ProTaper Universal Files Research Articles

The influence of the manufacturing process of rotary files on the shaping of L-shaped canals.

The nickel-titanium alloy used in the production of nickel-titanium files contains approx. 56% nickel and 44% titanium by weight. To improve the properties of nickel-titanium files, the manufacturers introduce some innovations in the production process. Their purpose is primarily to decrease the stiffness of the instruments while increasing the resistance to cyclic fatigue, which reduces the risk of file separation. One of the most popular processes is the heat treatment of the nickel-titanium alloy. The aim of the research was to determine the influence of the manufacturing process of rotary files on the shaping of L-shaped canals. Fifty L-shaped resin canals were instrumented (10/group) with ProTaper Universal ®, ProTaper Next®, Hyflex CM®, Hyflex EDM®, or WaveOne Gold® files, with the same apical size of 25. Each L-shaped resin canal was photographed both before and after instrumentation. Differences between the change of the working length and apical transportation were analyzed statistically. The smallest mean loss of the working length was observed after instrumentation with Hyflex CM files. Statistically significant differences in the working length were found between ProTaper Universal and Hyflex CM (p = 0.0032), ProTaper Universal and Hyflex EDM (p = 0.021), and ProTaper Universal and WaveOne Gold (p = 0.0112) files. The lowest apical transportation was noted in the case of WaveOne Gold files. In terms of apical transportation, statistically significant differences were observed between ProTaper Universal and WaveOne Gold files (p = 0.0254). Shaping Lshaped canals with the ProTaper Universal file system resulted in the greatest changes in the working length (x = 0.35 mm) and apical transportation (x = 0.034 mm). The study, with its limitations, shows that in the files whose nickel-titanium alloy was subjected to a thermal treatment process, a smaller loss of the working length and lower values of apical transportation were observed.

Incidence of Dentinal Crack Formation Using ProTaper Universal and WaveOne Systems in Straight and Curved Root Canals

Introduction: This study aimed to compare dentinal micro crack formation following root canal instrumentation with ProTaper Universal (PTU) and WaveOne (WO) rotary systems in straight and curved root canals. Methods and Materials: One hundred mesiobuccal (MB) straight and curved canals of mandibular molars meeting inclusion criteria were divided into two control ( n =10) and four experimental groups ( n =20). After mounting the teeth and simulating the periodontal ligament, all the MB canals were coronally flared using Gates-Glidden drills #3 and 2 respectively. Then, in the experimental groups, the canals were instrumented with either PTU files (S x , S 1 , S 2 , F 1 , F 2 ), or Primary WO (25/0.08). Afterwards, roots were horizontally sectioned at 2, 4, and 6 mm from the apices, and evaluated under a microscope under 20× magnification. Data were analyzed with the Chi -Square and Kruskal-Wallis tests. The significance level was set at 0.05. Results: The control groups showed no cracks. There was no significant difference between the two systems in the straight root canals ( P >0.05). But in the curved root canals, PTU produced significantly more cracks ( P <0.05) with the complete crack type which was dominant ( P =0.013) compared to WO. Conclusions : This in vitro study showed that in curved root canals, instrumentation with reciprocal WO system may be safer than full rotational PTU instruments regarding crack formation. Keywords: Crack; Dentin; Instrumentation; Reciprocating; Root Canal Preparation

Effect of root canal preparation, obturation, and retreatment on the induction of dentinal microcracks: A microcomputed tomography study.

Introduction:This study evaluated the effect of root canal preparation, obturation, and different techniques of retreatment on the percentage increase in the number of dentinal microcracks using microcomputed tomography (CT) analysis.Materials and Methods:Forty-five mandibular premolars after micro-CT scanning were prepared using Protaper universal files up to F4 and obturated. After the second micro-CT scanning again, the samples were randomly divided into three groups (n = 15) for retreatment procedure. In Group 1, retreatment was done with Protaper universal D1, D2, and D3 retreatment files followed by Protaper universal file till F4. In Group 2, retreatment was performed with R-Endo reciprocating motion, Re, R1, R2, R3, and Rs followed by Hero Shaper size #40. In Group 3, retreatment was performed with H-files and xylene till size #40. After gutta percha removal, the samples were again scanned for micro-CT for the evaluation of percentage increase in dentinal microcracks. Data were analyzed using “Kruskal–Wallis test ANOVA” and “student t-test” at 5% level of significance.Results:Few unprepared samples showed preexisting microcracks. There were statistically significant percentage increase dentinal cracks after root canal preparation and obturation as well as after retreatment procedure with statistically significant percentage increase in the number of dentinal microcracks between all three groups.Conclusion:Intraradicular procedures such as shaping and cleaning and obturation as well as the use of retreatment file lead to the induction and propagation of dentinal microcracks. In the present study, the maximum microcracks were produced with Protaper universal retreatment file system followed by R-Endo system. H-files produced minimum cracks during retreatment procedures.

Effect of three different rotary instrumentation systems on crack formation in root dentin: An in vitro study

Introduction: Biomechanical preparation (BMP) of root canal damages the root dentin which becomes a gateway to dentinal cracks and thereby causing failure of the treatment. Therefore, there is a need of best instruments to minimize the failure of endodontic treatment. Aims and Objective: The objective of this study is to compare the incidence of cracks observed in the root dentin after root canal preparation with three different rotary instrument systems. Material and Methods: Seventy-five freshly extracted permanent maxillary incisors were randomly selected. Teeth were divided into five groups (n = 15), Group 1 – Untreated (negative control group), Group 2 – BMP done with nickel–titanium K-files (positive control group), Group 3 – BMP done with ProTaper Universal files, Group 4 – BMP done with ProTaper Next files, and Group 5 – BMP done with HyFlex EDM files. Roots were sectioned horizontally at 2 mm, 4 mm, and 6 mm from the apex. All slices were then viewed under stereomicroscope. All findings were analyzed using Chi-square test. Observations and Results: In the apical third, Group 5 had maximum number of fracture cases while Group 4 had lesser number and Group 3 had the least. In the middle third, Group 3 had maximum number of fracture cases while Group 4 and Group 5 showed lesser number of fractures. In the cervical third, Group 3 and Group 4 showed equal and maximum number of fracture cases. Group 5 showed no fracture cases. Group 1 and Group 2 showed no fracture cases in all the root sections. Conclusion: Conventional hand instrumentation is the best as compared to rotary instrumentation. However, rotary systems render various benefits with an acceptable success in comparison to the conventional hand instrumentation. In our study, we found that HyFlex EDM rotary system was the best with least number of fracture as compared to other systems used.

Incidence of Dentinal Crack Formation Using ProTaper Universal and WaveOne Systems in Straight and Curved Root Canals.

This study aimed to compare dentinal micro crack formation following root canal instrumentation with ProTaper Universal (PTU) and WaveOne (WO) rotary systems in straight and curved root canals. One hundred mesiobuccal (MB) straight and curved canals of mandibular molars meeting inclusion criteria were divided into two control (n=10) and four experimental groups (n=20). After mounting the teeth and simulating the periodontal ligament, all the MB canals were coronally flared using Gates-Glidden drills #3 and 2 respectively. Then, in the experimental groups, the canals were instrumented with either PTU files (Sx, S1, S2, F1, F2), or Primary WO (25/0.08). Afterwards, roots were horizontally sectioned at 2, 4, and 6 mm from the apices, and evaluated under a microscope under 20× magnification. Data were analyzed with the Chi-Square and Kruskal-Wallis tests. The significance level was set at 0.05. The control groups showed no cracks. There was no significant difference between the two systems in the straight root canals (P>0.05). But in the curved root canals, PTU produced significantly more cracks (P<0.05) with the complete crack type which was dominant (P=0.013) compared to WO. This in vitro study showed that in curved root canals, instrumentation with reciprocal WO system may be safer than full rotational PTU instruments regarding crack formation.

A comparative evaluation of the antimicrobial efficacy of calcium hydroxide, chlorhexidine gel, and a curcumin-based formulation against Enterococcus faecalis.

Aim:This study aimed for a comparative evaluation of the antimicrobial efficacy of calcium hydroxide, chlorhexidine gel, and a curcumin-based formulation against Enterococcus faecalis.Methods:Thirty single-rooted teeth were taken. Access preparation was done. Biomechanical preparation was done using Protaper universal file till F3. Teeth were decoronated to a standardized root length of 14 mm, and the apical end from outside was sealed using paraffin wax. Teeth were autoclaved under standard conditions and after autoclaving, Phosphate-buffered saline solution was introduced into the roots and was incubated for 24 h to check for the disinfection of roots. Once the disinfection of roots was achieved, the wild strain of E. faecalis, i.e., ATC 29212 strain, was introduced into the teeth and allowed to incubate for 24 h. Following bacterial colonization inside the roots, antimicrobials were introduced and efficacy was checked. The data obtained were subjected to statistical analysis using paired t-test for significance.Results:Significant difference was observed between all the test groups. However, chlorhexidine gel showed the best value of mean difference, indicating it as the best antibacterial medicament.Conclusion:Within the limitations of this study, it can be concluded that chlorhexidine gel showed better antimicrobial properties against E. faecalis than other medicaments.

Desempenho do Protaper Universal e Protaper Next em relação à extração apical de detritos

Objetivo: o objetivo desta revisão de literatura foi avaliar a extrusão de detritos apicais após o preparo do canal radicular com os sistemas Protaper Universal e Protaper Next Rotary. Material e Métodos: a questão que sustentou a coleta de evidências científicas para o presente estudo foi: Qual sistema rotatório apresenta melhor desempenho quanto à extrusão apical de detritos: Protaper Universal ou Protaper Next? A partir das bases de dados de busca online, foi realizada uma pesquisa bibliográfica abrangendo pesquisas originais, utilizando como descritores: detritos de extrusão apical, Protaper Universal e Protaper Next. Os artigos tinham que atender aos seguintes critérios de inclusão: deveriam ter sido publicados no idioma inglês de 2014 a 2017 e comparar os dois sistemas de arquivos rotatórios mencionados em relação à extrusão apical de detritos no mesmo estudo. Noventa e seis artigos foram encontrados após a pesquisa e seis foram incluídos para esta revisão integrativa. Resultados: seis estudos permaneceram incluídos após a análise dos critérios de inclusão. Destes, 50% foram publicados em 2016, 16,6% em 2015 e 33% em 2014. O estabelecimento do peso do material extrudido foi a metodologia utilizada em todos os estudos para avaliar o desempenho dos arquivos. Ao analisar a quantidade de material apicalmente extrudado, Verificou-se que o sistema Protaper Universal extrudiu mais quantidade do que o sistema Protaper Next. Conclusão: concluiu-se que, embora não exista um sistema capaz de realizar a instrumentação sem promover a extrusão apical, o sistema de limas rotativas Protaper Next apresentou melhor desempenho quando comparado ao sistema de arquivos Protaper Universal, quanto à extrusão de detritos apicais.

Clinical Evaluation of Quality of Obturation and Instrumentation Time using Two Modified Rotary File Systems with Manual Instrumentation in Primary Teeth.

Pulp therapy in primary teeth has been performed using various instrumentation techniques. However, the conventional instrumentation technique used for root canal preparation in primary teeth is hand instrumentation. Various Nickel-Titanium (Ni-Ti) instruments are available to perform efficient root canal preparation in primary teeth. These Ni-Ti instruments has been designed to aid in better root canal preparation in permanent teeth but are rarely used in primary teeth. It is necessary to assess the feasibility of using these adult rotary files with a modified sequence in primary teeth. To compare the quality of obturation and instrumentation time during root canal preparation using hand files and modified rotary file systems in primary molars. Forty-five primary mandibular molars were randomly assigned to three experimental groups (n=15). Group I was instrumented using k-hand files, Group II with S2 ProTaper universal file and Group III with 0.25 tip 4% taper K3 rotary file. Standardized digital radiographs were taken before and after root canal instrumentation. Root canal preparation time was also recorded. Statistical analysis of the obtained data was done using SPSS Software version 17.0. An intergroup comparison of the instrumentation time and the quality of obturation was done using ANOVA and Chi-square test with the level of significance set at 0.05. No significant differences were noted with regard to the quality of obturation (p=0.791). However, a statistically significant difference was noted in the instrumentation time between the three groups (p<0.05). ProTaper rotary system had significantly lesser instrumentation time when compared to that of K3 rotary system and hand file system. The hand files, S2 ProTaper Universal and K3 0.25 tip 4% taper files systems performed similarly with respect to the quality of obturation. There was a significant difference in instrumentation time with manual instrumentation compared to the modified rotary file systems in primary teeth.

Shaping ability of ProTaper Gold and ProTaper Universal files by using cone-beam computed tomography.

This study evaluated and compared the shaping ability of ProTaper Gold (PG) (PG; Dentsply, Tulsa Dental Specialties, Tulsa, OK, USA) system with ProTaper Universal (PU) (PU; Dentsply Maillefer, Ballaigues, Switzerland) using cone-beam computed tomography (CBCT) imaging. Forty mesiobuccal canals of mandibular first molars with curvatures of 25-30° were divided into two experimental groups (n = 20) according to the rotary nickel-titanium (NiTi) file system used in canal instrumentation as follows: Group PG and group PU. Canals were scanned before and after instrumentation using CBCT scanner to evaluate root canal transportation and centering ratio at 3, 5, and 7 mm from the apex and volumetric changes. Data were statistically analyzed using independent t-tests and the significance level was set at P < 0.05. There was no significant difference between PG and PU systems in the mean volume of removed dentine, canal transportation, and centering ratio (P > 0.05). The PG and PU NiTi rotary systems showed similar root canal shaping abilities in the preparation of mesial canals of mandibular first molars.

Screw-in forces during instrumentation by various file systems.

ObjectivesThe purpose of this study was to compare the maximum screw-in forces generated during the movement of various Nickel-Titanium (NiTi) file systems.Materials and MethodsForty simulated canals in resin blocks were randomly divided into 4 groups for the following instruments: Mtwo size 25/0.07 (MTW, VDW GmbH), Reciproc R25 (RPR, VDW GmbH), ProTaper Universal F2 (PTU, Dentsply Maillefer), and ProTaper Next X2 (PTN, Dentsply Maillefer, n = 10). All the artificial canals were prepared to obtain a standardized lumen by using ProTaper Universal F1. Screw-in forces were measured using a custom-made experimental device (AEndoS-k, DMJ system) during instrumentation with each NiTi file system using the designated movement. The rotation speed was set at 350 rpm with an automatic 4 mm pecking motion at a speed of 1 mm/sec. The pecking depth was increased by 1 mm for each pecking motion until the file reach the working length. Forces were recorded during file movement, and the maximum force was extracted from the data. Maximum screw-in forces were analyzed by one-way ANOVA and Tukey's post hoc comparison at a significance level of 95%.ResultsReciproc and ProTaper Universal files generated the highest maximum screw-in forces among all the instruments while M-two and ProTaper Next showed the lowest (p < 0.05).ConclusionsGeometrical differences rather than shaping motion and alloys may affect the screw-in force during canal instrumentation. To reduce screw-in forces, the use of NiTi files with smaller cross-sectional area for higher flexibility is recommended.

Comparison of Smear Layer Removal Using the Nd:YAG Laser, Ultrasound, ProTaper Universal System, and CanalBrush Methods: An In Vitro Study

IntroductionThe aim of this study was to compare the efficacy of the Nd:YAG laser, ultrasound, the ProTaper Universal system (Dentsply Maillefer, Ballaigues, Switzerland), and the CanalBrush (Coltene Whaledent, Langenau, Germany) methods for the removal of the smear layer from the apical third of root canals. MethodsFifty distal root canals from extracted human mandibular first molars were instrumented up to ProTaper Universal F5 and divided randomly into 5 groups (n = 10) according to the following final irrigation agitation techniques: no agitation (control), ProTaper Universal file, ultrasound, CanalBrush, and Nd:YAG laser. Specimens were observed under a scanning electron microscope. The presence of the smear layer was evaluated using a 3-grade scoring system. The data were analyzed with Cohen kappa, Kruskal-Wallis, and Mann-Whitney U tests. A level of significance of .05 was adopted. ResultsThe ultrasound group performed significantly better than the rest of the groups; 56.6% of the specimens revealed no smear layer, 44.4% showed the presence of a moderate smear layer, and no heavy smear layers were observed. In the Nd:YAG laser group, 30% of the specimens presented with no smear layer, 70% showed the presence of a moderate smear layer, and no heavy smear layers were observed. In contrast, a heavy smear layer was observed on the surfaces of the root canals in the CanalBrush (23.4%), ProTaper Universal (13.4%), and control (86.6%) groups. Statistically significant differences were observed (P < .05). ConclusionsNone of the agitation methods completely removed the smear layer. However, the ultrasound method performed significantly better followed by the Nd:YAG laser, the CanalBrush, and the ProTaper Universal system. Agitation of the irrigant improved smear layer removal in the apical third of the canal.

Scanning Electron Microscopic Evaluation of Residual Smear Layer Following Preparation of Curved Root Canals Using Hand Instrumentation or Two Engine-Driven Systems.

Introduction:In this experimental study, the amount of smear layer (SL) remnants in curved root canals after chemomechanical instrumentation with two engine-driven systems or hand instrumentation was evaluated. Methods and Materials:Forty-eight mesiobuccal roots of mandibular first molars with curvatures ranging between 25 and 35 degrees (according to Schneider’s method) were divided into three groups (n=16) which were prepared by either the ProTaper Universal file series, Reciproc single file system or hand instrumentation. The canals were intermittently irrigated with 5.25% NaOCl and 17% (ethylenediaminetetraacetic acid) EDTA, followed by distilled water as the final rinse. The roots were split longitudinally and the apical third of the specimens were evaluated under 2500× magnification with a scanning electron microscope (SEM). The mean scores of the SL were calculated and analyzed using the non-parametric Kruskal-Wallis and Mann-Whitney U tests. Results:The mean scores of the SL were 2.00±0.73, 1.94±0.68 and 1.44±0.63 µm for the ProTaper Universal, Reciproc and hand instrumentation, respectively. Mean score of SL was significantly less in the hand instrumentation group than the ProTaper (P=0.027) and Reciproc (P=0.035) groups. The difference between the two engine-driven systems, however, was not significant (P=0.803). Conclusion:The amount of smear layer in the apical third of curved root canals prepared with both engine-driven systems was similar and greater than the hand instrumentation technique. Complete cleanliness was not attained.

Shaping Ability of WaveOne Primary Reciprocating Files and ProTaper System Used in Continuous and Reciprocating Motion

IntroductionThe purpose of this study was to compare the shaping effects of Wave One (Dentsply Maillefer, Ballaigues, Switzerland) and full-sequence ProTaper nickel-titanium (NiTi) files (Dentsply Maillefer) used in reciprocating and conventional movements in a simulated canal. MethodsSeventy-five S-shaped canals in resin blocks were randomly allocated to 3 groups (n = 25): WaveOne (group 1), full sequence of ProTaper Universal files in conventional movements (group 2), and full sequence of ProTaper Universal files in reciprocating movements (group 3). Preoperative and postoperative photographs of the simulated canals were taken under standardized conditions, after which they were accurately superimposed. Two methods were adopted to evaluate the shaping ability of the 3 approaches: measuring the differences in apical and coronal curvature modifications and measuring the amount of resin removed for both curvatures on the right and left sides of the simulated canals. Differences in canal curvature modifications and in the amount of resin removed were analyzed using 1-way analysis of variance (P < .0001) followed by a Tukey-Kramer multiple comparison post hoc test and mixed-effects linear model (P < .05), respectively. MethodsGroup 3 maintained better coronal and apical canal curvature and less straightening of the simulated canals with respect to groups 1 and 2. ConclusionsWhen preparing S-shaped canals, full-sequence ProTaper Universal NiTi files used in a reciprocating motion exhibited better shaping effects than full-sequence ProTaper Universal NiTi files used in a conventional motion and WaveOne.

Time Required to Remove GuttaCore, Thermafil Plus, and Thermoplasticized Gutta-percha from Moderately Curved Root Canals with ProTaper Files

IntroductionA novel carrier-based obturation system, GuttaCore, was developed to facilitate more efficient nonsurgical retreatments. This ex vivo study evaluated the time required for re-treating GuttaCore and 2 other common obturation materials in moderately curved canals with ProTaper retreatment and ProTaper files. MethodsSixty mesial roots of mandibular molars with the same mean curvature were randomly divided into 3 experimental groups: warm vertical, Thermafil Plus, and GuttaCore. Ten teeth served as positive and negative controls. The mesiobuccal canal in each sample was prepared to ISO size 30 with 0.04 taper. The warm vertical group was obturated by using a continuous-wave technique of gutta-percha compaction, and the Thermafil Plus and GuttaCore groups were obturated according to manufacturers' instructions. After allowing sealer to set, each specimen was sequentially treated with ProTaper Retreatment files D1, D2, and D3 and ProTaper Universal file F3 to the predetermined working length. The time taken to reach working length (T1) and the time required for obturation material removal (T2) were recorded. ResultsOne-way analysis of variance followed by post hoc Tukey-Kramer test indicated that the mean total time to remove filling material for the GuttaCore group was significantly shorter than those observed in the other groups (P < .05). No significant difference was observed between warm vertical and Thermafil Plus groups. ConclusionsGuttaCore is removed in less time from moderately curved canals with ProTaper files than either thermoplasticized gutta-percha or Thermafil Plus materials.

Vertical Root Fractures and Dentin Defects: Effects of Root Canal Preparation, Filling, and Mechanical Cycling

IntroductionThe aim of this study was to evaluate the ex vivo effects of root canal preparation, filling techniques, and mechanical cycling (MC) on the incidence of dentin defects and vertical root fractures (VRFs). MethodsSeventy extracted single-rooted teeth were divided into 6 groups. The first 2 groups were the unprepared and unprepared/MC groups. The other groups were prepared by using Gates Glidden drills and ProTaper Universal files up to F3 and were grouped according to the following: prepared teeth and the absence of root canal filling, passive technique, lateral compaction, and Tagger's hybrid technique. All of the groups except the unprepared group were subjected to MC (1,000,000 cycles, 90 N, 4 Hz, 37°C). The roots were then sectioned horizontally at 3, 6, and 9 mm from the apex and observed under a ×10 stereomicroscope. The defects were categorized as no defect, vertical root fracture, and other defects. The differences between the groups were analyzed by using the Fisher exact and χ2 tests. ResultsMC by itself did not influence the incidence of dentinal defects (P > .05, between the unprepared and unprepared/MC groups). The filled groups presented a similar incidence of other defects (P > .05), although VRFs were observed only when the MC was associated with pressure filling techniques (the lateral compaction and Tagger's hybrid groups). ConclusionsMC by itself did not induce VRF. When associated with apical pressure filling techniques, however, VRF occurred in 13.3% (lateral compaction) and 33.3% (Tagger's hybrid) of the cases.

Centring ability and apical transportation after overinstrumentation with ProTaper Universal and ProFile Vortex instruments

To evaluate morphological changes to the major foramen after overinstrumentation with ProTaper Universal and ProFile Vortex Ni-Ti rotary instruments. Twenty-eight mesiobuccal canals of maxillary and mandibular first molars were divided into two groups of 14 canals each. The root canals were prepared with ProTaper Universal or ProFile Vortex instruments. ProTaper and Vortex instruments were used until the file tip protruded 1 mm beyond the working length (0.5 mm beyond the major foramen). The major foramen was photographed before and after overinstrumentation with each file of the two systems used. The images were superimposed and evaluated using Adobe Photoshop. The parameters evaluated were canal transportation, centring ability and shape of the major foramen. Transportation and centring ability were calculated in two directions: the direction of maximum curvature (MC) and a direction vertical to the maximum curvature (VC). Measurements of canal transportation and centring ability were analysed by anova followed by post hoc least significance difference (LSD) multiple comparisons. No significant differences were observed amongst the different instruments with respect to centring ability in either direction (P > 0.05). The F3 ProTaper Universal instrument was associated with a higher mean values for transportation in the direction of MC (P < 0.05) than the S1, S2 and F1 ProTaper Universal instruments and the size 15, 0.06 taper, size 20, 0.06 taper, and size 25, 0.06 taper ProFile Vortex instruments. The size 30, 0.06 taper ProFile Vortex instrument had a larger mean value for transportation in the direction of MC (P < 0.05) than the S1 ProTaper Universal and size 15, 0.06 taper ProFile Vortex instruments. The S1, S2, F1, F2 and F3 ProTaper Universal files and the size 15, 0.06 taper, size 20, 0.06 taper, size 25, 0.06 taper, and size 30, 0.06 taper ProFile Vortex files produced an oval foramen in 71%, 71%, 85%, 85%, 71%, 71%, 85%, 85% and 89% of the cases, respectively. In most samples, the ProTaper Universal and ProFile Vortex files produced transportation of the major foramen and created an oval-shaped major foramen after overinstrumentation.

Torsional Resistance of Retreatment Instruments

Introduction This study compared the torsional resistance of two brands of rotary nickel-titanium (NiTi) instruments indicated for endodontic retreatment. Methods Mtwo retreatment instruments #15 and #25 (VDW, Munich, Germany) and ProTaper Universal retreatment instruments D2 and D3 (Maillefer/Dentsply, Ballaigues, Switzerland) were subjected to a torsional assay in clockwise rotation. The two parameters evaluated were maximum torque and angular deflection at failure. Fractured instruments had their fractured surfaces and helical shafts examined by scanning electron microscopy. Results The results indicated that the angular deflection at fracture decreased in the following order: Mtwo retreatment file #15 > Mtwo retreatment file #25 > ProTaper Universal retreatment file D2 > ProTaper Universal retreatment file D3. As for the maximum torque values, the results revealed the following descending order: ProTaper Universal file D2 > Mtwo retreatment file #25 > ProTaper Universal file D3 > Mtwo retreatment file #15. Scanning electron microscopic analysis revealed that plastic deformation occurred along the helical shaft of the fractured instruments. Fractured surfaces were of the ductile type. Conclusions The instruments tested showed different torsional behavior depending on the parameter evaluated. If one considers that high angular deflection values may serve as a safety factor, then the Mtwo retreatment instruments showed significantly better results.

Instrument Separation Analysis of Multi-used ProTaper Universal Rotary System during Root Canal Therapy

Introduction The purpose of this study was to identify the influential factors responsible for clinical instrument separation of reused ProTaper Universal rotary instruments (Dentsply Maillefer, Ballaigues, Switzerland). Methods Six thousand one hundred fifty-four root canals in 2,654 teeth were prepared using ProTaper Universal files in endodontic clinics. Separation incidence was determined based on the number of treated teeth or canals. Data were collected including the size of fractured instrument, the length and location of a broken segment within the root canal, and the curvature of canal. The chi-square test and independent samples t test were used to determine the statistical significance. Results The overall instrument separation incidences were 2.6% according to the number of teeth and 1.1% according to the canal number, respectively. Separation incidences according to the number of teeth or canals were significantly higher ( P < .05) in molars than those in premolars or anterior teeth. Because of its largest diameter, F3 file presented the highest separation incidence according to the number of teeth (1.0%) or canals (0.4%); 47.5% instrument separation of mandibular molars and 61.5% instrument separation of maxillary molars happened in the mesiobuccal canals. Moreover, 91.4% fragments were located in the apical third of root canals, and 54.2% instrument separation occurred in severely curved canals. There was a significant difference ( P < .05) in the mean fracture length between shaping (2.42 ± 0.73 mm) and finishing files (3.32 ± 0.73 mm). Conclusions Separation incidence according to the canal number is more reliable than that according to the number of teeth because of the variable canal number in different teeth. The tooth type, rotary file size, canal location, and anatomy were correlated with the instrument separation of reused ProTaper Universal files.

Comparison of debris extruded apically and working time used by ProTaper Universal rotary and ProTaper retreatment system during gutta-percha removal

ObjectiveThe aim of this study was to evaluate the in vitro action of ProTaper retreatment files and ProTaper Universal in the retreatment of mandibular premolars. Material and methodsThe amount of debris extruded apically was measured and the time to reach the working length and to complete the removal of gutta-percha was observed. Thirty teeth had their canals prepared using ProTaper Universal files and were obturated by the single cone technique. The teeth were then stored at 37ºC in a humid environment for 7 days. During the use of the rotary instruments for root canal filling removal, the apical portions of the teeth were attached to the open end of a resin tube to collect the apically extruded debris. ResultsProTaper Universal files were significantly faster (p=0.0011) than the ProTaper retreatment files to perform gutta-percha removal, but no significant difference was found between the files regarding the time to reach the working length or the amount of apical extrusion. ConclusionsProTaper Universal rotary had better results for endodontic retreatment, and both techniques promote similar apical extrusion of debris.