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Endodontic therapy conserves the natural tooth by treating diseased pulp and promoting periapical healing. Curved root canals pose challenges in transportation, ledges, perforations, and instrument separation, impacting treatment results. Effective assessment and management are essential. Methodologies such as Schneider's and Weine's techniques, along with cone-beam computed tomography, refine the accuracy of curvature measurements. Proper techniques, involving anti-curvature filling and tactile controlled activation, are pivotal for successful treatment. Understanding root canal curvature and employing applicable approaches are vital for minimizing the complications and refining treatment success. An acclimatized approach grounded on curvature characteristics enhances endodontic sequels. This article reviews the cases involving patients with curved root canals, emphasizing treatment avenues and outcomes. [ABSTRACT FROM AUTHOR]

Objective To study anatomical structures of the maxillary second molars (MSM) roots and canals and the relationship between root apices and the maxillary sinus. Methods Cone beam computed tomography imaging data of 526 MSM from 263 patients were evaluated retrospectively. The patient age, number of roots and canals, number of fused roots, type of root canal curvature, and anatomical relationship to the sinus floor were all documented and analyzed. Results It was found that the majority of MSM had three roots (59.1%), and the incidence of three root canals with three roots was the highest (47.3%). Fused roots were found in 192 (36.5%) of the teeth examined. Palatal root canals of two-root, two-canal, and three-root, three-canal teeth had more curvature in the buccolingual direction than in the mesiodistal direction. The mesial buccal roots of MSM with three roots tended to extend into the maxillary sinus and the palatine roots of the three-rooted MSM tended to separate from the maxillary sinus. The distance between MSM and the sinus floor increased with age(P

Background: It is not uncommon for a dentist to encounter endodontic cases of severely curved root canals. Performing endodontic treatment on severely curved root canals can be a daunting task due to the notable risk of creating an iatrogenic error including ledge, perforation, or even instrument separation. Therefore, radiograph image analysis, proper endodontic treatment planning, selection of appropriate instruments and technique is essential to ensure success in endodontic treatment of severely curved root canals. Purpose: This case series aims to elaborate the instruments and technique to safely negotiate, clean, shape, and seal root canals with severe curvature. Cases: Three patients came to Universitas Airlangga Dental Hospital due to a severe toothache. After anamnesis and examination, diagnosis was established, and endodontic treatment was deemed necessary. During radiographic image analysis, it is visible that the root canal had a severe curvature. Case Managements: Access opening was performed to allow a straight-line access, orifices were preflared, root canals were negotiated, and glide path was established. Then, shaping, cleaning, and sealing can be performed conveniently until the root canal terminus. Subsequently, coronal restoration was fabricated to restore function and esthetics. Conclusion: With proper knowledge, case analysis, appropriate instruments and techniques, severely curved root canals can be safely and predictably negotiated, cleaned, shaped, and sealed.

Abstract Background Root canal therapy is one of the main treatments for root canal diseases, and effective irrigation is the key to successful treatment. Side-vented needle is one of the commonly used needle types in clinic. In the real root canal, due to the influence of the curvature of the root canal, the irrigation flow field in different needle directions shows obvious differences. At the same time, changes in root canal curvature and working depth will lead to changes in irrigation efficiency and the flow field. Both the mainstream of the irrigation flow and the shear stress near the wall changes significant. Consequently, either the replacement in the root canal or the removal efficiency of the smear layers is apparently modified. Materials and methods In this paper, the permanent root canal of the maxillary first molar prepared until 15/04 were scanned by micro-CT, and then imported into the software for 3D reconstruction. The key parameters of flushing efficiency of 30G side needle at different working depths of 4.75 mm, 5 mm, 5.25 mm and 5.5 mm were compared. Meanwhile, the simulated models with different curvatures of 0°, 5°, 10°, 20° and 30° based on the real root canal were reconstructed to investigate the curvature effect on the irrigation efficiency. Results The results show that moderate working depth (such as 4.75 mm and 5.25 mm in present paper) helps to improve the replacement capacity of irrigation flow. At the same time, the apical pressure decreased as the working depth increased. The curvature of the root canal seriously affects the removal depth of the smear layers of the root canal. A root canal with a large curvature (especially 20° and 30°) can significantly improve the difficulty of irrigation. Conclusions (1) Moderate working depth helps to improve the displacement capacity, the ERD of the irrigation flow is generally improved at the working depths of 4.75 mm and 5.25 mm, and the apical pressure will decrease with the increase of working depth. (2) The large curvature of the root canal can significantly improve the difficulty of irrigation. The curvature of the root canal can severely influence the removal depth of the smear layer on the wall. It can be found both the span and the depth of the ESS for little curvatures (5° and 10°) root canals are higher than those for large curvatures (20° and 30°).

Background: Root canal therapy is one of the main treatments for root canal diseases, and effective irrigation is the key to successful treatment. Side-vented needle is one of the commonly used needle types in clinic. In the real root canal, due to the influence of the curvature of the root canal, the irrigation flow field in different needle directions shows obvious differences. At the same time, changes in root canal curvature and working depth will lead to changes in irrigation efficiency and the flow field. Both the mainstream of the irrigation flow and the shear stress near the wall changes significant. Consequently, either the replacement in the root canal or the removal efficiency of the smear layers is apparently modified. Materials and methods: In this paper, the permanent root canal of the maxillary first molar prepared until 15/04 were scanned by micro-CT, and then imported into the software for 3D reconstruction. The key parameters of flushing efficiency of 30G side needle at different working depths of 4.75 mm, 5 mm, 5.25 mm and 5.5 mm were compared. Meanwhile, the simulated models with different curvatures of 0°, 5°, 10°, 20° and 30° based on the real root canal were reconstructed to investigate the curvature effect on the irrigation efficiency. Results: The results show that moderate working depth (such as 4.75 mm and 5.25 mm in present paper) helps to improve the replacement capacity of irrigation flow. At the same time, the apical pressure decreased as the working depth increased. The curvature of the root canal seriously affects the removal depth of the smear layers of the root canal. A root canal with a large curvature (especially 20° and 30°) can significantly improve the difficulty of irrigation. Conclusions: (1) Moderate working depth helps to improve the displacement capacity, the ERD of the irrigation flow is generally improved at the working depths of 4.75 mm and 5.25 mm, and the apical pressure will decrease with the increase of working depth. (2) The large curvature of the root canal can significantly improve the difficulty of irrigation. The curvature of the root canal can severely influence the removal depth of the smear layer on the wall. It can be found both the span and the depth of the ESS for little curvatures (5° and 10°) root canals are higher than those for large curvatures (20° and 30°). [ABSTRACT FROM AUTHOR]

Objective: To evaluate the impact of different file access angles and root canal curvature's location on the fatigue failure of One Curve (OC) and E3 Azure (EZ) NiTi files using a dynamic model at simulated body temperature. Methods: Eighty new instruments with similar tip sizes and taper (#25/0.06) from two NiTi rotary systems, One Curve and E3 Azure, were tested at simulated body temperatures (37°C) using a custom-made dynamic cyclic fatigue device. Instruments were divided into four subgroups according to the location of root canal curvature (a coronal curve 5 mm from the root canal orifice and an apical curve 10 mm from the root canal orifice) and the angle of file access (0° or 30°). Instruments were operated in simulated stainless-steel canals having a 60° curve and a 3 mm radius. A custom-made device produced controlled vertical pecks during file rotation. Time to failure (sec) was registered, and the length of the fragment segments was measured (mm). Data were analysed statistically with One-Way ANOVA and Tukey post hoc tests. The significance level was set at 5%. All separated instruments were examined by scanning electron microscope. Results: One-way ANOVA (p<0.05) found a significant difference among the tested instruments. Post Hoc analysis revealed lower cyclic fatigue resistance when the angle of file access was 30º, and the root canal curvature was located coronally for both files (p<0.0001). Three-way ANOVA showed that the angle of file access was the most influential contributor to cyclic fatigue, followed by the location of file curvature and, finally, the file type (p<0.0001). The fractographic examination revealed a predominantly ductile fracture mode for all tested instruments. The lengths of all fractured segments showed no significant difference (p>0.05), indicating an accurate trajectory during testing. Conclusion: OC files had superior cyclic fatigue resistance than EZ files; coronal curvatures negatively impacted cyclic fatigue resistance compared to apical curvatures, while the angle of file access presented the highest impact on dynamic cyclic fatigue. [ABSTRACT FROM AUTHOR]

Abstract Backgrounds To compare the irrigation efficiency with different needle working length and different root canal curvature based on a real unshaped root canal using computational fluid dynamics (CFD) method. Methods Images of the root canal of the maxillary first molar after being prepared to .04/15 were scanned using micro-CT, and then imported into the software for three-dimensional reconstruction. A palatal root canal with a curvature of 23.4° was selected as the experiment canal. The needle working length of the 30-G flat needle was 4.75 mm, 5 mm, 5.25 mm and 5.5 mm short of apical foramen respectively, the flow pattern, irrigation velocity, shear stress were compared. The modified curved canals with a curvature of 0°, 5°, 10°, 20° and 30°were reconstructed via software. The flat needle was replaced at the optical inserted depth, and key parameters of irrigation efficiency were analyzed. Results Decreased needle working length had a positive impact on irrigation efficiency. With the optimal needle working length, the replacement of the apical irrigation fluid, the effective velocity, and wall shear stress were significantly improved in more severely curved root canals. With the same needle working depth and analogous canal curvature, irrigation efficiency is higher in real canal than that of modified canal. Conclusions Short needle working depth, large curvature and the anomalous inner wall of canals help to improve irrigation efficiency.

Backgrounds: To compare the irrigation efficiency with different needle working length and different root canal curvature based on a real unshaped root canal using computational fluid dynamics (CFD) method. Methods: Images of the root canal of the maxillary first molar after being prepared to.04/15 were scanned using micro-CT, and then imported into the software for three-dimensional reconstruction. A palatal root canal with a curvature of 23.4° was selected as the experiment canal. The needle working length of the 30-G flat needle was 4.75 mm, 5 mm, 5.25 mm and 5.5 mm short of apical foramen respectively, the flow pattern, irrigation velocity, shear stress were compared. The modified curved canals with a curvature of 0°, 5°, 10°, 20° and 30°were reconstructed via software. The flat needle was replaced at the optical inserted depth, and key parameters of irrigation efficiency were analyzed. Results: Decreased needle working length had a positive impact on irrigation efficiency. With the optimal needle working length, the replacement of the apical irrigation fluid, the effective velocity, and wall shear stress were significantly improved in more severely curved root canals. With the same needle working depth and analogous canal curvature, irrigation efficiency is higher in real canal than that of modified canal. Conclusions: Short needle working depth, large curvature and the anomalous inner wall of canals help to improve irrigation efficiency. [ABSTRACT FROM AUTHOR]

Root canal curvature and calcification introduce factors that increase the risk of procedural accidents during root canal treatment. The inability to achieve patency to the apical third, asymmetrical dentine removal leading to transportation, perforation, and instrument fracture inside the curved trajectories are some of the procedural problems that might jeopardize the management of intraradicular infection and result in poor treatment outcomes. In fact, curved and constricted canals introduce such complexity that total instrumentation concepts and specially designed instruments have been developed to deal with the challenge. This narrative review seeks to provide and consolidate the principles necessary for understanding the dynamics of curved and constricted canal management and to improve the understanding for future developments in this field. [ABSTRACT FROM AUTHOR]

The purpose of this study was to comprehensively assess by micro–computed tomographic imaging the anatomic features of distolingual (DL) roots and canals in mandibular first molars collected from 1 population. One hundred two specimens were examined for the location and initial direction of the DL canal and the relationship between the distance of apical deviation and the angle of root curvature. All DL roots had only 1 canal. A new 7-category classification system is proposed for the DL roots of mandibular first molars. Most DL roots were type IV (28 teeth), type III (26 teeth), and type V (25 teeth). The average canal curvature in all root types was over 25°. There was a positive correlation between the angles of root and canal curvature for types II, IV, and V (P <.05) but not for types I and III (P >.05). In the buccolingual view, most DL roots were straight, whereas in the mesiodistal view the root curvature was close to the maximum value. The orifice of the DL canal was 4 times further from the line that bisects a line between the mesiobuccal and mesiolingual canal orifices than the distobuccal canal. The angle between the mesiobuccal-mesiolingual line and the horizontal projection of the coronal third of the DL canal on the pulp floor was 8.1° ± 10.0° and 6.1° ± 8.2° for teeth from the left and right side, respectively. The angle between the inserted simulated file and the cementoenamel junction was 57.9° ± 6.3°. Seventy-three percent of the DL canals had no constriction in the apical area. The DL canals were narrow and had a conical frustum-like shape with a 0.04 taper at the apical portion. The novel classification of the DL roots helps to better understand the clinically challenging anatomy of the root and canal. [ABSTRACT FROM AUTHOR]

The successful outcome of endodontic treatment is dependent on complete cleaning, shaping as well as three dimensional obturation of the root canal system. A conventional radiograph is a two-dimensional replication of a three-dimensional object and does not provide any conclusive evidence for canal curvatures. An accurate knowledge of the tooth anatomy and curvature is essential to avoid procedural errors. 100 freshly extracted human teeth were used in this study. Digital images were obtained using the plywood JIG and Schneider's technique. These images were analyzed using the VixWin Pro digital image analyzing software (Gendex system). Statistical analysis was done using paired t test. The canal curvature average values measured using Jig method and Schneider method for mandibular teeth are 28.23° (±9.96) and 22.07° (±9.46) respectively. The smallest/largest curvature angles measured using Jig method and Schneider technique are 12/52° and 8/44° respectively. Canal curvature average values measured using Jig method and Schneider method for maxillary teeth were 23.40° (±11.36) and 19.23° (±11.94) respectively. The smallest/largest average curvature angles measured using Jig method, Schneider technique were 9/70° and 5/72° respectively. The values of the canal curvature angle obtained during routine radiographs in clinics have lower curvature angle and higher radius values as compared to the values obtained by this innovative JIG technique. Therefore, a clinician should always keep in mind the difference while measuring the curvature angle on radiographs during root canal treatment. [ABSTRACT FROM AUTHOR]

Aim: Reciproc and WaveOne (WO) system was used to evaluate the canal centering ability and apical transportation by cone-beam computed tomography. Materials and Methods: Forty extracted human single-rooted mandibular premolars were used in the present study. Preinstrumentation scans of all teeth were taken; canal curvatures were calculated; and the samples were randomly divided into two groups with 20 samples in each group, where Group 1-Reciproc system and Group 2-WO reciprocation system. Postinstrumentation scans were performed using DICOM software and the two scans were compared to determine centering ability and canal transportation at 3, 6, and 9 mm from the root apex. Results: Using Student's unpaired t-test results were as follows, for centering ability Group 1 showed nonstatistically significant difference at 3 mm and 9 mm, whereas a statistically significant difference (P < 0.05) at 6 mm was obtained. For canal transportation, Group 1 showed a statistically significant difference (P < 0.05) at 3 mm and 6 mm, and nonsignificant difference was obtained at 9 mm, but for Group 2, nonstatistically significant difference (P > 0.05) was obtained at 3 mm, 6 mm, and 9 mm. Conclusion: WO single reciprocation file has better centering ability, maintains original canal curvature, and causes lesser canal transportation as compared to reciproc.

Introduction: The aim of this study was to investigate the effect of instrument material, taper and degree of root canal curvature, and the interaction between these factors on the cyclic fatigue of rotary nickel-titanium instruments. Materials and methods: Two types of rotary NiTi root canal instruments made from different materials were tested: ProFile GT and Profile GT Series X (both Dentsply Tulsa Dental, Tulsa, OK, USA). For each system, 60 instruments of similar size (size 30) were divided into three equal groups according to instrument taper (0.04, 0.06, or 0.08). Then each group was tested for cyclic fatigue resistance in simulated root canals exhibiting 5 mm radius of curvature, and either a 45- or 60-degree angle of curvature. The number of cycles to failure were analysed by one-way analysis of variance (ANOVA), followed by Tukey-Kramer multiple-comparison post hoc test. Then three-way analysis of variance was performed to assess the interaction between instrument material, taper and canal curvature on cyclic fatigue. Results: The results of the one-way ANOVA revealed that there was a significant effect for each of the studied variables on cyclic fatigue. The results of the three-way ANOVA revealed that the interaction between the variables significantly but unequally affected cyclic fatigue. Conclusions: The most effective variable was the degree of root canal curvature, followed by instrument taper, and finally the material used for manufacturing of the instruments. [ABSTRACT FROM AUTHOR]

The purpose of the mechanical root canal preparation is to clean it and give it the right shape. The preparation should be carried out in a way that maintains the original curvature and initial orientation of the apical end. Insufficient root canal preparation may prevent effective chemical decontamination and obturation to the full working length. The study aims to evaluate the shaping ability and effectiveness of the NiTi rotary and reciprocating endodontic instruments, compared to standard hand files using magnetic resonance imaging based on spin echo. Material and methods: A comparative study of severely curved root canals' shaping abilities using three NiTi systems and K-type hand files was performed, with 40 training "endo-blocks" presenting with "L-shaped" canal. The root canal topography and geometry "before" and "after" mechanical preparation obtained by the magnetic resonance imaging based on the spin echo was used. The main measurement was made using the RARE sequence, with slice thickness reduced to 100 micrometers. In order to improve the signal-to-noise ratio, NA = 25 was used. To minimize the measurement time, the field of view was limited to a cuboid 17 × 16 × 3 mm, with a resolution of 33 × 31 × 100 micrometers. Each 3D image consisted of 512 × 512 × 30 voxels. The imaging plane has been selected in such a way as to fully illustrate the course of curvature of the model root canal. For TR = 5 s and effective TE = 36 ms, TA was 1.5 h. Measurements were performed twice, before and after the preparation of endo-blocs with a selected type of endodontic tools. Results: The use of rotary NiTi instruments caused a substantial alteration in the curvature topography and angle of the canals and change in the curvature length. The substantial discrepancy was observed during the preparation of simulated root canals with the reciprocating instruments and the use of WaveOne files led to the largest volume variation. No dependence between the amount of material removed and the measured intracanal side was observed when NiTi instruments were used. Preparation with hand K-type files revealed a relationship between the measuring side and the amount of material removed, with the lower values obtained for the canals' internal curvatures. Conclusions: All the studied endodontic instruments allow a safe preparation of curved root canals in simulating in vivo conditions. The abbreviation of original root canals topography does not seem to be significantly altered following mechanical preparation of simulated, severely curved root canals. The spin echo-based magnetic resonance imaging technique can be utilized for visualization of the internal topography of the root's canals in vitro before and after their mechanical preparation in in vitro conditions. In the future, magnetic resonance microscopy may become a diagnostic tool supporting the work of a clinician. [ABSTRACT FROM AUTHOR]

The endodontic treatment of a tooth with radix entomolaris can present significant challenges due to the presence of root curvature. The present report describes the endodontic treatment of a permanent mandibular first molar with type II radix entomolaris and separation of endodontic file in the root canal followed by its retrieval using the trephining technique. A 38 years old female patient visited the Department of Operative Dentistry at the Dow University of Health Sciences w ith complain of spontaneous and lingering pain and food impaction in tooth #46 since six months. On intraoral examination, tooth #46 had class II cavity. On periapical radiograph, an accessory root w'as observed. Endodontic treatment of the tooth was initiated. During shaping of the accessory canal, SX separated. The separated file was bypassed and successful retrieval was performed using the trephining technique. Endodontic treatment of the tooth w'as completed. The tooth was found to be asymptomatic in the followup visits and the patient was referred for a full coverage crown. [ABSTRACT FROM AUTHOR]

The successful outcome of endodontic treatment is dependent on complete cleaning, shaping as well as three dimensional obturation of the root canal system. A conventional radiograph is a two-dimensional replication of a three-dimensional object and does not provide any conclusive evidence for canal curvatures. An accurate knowledge of the tooth anatomy and curvature is essential to avoid procedural errors. 100 freshly extracted human teeth were used in this study. Digital images were obtained using the plywood JIG and Schneider’s technique. These images were analyzed using the VixWin Pro digital image analyzing software (Gendex system). Statistical analysis was done using paired t test. The canal curvature average values measured using Jig method and Schneider method for mandibular teeth are 28.23° (±9.96) and 22.07° (±9.46) respectively. The smallest/largest curvature angles measured using Jig method and Schneider technique are 12/52° and 8/44° respectively. Canal curvature average values measured using Jig method and Schneider method for maxillary teeth were 23.40° (±11.36) and 19.23° (±11.94) respectively. The smallest/largest average curvature angles measured using Jig method, Schneider technique were 9/70° and 5/72° respectively. The values of the canal curvature angle obtained during routine radiographs in clinics have lower curvature angle and higher radius values as compared to the values obtained by this innovative JIG technique. Therefore, a clinician should always keep in mind the difference while measuring the curvature angle on radiographs during root canal treatment.

The purpose of the mechanical root canal preparation is to clean it and give it the right shape. The preparation should be carried out in a way that maintains the original curvature and initial orientation of the apical end. Insufficient root canal preparation may prevent effective chemical decontamination and obturation to the full working length. The study aims to evaluate the shaping ability and effectiveness of the NiTi rotary and reciprocating endodontic instruments, compared to standard hand files using magnetic resonance imaging based on spin echo. Material and methods: A comparative study of severely curved root canals’ shaping abilities using three NiTi systems and K-type hand files was performed, with 40 training “endo-blocks” presenting with “L-shaped” canal. The root canal topography and geometry “before” and “after” mechanical preparation obtained by the magnetic resonance imaging based on the spin echo was used. The main measurement was made using the RARE sequence, with slice thickness reduced to 100 micrometers. In order to improve the signal-to-noise ratio, NA = 25 was used. To minimize the measurement time, the field of view was limited to a cuboid 17 × 16 × 3 mm, with a resolution of 33 × 31 × 100 micrometers. Each 3D image consisted of 512 × 512 × 30 voxels. The imaging plane has been selected in such a way as to fully illustrate the course of curvature of the model root canal. For TR = 5 s and effective TE = 36 ms, TA was 1.5 h. Measurements were performed twice, before and after the preparation of endo-blocs with a selected type of endodontic tools. Results: The use of rotary NiTi instruments caused a substantial alteration in the curvature topography and angle of the canals and change in the curvature length. The substantial discrepancy was observed during the preparation of simulated root canals with the reciprocating instruments and the use of WaveOne files led to the largest volume variation. No dependence between the amount of material removed and the measured intracanal side was observed when NiTi instruments were used. Preparation with hand K-type files revealed a relationship between the measuring side and the amount of material removed, with the lower values obtained for the canals’ internal curvatures. Conclusions: All the studied endodontic instruments allow a safe preparation of curved root canals in simulating in vivo conditions. The abbreviation of original root canals topography does not seem to be significantly altered following mechanical preparation of simulated, severely curved root canals. The spin echo-based magnetic resonance imaging technique can be utilized for visualization of the internal topography of the root’s canals in vitro before and after their mechanical preparation in in vitro conditions. In the future, magnetic resonance microscopy may become a diagnostic tool supporting the work of a clinician.

Aim: To determine the influence of biomechanical preparation on various parameters of root canal curvature., Materials and Methods: A total of 72 tooth roots with moderate (10-25°) and severe canal curvature (26-75°) were selected and embedded in autopolymerizing acrylic resin for which cone-beam computed tomography (CBCT) image analysis was performed. Schneider angle, canal access angle (CAA), and the radius of curvature were determined preoperatively using auto-computer-aided design (CAD) 2021 software. Protaper gold rotary nickel-titanium (Ni-Ti) files were used to prepare the root canals. All angular and linear values were measured in auto-CAD and compared using postoperative CBCT pictures. The difference in pre- and postoperative values was assessed using paired samples t -test and independent samples t -test., Results: There was a statistically significant difference between the Schneider angle ( p = 0.002), ( p < 0.001), CAA ( p < 0.001), ( p = 0.001), and radius of curvature ( p = 0.01), ( p = 0.001) pre- and postoperatively in both moderate and severe canal curvature groups, respectively. This difference was greater in the severe curvature group ( p -value = 0.027) than in the group exhibiting moderate curvature. Among the parameters tested, Schneider angle has shown maximum difference pre- and post before and after mathematical processing (BMP) compared to other parameters., Conclusion: This approach is a new and objective way of measuring root canal geometric changes. The current findings suggest that the Schneider angle, CAA, and the radius of curvature can be used as parameters to evaluate the changes in canal geometry following biomechanical preparation., How to Cite This Article: Nekkanti H, Enuganti S, Avula JSS, et al. Assessment of Biomechanical Preparation Influence on Various Root Canal Curvatures. Int J Clin Pediatr Dent 2024;17(2):130-135., Competing Interests: Source of support: Nil Conflict of interest: None, (Copyright © 2024; The Author(s).)

Objective: In this study, the three-dimensional (3D) modification of root canal curvature was measured, after the application of Reciproc instrumentation technique, by using cone beam computed tomography (CBCT) imaging and a special algorithm developed for the 3D measurement of the curvature of the root canal.Materials and Methods: Thirty extracted upper molars were selected. Digital radiographs for each tooth were taken. Root curvature was measured by using Schneider method and they were divided into three groups, each one consisting of 10 roots, according to their curvature: Group 1 (0°-20°), Group 2 (21°-40°), Group 3 (41°-60°). CBCT imaging was applied to each tooth before and after its instrumentation, and the data were examined by using a specially developed CBCT image analysis algorithm.Results: The instrumentation with Reciproc led to a decrease of the curvature by 30.23% (on average) in all groups.Conclusions: The proposed methodology proved to be able to measure the curvature of the root canal and its 3D modification after the instrumentation. [ABSTRACT FROM AUTHOR]

Brief Background (1) To evaluate the correlation between the inter-orificial distance between the ML & MB orifices in permanent mandibular first molar and the degree of canal curvature (2) The correlation between the inter-orificial distance and prevalence of root canals configuration according to Vertucci's classification. Materials and Methods One hundred mandibular first molars were selected for the study. Teeth were decoronated using a diamond disc under water cooling. Teeth were radiographed in buccolingual(Proximal view) with 15 number K file placed in ML & MB canals for accessing the canal configuration and canal curvature. Sectioned tooth were viewed under stereomicroscope at 10X magnification. Data collected was statistically analyzed. Results Pearson's correlation with SPSSV21.0 software was performed. Results showed that there was very small negative correlation between the inter-orificial distance and MB & ML canal curvature respectively. But there was a significant effect (p=.006<.005) of the inter-orificial distance in predicting the type of canal configuration. Summary and Conclusions Within the limitations of the study it can be concluded that there is statistically significant correlation between the inter-orificial distance and the type of canal configuration but there is no statistically significant correlation between the inter-orificial distance and the canal curvature in permanent mandibular first molar in Indian (North) population. [ABSTRACT FROM AUTHOR]

Aim To evaluate the inter- and intra-observer agreement between training/trained endodontists regarding the ex vivo classification of root canal curvature into three categories and its measurement using three quantitative methods. Methodology Periapical radiographs of seven extracted human posterior teeth with varying degrees of curvature were exposed ex vivo. Twenty training/trained endodontists were asked to classify the root canal curvature into three categories (<10°, 10-30°, >30°), to measure the curvature using three quantitative methods (Schneider, Weine, Pruett) and to draw angles of 10° or 30°, as a control experiment. The procedure was repeated after six weeks. Inter- and intra-observer agreement was evaluated by the intraclass correlation coefficient and weighted kappa. Results The inter-observer agreement on the visual classification of root canal curvature was substantial ( ICC = 0.65, P < 0.018), but a trend towards underestimation of the angle was evident. Participants modified their classifications both within and between the two sessions. Median angles drawn as a control experiment were not significantly different from the target values ( P > 0.10), but the results of individual participants varied. When quantitative methods were used, the inter- and intra-observer agreement on the angle measurements was considerably better ( ICC = 0.76-0.82, P < 0.001) than on the radius measurements ( ICC = 0.16-0.19, P > 0.895). Conclusions Visual estimation of root canal curvature was not reliable. The use of computer-based quantitative methods is recommended. The measurement of radius of curvature was more subjective than angle measurement. Endodontic Associations need to provide specific guidelines on how to estimate root canal curvature in case difficulty assessment forms. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: Root canal curvature can affect the technical quality of endodontic treatment. Prior studies measured canal curvature mainly by 2-dimensional radiography. The aim of this study was to measure the 3-dimensional (3D) root canal curvature and canal direction of maxillary lateral incisors by using cone-beam computed tomography (CBCT) and mathematical modeling. Methods: The CBCT images of 186 maxillary lateral incisors from 110 patients were used to measure 3D root canal curvature by using V-works and kappa software. In addition, the direction of each root canal was determined by measuring the orientation of the apical one-third with respect to the coronal two-thirds. Results: All 186 maxillary lateral incisors were found to have canal curvature that was mainly oriented in the disto-palatal direction. The point of maximum curvature was located 0.5 mm from the root apex. Conclusions: Maxillary lateral incisors have 3D canal curvature that is maximal near the root apex, oriented in the disto-palatal direction. These CBCT analyses provide valuable information for root canal instrumentation of maxillary lateral incisors. [Copyright &y& Elsevier]

Abstract: Introduction: Little is known about the lingual canal in the Vertucci type V mandibular first premolar. This study investigated the location of the lingual canal orifice and the curvature of the lingual canal by using micro–computed tomography. Methods: One hundred fifteen mandibular first premolars were scanned by micro–computed tomography, reconstructed 3-dimensionally by using Mimics 10.01 software, and displayed in parallel projection mode. Twenty-six teeth with Vertucci type V canal were selected for further study. The lingual canal orifice was located by measurements made in both lingual and proximal views. The angle alpha (α) between the start of the lingual canal and the main canal and the angle beta (β) of the curvature of lingual canal were also measured. Results: In proximal view, 69% of lingual canals were located in the middle third of the tooth and the remainder in the apical third. In lingual view, 73% were located in the middle third of the root and the remainder in the coronal third. Mean angle α and angle β were 33.54° and 26.66°, respectively, in proximal view and 8.31° and 11.31°, respectively, in lingual view (P < .05). The highest values of angles α and β were observed in proximal view (65.24°and 43.39°, respectively). In most cases, angles α and β were severely curved in proximal view and straight or only slightly curved in lingual view. Conclusions: Detailed information on the lingual canal is essential for successful endodontic treatment in patients with mandibular first premolar. The view used for imaging influences the information obtained. [Copyright &y& Elsevier]

Abella F, Mercadé M, Duran-Sindreu F, Roig M. Managing severe curvature of radix entomolaris: three-dimensional analysis with cone beam computed tomography. International Endodontic Journal, 44, 876-885, 2011. Abstract Aim To present a case of a mandibular first molar with an additional distolingual root [radix entomolaris (RE)] and to discuss the use of cone beam computed tomography (CBCT) for its identification and management during root canal treatment. Summary A 52-year-old Caucasian woman was referred for root canal treatment of the right mandibular first molar (tooth 46). After clinical and radiographic examination, a symptomatic irreversible pulpitis was diagnosed. Three periapical radiographs with different horizontal angulations revealed the presence of an additional distolingual root. This extra root, termed RE, has an incidence of <5% in the Caucasian population. A CBCT examination was also taken, which revealed a severe root canal curvature, especially in the middle third, of this supernumerary root. CBCT provided more accurate information in terms of RE inclination and root canal curvature before commencing root canal treatment. The conventional access opening was modified into a more trapezoidal cavity, and five root canals were found. All canals were instrumented with new nickel-titanium (NiTi) files to reduce the risk of fractured instruments. After preparation, the root canals were filled using thermoplastified techniques. The 1-year follow-up periapical radiographs and CBCT images revealed a continuous periodontal space with no signs of apical periodontitis. Key learning points [ABSTRACT FROM AUTHOR]

Abstract: Introduction: The aim of this investigation was to study cyclic fatigue resistance of various nickel-titanium (NiTi) rotary files under various root canal curvatures by correlating cyclic fatigue fracture tests with finite-element analysis (FEA). Methods: Four NiTi rotary instruments with different cross-sectional geometries but comparable sizes were selected for this study: ProTaper (Dentsply Maillefer, Ballaigues, Switzerland), ProFile (Dentsply Maillefer), HeroShaper (Micromega, Besançon, France), and Mtwo (VDW, Munich, Germany). The ProFile and HeroShaper files were of size 30/.06 taper, the Mtwo was of size 30/.05 taper, and the ProTaper was F3. The cyclic fatigue test was conducted in a custom-made device that simulated canals with 25°, 35°, and 45° curvature. For the FEA, the file models were meshed, and 17-mm long curved canals were modeled to have same curvatures as the cyclic fatigue tests. Numerical analysis was performed to determine the stress distributions in the NiTi instruments while they rotated in the simulated curved canals. Results: ProTaper (the stiffest instrument) showed the least cyclic fatigue resistance and highest stress concentration for all tested curvatures, whereas Mtwo showed the best cyclic fatigue resistance. A comparison between the FEA and fatigue results showed that when stresses increased, the number of instrument rotations to fracture decreased. Maximum stresses in the instruments predicted the approximate location of the fatigue fracture. Conclusions: The stiffer instrument had the highest stress concentration in FEA and the least number of rotations until fracture in the cyclic fatigue test. Increased curvature of the root canal generated higher stresses and shortened the lifetime of NiTi files. Finite-element stress analysis reflected cyclic fatigue fracture resistance. [Copyright &y& Elsevier]

Abstract: Introduction: The distolingual (DL) roots of three-rooted mandibular molars often challenge clinicians during root canal therapy. This study investigated canal curvatures in permanent three-rooted mandibular first molars by using micro–computed tomography (micro-CT) scans. Methods: Twenty three-rooted (group 1) and twenty-five two-rooted mandibular first molars (group 2) were scanned by micro-CT. The specimens were reconstructed 3-dimensionally by the software Mimics 10.01 and shown in a parallel projection mode. The images of the root canals in clinical view (CV) and proximal view (PV) were analyzed by the software Image-Pro Plus. Schneider method and a modified Pruett method were used to measure the angles and radius of canal curvatures. Results: In the three-rooted molar group in a CV, the average angles of primary curvatures were 24.34 degrees for the mesiobuccal, 22.39 degrees for the mesiolingual, 13.71 degrees for the distobuccal (DB), and 13.81 degrees for the DL canal. In a PV, the average angles were 16.60 degrees for the DB and 36.06 degrees for the DL canal, respectively. Secondary curvatures were frequently seen in a CV (60%) for the DB canals, with an average angle of 26.94 degrees. In a PV, the average central angle of curvature was 59.04 degrees for the DL canal, and the average radius and curve length were 6.17 and 5.73 mm, respectively. In general, no statistically significant difference was found for canal curvatures in the mesial roots between the three-rooted and two-rooted molar groups (P > .05). Conclusions: A better understanding of the canal curvatures is essential for successful endodontic treatment of three-rooted mandibular first molars. [Copyright &y& Elsevier]

PURPOSE: To compare the shaping ability of two nickel-titanium rotary systems: Mtwo and K3. METHODS: Thirty-six mesio-buccal root canals of maxillary first molars were divided into two groups: group A (≥20°) and group B (<20°),according to the angle of the canal. Then, each group was randomly divided into two subsets and prepared by Mtwo,K3, respectively. All root canals were injected with the contrast medium and digital images of all canals were recorded before and after instrumentation. The computer assistant analyze image software was used to form the geometrical central line of pre-instrumented canals. Then the central line was imaged to the post-instrumented canals. The canal transportation and the decrease of curvature were measured. All the data was analyzed with SPSS 11.0 software package. RESULTS: Difference between groups was compared using t test. When the curvature of canal ≥20° , the transportation at the beginning of the curvature and the decrease of curvature of Mtwo were significantly less than those of K3 (P<0.05). When the curvature of canal <20°, there was no significant difference between Mtwo and K3 in the transportation and decrease of curvature(P>0.05). CONCLUSIONS: Both Mtwo and K3 systems show good preservation of the original geometry of the root canals; the Mtwo system can better preserve original curvature of canals, when the curvature of canal is larger than 20°. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the shaping characteristics of different root canal instruments in teeth with different root canal forms. A total of 420 extracted human roots were embedded in resin blocks. The embedded roots were divided into three groups, i.e., roots with (i) straight (I form), (ii) apically curved (J form), and (iii) entirely curved canals (C form) with reference to the Schneider's angle and the length of the radius of arc of the curvature of the root canals. Each of the three groups containing 140 roots were randomly divided into seven subgroups prior to preparation. The canals were enlarged manually with traditional and flexible hand instruments, three different engine driven instruments and sonically and ultrasonically powered instruments.. The shortcomings of the seven preparation methods were assessed by superimposition of projected radiographs taken in bucco-lingual and mesio-distal views before and after preparation. Results showed that observation of perforation, incidence of elbow and of asymmetrical preparation of the root canals depended on root canal configuration. It was striking that the coronal transposition of the apical stop, uneven wall contour, ledge formation and incidence of zip were independent of root canal morphology. Evaluation of data of asymmetry of preparation (canal transposition) revealed, significant differences (p<0.05). Asymmetry of preparation was the most frequent aberration of the prepared root canals and it was possible to study it with precision. It was concluded that this measurement should be a priority for future instrument testing. The shaping characteristics of hand and engine driven instruments was modified by root canal morphology., but that of sonic and ultrasonic instruments was less dependent on the original anatomical form of root canals. [ABSTRACT FROM AUTHOR]

Abstract The aim of the present roentgenographic in vitro study was to determine the initial straight length from the cemento-enamel junction (CEJ) to the appearance of a root canal curvature in human mandibular premolars. A total number of 282 mandibular premolars were examined. Exclusion criteria comprised root caries, extensive restorations and endodontically treated teeth. The teeth were fixed and digitally radiographed by means of a specially developed fixation device with standardized and reproducible distances with the parallel technique (Heliodent MD; Merlin 2.1). The distances from the CEJ to the first curvature (> 5°) (distance I), from the first curvature to a second curvature (distance II), and from the first or second curvature to the radiological apex (distance III) were recorded. The lengths of the initial straight distance and the appearance of a curvature were statistically analyzed and related to each other. In first mandibular premolars, the mean value for distance I was 10.9 mm, for distance II 3.7 mm and for distance III 3.04 mm. The mean values for the second mandibular premolars were 1.1 mm in distance I, 4.3 mm in distance II and 3.1 mm in distance III. No statistically significant differences between left and right mandibular premolars could be observed regarding the canal curvature location and the angle values. The results of this investigation show that curvatures are increasingly observed 9 to 12 mm from the original path in mandibular premolars.

The article presents a case study of a 38-year-old woman with a complaint of pain in lower left back region of jaw along with mandible abnormalities.