Influence of Different Apical Foramen Morphologies on the Accuracy of Four Electronic Foramen Locators.

OBJECTIVE: The aim of this study was to evaluate the accuracy of the Root ZX II (RZX), Raypex 6 (RAY), EPex Pro (EPEX), and CanalPro (CNP) electronic foramen locators (EFLs) in different foraminal morphologies (fully formed foramen, immature foramen with parallel walls, and immature foramen with divergent walls); this article also evaluated the influence of different penetration levels (0.0 mm and -1.0 mm). MATERIALS AND METHODS: Thirty single-rooted human premolars were accessed and had their cervical/middle thirds prepared with SX ProTaper files. The apical foramens (AF) were standardized to 250 µm and the initial root canal length (RCL1) was measured under 16x magnification with aid of a digital caliper. Using the alginate model, electronic measurements (EM) were taken 1.0 mm up to AF (EM1/-1) and at AF (EM1/0), always using adjusted hand K-files. The root apexes were then cross-sectioned 3.0 mm from the foramen; then, new RCL (RCL2) and electronic measurements were performed (EM2/-1 and EM2/0.0). Finally, retropreparations were performed with instruments SX ProTaper files introduced 4.0 mm in the apicocervical direction. Then new RCL (RCL3) and electronic measurements (EM3/-1 and EM3/0) were performed. STATISTICAL ANALYSIS: Values were tabulated and tested for normality using the Shapiro-Wilk test, which yielded nonparametric distributions of the data. Data were subjected to the Kruskal-Wallis and Dunn tests to estimate possible differences between devices as a function of foramen morphology and/or apical limit. The significance level was set at 5.0%. RESULTS: In general, the EFLs were accurate in determining the RCL. Statistically significant differences were observed between EPEX and RAY at 0.0, when measuring the divergent AF canals (p < 0.05). Regarding the different foramen morphologies in each EFL, RZX and EPEX showed no interference (p > 0.05), whereas RAY and CNP had lower accuracy levels at 0.0 with divergent AF (p < 0.05). CONCLUSION: The four devices evaluated are accurate to determine the RCL in the conditions tested. The apical limit of penetration did not have significant influence on their accuracy. Conversely, the presence of divergence in the AF walls negatively influenced de RAY and CNP precisions at the foraminal level.

To flat or not to flat? Exploring the impact of flat-side design on rotary instruments using a comprehensive multimethod investigation.

AIM: To assess the influence of a flat-side design on the geometry, metallurgy, mechanical performance and shaping ability of a novel nickel-titanium rotary instrument. METHODOLOGY: Sixty-five new 25-mm flat-side rotary instruments (size 25, taper 0.04) and their nonflat-side prototypes (n = 65) were assessed for major deformations and examined regarding macroscopic and microscopic design, determination of nickel and titanium elements ratio, measurement of phase transformation temperature and evaluation of mechanical performance parameters including time/cycles to fracture, maximum torque, angle of rotation, maximum bending and buckling strengths and cutting ability. Additionally, unprepared canal areas, volume of hard tissue debris and percentage reduction of dentine thickness were calculated for each tested instrument after preparing mesial canals of mandibular molars (n = 12), using micro-CT imaging. Statistical analyses were performed using the U-Mann-Whitney test and independent Student t-test (α = 5%). RESULTS: The number of spirals (n = 8) and blade direction (clockwise) were similar between both flat and nonflat instruments, whilst the helical angles were equivalent (⁓25°). Flat-instruments showed inconsistencies in the homogeneity of the gold colour on the flat-side surface, blade discontinuity, and incomplete and variable S-shaped cross-sections. The titanium-to-nickel ratios were equivalent, but significant differences in the R-phase finish and austenitic start phase transformation temperatures were observed between the flat and nonflat-side instruments. The flat-side instruments demonstrated superior cutting ability compared to the nonflat instruments, as well as, significantly lower values for time to fracture, rotation to fracture and maximum torque to fracture (p < .001). No statistical difference was observed between tested instruments regarding angle of rotation (p = .437), maximum bending (p = .152) and buckling load (p = .411). Preparation protocols using flat and nonflat instruments did not show any statistically significant differences (p > .05). All flat-side instruments exhibited deformation after shaping procedures. CONCLUSIONS: The flat-side instrument showcased enhanced cutting ability compared to its nonflat counterpart. However, it exhibited inferior performance in terms of time, rotation and maximum torque to fracture, along with distinct phase transformation temperatures. No differences were observed in the titanium-to-nickel ratios, angle of rotation, maximum bending, buckling load, preparation time, percentage of untouched canal walls, volume of hard tissue debris and percentage reduction of dentine thickness.

Impact of kinematics on the efficiency and safety of an engine-driven file for glide path preparation in MB2 canals of maxillary molars.

AIM: To evaluate the influence of different kinematics on the efficiency and safety of an engine-driven file for glide path preparation in second mesiobuccal canals (MB2) of maxillary molars. In addition, the torsional resistance of the file was assessed after use. METHODOLOGY: Thirty-six maxillary first and second molars with two canals in the mesiobuccal root were selected and the anatomy of the canals was verified by micro-CT. The teeth were divided into 4 groups (n = 9) according to the kinematics used for glide path preparation: continuous rotation (CR), 30°/150° reciprocation (REC 30°/150°), 30°/90° reciprocation (REC 30°/90°), and 90° optimum glide path motion (OGP 90°). The duration of the procedure, number of canals in which the file reached the full working length (RFWL), canal volume before and after the procedure, rate of file fracture, and file torsional strength after use were evaluated. The ANOVA and Tukey tests or Kruskal-Wallis and Dunn tests were used for statistical analysis. RESULTS: No significant differences among the groups were found for procedure duration, success at reaching the FWL, distance from the file to apex, and number of fractured files (P > 0.05). The CR group showed a significant decrease in rotation angle compared with REC 90° and OGP 90° groups (P < 0.05). There was no significant difference in canal volume among the groups (P > 0.05). CONCLUSION: The type of kinematics used did not affect the efficiency, success rate, and shaping ability of the file during glide path preparation. CR seems to induce more torsional stress than the other kinematics. CLINICAL RELEVANCE: The glide path preparation of narrow canals such as the MB2 is difficult and accidents such as file fracture may occur. This study showed that reciprocation with different file angulations can be safer during this challenging stage.

Cyclic and Torsional Fatigue Resistance of Seven Rotary Systems.

Introduction: This study aims to evaluate the cyclic and torsional fatigue resistance of seven rotary systems. Methods and Materials: A total of 140 instruments were tested, 20 of each system including Genius (GN) 25/0.04, TruShape (TS) 25/0.06, Logic (LOG) 25/0.06 taper, Vortex Blue (VB) 25/0.06, ProTaper Gold (PTG) 25/0.08, Hyflex CM (HCM) 25/0.06 and Hyflex EDM (EDM) 25/0.08 taper. Cyclic fatigue resistance testing was performed using an artificial stainless steel canal with a curvature (60° angle and 5-mm radius) located at 5 mm from the tip. The files (n=10) rotated until fracture, and time was recorded in seconds. The torsional test was evaluated according to ISO 3630-1. Data were analysed with one-way ANOVA and Tukey's tests (α=5%). The fractured surface of the instruments were assessed using scanning electron microscopy to confirm the type of fracture. Results: The cyclic fatigue resistance value of EDM was significantly higher than those of all tested instruments (P<0.05). LOG showed a higher cyclic fatigue resistance than GN or TS (P<0.05). There was no difference among the other groups (P>0.05). The torsional test showed that PTG 25/0.08 had the highest torsional strength value of all instruments tested followed by VB and EDM (P<0.05). The LOG showed significant difference only with GN (P<0.05). No difference was found among the other groups (P>0.05). In relation to angular deflection, the GN; TS; HCM, and EDM showed significantly higher values until fracture than the other groups (P<0.05). No difference was found among PTG, LOG, and VB (P>0.05). Conclusion: Our in vitro study EDM group had the highest cyclic fatigue resistance among all the tested instruments. For the torsional test, the PTG showed highest torsional strength and lowest angular deflection values.

Computed microtomography evaluation of calcium hydroxide-based root canal dressing removal from oval root canals by different methods of irrigation.

The aim of this study was to evaluate the capacity of conventional irrigation, passive ultrasonic irrigation (PUI), and Easy Clean for removing calcium hydroxide-based root canal dressing from oval root canals. Thirty mandibular uniradicular incisors with oval canals were used, and subjected to chemical-mechanical preparation with Reciproc R40 instruments. The main canal was filled with a paste based on Ca(OH)2 P.A., iodoform and propylene glycol in the ratio of 3:1:1. The teeth were stored in 100% humidity at a temperature of 37°C for 14 days. Afterwards, the teeth were divided into three groups (n = 10) according to the method of irrigation used (conventional irrigation, PUI, and Easy Clean). The specimens were analyzed by computed microtomography at three time intervals: before placing the root canal dressing, with the root canal dressing in place, and after application of the irrigation methods for removing it. The data were submitted to Kruskal-Wallis and Dunn tests for analyzing the canal as a whole, and Friedman and Dunn for analyzing the root thirds. The results showed that conventional irrigation was less efficient for removing the root canal dressing in comparison with the methods that agitated the irrigant solution (p < .05). When the root canal was analyzed as a whole, Easy Clean, and PUI were similar (p > .05). In analysis of the thirds, Easy Clean was more efficient than conventional irrigation in all the thirds, while PUI showed this behavior only in the cervical third (p < .05). The authors concluded that in oval canals, none of the irrigation methods were capable of removing all the root canal dressing, however, the methods that agitated the irrigant solution were more efficient than conventional irrigation.

Laser therapy as an adjunct in the treatment of sodium hypochlorite extrusion through a root perforation: a case report.

Accidental sodium hypochlorite extrusion can occur during endodontic irrigation procedures. The symptoms appear immediately and include severe pain, swelling, and probable tissue necrosis adjacent to the root of the treated tooth. Treatment of sodium hypochlorite extrusion involves immediate and copious saline irrigation to neutralize the area and prescription of analgesic, anti-inflammatory, and antibiotic medications. Low-level laser therapy (LLLT) might be useful as an adjuvant treatment for damaged soft tissues to improve healing. This case report describes the treatment of accidental extrusion of 1% sodium hypochlorite through a root canal perforation in a mandibular incisor during endodontic treatment. The extrusion caused minor swelling within the mentolabial sulcus and a large area of necrosis in the gingivolabial mucosa and right edentulous premolar area. Conventional treatment was performed in association with LLLT. Clinical and radiographic examinations after 6 months showed complete healing of the necrotic area without paresthesia and the repair of apical tissues.

Cyclic and Torsional Fatigue Resistance of Reciprocating Single Files Manufactured by Different Nickel-titanium Alloys.

INTRODUCTION: The aim of this study was to evaluate the cyclic and torsional fatigue resistance of the following reciprocating single-file systems: ProDesign R 25.06 (Easy Equipamentos Odontológicos, Belo Horizonte, Brazil), Reciproc R25 (VDW GmbH, Munich, Germany), and Unicone L25 (Medin SA, Nové Mesto in Morave, Czech Republic). METHODS: Sixty instruments of the ProDesign R, Reciproc R25, and Unicone L25 systems (n = 20) were used. Cyclic fatigue resistance was tested measuring the time to failure in an artificial stainless steel canal with a 60° angle and a 5-mm radius of curvature (n = 10). Torque and angle of rotation at failure of new instruments (n = 10) in the 3 mm from the tip portion were measured during torsional testing according to ISO 3630-1. The fractured surface of each fragment was examined by scanning electron microscopy. Data were analyzed using 1-way analysis of variance and Tukey tests, and the level of significance was set at 5%. RESULTS: The cyclic fatigue resistance values of ProDesign R 25.06 were significantly higher than the other groups (P < .05). Reciproc R25 showed higher fatigue resistance than Unicone L25 (P < .05). In relation to the torsional test, the ProDesign R 25.06 and Unicone L25 systems showed higher angular rotation until fracture than Reciproc R25 (P < .05). However, Reciproc R25 and Unicone L25 showed higher torque load than ProDesign R 25.06 (P < .05). Scanning electron microscopic analysis showed similar and typical features of cyclic and torsional failure for all instruments tested. CONCLUSIONS: ProDesign R presented the highest cyclic fatigue resistance and angular rotation to failure compared with Reciproc and Unicone. However, Reciproc showed higher torsional strength to failure.

Unicone: um novo sistema reciprocante para preparo dos canais radiculares / Unicone: a new reciprocating system for root canal shaping

O preparo biomecânico é uma das etapas mais importantes para o sucesso do tratamento endodôntico. A instrumentação mecanizada revolucionou o preparo dos canais radiculares, proporcionando preparos rápidos, demandando menor tempo clínico e menor estresse ao operador. A cinemática reciprocante surgiu como alternativa a rotação continua, utilizando menor número de instrumentos para o preparo, menor tempo e menor curva de aprendizado. Na atualidade tem sido dado um destaque especial aos sistemas reciprocantes sendo representados pelo Reciproc e Wave-One. A Medin apresentou um novo sistema reciprocante, o sistema Unicone. O objetivo deste artigo é a apresentação desse novo sistema, suas vantagens e performance na realização do tratamento endodôntico.

Mechanical preparation is one of the most important steps for successful endodontic treatment. The mechanized instrumentation modernized the root canals treatment, providing fast preparations and requiring less clinical time and less stress to the operator. The reciprocating kinematics emerged as an alternative to continuous rotation, using less instruments and less time to prepare the root canal system. It also shortens the learning curve. Currently has been given a special emphasis on reciprocating systems being represented by Reciproc and Wave-One files. The Medin introduced a new reciprocating system called Unicone. The purpose of this article is to presentate this new system, its advantages and performance in accomplishing the endodontic treatment.

O uso dos localizadores foraminais na endodontia: revisão de literatura / The use of apex locator in endodontics: a literature review

A correta determinação do comprimento real de trabalho (CRT) é um fator importante que corrobora no sucesso do tratamento endodôntico. Diversos estudos mostram que o uso de localizadores foraminais eletrônicos é recomendado devido à sua eficácia e benefícios quando utilizados na terapia endodôntica. O princípio de ação desses aparelhos está relacionado às propriedades que os tecidos orais apresentam quando submetidos a diversos componentes elétricos como resistência, frequência e impedância. Os localizadores foraminais podem ser utilizados em diversas situações na prática clínica, como nos tratamentos de dentes vitais e não vitais até nos casos de retratamentos. O objetivo deste estudo é analisar por meio de revisão da literatura a eficácia dos localizadores foraminais eletrônicos na determinação do comprimento real de trabalho durante a realização do tratamento endodôntico.

An important operatory stage that can determine the success of the endodontic treatment is the correct determination of the real working length. Several studies recommended the use of apex locators due to their effectiveness and benefits when they were used in endodontic therapy. The operating principles of these devices are related to the oral tissues properties when submitted to different electrical components such as resistance, frequency and impedance. Apex locators can be used in a variety of clinical situations, such as vital or non-vital teeth and retreatment. The aim of this study was to analyze the literature regarding the effectiveness of apex locators in endodontic treatments under different situations and compares their accuracy in determination of the apical foramen location.

RECIPROC: comparativo entre a cinemática reciprocante e rotatória em canais curvos / RECIPROC: a comparison between reciprocating and rotational kinematics in curved canals

Objetivo: Comparou o tempo de preparo, ocorrência de fratura e manutenção do trajeto do canal em canais artificiais do instrumento Reciproc R25 em movimento reciprocante e rotação contínua anti-horária. Material e Métodos: Foram utilizados dois grupos contendo 10 canais artificiais em blocos de acrílico cada, sendo um o grupo controle, instrumentado com movimento reciprocante, e o grupo teste utilizando rotação contínua anti-horária a 300rpm para a instrumentação. Resultados: os resultados mostraram que houve diferença estatística significante em relação ao tempo de preparo entre os grupos, uma vez que a rotação contínua anti-horária proporcionou um menor tempo de preparo; ambos mantiveram o trajeto original do canal sem qualquer desvios no terço apical e ocorreu uma fratura no grupo da rotação contínua. Conclusão: o sistema Reciproc manteve a trajetória original do canal, não influenciou na incidência de fratura dos instrumentos e demandou menor tempo de preparo utilizando rotação contínua. Portanto, o sistema Reciproc pode ser utilizado com rotação contínua anti-horária desde que velocidade, torque e pressão apical sejam respeitados e se empregue os instrumento uma única vez.

Objective: This study aimed to compare the preparation time, occurrence of fracture and maintenance of the canal path in artificial canals using Reciproc R25 instrument moving reciprocating and continuous counterclockwise rotation. Methods: Two groups of 10 Simulated rootcanals, each one in an artificial acrylic block, was instrumented with reciprocating motion (control group) and using counterclockwise continuous rotation to 300rpm (test group). Results: The results showed statistically significant difference in relation to the preparation time between the groups, since the counterclockwise continuous rotation allowed shorter preparation time, both kinematics kept the original route of the canal without any deviations in the apical third. A fracture occurred in the group of continuous rotation. Conclusion: The Reciproc system kept the original trajectory of the canals and did not influence the incidence of instruments fracture. A less preparation time was required when the continuous rotation was used. Therefore, the Reciproc system can be used with counterclockwise continuous rotation since that speed, torque and apical pressure are respected. The instrument also should be employed just one time.