronal (64%) sections. The 3D Accuitomo CBCT system showed the lowest presence of the hypodense band. Areas of both light and dark artefacts were significantly larger in the coronal third than in the apical and middle thirds. CONCLUSION: Artefacts in the coronal locations and in buccal-lingual sections were more evident in the CS 9300 3D system with a 0.18-mm voxel size.

Thermal and volumetric assessment of endodontic filling techniques using infrared thermography and micro-CT.

PURPOSE: To assess root temperature during filling techniques and quantify the volume of endodontic filling materials using infrared thermography (IT) and micro-computed tomography (micro-CT). METHODS: Ninety premolars were divided into three groups: lateral condensation (LC), single cone (SC) and thermomechanical compaction (TMC). For thermal analysis, 45 teeth were assessed using a FLIR T650sc IT camera during filling techniques and 45 teeth were scanned using a Nikon micro-CT to assess gutta-percha, cement, and void volumes. Descriptive and inferential statistical analyses were performed (non-parametric Mann-Whitney test, Kruskal-Wallis test, and Friedman test with Tukey's bidirectional analysis of variance). RESULTS: TMC showed the highest temperature increase at 15 s after the procedure and a significant temperature decrease at 45 s after its completion. TMC showed the largest volume of gutta-percha and LC the highest void volume. CONCLUSION: The temperature increase generated by gutta-percha endodontic filling techniques is within acceptable limits. A greater volume of endodontic cement was observed for the SL and LC filling techniques.

Assessment of the Performance and Surface Alteration of Two Single-file Systems According to the Number of Uses

Abstract The aim of this study was to assess the performance and surface alteration of two single-file systems according to the number of uses. Ten WaveOne Primary files (25/.08) and ten One Shape NG files (25/.06) were used for instrumentation of mesial root canals of mandibular molars. Each instrument was cleaned and sterilized after the preparation of two root canals and then reused. The time spent for instrumentation of each root canal was recorded and analyzed by using t-test. Microphotographs of the surface of the instruments were taken with a scanning electron microscope at different magnifications (i.e. 18x, 160x, 500x and 1000x) and at a distance of 4 mm from the instrument's tip before being analyzed by four observers. Presence of disruption of cutting edge, crack, craters and unwinding was assessed and submitted to Fisher's exact test. Both systems showed manufacturing defects and cracks. The presence of disruption of cutting edges was major in WaveOne files from the sixth use, whereas One Shape NG files showed more unwinding. Only preparation time using WaveOne files was influenced by the number of uses. One can conclude that WaveOne files had more disruption of cutting edges and took longer time for root canal preparation from the sixth use onwards, whereas the One Shape NG files showed more unwinding at the tenth use.

Accuracy of CBCT images in the volumetric assessment of residual root canal filling material: Effect of voxel size.

AIMS: Our aim was to compare three different voxel sizes of CBCT images for the determination of residual filling material volume in root canals when compared with micro CT. MATERIAL AND METHODS: Forty-two root canals of 14 extracted human maxillary molar teeth were retreated by using ProFile® instruments. Images were obtained after retreatment by using ProMax 3D Max CBCT at 3 different voxel sizes (1) High resolution (0.1 mm); (2) High definition (0.15 mm); and (3) Normal resolution (0.2 mm). Two observers measured volumes of residual filling materials in exported CBCT images by means of 3D Doctor Software. Micro CT measurements were served as gold standard. Mann-Whitney U test and Wilcoxon Test were used for the comparison of CBCT and micro CT measurements. Statistical significance was set at P < 0.05. RESULTS: No statistically differences were found between the two observers for all measurements (P > 0.05). There were no significant differences among different CBCT voxel sizes used (0.1 mm, 0.15 mm, and 0.2 mm) (P > 0.05). The Spearman correlation coefficients between CBCT at different voxel sizes significantly highly correlated with micro CT measurements for each observer (P < 0.05). Furthermore, no significant differences were found between the measurements obtained by the two observers in consideration to root canal location (P > 0.05). CONCLUSION: CBCT images may provide useful information in the volumetric assessment of the amount of residual filling material in root canals for retreatment procedures.

Assessment of the apically extruded debris between a rotary system, a reciprocating system and hand files during the root canal instrumentation of the deciduous molars.

BACKGROUND: One of the factors that most negatively affect the endodontic instrumentation process in primary teeth is the presence of extruded debris in the periapical region. Therefore, different techniques have been evaluated to reach an answer to the question regarding which root canal preparation method produces the least amount of debris extrusion. OBJECTIVES: The main objective of this study was to assess the amount of debris extrusion as well as irrigation associated with 3 different instrumentation techniques: a rotary system (PROTAPER NEXT® - PTN), a reciprocating system (WaveOne® - WO) and hand K-files. MATERIAL AND METHODS: Forty-eight primary mandibular molars with a single distal canal were selected and randomly divided into 3 groups (n = 16). Three different techniques were used for the canal instrumentation of each group, comprising PTN, WO and hand K-files. Pre-weighed Eppendorf tubes were used for the collection of debris extrusion, then stored in an incubator at 70°C for 5 days. A one-way analysis of variance (ANOVA) test was used for data analysis, followed by Tukey's post hoc test. RESULTS: Statistically significant differences were found while comparing the PTN and WO systems with the hand files. Both PTN and WO showed less debris extrusion toward the periapical tissues than the hand files. Still, no statistically significant differences were seen between the PTN and WO groups. CONCLUSIONS: Generally, debris extrusion occurred in all of the 3 experimental groups. The PTN and WO systems showed the least debris extrusion as compared to the hand files during the root canal instrumentation of the primary teeth, and for these reasons along with the shorter operating time, it may be concluded that using rotary and reciprocating systems rather than manual files is highly advisable. However, a clinical assessment is suggested.

Comparative assessment of dentin removal following hand and rotary instrumentation in primary molars using cone-beam computed tomography.

OBJECTIVE: Pediatric endodontics has witnessed many advances in recent years, thus facilitating a faster and efficient treatment option in root canal therapy in children. This in vitro evaluation aims to determine the amount of dentin removal in primary mandibular first and second molars instrumented with hand and rotary files using cone-beam computed tomography (CBCT). MATERIALS AND METHOD: Sixty primary mandibular molars were divided into two groups: Group I was prepared by manual instrumentation using K-type files and Group II was prepared with rotary instrumentation using 0.04 Hero Shaper Classics. Both these groups were further divided into two subgroups, namely (a) primary mandibular first molar and (b) primary mandibular second molar. All the root canals were prepared up to size 30 using the stepback technique. They were mounted on silicone-based impression material and subjected to CBCT scans for the evaluation of dentin removal before and after instrumentation. Dentin removal was calculated by superimposing images using the InVivo 5.1 Anatomage software. Data were statistically analyzed using independent samples t- test. RESULTS: An average amount of dentin removed was found to be significantly higher in manual instrumentation compared to rotary instrumentation in both primary mandibular first and second molars (P < 0.001). CONCLUSIONS: Rotary technique serves as an efficient alternative to the traditional manual instrumentation by overcoming its shortcomings in terms of conservation of the remaining dentin thickness and the time required for its preparation.

Assessment of Regaining Pulp Sensibility in Mature Necrotic Teeth Using a Modified Revascularization Technique with Platelet-rich Fibrin: A Clinical Study.

INTRODUCTION: The aim of the present study was to evaluate the possibility of regaining pulp sensibility in mature necrotic teeth using modified regenerative endodontic procedures by inducing bleeding in root canals and using platelet-rich fibrin (PRF). METHODS: Fifteen patients with necrotic pulp with symptomatic or asymptomatic apical periodontitis were included. At the first visit, the tooth was anesthetized, and an access cavity was performed. Mechanical preparation of root canals was performed using the standardized technique reaching apical canal preparation to K-file size #60-80. Double antibiotic paste was injected into the canal, and the cavity was temporarily sealed using glass ionomer cement. Three weeks from the first visit, regenerative endodontic procedures were performed by inducing bleeding, and a freshly prepared PRF membrane was placed in the canal. White mineral trioxide aggregate was placed directly over the PRF matrix, and the tooth was restored with a glass ionomer cement base and resin composite restoration. The electric pulp test was used to record if the teeth included in the study regained sensibility or not every 3 to 12 months follow-up. Readings at different times were compared as categoric qualitative data using the chi-square test and compared as means and standard deviations using the analysis of variance test. RESULTS: Readings of tooth sensibility revealed a highly significant difference (P < .0001) between baseline and the 12-month follow-up period. CONCLUSIONS: The presence of sensibility is indicative of the formation of vital pulplike tissue. Reestablishing real pulp tissue after regenerative endodontic treatment is debatable and still needs high level of evidence with large-scale investigations.

Micro-computed Tomography Shaping Ability Assessment of the New Blue Thermal Treated Reciproc Instrument.

INTRODUCTION: The present study aimed to assess canal preparation outcomes achieved by the new Reciproc Blue instrument using micro-computed tomography technology. M-Wire Reciproc was used as a reference instrument for comparison. METHODS: Seven pair-matched mesial roots of mandibular molars presenting similar anatomic features of the canal (length, volume, surface area, and configuration) were selected after scanning procedures and assigned to 1 of the 2 groups according to the instrument used, M-Wire Reciproc and Reciproc Blue. After canal instrumentation, the specimens were rescanned, and the registered preoperative and postoperative datasets were examined to evaluate the percentages of removed dentin, untouched canal walls, and degree of canal transportation. Comparisons regarding the above outcomes between the 2 groups were done by using paired t test with the alpha-type set at 5%. RESULTS: Root canals prepared with conventional M-Wire Reciproc or Reciproc Blue were found to present similar shaping properties with no significant differences in the tested parameters. CONCLUSIONS: M-Wire Reciproc and Blue Reciproc presented similar shaping outcomes.

Assessment of apical transportation caused by nickel-titanium rotary systems with full rotation and reciprocating movements using extracted teeth and resin blocks with simulated root canals: A comparative study.

OBJECTIVES: : We compared apical transportation in the WaveOne and ProTaper Next systems, which are rotary nickel-titanium systems with reciprocating and continuous rotation movements, respectively, using manual measurements obtained from resin blocks with simulated root canals and double digital radiographs of extracted teeth. MATERIALS AND METHODS: : We used 30 resin blocks with simulated root canals and 30 extracted teeth for this study. The same endodontist performed root canal shaping using the WaveOne or ProTaper Next system. We assessed apical transportation by measuring the amounts (in mm) of material lost 1 mm from the apical foramen in the resin blocks and by using double digital radiography for the extracted teeth. Significant differences between groups were assessed using t-tests. P < 0.05 was considered statistically significant. RESULTS: : The amount of apical transportation differed significantly between the two systems when resin blocks were used for assessment (P < 0.05), but there were no significant differences when extracted teeth were used (P < 0.05). CONCLUSIONS: In the current study, there was no significant difference in apical transportation between natural teeth prepared using WaveOne and those prepared using ProTaper Next. However, significant differences were observed between the two systems with resin blocks. These findings indicate that the use of resin blocks is not an accurate method for apical transportation evaluation.

Rotary Versus Reciprocation Root Canal Preparation: Initial Clinical Quality Assessment in a Novice Clinician Cohort.

INTRODUCTION: Reports comparing clinical outcomes using nickel-titanium (NiTi) reciprocating instruments with other instrumentation modalities are scarce. This study examined initial shaping outcomes after an instrumentation change of root canal instrumentation technique in a doctor of dental surgery educational program. Student characteristics, faculty/student ratio, facility, and overall endodontic treatment guidelines remained unchanged. METHODS: A total of 200 nonsurgical initial molar root canal treatments completed by third-year dental students were evaluated. The cases were examined regarding the number of treatment appointments, access cavity preparation, canal taper, canal transportation, perforations, missed canals, presence of ledges, fractured instruments, obturation length, obturation quality, and sealer extrusion. Two independent evaluators determined the number of appointments per case; 4 independent and blinded evaluators analyzed radiographs at 4 treatment stages: preoperative situation, working length, cone fit, and obturation. RESULTS: The following factors were significantly different between the 2 cohorts: the number of appointments, preparation length, taper, and occurrence of ledges. The WaveOne (Dentsply Sirona, York, PA) cohort had a significantly reduced treatment time compared with hand/GT rotary instrumentation (Dentsply Tulsa Dental, Tulsa, OK) (average of 3.3 vs 4.3 appointments). Appropriate length control and adequate taper were significantly more frequent in the WaveOne group. The frequency of ledges was significantly larger in the hybrid group. Other variables, such as access cavity preparation, canal transportation, perforations, missed canals, fractured instruments, obturation quality, and sealer extrusion, were statistically similar between the 2 groups. CONCLUSIONS: NiTi reciprocation instrumentation was superior to hybrid hand/NiTi rotary instrumentation in reducing both patient appointments and the incidence of ledging and in improving obturation length and taper in a dental student clinic setting.

Quantitative Assessment of apically Extruded Bacteria using different Instrumentation Techniques and Preparation Taper.

BACKGROUND: Cleaning and shaping of the pulp canal is one of the most important steps of endodontic therapy. Serious complications occur by the apical extrusion of bacteria during the instrumentation procedures. Both crown-down (CD) and full-length linear motion (FM) techniques are routinely used as a component of taper rotary instrument procedures for achievement of thorough cleaning and shaping of the pulp canal space. Hence, we aimed for this study to assess the change in the amount of apically extruded bacteria using CD and FM instrumentation techniques produced by differences in taper between the instruments used during biomechanical preparation of root canals. MATERIALS AND METHODS: The present study included assessments of 132 extracted maxillary central incisor teeth. To achieve a uniform teeth length of 21 mm, the height of the tooth crown was reduced for preserving the coronal portion of teeth. A modified glass vial model was constructed for the estimation of amount of bacterial extrusion through the apical region. For filling of each pulp canal specimen, 20 mL of Enterococcus faecalis suspension was used followed by the use of a number 10 K-file for carrying the bacteria down the lengths of pulp canals. All the contaminated teeth specimens were divided into six study groups with groups I to III containing specimens prepared in the CD manner, while groups IV to VI contained specimens prepared in the FM manner. Six teeth were taken as negative control with three specimens with each technique, and another six specimens were taken as positive controls. Cultivable bacterial counts were determined by evaluating 100 mL saline solution from each vial followed by its inoculation on blood agar. All the colony-forming unit (CFU) values were log-transformed (base 10), and the results were analyzed by Statistical Package for the Social Sciences software. RESULTS: A significantly lower quantity of CFU values was observed during CD instrumentation procedures with 0.02 files in comparison with all other study groups. However, while comparing both the instrumentation procedures when different taper files, other than 0.02 taper, were used for biomechanical preparation of root canal, nonsignificant results were obtained. CONCLUSION: With 0.02 taper preparations, significantly less amount of extrusion of bacteria is associated when done with CD technique. CLINICAL SIGNIFICANCE: No change in the amount of apical extrusion of bacteria will be seen by changing the type of instrumentation procedures. Amount of bacteria extruded can be minimized using 0.02 taper. Key words: Bacteria, Instrumentation, Taper.

Assessment of Coronal Leakage of Temporary Restorations in Root Canal-treated Teeth: An in vitro Study.

INTRODUCTION: Coronal leakage is one of the constant concerns in routine dental practice. It is one of the factors responsible for the failure of root canal therapy. Permanent restorations should be given as soon as possible after the completion of root canal therapy. If unavoidable, provisional restoration should be given in such a way that it maximally reduced the leakage of microorganisms and fluids from the external environment into the canal space. Hence, we evaluated the effect of saliva on the coronal leakage of temporary restorations. MATERIALS AND METHODS: Biomechanical preparation of the root canals of 204 fresh mandibular first premolar teeth was done using endodontic files with intermittent irrigation of sodium hypochlorite solution and ethylenediaminetetraacetic acid. Alternate irrigation with normal saline was done periodically. After preparation, drying of the canals was done using paper points followed by sealing of the apical foramen. For the assessment of the microleakage, Siqueira et al apparatus and method was used. All the specimens were divided into four groups based on the provisional restorative material used. All the groups were further divided into three subgroups based on the presence and absence of intracanal medicaments. Verissimo et al's criteria were used to check the turbidity at 1-, 2-, 3-, and 4-week interval respectively. All the results were analyzed by Statistical Package for the Social Sciences (SPSS) software. Chi-square test was used to measure the level of significance, and p < 0.05 was considered to be significant. RESULTS: In group I, all the subgroups' specimens showed significant difference at 1 week's time. Only the subgroup with no intracanal medicaments in Cavit-containing provisional restoration showed nonsignificant alterations. Statistically significant alterations were seen at 1, 2, and 3 weeks' interval in all the subgroups except for one with intracanal medicaments. CONCLUSION: All the temporary restorative materials were not able to prevent microleakage after 1 week's time, with worst bacterial resistance shown by Ketac Molar and ionomer restorative material. Future studies are advocated for better prognosis of root canal therapy.

Micro-computed Tomography Assessment of Dentinal Micro-cracks after Root Canal Preparation with TRUShape and Self-adjusting File Systems.

INTRODUCTION: The aim of the present study was to evaluate the percentage frequency of dentinal micro-cracks observed after root canal preparation with TRUShape and Self-Adjusting File (SAF) systems by means of micro-computed tomography imaging analysis. A conventional full-sequence rotary system (BioRace) and a single-file reciprocation system (Reciproc) were used as reference techniques for comparison because of their known assertive cutting efficiency. METHODS: Forty anatomically matched mandibular incisors were selected, scanned at a resolution of 14.25 µm, and assigned to 4 experimental groups (n = 10), according to the preparation protocol: TRUShape, SAF, BioRace, and Reciproc systems. After the experimental procedures, the specimens were scanned again, and the registered preoperative and postoperative cross-section images of the roots (n = 70,030) were screened to identify the presence of dentinal micro-cracks. RESULTS: Overall, dentinal defects were observed in 28,790 cross-section images (41.11%). In the TRUShape, SAF, BioRace, and Reciproc groups, dentinal micro-cracks were visualized in 56.47% (n = 9842), 42.38% (n = 7450), 32.90% (n = 5826), and 32.77% (n = 5672) of the slices, respectively. All dentinal defects observed in the postoperative data sets were already present in the corresponding preoperative images. CONCLUSIONS: None of the preparation systems induced the formation of new dentinal micro-cracks.

Assessment of rotary and reciprocating movements in root canal filling material removal / Análise dos sistemas rotatórios e reciprocante com diferentes ligas na desobturação em retratamento endodônticos

The aim of this study was to evaluate the effects of preparation, filling removal material, reinstrumentation and reobturation of root canals with different Ni-Ti alloys in endodontic retreatment. Firstly, the selection and pairing of mesial root canals of mandibular molars (n = 45) were performed by computerized micro-tomography (micro-CT). After pairing, the specimens were divided into three groups (n = 15), instrumented with the Mtwo® (up to file 25.06), ProDesign Logic (25.06) and ProDesign R (25.06) systems. After this, the specimens were scanned again for root canal deviation analysis at 2, 4, 6, 8 and 10 mm from the apex and the volume increase of these root canals was evaluated through CTan Then, the root canals were filled with Endofill® with 0.1% rhodamine B and scanned in micro-CT once again. For the retreatment of the specimens, 3 groups were established according to the system used (Reciproc®, Hyflex® and ProDesign Duo Hybrid®). During the retreatment, the specimens were scanned in micro-CT in two more phases, after removal of filling material and after reinstrumentation of the root canals. All the images obtained previous and post-retreatment were compared to evaluate the capacity of removal filling material of each system through the volume of material remaining at 3mm in the apical third. Possible deviation of the root canal was assessed at 2, 4, 6, 8 and 10 mm from the apex. In addition, the times of preparation, removal filling material and reinstrumentation of these files were also evaluated. After the removal filling material and reinstrumentation of the root canals, they were refilled with AH Plus with 0.1% fluorescein. The specimens were sectioned crosswise into 2 mm slices to be analyzed by a confocal laser scanning microscope (CLSM) at 1, 3 and 5 mm from the apex, where the volume of material was evaluated through LAS X 3D and 2D software. The time of preparation, removal filling material and reinstrumentation of the root canals between the different systems was measured by a digital timer. The evaluation of canal volumetric increase and preparation time between Mtwo and ProDesign Logic systems were conducted using Student t-test analysis. Non-parametric Wilcoxon test was used to the intragroup comparison at the 2, 4, 6, 8 and 10 mm levels and non-parametric Mann-Whitney test was used to the comparison between groups in the root canal transportation in all sections of the root canal. The intra-group comparison regarding the presence or absence of root canal deviation after removal of root canal filling material and re-instrumentation was submitted to the parametric T-paired statistical test, since it had a normal distribution. The working time with the different alloys used to removal filling material an reinstrumentation was analyzed through parametric ANOVA e Tukey statistical test. The analysis of the remaining material present in the root canals was performed with nonparametric Kruskal-Wallis and Dunn tests. For the intra-group comparison between the different slices (1, 3 and 5 mm), the data were submitted to nonparametric Friedman and Dunn tests. The level of significance was established at 5% in all analysis. After the initial preparation of the root canals, the ProDesign Logic system proved to be faster than Mtwo system, with statistical difference between them (P <0.05). There was no statistical difference in root canal deviation after initial preparation and after retreatment (P> 0.05). In addition, the groups did not present a significant statistical difference to the volume increase of the root canals after the initial preparation or to the volume of filling material remaining after the retreatment (P> 0.05). The Reciproc system proved to be the fastest system for the removal filling material and reinstrumentation of the root canals (P <0.05). The present study demonstrated that the Prodesign Logic and Mtwo systems presented similar capacity of preparation of mesial root canals. The Reciproc, Hyflex and ProDesign Duo Hybrid systems are similar in the removal of filling material, preserving the original root canal shape in endodontic retreatment. However, Reciproc was the fastest compared to the other groups.(AU)

O presente trabalho teve como objetivo avaliar os efeitos decorrentes do preparo inicial, desobturação, reinstrumentação e reobturação de canais radiculares com diferentes ligas de Ni-Ti em casos de retratamento endodôntico. Primeiramente, foi realizado a seleção e o pareamento da anatomia de canais mesiais de primeiros molares inferiores (n=45) através de micro-tomografia computadorizada (micro-CT). Após o pareamento dos espécimes, os mesmos foram divididos em três grupos (n =15), instrumentados com os sistemas Mtwo® (até a lima 25.06), ProDesign Logic (25.06) e ProDesign R (25.06) sendo escaneados novamente para análise de desvio do canal radicular a 2, 4, 6, 8 e 10 mm, além do aumento de volume desses canais, avaliados através do CTan. Em seguida, os canais radiculares foram obturados com o cimento Endofill® acrescido de 0,1% de rodamina B e escaneados em micro-CT mais uma vez. Para o retratamento dos espécimes, foram estabelecidos 3 grupos, de acordo com o sistema utilizado (Reciproc®, Hyflex® e ProDesign Duo Híbrido®). Durante o retratamento, os espécimes foram escaneados em micro-CT em mais duas etapas, após a desobturação e a após a reinstrumentação dos canais. Todas as imagens obtidas referentes ao pré e pós retratamento foram confrontadas com o intuito de avaliar a capacidade de remoção de material obturador de cada sistema através do volume de material remanescente nos 3 mm apicais, além de avaliar possíveis desvios dos canais a 2, 4, 6, 8 e 10 mm do ápice. Foram avaliados também, o tempo efetivo de preparo, desobturação e de reinstrumentação desses instrumentos. Após a desobturação e reinstrumentação dos canais, os mesmos foram reobturados com cimento AH Plus acrescido de 0,1% de fluoresceína. Os espécimes foram seccionados transversalmente em fatias de 2 mm para serem analisados em microscópio confocal de varredura a laser (MCVL) a 1, 3 e 5 mm do ápice, onde foi avaliado, através do software LAS X 3D e 2D, o volume de material obturador antigo. O tempo de preparo, desobturação e reinstrumentação dos canais entre os diferentes sistemas foi marcado através de um cronômetro digital. A análise do aumento volumétrico e tempo de preparo entre os sistemas Mtwo e ProDesign Logic foi feita através do teste estatístico Student t. Para a análise do desvio do canal radicular após o preparo inicial, o teste não-paramétrico Wilcoxon foi utilizado para a comparação intra-grupos nos níveis a 2, 4, 6, 8 e 10 mm do ápice, enquanto o teste não-paramétrico Mann-Whitney foi utilizado para comparação entre os grupos nos mesmos níveis. Para a análise do desvio do canal radicular após a desobturação e reinstrumentação dos canais, os dados foram submetidos ao teste paramétrico T-pareado. O tempo de desobturação e reinstrumentação com os diferentes sistemas foi analisado através do teste ANOVA e Tukey. Os dados referentes ao remanescente de material obturador foram analisados através dos testes não-paramétrico Kruskal-Wallis e Dunn. Para a comparação intra-grupos entre os diferentes níveis (1, 3 e 5 mm) foram utilizados os testes não-paramétricos Friedman e Dunn. O nível de significância foi estabelecido a 5% em todas as análises. Após o preparo inicial dos canais, o sistema ProDesign Logic demonstrou ser mais rápido que o sistema Mtwo, havendo diferença estatística entre eles (P < 0.05). Não houve diferença estatística quanto ao desvio do canal radicular tanto após o preparo inicial quanto após o retratamento (P > 0.05). Além disso, os grupos também não apresentaram diferença estatística significante quanto ao aumento do volume dos canais após o preparo inicial, nem em relação ao volume de remanescente de material obturador após o retratamento (P > 0.05). O sistema Reciproc demonstrou ser o mais rápido dentre os sistemas quanto à desobturação e reinstrumentação dos canais (P < 0.05). O presente trabalho demonstrou que os sistemas Prodesign Logic and Mtwo apresentaram capacidade similar de preparo dos canais mesiais de molares inferiores. Os sistemas Reciproc, Hyflex e ProDesign Duo Híbrido são parecidos quanto à remoção de material obturador, preservando o formato original do canal em casos de retratamentos entodônticos. Entretanto, Reciproc foi o mais rápido comparado aos outros grupos.(AU)

On the Causality Between Dentinal Defects and Root Canal Preparation: A Micro-CT Assessment.

This study aimed to evaluate the cause-effect relationship between canal preparation with ProTaper Universal (PTU) system and dentinal defects formation using micro-computed tomography (micro-CT) analysis. Forty mesial canals of mandibular molars with a type II Vertucci's canal configuration were scanned at an isotropic resolution of 14.16 µm. The sample was assigned to an experimental (n = 30) and a control (n = 10) groups, and the mesial canals were prepared with PTU system up to F2 instrument. The specimens from the experimental group were scanned and the cross-section images of the mesial roots, before and after preparation, were screened to identify the presence of dentinal defects. In the control group, the specimens were sectioned perpendicularly to the long axis of the root into 1-mm-thick slices (n = 80) and examined under optical microscope. Once a dentinal defect was detected, the slice was scanned through micro-CT. In the experimental group, dentinal micro-cracks were observed in 4,828 slices (24.04%). In all cross-section images, dentinal defects identified in the postoperative images were already present in the corresponding preoperative image. In the control group, 13 out of 80 slices (16.25%) had at least one dentinal defect visualized under stereomicroscopy, which was identified after a further micro-CT scanning. Micro-CT showed reliability as similar as optical microscopy in detecting dentinal defects, adding the possibility of tracking the dentinal tissue, before and after canal preparation, and providing a clear visualization of micro-cracks. Root canal preparation with PTU system did not induce the formation of new dentinal defects.

On the Causality Between Dentinal Defects and Root Canal Preparation: A Micro-CT Assessment

Abstract This study aimed to evaluate the cause-effect relationship between canal preparation with ProTaper Universal (PTU) system and dentinal defects formation using micro-computed tomography (micro-CT) analysis. Forty mesial canals of mandibular molars with a type II Vertucci's canal configuration were scanned at an isotropic resolution of 14.16 µm. The sample was assigned to an experimental (n = 30) and a control (n = 10) groups, and the mesial canals were prepared with PTU system up to F2 instrument. The specimens from the experimental group were scanned and the cross-section images of the mesial roots, before and after preparation, were screened to identify the presence of dentinal defects. In the control group, the specimens were sectioned perpendicularly to the long axis of the root into 1-mm-thick slices (n = 80) and examined under optical microscope. Once a dentinal defect was detected, the slice was scanned through micro-CT. In the experimental group, dentinal micro-cracks were observed in 4,828 slices (24.04%). In all cross-section images, dentinal defects identified in the postoperative images were already present in the corresponding preoperative image. In the control group, 13 out of 80 slices (16.25%) had at least one dentinal defect visualized under stereomicroscopy, which was identified after a further micro-CT scanning. Micro-CT showed reliability as similar as optical microscopy in detecting dentinal defects, adding the possibility of tracking the dentinal tissue, before and after canal preparation, and providing a clear visualization of micro-cracks. Root canal preparation with PTU system did not induce the formation of new dentinal defects.

Resumo O objetivo deste estudo foi avaliar a relação de causa-efeito entre o preparo do canal radicular com o sistema ProTaper Universal (PTU) e a formação de defeitos dentinários usando a análise por micro-tomografia computadorizada (micro-CT). Quarenta raízes mesiais de molares inferiores com a configuração tipo II de Vertucci foram escaneadas com resolução isotrópica de 14.16 μm. A amostra foi distribuída em um grupo experimental (n = 30) e um grupo controle (n = 10), e os canais mesiais foram preparados com o sistema PTU até a lima F2. As amostras do grupo experimental foram escaneadas e as imagens de secção transversal das raízes mesiais, antes e após o preparo, foram analisadas ​​para identificar a presença de defeitos dentinários. No grupo controle, os dentes foram seccionados perpendicularmente em relação ao longo eixo da raiz em fatias de 1 mm de espessura (n = 80) e examinados ao microscópio óptico. Uma vez detectado um defeito dentinário, a fatia foi escaneada através da micro-CT. No grupo experimental, defeitos dentinários foram observados em 4.828 secções transversais (24,04%). Em todas as imagens de secção transversal, os defeitos dentinários após os procedimentos experimentais já estavam presentes na secção pré-operatória correspondente. No grupo controle, 13 das 80 fatias (16,25%) apresentaram pelo menos um defeito dentinário visualizado através do microscópio, o qual foi identificado em um escaneamento posterior. A micro-CT mostrou confiabilidade com a microscopia óptica para detecção e visualização dos defeitos dentinários, permitindo acompanhar o tecido dentinário antes e depois do preparo do canal. O preparo do canal radicular com o sistema PTU não induziu a formação de novos defeitos dentinários.