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Introduction: The anatomical configuration classified as Vertucci's type III is described as the second most prevalent in mandibular incisors. Methods: Thirty-six Vertucci's type III mandibular incisors were evaluated by micro-computed tomography (micro-CT) and divided into 3 groups (n = 12) according to the root canal preparation protocol (HyFlex CM [HCM], HyFlex EDM [HEDM], and Sequence Rotary File [SRF]). The teeth were scanned before and after performing 0.25 mm and 0.40 mm apical diameter preparations. The canal volume, dentin thickness, percentage of accumulated debris and untouched canal areas, transportation, and centering ability were measured. The data were statistically analyzed by ANOVA, Tukey, Kruskal-Wallis, and Dunn tests (P < 0.05). Results: The volume increase was more evident in the apical third. After 0.40 mm preparation, the SRF system provided a higher reduction (P < 0.05) in dentin thickness on the buccal surface 1 mm from the apex. There was higher canal transportation in the bucco-lingual direction. The 0.40 mm apical preparation reduced the percentage of untouched canal areas. The apical third had the highest percentage of untouched canal areas. The cervical third had the lowest volume of accumulated debris. Conclusions: Increasing the apical preparation to a diameter of 0.40 mm with the HCM, HEDM, and SRF systems in Vertucci's type III root canals of mandibular incisors proved to be safe and effective, reducing untouched canal areas. Clinical relevance: Root flattening can be intense to the point of generating a root canal bifurcation. Despite the decrease in the root canal diameter, a greater enlargement of the apical region is necessary and safe.

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This study aimed to evaluate the influence of large apical preparations with Reciproc (REC), Hyflex CM (HCM) and Twisted File Adaptive (TFA) systems using micro-computed tomography (MCT). Ninety mesiobuccal (MB) and distobuccal (DB) root canals of maxillary molars (n = 45) were scanned using MCT before and after the shaping procedures. The root canals (n = 15) were prepared until REC 40.06, HCM 40.04 and TFA 35.04. The root canal transportation (RCT), centring ability (CA), change in volume of the root canal and at different levels (VC), remaining dentine thickness (RDT), removal of dentine wall (RDW) and working time (WT) were evaluated. Data were analysed using the Kruskal-Wallis and Dunn tests, and the one-way ANOVA and Tukey tests with a level of significance set at 5%. No significant difference among the instruments was found regarding the RCT, CA, RDT, RDW and WT (P > 0.05), in larger apical preparations in curved MB and straight DB canals of maxillary molars.

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This study assessed the apical transportation using Mani GPR or HyFlex NT during the retreatment of curved root canals. Thirty-eight roots were analysed using micro-CT for the comparison of apical transportation produced by two retreatment systems. Longitudinal transportation, horizontal transportation, variation in the canal angle of curvature and variation in the canal/root width ratio were analysed. Longitudinal transportation was frequently observed, regardless of the system used. The canals retreated with Mani GPR showed a significantly higher horizontal transportation at 1 mm from the root apex (P < 0.01) and greater variation of the canal curvature angle (P < 0.01). The canal/root width ratio was similar between groups (P > 0.05). In conclusion, longitudinal transportation occurred more frequently in the mesial canal walls. Mani GPR showed greater horizontal transportation at 1 mm short of the apex, and higher variation of the canal curvature angle compared with HyFlex NT.

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OBJECTIVES: This study compared canal transportation and centering ratio produced after instrumentation with a single heat-treated reciprocating system, WaveOne Gold (WOG; Dentsply Sirona, Tulsa, OK, USA) and a single heat-treated rotary instrument, XP-endo Shaper (XPS; FKG, La Chaux-de-Fonds, Switzerland), using micro-computed tomographic (micro-CT) imaging, and evaluated the ability of double-digital radiography (DDR) to detect canal transportation. MATERIALS AND METHODS: Mesial root canals of mandibular molars with severe curvature (25-70°) were randomly assigned to either WOG or XPS groups for preparation. Centering ratio was measured by micro-CT imaging, while canal transportation was measured by micro-CT and DDR methods at 3, 5, and 7 mm from the apex. Data were statistically compared between groups using the t test (α = 5%). RESULTS: The micro-CT method showed that XPS's shaping ability regarding the centering ability (P = 0.030) and canal transportation (P = 0.028) was significantly better than WOG only at the 7-mm level. The DDR technique detected no difference in canal transportation between groups at any level (P > 0.05); however, a significant difference between evaluation methods was detected at the 5-mm level in the WOG group (P = 0.023). CONCLUSIONS: Micro-CT technique revealed a significantly better centering ability and less canal transportation with XPS compared to WOG. The DDR technique was not capable of detecting the significant difference between the tested groups. CLINICAL RELEVANCE: Root canal curvatures may lead to procedural errors during endodontic treatment. Thus, differences on the shaping ability of single heat-treated reciprocating and rotary systems should be known.

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Objective: There is a high prevalence of root canal transportation in the teeth with the curve. Effect of root canal transportation on the success of root canal therapy of tooth is negative and there is no study about comparing RaCe and Neoniti files in root canal transportation. The aim of this study is assessment and comparing two different RaCe and Neoniti files to determine transportation error in various parts of root using CBCT assessment and comparing them with each other. Material and Methods: In this experimental study 50 extracted mandibular molar teeth selected. Teeth were divided randomly into two groups i.e. 25 teeth threated with RaCe file (first group) and 25 teeth threated with Neonitu files (second group). CBCT images were used to measurement thickness of dentine, before and after instrumentation that obtain from NNT viewer 6.1.0 software. Results: In the first group, the mean tooth transportation in 5 mm of apex was 0.15 and, in the second group, the mean tooth transportation in 5 mm of apex was 0.18 mm. There was no statistically significant difference in canal transportation between RaCe and Neoniti files in five millimeters distant from apex area (p = 0.492) and the mean transportation from 9 mm of apex were 0.14 in the second group. There was no statistically significant difference in canal transportation between two groups (p = 0.911). Conclusion: In comparison of these two rotary files, both are equally safe regarding the extent of apical transportation. (AU)

Objetivo: Existe uma alta prevalência de desvio apical em canais radiculares curvos. O efeito do desvio apical no canal radicular sobre o sucesso da terapia endodôntica é desfvorável e não há nenhum estudo comparando as limas RaCe e Neoniti em relação ao desvio apical dos canais radiculares durante o preparo. O objetivo deste estudo é avaliar e comparar duas diferentes limas, RaCe e Neoniti, a fim de para determinar o erro de desvio em várias porções radiculares através de análise por TCCB e compará-los entre eles. Material e Métodos: Neste estudo experimental, 50 dentes molares mandibulares extraídos foram selecionados. Os dentes foram divididos aleatoriamente em dois grupos, ou seja, 25 dentes preparados com as limas RaCe (primeiro grupo) e 25 dentes preparados com limas Neoniti (segundo grupo). Neste estudo para medir a espessura da dentina através do escaneamento, antes e depois da instrumentação, ao mesmo tempo, usamos imagens axiais obtidas do software NNT viewer 6.1.0. Resultados: No primeiro grupo, o desvio apical médio a 5 mm do ápice foi de 0,15 e no segundo grupo o desvio apical médio a 5 mm do ápice foi de 0,18 mm, não havendo diferença estatisticamente significante entre as limas RaCe e Neoniti a cinco milímetros da porção apical (p = 0,492) e o transporte médio a 9 mm do ápice foi de 0,14 no segundo grupo não havendo diferença estatisticamente significante no desvio apical entre os dois grupos (p = 0,911). Conclusão: Os resultados indicaram que não houve diferença significativa no desvio apical médio entre dois sistemas de limas em 3, 9, 7, 5 e 11 mm do ápice e ambos as limas foram seguras (AU)

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INTRODUCTION: This study compared the cyclic fatigue and the canal transportation promoted by Twisted File (TF) Adaptive and Navigator EVO systems when used with 2 different motions. METHODS: Forty mesiobuccal roots of maxillary molars were scanned by using micro-computed tomography imaging before and after root canal preparation with the 2 instrument systems used with 2 motions (adaptive and continuous rotation). Samples were divided into 4 groups: TFA, TF Adaptive instruments under adaptive motion; TFC, TF Adaptive instruments under continuous motion; NA, Navigator instruments under adaptive motion; and NC, Navigator instruments under continuous motion. Root canals were prepared until 35.04 instruments. Apical transportation was analyzed by using micro-computed tomography at 3 levels: 3, 6, and 9 mm from the apex. The cyclic fatigue tests were performed by using a custom-made device. Ten instruments of each brand were activated by using a 6:1 reduction handpiece powered by a torque-controlled motor using the preset programs "custom mode" and "TF Adaptive" to activate 25.06 and 35.04 instruments. Kruskal-Wallis and Dunn tests were used to assess canal transportation, centering ability, and canal volume. The Student t test was used to evaluate cyclic fatigue (P = .05). RESULTS: At 3 and 9 mm, the canal transportation and centering ability were similar in all groups (P > .05). At 6 mm, TFC presented higher canal transportation toward furcal region than NA and NC (P < .05). After canal preparation, TFA promoted great dentinal excision, presenting higher canal volume than NA and NC (P < .05). Higher cyclic fatigue resistance was observed under continuous than adaptive motion regardless of system or tip/diameter of the instrument (P < .05). CONCLUSIONS: Both systems can be used under adaptive or continuous rotation. However, the life span of the instruments was higher when used under continuous rotation. Small canal transportation occurred when mesiobuccal root canals from maxillary molars were prepared until 35.04 instruments.

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Objective: To evaluate transportation (T) and centering ability (CA) of root canal preparations using continuous or reciprocating nickel-titanium endodontic files. Materials and Methods: Ninety-six mesiobuccal root canals of mandibular first and second molars were randomly divided into 6 groups (n=16) according to the rotary file used: 1. ProTaper Next; 2. ProTaper Gold; 3. Mtwo; 4. BioRaCe; 5. WaveOne Gold; 6. Reciproc. Root canals were prepared according to manufacturer's instructions. Cone beam computed tomography scans were obtained before and after root canal preparation. Measurements were made at six different reference points: 2, 3 and 4 mm from the apex and 2, 3 and 4 mm below furcation in different directions. Results: The greatest Mesiodistal (MD) Transportation (T) was found for Reciproc files (p<0.05), and the greatest buccolingual (BL) T, for Reciproc, ProTaper Gold and ProTaper Next files (p<0.05). The greatest Mesiodistal (MD) Centering Ability (CA) was found for BioRaCe files (p<0.05), and the greatest Buccolingual (BL) CA, for BioRaCe and Mtwo files (p<0.05). Conclusion: All systems produced root canal transportation. No file system achieved perfect CA of root preparation. Reciproc files had the greatest MD T and BL T. BioRaCe files had the greatest MD CA, whereas BL CA was similar for BioRaCe and Mtwo files.

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Introduction: The aim of this study was to evaluate the canal transportation and centering ability of ProTaper Next (PTN), WaveOne Gold (WOG) and Reciproc Blue (RCB) in simulated curved resin canals. Methods and Materials: A total of 43 blocks of simulated resin canals with 40° of curvature were prepared to an apical size of 0.02. Flexofile #15 instruments were used along the root canal to reach patency. The blocks were randomly assessed and sequence instruments were used according to each system: PTN, RCB and WOG. The imposition of pre and post instrumentation images were composited and analyzed. The canal transportation and apical centralization were measured using the software GIMP (2.8.4, Creative Commons - Share Alike 4.0 International License, 2013). Data were statistically analyzed using the Shapiro-Wilk test, ANOVA test and Tukey's test. The level of significance was set at 0.05. Results: There were no statistical differences in canal transportation between three systems. The general assessment of three systems presented the RCB group with higher values of centralization and more numbers of centralized points with significant differences between the PTN and RCB groups (P<0.05). Conclusion: In this in vitro study, there were no statistical differences in canal transportation between the RCB, WOG and PTN systems. The lowest transportation was observed in the apical region at 3 mm performed with RCB system, followed by WOG and PTN systems. The RCB demonstrated higher values of centralization and more centralized points when assessed by regions.

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INTRODUCTION: This study compared the shaping ability of ProTaper Next (Dentsply Sirona, Tulsa, OK) and BT-RaCe (FKG Dentaire, La Chaux-de-Fonds, Switzerland) instrument systems in the mesial canals of mandibular molars using micro-computed tomographic (micro-CT) imaging. METHODS: A total of 17 type IV mesial roots of extracted first mandibular molars were scanned using micro-CT imaging before and after root canal preparation with the 2 instrument systems. Both systems were used in the same root but alternating the mesial canals from root to root. The following parameters were analyzed: root canal volume, surface area, unprepared surface areas, transportation, canal/root width ratio, and preparation time. RESULTS: There were no statistically significant differences between the 2 systems for all evaluated parameters (P > .05). The unprepared surface areas for the full canal length and the apical 5-mm segment were 33% and 14% for BT-RaCe and 31% and 14% for ProTaper Next, respectively. After preparation, all root canals had a diameter that was not larger than 35% of the root diameter at the coronal and middle segments. CONCLUSIONS: The 2 systems showed no differences in any of the evaluated shaping parameters. None of the tested systems put the roots at risk of fracture because of excessive dentin removal.

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INTRODUCTION: The aim of this study was to evaluate, using cone-beam computed tomography (CBCT), transportation and centralization of different nickel-titanium (NiTi) rotary instruments. METHODS: One hundred and twenty eight mandibular premolars were selected and instrumented using the following brands of NiTi files: WaveOne, WaveOne Gold, Reciproc, ProTaper Next, ProTaper Gold, Mtwo, BioRaCe and RaCe. CBCT imaging was performed before and after root canal preparation to obtain measurements of mesial and distal dentin walls and calculations of root canal transportation and centralization. A normal distribution of data was confirmed by the Kolmogorov-Smirnov and Levene tests, and results were assessed using the Kruskal-Wallis test. Statistical significance was set at 5%. RESULTS: ProTaper Gold produced the lowest canal transportation values, and RaCe, the highest. ProTaper Gold files also showed the highest values for centering ability, whereas BioRaCe showed the lowest. No significant differences were found across the different instruments in terms of canal transportation and centering ability (P > 0.05). CONCLUSION: Based on the methodology employed, all instruments used for root canal preparation of mandibular premolars performed similarly with regard to canal transportation and centering ability.

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AIM: To evaluate canal transportation and centring ability of ProTaper Next (PTN) and Twisted File Adaptive (TFA) systems using microcomputed tomographic (micro-CT) imaging. METHODOLOGY: Twenty isthmus-containing mesial roots of mandibular molars were anatomically matched based on similar morphological dimensions using micro-CT evaluation (resolution of 14.25 µm) and assigned to two experimental groups (n = 10) according to the system used for root canal preparation: PTN and TFA groups. Then, the specimens were scanned again and the matched images of the mesial canals, before and after preparation, were examined at three cross-section levels (3, 5 and 7 mm from the apical end of the root) to analyse canal transportation and centring ratio. Independent-samples t-test was used to compare canal transportation and centring ratio between the groups. All statistical procedures were performed with a significance level set at 5%. RESULTS: Root canals prepared with either PTN or TFA systems had similar canal transportation and centring ratios at all levels (P > 0.05). CONCLUSION: PTN and TFA had similar results regarding canal transportation and centring ability.

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OBJECTIVES: The purpose of this study was to assess the ability of ProTaper Gold (PTG, Dentsply Maillefer) in maintaining the original profile of root canal anatomy. For that, ProTaper Universal (PTU, Dentsply Maillefer) was used as reference techniques for comparison. MATERIALS AND METHODS: Twenty simulated curved canals manufactured in clear resin blocks were randomly assigned to 2 groups (n = 10) according to the system used for canal instrumentation: PTU and PTG groups, upto F2 files (25/0.08). Color stereomicroscopic images from each block were taken exactly at the same position before and after instrumentation. All image processing and data analysis were performed with an open source program (FIJI). Evaluation of canal transportation was obtained for two independent canal regions: straight and curved levels. Student's t test was used with a cut-off for significance set at α = 5%. RESULTS: Instrumentation systems significantly influenced canal transportation (p < 0.0001). A significant interaction between instrumentation system and root canal level (p < 0.0001) was found. PTU and PTG systems produced similar canal transportation at the straight part, while PTG system resulted in lower canal transportation than PTU system at the curved part. Canal transportation was higher at the curved canal portion (p < 0.0001). CONCLUSIONS: PTG system produced overall less canal transportation in the curved portion when compared to PTU system.

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INTRODUCTION: The aim of this study was to evaluate through computed microtomography the transportation and centralization of root canals instrumented using the WaveOne system (Dentsply Maillefer, Ballaigues, Switzerland) associated or unassociated with previous apical and cervical enlargements. METHODS: Thirty-six mandibular molars were selected with independent mesial roots and curvatures and randomized into the following groups: PathFile (Dentsply Maillefer) before WaveOne Primary (the PFWO group), ProTaper Universal SX (Dentsply Maillefer) before WaveOne Primary (the SXWO group), and WaveOne Primary (the WO group). Computed microtomographic imaging was performed pre- and postpreparation to obtain measurements of mesial and distal dentin walls and calculations of root canal transportation (%) and centralization. One-way analysis of variance was performed to compare the different groups, repeated measures analysis of variance for comparison of the root thirds in each group, and the Student t test for comparisons between the mesiobuccal and mesiolingual canals. RESULTS: Transportation of the cervical and middle thirds to the danger zone was observed in both roots, whereas the apical thirds were transported to the outer face of the curvature. In the PFWO and SXWO groups, less transportation was observed in the middle thirds of the mesiobuccal canals compared with the WO group (P < .05). Centralization remained almost unchanged in the SXWO group (P < .05). CONCLUSIONS: In each group, transportation toward the danger zone was mostly observed in the cervical thirds of the mesiobuccal canals. Cervical or apical enlargement resulted in reduced transportation and improved centralization of the middle thirds compared with the exclusive use of the WaveOne system.

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INTRODUCTION: The aim of this study was to make a 3-dimensional comparison of the canal transportation and changes in apical geometry using micro-computed tomographic imaging after canal preparation with K3 (SybronEndo, Orange, CA) and K3XF (SybronEndo) file systems. METHODS: Twenty-eight mandibular molars were randomly divided into 2 groups according to the rotary system used in instrumentation: K3 or K3XF. The specimens were scanned by micro-computed tomographic imaging before and after instrumentation. Images before and after instrumentation from each group were compared with regard to canal volume, surface area, and structure model index (SMI) (paired t test, P < .05). After instrumentation, the canals from each group were compared regarding the changes in volume, surface area, SMI, and canal transportation in the last 4 apical mm (t test, P < .05). RESULTS: Instrumentation with the 2 rotary systems significantly changed the canal volume, surface area, and SMI (P < .05). There were no significant differences between instrument types concerning these parameters (P > .05). There were no significant differences between the 2 groups with regard to canal transportation in the last 4 apical mm (P > .05). CONCLUSIONS: Both rotary systems showed adequate canal preparations with reduced values of canal transportation. Heat treatment did not influence changes in root canal geometry in the apical region.

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This study used computed tomography (CT) to compare apical canal transportation in mesiobuccal canals of maxillary molars prepared with different techniques. Sixty teeth were assigned to 3 groups (n=20), according to the technique used for root canal instrumentation: hand instrumentation with K-Flexofiles, K-Flexofiles activated by an oscillatory system and ProTaper NiTi rotary system. Pre and post-instrumentation CT images were obtained 3 mm short of the apical foramen and were superimposed to compare canal transportation. Data were analyzed statistically by ANOVA and Tukey's test using the SPSS software (α=0.05). In the buccal direction, the manual technique produced significantly less canal transportation than the oscillatory technique (p<0.05) and both were similar to the rotary technique (p>0.05). In the distal and distopalatal directions, the oscillatory technique produced more canal transportation (p<0.05). In the mesiopalatal direction, the oscillatory technique produced more canal transportation than the manual technique (p<0.05), and both were similar to the rotary technique (p>0.05). In conclusion, all techniques produced canal transportation, and the oscillatory technique produced the greatest removal of root dentin toward the innerside of the root curvature.

Este estudo utilizou a tomografia computadorizada (TC) para comparar o transporte do canal radicular nos canais mésio-vestibulares de molares superiores preparados por diferentes técnicas. Sessenta molares superiores foram divididos em 3 grupos (n=20) de acordo com a técnica utilizada para o preparo do canal radicular: instrumentação manual com limas K-Flexofile, limas K-Flexofile acopladas a um sistema oscilatório e sistema rotatório ProTaper. Imagens de TC pré e pós-instrumentação foram obtidas 3 mm aquém do forame apical e superpostas para comparar o transporte do canal. Os dados foram analisados estatisticamente pela Análise de Variância (ANOVA) e Teste de Tukey utilizando o software SPSS (α=0,05). Na direção vestibular, a técnica manual produziu significantemente menos transporte do canal radicular do que a técnica oscilatória (p<0,05) e ambas foram similares a técnica rotatória (p>0,05). Nas direções distal e disto-palatina, a técnica oscilatória produziu mais transporte do canal radicular (p<0,05). Na direção mésio-palatina, a técnica oscilatória produziu mais transporte do canal radicular do que a técnica manual (p<0,05), sendo que ambas foram similares à técnica rotatória (p>0,05). Em conclusão, todas as técnicas produziram transporte do canal radicular e a técnica oscilatória produziu os maiores desgastes de dentina na direção interna da curvatura.

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This study investigated the occurrence of canal transportation in the apical third of simulated root canals instrumented with progressive and constant taper shaft designed rotary instruments. Thirty simulated resin canals were prepared with progressive taper (ProTaper Universal) and constant taper (Hero 642 and K3) Ni-Ti rotary systems, with 10 canals per group. The pre and post-instrumentation images of the canals were superimposed and the composite images were analyzed with Image Pro Plus 5.0 software. Centering ability of the instruments was assessed by subtracting the amount of resin removed at the inner wall from that removed at the outer wall. Total amount (in mm) of resin removed was recorded by adding the amount of resin removed at the inner and outer walls, comparing the pre and post-preparation images. Data were analyzed statistically by Kruskal Wallis and Median tests (α=5%). There was statistically significant difference (p<0.05) among the groups. ProTaper produced the greatest canal transportation in the apical third. In conclusion, canal transportation occurred in all groups; the constant taper rotary instruments (Hero 642 and K3) presented greater centering ability towards the original canal curve and caused less canal transportation than the progressive taper instruments (ProTaper).

Este estudo investigou a ocorrência do transporte do canal no terço apical de canais simulados preparados com instrumentos rotatórios de conicidade progressiva e constante. Trinta canais simulados em blocos de resina foram preparados com sistemas rotatórios de Ni-Ti de conicidade progressiva (ProTaper Universal) e de conicidade constante (Hero 642 e K3), com 10 canais simulados por grupo. As imagens pré e pós-operatórias dos canais foram superpostas e analisadas com o Programa Image Pro Plus 5.0. A capacidade de manter a centralização do canal foi avaliada pela subtração da quantidade de resina removida da parede interna daquela removida na parede externa. A quantidade total de resina (em mm) removida foi obtida por meio da soma da resina removida das paredes internas e externas do canal, comparando as imagens pré e pós-operatórias. Os dados foram analisados estatisticamente pelo teste de Kruskal Wallis e Teste das medianas (α=5%). Houve diferença estatisticamente significativa (p<0.05) entre os grupos. O Sistema ProTaper produziu o maior transporte do canal no terço apical. Em conclusão, o transporte do canal ocorreu em todos os grupos; os intrumentos rotatórios de conicidade constante (Hero 642 e k3) apresentaram uma grande capacidade de manter o canal centrado e causaram menos transporte do canal do que os instrumentos de conicidade progressiva (ProTaper).

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OBJECTIVE: This study evaluated the wear in the apical third of simulate canals after preparation with ProTaper Universal Rotary System. MATERIAL AND METHODS: 24 sets of instruments were used in 24 simulated canals in transparent epoxy resin blocks with degree of curvature of either 20°or 40°. The canals were photographed preoperatively and after preparation of the apical stop with ProTaper F3, F4 and F5 instruments. The initial and final images were exported to Adobe Photoshop® software and superimposed to detect the root canal wall differences (in mm) between them, in two points located 1 (A) and 5 (B) mm from the point where the working length was established. Data were subjected to analysis of variance to verify the existence of interaction among the factors: canal curvature, instrument size and curve location. Significant level was set at 5 percent. RESULTS: Regardless of the location and the canal curvature, F4 and F5 instruments produced the greatest wear (p<0.05). CONCLUSIONS: There was a deviation from the original pathway towards the outside of the root curvature in both analyzed points. All instruments produced canal transportation, but the F4 and F5 instruments produced more than the other instruments, and should thus be used with care in curved canals.

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