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Aims: The aim was to evaluate the cyclic and torsional fatigue resistance among thermally treated NiTi rotary instruments with different design features.Materials and methods: Sixty instruments of three systems were used (n=20): TruNatomy 26.04 (TN 26.04), BassiLogic 25.05 (BL 25.05), and Flat File 25.04 (FF 25.04). The cyclic fatigue test (n=10) was performed to evaluate the time to fracture (s) and the number of cycles until failure (NCF). The torsion test was performed to evaluate the torque (N.cm) and maximum angular deflection until fracture (n=10). The fracture surface of each fragment was examined under a scanning electron microscope. The data were analyzed by Tukey's test (p<0.05).Results: BL 25.05 and FF 25.04 instruments had a higher number of cycles and time to fracture compared with TN 26.04 (p<0.05). TN 26.04 instruments showed lower torque to fracture.Conclusions: Based on the proposed objectives and the methodology used, TruNatomy 26.04 instruments present lower resistance to cyclic fatigue and torsional fatigue when compared to BassiLogic 25.05 and Flat File 25.04 instruments.

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OBJECTIVE: This systematic review/meta-analysis investigated the influence of NaOCl on cyclic fatigue resistance of endodontic NiTi instruments. MATERIALS AND METHODS: A systematic search until July 2022 in PubMed/MEDLINE, Embase, Scopus, Web of Science, SciELO, Cochrane Library, and grey literature was conducted. According to the PECOS strategy, only in vitro studies evaluating the effects of NaOCl on the cyclic fatigue resistance of NiTi instruments were eligible. Cyclic fatigue resistance was the primary outcome. A modified Joanna Briggs Institute's Checklist was used for risk of bias assessment. RESULTS: Of the 2,445 records screened, 37 studies were included. Most studies used simulated canals made of stainless-steel block with severe to moderate curvatures. NaOCl concentration varied from 1-6%, mainly at 37 °C. Regarding fatigue resistance, 23 studies using 1.2% to 6% NaOCl showed a reduction in the resistance compared to the control groups, especially when pre-heated. Four meta-analyses were performed according to the tested NiTi systems. The meta-analyses indicated that the PTU F2 files had higher reduction of fatigue resistance after exposure to 5.25% NaOCl; no differences between NaOCl and no immersion were observed for Reciproc R25, WaveOne 25.08, and WaveOne Gold Primary files. Included studies had low risk of bias. CONCLUSION: NaOCl appears to reduce cyclic fatigue resistance of certain NiTi files, especially when they are pre-heated, particularly in conventional NiTi files compared to some heat-treated instruments. It is possible that the temperature of the solution may have a greater influence on resistance than NaOCl itself. Important to note that an overall tendency toward no significant influence was observed among various systems. CLINICAL RELEVANCE: Precautions are necessary when a pre-heated high-concentration NaOCl is used to enhance its properties during root canal preparation, mainly using conventional wire.

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NiTi endodontic instruments for glide path are the most susceptible to fractures inside the root canal, mainly as a result of high torsional stress. Objective: The present study investigated the resistance to torsion and angular deflection of instruments destined for the glide path: ProGlider #16.02; T-File #17.02 and the MK Life #16.02. Materials and methods: Thirty rotating NiTi glide path instruments (n=10) with 25mm lengths were selected. The torsion test was performed based on ISO 3630-01 (1992). Three millimeters from the tip of the instruments, it was attached to a small load cell by a lever arm connected to the torsion shaft. Torsional strength and angular deflection were evaluated. Fracture surfaces were examined by scanning electron microscopy with magnifications of 1000x and 5000x in the cross section, and 50x in the lateral section. Statistical analysis was performed using the Kruskal-Wallis H test, followed by the Down's post hoc test. Results: The ProGlider instrument showed greater torsional strength (p<0.05) compared to the T-File (p<0.05) and MK Life (p<0.05), respectively. However, the T-File showed greater angular deflection (p<0.05) than the other groups tested. Conclusion: It can be concluded that the ProGlider instrument presented greater torque for the fracture, while the T-File instrument presented greater angular deflection.

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Objectives: This systematic review (register-osf.io/wg7ba) compared the efficacy and safety of rotary and reciprocating kinematics in the removal of filling material from curved root canals. Materials and Methods: Only in vitro studies evaluating both kinematics during retreatment were included. A systematic search (PubMed/MEDLINE, Scopus, and other databases, until January 2021), data extraction, and risk of bias analysis (Joanna Briggs Institute checklist) were performed. Efficacy in filling removal was the primary outcome. Results: The search resulted in 2,795 studies, of which 15 were included. Efficacy was measured in terms of the remaining filling material and the time required for this. Nine studies evaluated filling material removal, of which 7 found no significant differences between rotary and reciprocating kinematics. Regarding the time for filling removal, 5 studies showed no difference between both kinematics, 2 studies showed faster results with rotary systems, and other 2 showed the opposite. No significant differences were found in apical transportation, centering ability, instrument failure, dentin removed and extruded debris. A low risk of bias was observed. Conclusions: This review suggests that the choice of rotary or reciprocating kinematics does not influence the efficacy of filling removal from curved root canals. Further studies are needed to compare the kinematics safety in curved root canals.

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OBJECTIVE: This study evaluates whether endodontic cavity access into molars influences the chemomechanical preparation of curved root canals. MATERIALS AND METHODS: Twenty mesiobuccal canals of maxillary molars were randomly divided into two experimental groups (n = 10), according to the type of endodontic access analyzed (conventional and minimally invasive). The preparations were made by a single operator, and the canals, after access, were prepared with Logic system (0.25, 0.04 taper) along the working length. Samples were scanned before and after canal preparation (SMX-90CT Plus (Shimadzu® microtomograph operated with 70 kV, 100 uA, FOV (XY) 13.3 mm, FOV (Z) 7.0 mm, and voxel size 0.013 mm/Pix)) to match canal volumes. Images were analyzed to evaluate surface areas, transport, and centralization at 3 mm from the canal entrance and 3 mm from the apex (OnDemand3DTM Dental software). Student's t test with a significance level of 5% was used for the statistical analysis. RESULTS: Regardless of the position of the analyzed canals, there was no difference in the prepared area regarding the transport and centralization of the endodontic instrument between the two types of cavity accesses performed. CONCLUSIONS: The conventional and minimally invasive access did not influence the action of the 0.25 and 0.04 taper instrument during the curved root canal preparation. CLINICAL RELEVANCE: The type of endodontic access did not influence the action of the rotary instrument during the curved root canal preparation.

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Abstract This study evaluated the efficiency of using a single instrument from three different rotary multi-file systems and compared them with that of a reciprocating single-file for endodontic retreatment by means of micro-CT. Sixty extracted canines were prepared using a size F2 ProTaper Universal file and obturated. After 30 days of storage at 37ºC and 100% humidity, the teeth were randomly divided into four groups (n=15) based on the type of instrument used to retreatment: ProTaper Next (PTN), ProTaper Gold (PTG), TRUShape 3D (TS), and WaveOne (WO). The canals were retreated using only the size 40 instrument from each system according to the manufacturer's recommendations for torque and speed. The time required to remove the filling material was recorded in seconds. The amount of initial and residual filling material and the quantity of dentin removed were assessed by means of micro-CT. Data were statistically analyzed (ANOVA and Kruskal-Wallis) at a 5% significance level. TS instruments required the highest (p<0.05) amount of time (mean, 384.80 ±144.92) compared with the WO (229.67±68.16) and PTG (248.67±64.22) and not so different from PTN instruments (327.67±133.3). No differences in the amount of dentin removed, initial and residual filling volume, and percentages of filling material were observed among the groups. The use of a single rotary instrument from the PTG, TS, and PTN systems was as effective as that of the single-file reciprocating WO system. However, none of the instruments was able to remove the filling materials completely.

Resumo Este estudo laboratorial avaliou por meio de micro-CT a eficiência do uso de um único instrumento de três sistemas rotatórios em retratamentos endodônticos, comparados a um instrumento único reciprocante. Sessenta caninos extraídos foram preparados usando o sistema ProTaper Universal (F2) e obturados. Após 30 dias de armazenamento a 37 ºC e 100% de umidade, os dentes foram divididos aleatoriamente em quatro grupos (n = 15), de acordo com o instrumento utilizado para remover as obturações endodônticas: ProTaper NEXT (PTN), ProTaper Gold (PTG), TRUShape 3D (TS) e WaveOne (WO). Os canais foram retratados usando apenas o instrumento tamanho 40 de cada sistema, seguindo as recomendações do fabricante para torque e velocidade. O tempo necessário para remover a obturação foi registrado em segundos. A quantidade de material remanescente e o volume de dentina removida foram avaliadas por meio de micro-CT. Análise estatística foi realizada (ANOVA e Kruskal-Wallis), com nível de significância de 5%. O tempo de trabalho no grupo TS foi significativamente maior (p<0.05) (média, 384,80 ± 144,92) comparado a WO (229,67 ± 68,16) e PTG (248,67 ± 64,22), e similar a PTN (327,67 ± 133,3). Não houve diferenças entre os grupos na quantidade de dentina removida e nas porcentagens de material obturador residual. O uso de apenas um instrumento rotatório dos sistemas PTG, TS e PTN foi tão eficaz quanto o do sistema WO reciprocante na remoção do material obturador. No entanto, nenhum dos instrumentos conseguiu remover completamente os materiais obturadores.

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INTRODUCTION: The aim of this study was to compare, using micro-computed tomographic imaging, the preparation of mesial canals of mandibular molars with the Reciproc (VDW GmbH, Munich, Germany) and XP-endo Shaper (FKG, La Chaux-de-Fonds, Switzerland) systems, evaluating changes in dentin and canal volume, the percentage of untouched walls, the volume of accumulated hard tissue debris, and root canal deviation in the apical third. METHODS: Twenty-four mandibular molars with 2 mesial root canals and a single foramen were anatomically paired and divided into 2 experimental groups (n = 12) according to the system used. The specimens were scanned before and after preparation with the SkyScan 1176 microtomographic scanner (Bruker-microCT, Kontich, Belgium) at a resolution of 17.42 µm. The resulting data were statistically compared at a significance level of 5% using the Student t test and the Mann-Whitney test. RESULTS: A significant difference was observed in the untouched surface area for the total canal and the cervical and middle thirds, with the lowest untouched surface area in the XP-endo Shaper group (P < .05). The volume of accumulated hard tissue debris was significantly higher in the Reciproc group in the total canal as well as in the middle and apical thirds. There was no significant difference between the groups regarding the volume of dentin removed or the increase in canal volume and surface area (P > .05). CONCLUSIONS: The XP-endo Shaper touched more walls and left less accumulated hard tissue debris in the root canal system than the Reciproc group. Although the XP-endo Shaper showed superior results, neither system was able to fully prepare the root canal.

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CONTEXT: It is essential to know if the immersion in sodium hypochlorite (NaOCl) influences the cyclic fatigue resistance of nickel-titaniumm (NiTi) files. AIM: This study was aimed to evaluate the resistance to the cyclic fatigue of three NiTi systems, as well as the influence of 5.25% NaOCl on their resistance. METHODS: Files from the Sequence Rotary File (MK life, Porto Alegre, Brazil), ProTaper Next (PTN) (Dentsply, Maillefer, Baillagues, Switzerland), and HyFlex EDM (Coltène Whaledent, Allstatten, Switzerland) systems were tested and separated into Group 1)-without immersion in NaOCl solution and Group 2 and Group 3-immersed in 5.25% NaOCl solution, for 1 min, and 5 min, respectively. All instruments were submitted to the cyclic fatigue test. Images of the instruments were observed by scanning electron microscopy, to evaluate the type of defect presented on the fractured surface. The test performed for the analysis of two independent factors was a two-way analysis of variance. RESULTS: HyFlex EDM presented a greater number of cycles until fracture when compared to others (P < 0.001). The control group showed a greater number of cycles until fracture than the same instruments submitted to NaOCl (P < 0.001). Sequence instruments showed the lowest values of cycles until fracture (P < 0.001). There was no statistically significant difference between treatments (P = 0.998). PTN, showed intermediate values of fracture resistance when compared to the HyFlex EDM and sequence instruments (P < 0.001), but without intragroup differences (P = 0.437). CONCLUSIONS: Hyflex EDM instruments were the most resistant to cyclic fatigue.

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AIM: To compare the dissolution time of two solutions, a fluoride solution and a sodium hypochlorite solution, both saturated with sodium chloride, during the electrochemical dissolution of instruments consisting of conventional nickel-titanium alloy and Gold thermomechanically treated nickel-titanium alloy. METHODOLOGY: Two solutions, an NaF solution consisting of 12 g L-1 NaF with 180 g L-1 NaCl and an NaOCl solution consisting of 2.5% NaOCl with 180 g L-1 NaCl, were evaluated in a polarization test of a sample of 48 ProTaper Universal F1 (PTU F1) and WaveOne Gold Small (WOGS) instruments. The electric potentials were 0.5 V and 5 V for the NaF and NaOCl solutions, respectively. The electrochemical cell consisted of three electrodes for the polarization test of the PTU F1 and WOGS instruments, which had 6 mm of the tip immersed in the test solutions. The electric current was recorded for 540 s. If complete dissolution of the immersed tip occurred in less than the expected time, the experiment was considered complete. The time variations (in seconds) of the instruments in the solutions were measured. Data were subjected to statistical analysis using the Mann-Whitney, Kruskal-Wallis and Dunn tests. The corrosion patterns of the instruments were evaluated by scanning electron microscopy (SEM). RESULTS: The NaF and NaOCl solutions were associated with significantly different (P = 0.000) dissolution times of the instrument, with mean values of 12.96 s and 83.63 s, respectively. There was no significant difference (P = 0.649) in dissolution time between the PTU F1 and WOGS instruments. CONCLUSIONS: NaF and NaOCl solutions were able to electrochemically dissolve PTU F1 and WOGS instruments. However, the NaF solution achieved dissolution in significantly less time.

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CONTEXT: Postoperative pain control after endodontic treatment is important to maintain patient comfort. AIM: The aim of this prospective clinical study was to evaluate the postoperative symptomatology of endodontic treatments performed in a single session, with or without photodynamic therapy (PDT), using Reciproc #40 file in necrotic unirradicular anterior teeth. MATERIALS AND METHODS: In a prospective clinical study, 40 teeth indicated for endodontic treatment were treated by a single endodontist according to a preestablished protocol. The teeth were randomly divided into two groups (n = 20): control group (CG) and laser group (LG). After 24 h, 72 h, and 1 week of endodontic treatment, patients' pain symptomatology was evaluated through a Visual Analog Scale (VAS) ranging from 0 to 10, in which 0 corresponds to no pain and 10 indicates extreme pain. In both workgroups, similar protocols were used for instrumentation with the Reciproc system (R40), irrigation with 2.5% sodium hypochlorite, and filling by the gutta-percha plastification technique, in which the CG did not use PDT, and the LG used PDT after the instrumentation sequence. After the visit, the patients were given a prescription for ibuprofen 400 mg to be taken every 6 h if they experienced pain. RESULTS: The results of the study, analyzing the VAS, did not show any difference in pain symptoms between the groups at 24 h, 72 h, and 1 week (P > 0.05). CONCLUSIONS: It was concluded that there was no statistical difference between the groups.

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AIM: To evaluate the influence of controlled memory (CM) thermal treatment on the torsional resistance and surface roughness of nickel-titanium instruments with identical geometric and dimensional characteristics. The influence of environmental temperature on torsional resistance was also evaluated. METHODOLOGY: A sample of 25 conventional NiTi alloy and 25 CM thermal-treated NiTi instruments, with an identical geometric design and a nominal size of 0.25 mm at D0 and a nominal taper of .06 mm mm-1 were selected. The torsional strength and the angle of rotation of the instruments were tested following ISO 3630-1 at two temperatures: 21 and 35 °C. The fracture surfaces of all tested instruments were verified with a scanning electron microscope. The surface roughness of the blades of conventional NiTi alloy and CM wire files was evaluated by using a New View 7100 Profilometer. Statistical analysis was performed using Student's t-test and paired t-test to analyse the torsional resistance and surface roughness at a significance level of P < 0.05. RESULTS: The torsional strength of thermally-treated instruments was significantly lower than nontreated instruments (P < 0.05). However, thermally-treated instruments had significantly greater angular rotation to fracture than nontreated instruments (P < 0.05). Temperature did not influence the torsional strength (P > 0.05) and the angular rotation (P > 0.05) of the instruments. Regarding the roughness measurements, groove depth was lower at the surface of thermally-treated instruments when compared to nontreated instruments (P < 0.05). CONCLUSION: Thermal treatment influenced the torsional resistance and surface roughness of NiTi instruments with identical geometric and dimensional characteristics. Temperature did not affect torsional behaviour.

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INTRODUCTION: The aim of this study was to analyse the potential occurrence of dentinal defects after root canal preparation using three engine-driven instruments. METHODS AND MATERIALS: Eighty permanent mandibular incisors were selected. Twenty teeth did not undergo preparation, and the remaining teeth were divided into three groups (n=20): Reciproc (REC), ProTaper Next (PTN) and WaveOne Gold (WOG). The samples were dyed with methylene blue, sectioned perpendicularly to the long axis in 3-, 6- and 9-mm slices and were finally observed under a stereomicroscope (under 25×). The absence/presence of dentinal defects was documented by two blind observers. The data were analysed using Pearson's chi-squared test with a confidence level of 95% (P=0.05). The time to prepare the samples was recorded, and the groups were compared using F-test (ANOVA). RESULTS: The control group did not present any defects, and the differences between the control and experimental groups were statistically significant (P<0.05). WOG, PTN and REC caused microcracks on 60%, 33.33% and 18.33% of the samples, respectively. No significant differences between the groups in the 3-mm sections (P=0.126) were observed. There were significant differences in the 6-mm (P=0.042) and 9-mm sections (P<0.001). When WOG and PTN were used to perform root canal preparation, a significant difference was found in the average time (P=0.047). CONCLUSION: All the used instruments caused dentinal defects in the root dentin. All the instruments were used to perform the preparation with a similar average time.

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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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OBJECTIVE: The aim of this retrospective clinical study was to evaluate the incidence of ProTaper Universal System instrument fractures, associated with observation of the arch, group of teeth, and root thirds in which these fractures occurred. METHODS: From analysis of charts, clinical record cards and radiographs of endodontic treatments performed by postgraduate students using the ProTaper Universal System at a reference center, a total of 1031 teeth and 2355 canals were analyzed. The general incidence of instrument fractures and their frequency, considering the group of teeth, arch and root thirds, were cataloged and the data obtained were statistically analyzed (Exact Fischer test, with level of significance of 1%). RESULTS: The general percentage of fractures, considering the number of teeth and number of root canals evaluated was 4.4% and 1.9%, respectively. Instrument fractures occurred more frequently in the mandibular first (8.8%) and second (9.6%) molars, however, without statistically significant difference between them (P=0.81). In the first and second maxillary molars, the incidence of fracture was 4.7% and 5.1%, respectively, also without significant difference (P=0.81). Considering the dental arches (maxillary and mandibular), the fractures occurred with significantly higher frequency in the mandibular arch (66.7%), in comparison with the maxillary arch (33.3%) (P<0.01). A significantly higher percentage of fractures occurred in the apical third (84.4%) compared with the middle third (15.6%) (P<0.01). CONCLUSION: The general percentage of fractures, considering the number of teeth and number of root canals evaluated was 4.4% and 1.9%, respectively. However, the arch (mandibular) and root third (apical) had a significant effect on the incidence of instrument fractures.

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he aim of this study was to evaluate the cyclic-fatigue fracture of different Nickel-Titanium motor-driven rotary instruments (ProTaper® Universal, ProFile®, and Mtwo® systems) in artificial canals by means of an Automatic Electronic Device (AED). The study was performed using NickelTitanium instruments 25/0.06 evaluated in canals with a 45-degree curvature and 2-mm radius. The analyses evaluated two parameters: fracture by cyclic fatigue, and time of fracture; in addition, the length of separated fragment was evaluated. Medians and range values were calculated for each group. Data were analyzed by the Kruskall-Wallis and Mann-Whitney U tests to determine statistical difference. The ProFile motor-driven rotator system exhibited highest resistance to fracture due to cyclic fatigue and highest fracture time compared with the ProTaper and Mtwo systems (p <0.05). The equipment proposed in this study (AED) demonstrated efficiency for recording information, automation, scheduled work times and durations, cycle number, time of fracture, pressure changes and, principally control of the human factor.

l objetivo del presente estudio fue evaluar la fractura a la fatiga cíclica de diferentes instrumentos rotatorios de Niquel-Titanio (sistemas ProTaper® Universal, ProFile® y Mtwo®) en conductos artificiales por medio de un Dispositivo Electrónico Automático (DEA). Se usaron instrumentos de Niquel-Titanio 25/0.06, los cuales se evaluaron en conductos con una curvatura de 45 grados y 2 milímetros de radio. Se analizaron dos parámetros: Fractura a la fatiga cíclica y tiempo a la fractura; además se evaluó la longitud del fragmento separado. Medianas y rangos fueron calculados para cada uno de los grupos. Los resultados fueron analizados por las pruebas de Kruskall-Wallis y U de Mann-Whitney para determinar diferencias estadísticas. El Sistema ProFile mostró una mayor resistencia y tiempo a la fractura en comparación con los sistemas ProTaper y Mtwo (p <0.05). El equipo propuesto en este estudio (DEA) demostró eficiencia para el registro de la información, tiempos de trabajo y duración, número de ciclos, tiempo a la fractura, cambios en la presión y principalmente control del factor humano.

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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 investigate changes in three-dimensional geometry, in various cross-sectional morphological parameters and in the centring ability of root canals prepared with different preparation systems using microcomputed tomographic imaging technology. METHODOLOGY: Sixty-four mesial canals of mandibular molars were matched based on similar morphological dimensions using micro-CT evaluation and assigned to four experimental groups (n = 16), according to the canal preparation technique: Reciproc, WaveOne, Twisted File and HyFlex CM systems. Changes in several 2D (area, perimeter, form factor, roundness, minor and major diameter) and 3D [volume, surface area, structure model index (SMI)] morphological parameters, as well as canal transportation, were compared with preoperative values using Kruskal-Wallis and anovapost hoc Tukey's tests with the significance level set at 5%. RESULTS: Preparation significantly increased all tested parameters in the experimental groups. No significant differences were observed between groups regarding changes in volume, surface area, SMI, form factor and roundness of the root canal after preparation (P > 0.05). In the apical third, the Reciproc group had significantly greater changes in canal area, perimeter, major and minor diameters than the other groups (P < 0.05). Overall, the Twisted File and HyFlex CM systems were associated with significantly less transportation than the reciprocating instruments, Reciproc and WaveOne (P < 0.05). CONCLUSIONS: Shaping procedures led to the enlargement of the root canal space with no evidence of significant preparation errors. Changes in 3D parameters were not different between groups whilst, in the apical third, Reciproc was associated with significantly greater changes in several 2D parameters compared to the other groups. Twisted File and HyFlex CM systems were able to maintain the original canal anatomy with less canal transportation than Reciproc and WaveOne; however, these differences are unlikely to be of clinical significance.

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INTRODUCTION: The newly developed single-file systems claimed to be able to prepare the root canal space with only 1 instrument. The present study was designed to test the null hypothesis that there is no significant difference in the preparation of oval-shaped root canals using single- or multiple-file systems. METHODS: Seventy-two single-rooted mandibular canines were matched based on similar morphologic dimensions of the root canal achieved in a micro-computed tomographic evaluation and assigned to 1 of 4 experimental groups (n = 18) according to the preparation technique (ie, Self-Adjusting File [ReDent-Nova, Ra'anana, Israel], WaveOne [Dentsply Maillefer, Ballaigues, Switzerland], Reciproc [VDW, Munich, Germany], and ProTaper Universal [Dentsply Maillefer] systems). Changes in the 2- and 3-dimensional geometric parameters were compared with preoperative values using analysis of variance and the post hoc Tukey test between groups and the paired sample t test within groups (α = 0.05). RESULTS: Preparation significantly increased the analyzed parameters; the outline of the canals was larger and showed a smooth taper in all groups. Untouched areas occurred mainly on the lingual side of the middle third of the canal. Overall, a comparison between groups revealed that SAF presented the lowest, whereas WaveOne and ProTaper Universal showed the highest mean increase in most of the analyzed parameters (P < .05). CONCLUSIONS: All systems performed similarly in terms of the amount of touched dentin walls. Neither technique was capable of completely preparing the oval-shaped root canals.

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RESUMO

O objetivo do presente trabalho foi avaliar, em microtomografia computadorizada (µCT), o preparo de canais de molares inferiores com diferentes sistemas acionados a motor. Foram selecionadas 58 raízes mesiais patentes, de diâmetro anatômico correspondente a #10. Para a avaliação em µTC, um anel de aço inoxidável foi confeccionado nos moldes do suporte para amostra do microtomógrafo, para que servisse de fôrma para a inclusão das raízes em resina Duralay, a fim de padronizar a posição do espécime no escaneamento inicial e final. Os canais foram preparados com os sistemas Reciproc R25 (n=16); WaveOne Primary File (n=16); Twisted File (n=14), e HyFlex (n=12). Após serem escaneados, foram reconstruídos tridimensionalmente e avaliados quantitativamente quanto à variação de volume (mm3), área de superfície (mm2) e structure model index (SMI). Foi, ainda, realizada a avaliação qualitativa das seções transversais por terço e por quadrante (MV, ML, DV, DL), sendo avaliado o toque de paredes. Os dados paramétricos foram analisados estatisticamente pelos testes ANOVA e t para amostras pareadas (α=5%). Não foi observada diferença estatística nos parâmetros quantitativos avaliados para Reciproc (142,77 ± 76,75; 42,22 ± 19,22; e 14,68 ± 17,69, respectivamente); WaveOne (105,09 ± 64,82; 29,54 ± 19,21; 14,81 ± 9,10, respectivamente); Twisted File (111,83 ± 43,09; 33,31 ± 18,40; 9,16 ± 6,57, respectivamente), e HyFlex (151,74 ± 149,37; 43,08 ± 41,44; 10,80 ± 8,52, respectivamente) (p=0,423). Dentro de cada grupo, foi observada diferença significante entre os resultados pré e pós-operatórios. O teste não paramétrico de Kruskal Wallis foi aplicado para a avaliação relativa ao toque de paredes. Foi observado que o sistema HyFlex apresentou a maior porcentagem de toques (82,3 ± 13,1), seguido por Reciproc (81,3 ± 16,9), Twisted File (78,3 ± 14,4) e, por fim, WaveOne (76,9 ± 21,7) (p>0,05). Em relação aos terços não foi observada diferença significativa (p=0,424). Os resultados da avaliação dos quadrantes intergrupo não demonstraram diferenças, porém indicaram tendência do preparo em direção à parede distal no terço cervical. Ao final, pôde-se concluir que os sistemas testados se equivalem quanto ao preparo de canais mesiais de molares inferiores; porém, nenhuma das técnicas foi capaz de tocar completamente em todas as paredes do canal radicular(AU)

The aim of this work was to analyze, in X-ray computed microtomography (µCT), the root canal preparation of mandibular molars with different engine driven systems. 58 mesial roots were selected, of anatomic diameter corresponding to #10. For the analysis in µTC, a stainless steel ring was manufactured in the same shape as the brace for µCT sampling, in order to serve as a mold to insert the roots in Duralay resin, so as to standardize the position of the specimen in the initial and final scanning. The canals were prepared with the Reciproc R25 (n=16), WaveOne Primary File (n=16), Twisted File (n=14) and HyFlex (n=12) systems. After being scanned, they were three-dimensionally reconstructed and quantitatively evaluated as regards the variation of volume (mm3), surface area (mm2) and structure model index (SMI). In addition, the qualitative evaluation of the cross sections by third and by quadrant (MV, ML, DV, DL) was carried out, along with the wall touching evaluation. The parametric data were statistically analyzed by ANOVA and t-tests for paired samples (α=5%). No statistical difference was observed in the qualitative parameters evaluated for Reciproc (142.77 ± 76.75; 42.22 ± 19.22; and 14.68 ± 17.69; respectively), WaveOne (105.09 ± 64.82; 29.54 ± 19.21; 14.81 ± 9.10; respectively), Twisted File (111.83 ± 43.09; 33.31 ± 18.40; 9.16 ± 6.57; respectively) and HyFlex (151.74 ± 149.37; 43.08 ± 41.44; 10.80 ± 8.52) (p=0,423). Significant difference was observed within each group between the pre- and post-results. The Kruskal-Wallis non-parametric test was applied for the evaluation as regards root canal wall touching. At the end, we observed that the HyFlex system presented the highest touching rate (82.3 ± 13.1), followed by the Reciproc (81.3 ± 16.9), Twisted File (78.3 ± 14.4) and, finally, WaveOne (76.9 ± 21.7) systems (p>0.05). As for the thirds, was not observed any significant difference (p=0.424). The results of the evaluation in the intergroup quadrants did not show any difference; however, they showed that there was a preparation trend towards the distal wall in the cervical third. At the end, it can conclude that the systems tested are equivalent as regards the preparation of mesial canals of mandibular molars, but none of the techniques was capable of fully touching all root canal walls(AU)

Assuntos

RESUMO

O objetivo do presente estudo foi analisar a conicidade e regularidade dos canais radiculares preparados com instrumentos rotatórios de níquel-titânio Race® e K3®, utilizando contra ângulo redutor Dentfex®. O experimento envolveu canais me-siais de trinta molares humanos, superiores e inferiores, sendo aleatoriamente distribuídos em dois grupos de quinze, de acordo com os dois tipos de instrumentos rotatórios: RaCe® e K3®. A partir de então, realizou-se a moldagem dos canais radiculares, para em seguida submeter os dentes a desmineralização em ácido clorídrico a 35%, obtendo dessa forma o molde dos mesmos. Esses moldes foram analisados, onde se verifcou a conicidade e regularidade dos canais radiculares preparados. Os dados foram tabulados e submetidos à análise estatística por meio dos testes de Mann-Whitney e Qui-quadrado. Os resultados obtidos indicam a predominância de formas regulares cônicas, em todos os terços (cervical, médio, apical), nos sentidos mésio vestibular e mésio lingual e palatino dos canais preparados com os instrumentos Race® e K3®, mas houve diferença estatisticamente signifcante entre o número de ocorrência da forma irregular cilíndrica nos moldes dos canais mésio-vestibulares inferiores, preparados com os instrumentos RaCe®.

The aim of this study was to analyze the taper and regularity of root canals prepared with rotary nickel-titanium system Race® and K3®, using angle reducer Dentfex®. The experiment involved mesial canals of thirty human molars, upper and lo-wer were randomly assigned to two groups of ffteen, according to the two types of rotary instruments: RaCe® and K3®. Since then, there was casting of root canals, to then subject the teeth to demineralization in 35% hydrochloric acid, thereby obtaining the same mold. These paterns were analyzed, where there was a taper and regularity of root canals prepared. The data were tabulated and analyzed statistically by the Mann-Whitney and Chi-square. The results indicate the predominance of regular conical forms, in all thirds (cervical, middle, apical) in mesial buccal and mesial lingual and palatine canals prepared with Race® and K3®, but statistically signifcant diference between the number of occurrence of irregular cylindrical shape along the lines of mesiobuccal canals below, prepared with RaCe®.