How do reused glide path files affect the cyclic fatigue resistance? / ¿Cómo afecta la reutilización de limas tipo glide path su resistencia a la fatiga cíclica?

ABSTRACT: The aim of this study was to compare the cyclic fatigue resistance (CFR) of PathFile (Dentsply Sirona, Ballaigues, Switzerland) and ScoutRace (FKG Dentaire, La Chaux-de-Fonds, Switzerland) glide path files which were either new or previously used. Forty PathFile (PF) 19/.02 and 40 ScoutRace (SR) 20/.02 instruments were used for this study. Half of the files in each group were used (PF-U and SR-U) in the 3D demo tooth models (FKG Dentaire, La Chaux-de-Fonds, Switzerland) for creating glide paths, while the other half was new (PF-N and SR-N) and directly subjected to the cyclic fatigue test. The new and used files (n=80) were rotated in the cyclic fatigue test device with an artificial stainless-steel canal (60° curvature, 5 mm radius 1.5 mm width and 3.0 mm depth) under the continuous irrigation with distilled water at 37°C until fracture occurred. Time to fracture was recorded and the Weibull reliability analysis was performed. Data were statistically analysed. Conformity to normal distribution was examined using the Shapiro-Wilk test. A paired two-sample t-test was used to compare the TTF values according to the time within the groups. The new instruments (PF-N and SR-N) showed better CFR than the used groups (PF-U and SR-U) (P SR-N>PF-U>SR-U. Reuse of both glide path instruments reduced the time to fracture and the cyclic fatigue resistance of the files.

RESUMEN: El objetivo de este estudio fue comparar la resistencia a la fatiga cíclica (CFR en inglés) de las limas PathFile (Dentsply Sirona, Ballaigues, Suiza) y ScoutRace (FKG Dentaire, La Chaux-de-Fonds, Suiza) de tipo glide path, nuevas o ya previamente utilizadas. Para este estudio se utilizaron 40 instrumentos PathFile (PF) 19/.02 y 40 ScoutRace (SR) 20/.02. La mitad de las limas de cada grupo se utilizaron (PF-U y SR-U) en los modelos dentales de demostración 3D (FKG Dentaire, La Chaux-de- Fonds, Suiza) para crear trayectorias de deslizamiento, mientras que la otra mitad se utilizaron nuevas directamente a la prueba de fatiga cíclica (PF-N y SR-N). Las limas nuevas y usadas (n=80) se hicieron girar en el dispositivo de prueba de fatiga cíclica con un canal artificial de acero inoxidable (curvatura de 60°, radio de 5mm, anchura de 1,5mm y profundidad de 3,0mm) bajo irrigación continua con agua destilada a 37°C hasta que se produjo la fractura. Se registró el tiempo hasta la fractura y se realizó el análisis de fiabilidad de Weibull. Los datos se analizaron estadísticamente. La conformidad con la distribución normal se examinó mediante la prueba de Shapiro- Wilk. Se utilizó una prueba t de dos muestras pareadas para comparar los valores de TTF según el tiempo dentro de los grupos. Los instrumentos nuevos (PF-N y SR- N) mostraron una mejor CFR que los grupos previamente utilizados (PF-U y SR-U) (p SR-N >PF-U >SR-U. La reutilización de ambos instrumentos tipo glide path redujo el tiempo hasta la fractura y la resistencia a la fatiga cíclica de las limas.

The effect of glide path preparation on the shaping ability of XP-endo® Shaper in simulated canals

Aims: To compare the shaping efficiency of the XP-endo Shaper with or without glide path preparation with sequenced Scout Race files in J-shaped resin blocks Material and Methods: Forty simulated J-shaped root canals were classified into two groups (n=20). While the root canals were shaped with XPS after a glide path was created with Scout Race files in Group 1, the same procedures were done without the glide path preparation in Group 2. The pre-and post-instrumentation images were taken and superimposed. Transportation value (TV), centering ability (CA) and the total amount of resin removed (TRR) was calculated by using the obtained images with Adobe Photoshop CS5 software. These parameters were calculated based on 18 reference points (9 inner/9 outer walls) with 1-mm intervals according to 3 sections (coronal, middle, and apical of the canals). The data were analyzed with Kruskal-Wallis and then Dunn's multiple comparison tests (p ≤ 0.05). Results: More resin was removed in Group 2 apical and coronal sections than in Group 1 (p=0.036). In Group 2, a higher transportation value was obtained in apical and middle sections compared to Group 1 (p<0.001). Group 1 showed a higher centering ratio in apical and middle sections than in Group 2 (p<0.001). The centering ability of the instruments was decreased in the curvature part (middle section) of the canals. Conclusions: Within the limits of this study, glide path preparation using Scout Race instruments improved the shaping ability of XPS instrument by leading to less transportation and maintaining centering ability.

Evaluation of glide path preparation and shaping ability of two nickel-titanium engine driven systems in moderate curved root canals / 上海交通大学学报（医学版）

Objective:To evaluate the clinical application effect of two nickel-titanium engine driven systems on moderate curved root canals. Methods:Ninety mesial root canals with moderate curvature of extracted human first mandibular permanent molar were randomly divided into three groups: M3 PRO Group, MTwo group and K group. The glide path was firstly prepared by using #10/04 file in M3 PRO group and MTwo group and #10 file in K group respectively.Then the preparation of root canals up to #25 was performed according to the instruction manual in each different group using standardized technique. All data including time required in glide path preparation, shaping preparation, total root canals preparation and changes of working length in root canal were recorded and analyzed statistically by using Analysis of Variance (ANOVA) and LSD-t tests (P<0.05). Results:Root canal glide path preparation time: MTwo group showed significantly less preparation time while M3 PRO group exhibited significantly the longest preparation time. There was significant difference between MTwo group and M3 PRO group (P=0.001). Root canal shaping preparation time: M3 PRO group showed significantly less preparation time while K group exhibited significantly the longest preparation time. Both MTwo group and M3 PRO group showed significantly less preparation time than K group (P=0.004, P=0.001), but there was no significant difference between MTwo group and M3 PRO group (P=0.573). Total root canal preparation time: MTwo group showed the shortest time while K group exhibited the longest time. There were significant differences between MTwo group, M3 PRO group and K group (P=0.004, P=0.033), but no significant difference between MTwo group and M3 PRO group (P=0.451). Changes of root canal working length: There were significant differences among the three groups (P=0.037, P=0.037, P=0.000). M3 PRO group showed a minimal change while K group exhibited significant changes. Conclusion:MTwo nickel-titanium engine driven system with #10/04 file preform a high efficiency in glide path preparation, whilst M3 PRO nickel-titanium engine driven system show less changes in working length. Under the circumstances where the total time required for root canal preparation is not significant, M3 PRO nickel-titanium engine driven system is more suitable for root canal preparation in moderate curved root canals.

Effect of glide path preparation with PathFile and ProGlider on the cyclic fatigue resistance of WaveOne nickel-titanium files

OBJECTIVES: The aim of this study was to investigate the effect of glide path preparation with PathFile and ProGlider nickel-titanium (NiTi) files on the cyclic fatigue resistance of WaveOne NiTi files. MATERIALS AND METHODS: Forty-four WaveOne Primary files were used and divided into four groups (n = 11). In the first group (0 WaveOne), the WaveOne Primary files served as a control group and were not used on acrylic blocks. In the 1 WaveOne Group, acrylic blocks were prepared using only WaveOne Primary files, and in the PF+WaveOne group and PG+WaveOne groups, acrylic blocks were first prepared with PathFile or ProGlider NiTi files, respectively, followed by the use of WaveOne Primary files. All the WaveOne Primary files were then subjected to cyclic fatigue testing. The number of cycles to failure was calculated and the data were statistically analyzed using one-way analysis of variance (ANOVA) and the Tukey honest significant difference multiple-comparison test at a 5% significance level. RESULTS: The highest number of cycles to failure was found in the control group, and the lowest numbers were found in the 1 WaveOne group and the PF+WaveOne group. Significant differences were found among the 1 WaveOne, PF+WaveOne, and control groups (p 0.05). CONCLUSION: Glide path preparation with NiTi rotary files did not affect the cyclic fatigue resistance of WaveOne Primary files used on acrylic blocks.

Comparison of the ability of Reciproc and Reciproc Blue instruments to reach the full working length with or without glide path preparation

OBJECTIVES: The purpose of the present study was to compare the mean preparation times and frequency with which Reciproc and Reciproc Blue instruments reached the full working length in mandibular molars, with or without glide path preparation. MATERIALS AND METHODS: Previously untreated mesiobuccal and mesiolingual canals with completely formed apices were randomly divided into 6 groups (n = 50) depending on the usage of Reciproc (RC; VDW), Reciproc Blue (RC Blue; VDW), C-Pilot (CP; VDW), and R-Pilot (RP; VDW) files: RC, RC Blue, RC + C-Pilot (RC-CP), RC-Blue + C-Pilot (RC Blue-CP), RC+R-Pilot (RC-RP), and RC Blue + R-Pilot (RC Blue-RP). A glide path was prepared using the hand-operated C-Pilot or the machine-operated R-Pilot instruments, respectively. The χ2 test, analysis of variance, and the Tukey post hoc test were used for statistical comparisons. RESULTS: No statistically significant differences were observed in the distribution of the frequency of reaching the full working length in the RC (94%), RC Blue (88%), RC-CP (94%), RC Blue-CP (90%), RC-RP (96%), and RC Blue-RP (92%) groups (p > 0.05). CONCLUSIONS: Preparation of a glide path did not have a significant effect on reaching the full working length using these systems.

Common endodontic treatment challenge in an elderly patient: Negotiating root canal impediments

@#A male elderly patient came with buccal mucosa swelling associated with tooth 46 and 47. Periapical radiograph confirmed the presence of periapical lesion and narrow root canals on both teeth. Challenging impediments were sensed upon negotiating most of the narrow root canals which were common in elderly patients. Glide path creation involved pre-flaring, K-file bending, watch winding movement, and very gentle strokes. After achieving patency, shaping, cleaning, and sealing phase can be performed.

Permeabilización del Canal Radicular y Transporte Apical: Comparación de Tres Sistemas / Root Canal Glide Path and Apical Transportation: Three System Comparison

La mantención de la anatomía original del canal radicular incide directamente en el éxito del tratamiento endodóntico. Para ello, los sistemas rotatorios de instrumentación requieren de canales radiculares permeables. Existen distintas limas y sistemas para la permeabilización o glide path como las limas tipo K manuales de acero inoxidable y los sistemas de NiTi rotatorios PathFile y ProGlider (Dentsply, Maillefer). Así, el objetivo de esta investigación fue comparar la capacidad de distintos sistemas de permeabilización para mantener la anatomía radicular sin producir transporte apical en canales mesiales de molares inferiores humanos extraídos. Se realizó un estudio cuantitativo experimental cuya muestra estuvo conformada por 36 canales mesiales de molares mandibulares humanos extraídos. Las muestras fueron divididas aleatoriamente en tres grupos conformados por 12 canales, cada uno de los cuales fueron sometidos a distintos sistemas de permeabilización (Lima K, PathFile y ProGlider). Las muestras fueron fotografiadas antes y después de la permeabilización utilizando un microscopio con magnificación 30X. Se cuantificó el desplazamiento del canal radicular en sentido mesio - distal y buco - lingual posterior a la permeabilización. Para el análisis de los datos se utilizó el paquete estadístico InfoStat/L y se aplicó la prueba de ANOVA / Tukey. Se observó que el sistema PathFile produce mayor transporte del canal radicular en su tercio apical en la dirección mesio-distal (p=0,77) y el sistema ProGlider en la dirección buco-lingual (p=0,57). Sin embargo, estas diferencias no fueron significativas. En conclusión, los sistemas de permeabilización analizados no presentaron diferencias en cuanto a su capacidad para mantener la anatomía sin producir transporte apical.

Preservation of the original root canal anatomy has a direct influence on the success of an endodontic treatment. In order to achieve this, rotary instrumentation systems require permeable root canals. Different files and systems are used for the establishment of a glide path such as manual stainless steel K files and NiTi rotatory systems like PathFile and ProGlider (Dentsply, Maillefer). Thus, the objective of this research was to compare the ability of different systems to create a glide path and maintain root canal anatomy without producing apical transportation in mesial root canals of extracted human lower molars. A quantitative experimental study was performed with a sample of 36 mesial root canals of extracted human mandibular molars. The samples were randomly divided into three groups consisting of 12 root canals each, which were subjected to different glide path systems (K-Files, PathFile and ProGlider). Samples were photographed before and after creating glide path using a microscope with 30X magnification. The displacement of the root canal in a mesio - distal and bucco - lingual direction was quantified after creating glide path. Data was analyzed using the statistical package InfoStat / L and the ANOVA / Tukey test was applied. The PathFile system produced greater transport of the root canal in its apical third in the mesio-distal direction (p = 0.77) and the ProGlider system in the bucco-lingual direction (p = 0.57). However, these differences were not significant. In conclusion, the glide path systems analyzed do not present any differences in their ability to maintain the anatomy without producing apical transportation.

Comparison of apical extrusion of intracanal bacteria by various glide-path establishing systems: an in vitro study

OBJECTIVES: This study compared the amount of apically extruded bacteria during the glide-path preparation by using multi-file and single-file glide-path establishing nickel-titanium (NiTi) rotary systems. MATERIALS AND METHODS: Sixty mandibular first molar teeth were used to prepare the test apparatus. They were decoronated, blocked into glass vials, sterilized in ethylene oxide gas, infected with a pure culture of Enterococcus faecalis, randomly assigned to 5 experimental groups, and then prepared using manual stainless-steel files (group KF) and glide-path establishing NiTi rotary files (group PF with PathFiles, group GF with G-Files, group PG with ProGlider, and group OG with One G). At the end of canal preparation, 0.01 mL NaCl solution was taken from the experimental vials. The suspension was plated on brain heart infusion agar and colonies of bacteria were counted, and the results were given as number of colony-forming units (CFU). RESULTS: The manual instrumentation technique tested in group KF extruded the highest number of bacteria compared to the other 4 groups (p < 0.05). The 4 groups using rotary glide-path establishing instruments extruded similar amounts of bacteria. CONCLUSIONS: All glide-path establishment instrument systems tested caused a measurable apical extrusion of bacteria. The manual glide-path preparation showed the highest number of bacteria extruded compared to the other NiTi glide-path establishing instruments.

Safe Mechanical Preparation with Reciprocation Movement without Glide Path Creation: Result from a Pool of 673 Root Canals

Abstract The aim of the present study was to prospectively assess the frequency of teeth in which the Reciproc instruments were able to reach the full working length (WL). This case series study enrolled 277 consecutive teeth requiring primary endodontic treatment performed with the Reciproc system (VDW) without a previous glide path by 3 experienced endodontists. Instruments R25, R40 or R50 were selected, respectively, for narrow, medium and large canals, according to the preoperative radiographs, as per manufacturer recommendation. Canals were instrumented and classified as reaching the full WL (RFWL) and not reaching the full WL (NRFWL), according to the ability of the Reciproc instrument to reach without a glide path the full electronically determined WL. Finally, canals were filled using a single matched cone technique. Pearson's squared-chi test compared the frequency distributions of canals classified as RFWL and NRFWL. From a total pool of 673 root canals, Reciproc instruments reached the FWL in 96.28% of cases and 3 fractures occurred. For narrow canals the percentage of RFWL was 95.37% with 3 fractures. For medium and large canals, the R40 or R50 instruments reached the FWL in 98.51% and 97.62% of the cases respectively, with no fracture. Enlarging of root canals using the Reciproc instruments up to the FWL without a glide path is successful in a great percentage of cases. This case series suggests the possibility of using a single instrument to enlarge the root canal space of teeth by a simpler approach without an a prioriglide path procedure.

Resumo O objetivo do presente estudo foi avaliar prospectivamente a frequência de dentes em que os instrumentos Reciproc foram capazes de alcançar o comprimento de trabalho (CT) completo. Este estudo com série de casos envolveu 277 dentes consecutivos que necessitavam de tratamento endodôntico primário realizado com o sistema Reciproc (VDW) sem a realização de uma via de penetração inicial (glide path) prévio por 3 endodontistas experientes. Instrumentos R25, R40 ou R50 foram selecionados, respectivamente, para canais estreitos, médios e largos, de acordo com as radiografias pré-operatórias, seguindo a recomendação do fabricante. Os canais foram instrumentados e classificados como atingindo o WL completo (ACTC) e de não atingindo o WL completo (NACTC), de acordo com a capacidade do instrumento Reciproc de alcançar o CT completo determinado eletronicamente, sem a realização de glide path. Finalmente, os canais foram preenchidos usando a técnica de obturação de cone único. O teste de qui-quadrado de Pearson comparou a frequência das distribuições de canais classificados como ACTC e NACTC. A partir de um pool total de 673 canais radiculares, instrumentos Reciproc atingiram o CTC em 96,28% dos casos e 3 fraturas ocorreram. Para canais estreitos, a percentagem de ACTC foi 95,37% com 3 fraturas. Para canais médios e largos, os instrumentos R40 e R50 atingiram o CTC em 98,51% e 97,62% dos casos, respectivamente, sem fratura. Ampliação dos canais radiculares utilizando os instrumentos Reciproc até o CTC sem a realização de glide pathfoi bem sucedida em uma grande porcentagem dos casos. Esta série de casos sugere a possibilidade de utilizar um único instrumento para ampliar o espaço do canal radicular usando uma abordagem mais simples, sem um procedimento prévio deglide path.

Canal preparation with nickel-titanium or stainless steel instruments without the risk of instrument fracture: preliminary observations

This report introduces a novel technique that allows a safe and predictable canal negotiation, creation of a glide path and canal preparation with reciprocating nickel-titanium or stainless steel engine-driven instruments in canals where the use of rotary and the newly developed reciprocating instruments is contraindicated. In this novel technique, the instruments are used in reciprocating motion with very small angles. Hand files are not used regardless of the complexity of the canal anatomy. It also allows achieving predictable results in canal negotiation and glide path creation in challenging canals without the risk of instrument fracture.

Effect of repetitive pecking at working length for glide path preparation using G-file

OBJECTIVES: Glide path preparation is recommended to reduce torsional failure of nickel-titanium (NiTi) rotary instruments and to prevent root canal transportation. This study evaluated whether the repetitive insertions of G-files to the working length maintain the apical size as well as provide sufficient lumen as a glide path for subsequent instrumentation. MATERIALS AND METHODS: The G-file system (Micro-Mega) composed of G1 and G2 files for glide path preparation was used with the J-shaped, simulated resin canals. After inserting a G1 file twice, a G2 file was inserted to the working length 1, 4, 7, or 10 times for four each experimental group, respectively (n = 10). Then the canals were cleaned by copious irrigation, and lubricated with a separating gel medium. Canal replicas were made using silicone impression material, and the diameter of the replicas was measured at working length (D0) and 1 mm level (D1) under a scanning electron microscope. Data was analysed by one-way ANOVA and post-hoc tests (p = 0.05). RESULTS: The diameter at D0 level did not show any significant difference between the 1, 2, 4, and 10 times of repetitive pecking insertions of G2 files at working length. However, 10 times of pecking motion with G2 file resulted in significantly larger canal diameter at D1 (p < 0.05). CONCLUSIONS: Under the limitations of this study, the repetitive insertion of a G2 file up to 10 times at working length created an adequate lumen for subsequent apical shaping with other rotary files bigger than International Organization for Standardization (ISO) size 20, without apical transportation at D0 level.

Effect of repetitive pecking at working length for glide path preparation using G-file

OBJECTIVES: Glide path preparation is recommended to reduce torsional failure of nickel-titanium (NiTi) rotary instruments and to prevent root canal transportation. This study evaluated whether the repetitive insertions of G-files to the working length maintain the apical size as well as provide sufficient lumen as a glide path for subsequent instrumentation. MATERIALS AND METHODS: The G-file system (Micro-Mega) composed of G1 and G2 files for glide path preparation was used with the J-shaped, simulated resin canals. After inserting a G1 file twice, a G2 file was inserted to the working length 1, 4, 7, or 10 times for four each experimental group, respectively (n = 10). Then the canals were cleaned by copious irrigation, and lubricated with a separating gel medium. Canal replicas were made using silicone impression material, and the diameter of the replicas was measured at working length (D0) and 1 mm level (D1) under a scanning electron microscope. Data was analysed by one-way ANOVA and post-hoc tests (p = 0.05). RESULTS: The diameter at D0 level did not show any significant difference between the 1, 2, 4, and 10 times of repetitive pecking insertions of G2 files at working length. However, 10 times of pecking motion with G2 file resulted in significantly larger canal diameter at D1 (p < 0.05). CONCLUSIONS: Under the limitations of this study, the repetitive insertion of a G2 file up to 10 times at working length created an adequate lumen for subsequent apical shaping with other rotary files bigger than International Organization for Standardization (ISO) size 20, without apical transportation at D0 level.

Utilidad de la conformación del túnel liso antes de usar limas rotatorias endodónticas de níquel-titanio / Usefulness of shaping the glide path before using rotary nickel-titanium endodontic files

Introducción: para prevenir la fractura de instrumentos endodonticos actualmente se siguen investigando materiales, técnicas y diseños los cuales buscan reducir su incidencia. La conformación de túnel liso (Glide Path) se ha propuesto con este fin, sin embargo su utilidad ha sido controvertida. Objetivo: comprobar teóricamente mediante la utilización de un análisis de elementos finitos, la utilidad de la conformación de túnel liso, antes de la utilización de limas rotatorias endodonticas de níquel-titanio. Métodos: se realizó una simulación numérica mediante un análisis de elementos finitos, para lo cual se construyeron modelos matemáticos de las limas rotatorias de níquel-titanio S1 y S2 de la serie Protaper®. Con el software Simulation multyphisics de Autodesk® se programaron las propiedades mecánicas de las limas y un límite de falla por fractura de 1270,588 MPa. Posteriormente se aplicó el torque recomendado por el fabricante y se fijo la punta del instrumento (sin conformación de túnel liso) aplicando allí restricciones en todos los grados de libertad.Para simular la realización de la conformación de túnel liso, se aplicaron restricciones en todos los grados de libertad a una determinada distancia de la punta del instrumento, simulando de esta forma que la punta del instrumento permanecía libre. Resultados: al fijar la punta de las limas, los esfuerzos máximos fueron 1545,77 MPa para la S1 y 1306,47 MPa para la S2, observando fractura de los instrumentos. Al fijar las limas a distancia de la punta no se observó fractura. Conclusiones: se demostró teóricamente que al impedir que se atrapen la punta de las limas, se previene su fractura y que dicho atrapamiento se evita con una conformación de túnel liso, por lo que se concluye que este procedimiento es útil para prevenir la fractura de los instrumentos rotatorios de níquel-titanio(AU)

Introduction: materials, techniques and designs continue to be studied with the purpose of reducing the incidence of fracture in endodontic instruments. Shaping of the glide path has been proposed for this end; however, its usefulness has been a matter of controversy. Objective: based on the finite element method, carry out a theoretical analysis of the usefulness of shaping the glide path before using rotary nickel-titanium endodontic files. Methods: numerical simulation was performed based on finite element analysis, to achieve which mathematical models were built of rotary nickel-titanium files S1 and S2 of the Protaper™ series. Autodesk™ Simulation Multiphysics software was used to program the mechanical properties of the files, as well as a fracture failure limit of 1270.588 MPa. The torque recommended by the manufacturer was then applied and the instrument tip fixed into place (without shaping the glide path) with restrictions on all degrees of freedom. In order to simulate glide path shaping, restrictions were applied to all degrees of freedom at a certain distance from the instrument tip, thus simulating that the instrument tip remained free. Results: on fixing the file tips, maximum efforts were 1545.77 Mpa for S1 and 1306.47 Mpa for S2. Instrument fracture was observed. When files were fixed at a distance from the tip, no fracture was observed. Conclusions: it was theoretically demonstrated that when file tips are prevented from being caught, fracture is prevented as well, and such catch is avoided by shaping the glide path. It is therefore concluded that the procedure is useful to prevent the fracture of rotary nickel-titanium instruments(AU)

Buckling resistance, bending stiffness, and torsional resistance of various instruments for canal exploration and glide path preparation

OBJECTIVES: This study compared the mechanical properties of various instruments for canal exploration and glide-path preparations. MATERIALS AND METHODS: The buckling resistance, bending stiffness, ultimate torsional strength, and fracture angle under torsional load were compared for C+ file (CP, Dentsply Maillefer), M access K-file (MA, Dentsply Maillefer), Mani K-file (MN, Mani), and NiTiFlex K-file (NT, Dentsply Maillefer). The files of ISO size #15 and a shaft length of 25 mm were selected. For measuring buckling resistance (n = 10), the files were loaded in the axial direction of the shaft, and the maximum load was measured during the files' deflection. The files (n = 10) were fixed at 3-mm from the tip and then bent 45degrees with respect to their long axis, while the bending force was recorded by a load cell. For measuring the torsional properties, the files (n = 10) were also fixed at 3-mm, and clockwise rotations (2-rpm) were applied to the files in a straight state. The torsional load and the distortion angle were recorded until the files succumbed to the torque. RESULTS: The CP was shown to require the highest load to buckle and bend the files, and the NT showed the least. While MA and MN showed similar buckling resistances, MN showed higher bending stiffness than MA. The NT had the lowest bending stiffness and ultimate torsional strength (p < 0.05). CONCLUSIONS: The tested instruments showed different mechanical properties depending on the evaluated parameters. CP and NT files were revealed to be the stiffest and the most flexible instruments, respectively.

Influence of glide path on the screw-in effect and torque of nickel-titanium rotary files in simulated resin root canals

OBJECTIVES: The purpose of this study was to investigate the screw-in effect and torque generation depending on the size of glide path during root canal preparation. MATERIALS AND METHODS: Forty Endo-Training Blocks (REF A 0177, Dentsply Maillefer) were used. They were divided into 4 groups. For groups 1, 2, 3, and 4, the glide path was established with ISO #13 Path File (Dentsply Maillefer), #15 NiTi K-file NITIFLEX (Dentsply Maillefer), modified #16 Path File (equivalent to #18), and #20 NiTi K-file NITIFLEX, respectively. The screw-in force and resultant torque were measured using a custom-made experimental apparatus while canals were instrumented with ProTaper S1 (Dentsply Maillefer) at a constant speed of 300 rpm with an automated pecking motion. A statistical analysis was performed using one-way analysis of variance and the Duncan post hoc comparison test. RESULTS: Group 4 showed lowest screw-in effect (2.796 +/- 0.134) among the groups (p < 0.05). Torque was inversely proportional to the glide path of each group. In #20 glide path group, the screw-in effect and torque decreased at the last 1 mm from the apical terminus. However, in the other groups, the decrease of the screw-in effect and torque did not occur in the last 1 mm from the apical terminus. CONCLUSIONS: The establishment of a larger glide path before NiTi rotary instrumentation appears to be appropriate for safely shaping the canal. It is recommended to establish #20 glide path with NiTi file when using ProTaper NiTi rotary instruments system safely.

Uso de rotatórios pathfile e mtwo como acesso inicial no preparo endodôntico: comparação com limas manuais em canais curvos / Use of rotation and pathfile MTwo as initial access in endodontic treatment: a comparison with hand files in curved canals

Introdução: Instrumentos rotatórios em níquel-titânio reduzem erros processuais e o tempo requerido para finalização do preparo do canal radicular. O objetivo deste estudo foi avaliar as ocorrências de transporte apical e aberrações nos canais produzidas com diferentes instrumentos utilizados para a criação de trajetória-guia (“glide path”) no preparo de canais curvos: limas manuais K e limas rotatórias em níquel-titânio PathFile e Mtwo. Material e Métodos: Os canais mesiais de 45 primeiros e segundos molares inferiores (com ângulos de curvatura entre 25 e 35 graus) foram selecionados para o estudo. As amostras foram divididas aleatoriamente em três grupos de 15 canais cada e o preparo foi realizado por um endodontista utilizando limas manuais de aço inoxidável tipo K #10-15-20, conicidade 0,02 (grupo M), instrumentos rotatórios PathFile #13-16-19, conicidade 0,02 (grupo PF) e instrumentos rotatórios Mtwo #10/04- #15/05- #20/06 (grupo MT). Foi utilizada a técnica da dupla radiografia digital, pré e pós-instrumentação, para avaliar se ocorreu transporte apical e/ou aberrações na morfologia dos canais. Por meio de uma análise computadorizada e com o auxílio de magnificação, as imagens inicial e final do eixo central foram comparadas por meio de sua sobreposição. Os espécimes foram analisados por 3 avaliadores, cuja calibração foi checada por meio do teste de concordância de Kendall. Resultados: Não ocorreu transporte apical nem aberração na morfologia do canal em 100% dos dentes, portanto nenhuma análise estatística foi realizada. Conclusão: Tanto os instrumentos rotatórios PathFile e Mtwo quanto os instrumentos manuais utilizados para a criação de trajetória-guia não exerceram influência sobre a ocorrência de transporte apical nem promoveram aberrações na morfologia dos canais .

Introduction: Nickel-titanium rotary instruments reduce procedural errors and the time required to finish root canal preparation.The goal of this study was to evaluate the occurrences of apical transportation and canal aberrations produced with different instruments used to create a glide path in the preparation of curved root canals, namely: manual K files and PathFile and Mtwo nickel-titanium rotary files. Methods:The mesial canals of 45 mandibular first and second molars (with curvature angles between 25 and 35 degrees) were selected for this study. The specimens were divided randomly into three groups with 15 canals each, and canal preparation was performed by an endodontist using #10-15-20 K-type stainless steel manual files (Group M), #13-16-19 PathFile rotary instruments (Group PF), and #10-15-20 Mtwo rotary instruments (Group MT). The double digital radiograph technique was used, pre- and post-instrumentation, to assess whether apical transportation and/or aberration in root canal morphology occurred. The initial and final images of the central axis of the canals were compared by superimposition through computerized analysis and with the aid of magnification. The specimens were analyzed by 3 evaluators, whose calibration was checked using the Kendall agreement test. Results: No apical transportation or aberration in root canal morphology occurred in any of the teeth; therefore, no statistical analysis was conducted. Conclusion: Neither the manual instruments nor the PathFile or Mtwo rotary instruments used to create a glide path had any influence on the occurrence of apical transportation or produced any canal aberration

The influence of torque and manual glide path on the defect or separation rate of NiTi rotary instruments in root canal therapy.

Introduction: One of the effecting factors in prognosis of root canal therapy is accidental procedure as broken files that may be unpreventable. Many manufacturers have designed and marketed various electromotors that can control rotational speed and torque. On the other hand, some studies have recommended applying a manual glide path to diminish contact area between the file and canal walls. The purpose of this study was evaluation of the effect of torque and a manual glide path on defects as separation of Nickel-titanium (NiTi) rotary files. Materials and Methods: This ex vivo randomized controlled trial study was carried out on 160 canals of human's matured molars with mild curvature (15-338). After initial preparation of samples and checking for inclusion criteria, in first group, preparation was carried out with air-driven handpiece, and in group two, Endo IT was used as electromotor. In both groups, Mtwo files with simultaneous technique were used for preparation. Then all data were collected and analyzed with Mann Whitny, Mantel Cox, and t-test. Results: No significant differences between two groups (P < 0.05) were observed. Based on survival analysis, safety probability of files after preparation of nine canals is 64% in group one and 69.9% in group two. There was no significant differences between this safety probability in two groups (P = 0.272). Conclusion: Usage of torque control handpiece is not an important factor, comparing instrumentation technique.