Comparação da expressão de torque entre fios de níquel titânio convencionais e estéticos / Comparison of torque expression between aesthetic and conventional nickel wires Leniana

Resumo O propósito deste estudo foi comparar a magnitude de torque de fios retangulares de níquel titânio (NiTi) estéticos e convencionais submetidos aos testes de torção. Foram testados fios comerciais de NiTi pré-contornados estéticos e convencionais de 4 marcas comerciais (American Orthodontics, Eurodonto, Orthometric e TP Orthodontics) de secção transversal 0.016" x 0.022". Os testes foram realizados em máquina de torção com rotação de 0° a 90° e foi analisado o comportamento na desativação em 20° e no torque máximo a 90°. Aos 20° no descarregamento, os fios estéticos e convencionais da American Orthodontics tiveram maior expressão de torque, enquanto os fios da Eurodonto convencional e TP Orthodontics estético apresentaram menor torque. No torque máximo a 90°, os fios que tiveram maior expressão foram da TP Orthodontics convencional e American Orthodontics estético, e os fios de menor torque foram da Eurodonto convencional e Orthometric estético. Não foram encontradas diferenças estatisticamente significativas quando os fios estéticos foram comparados entre si. Ao comparar fios estéticos e convencionais de mesma marca comercial, a única que apresentou diferença estatisticamente significativa foi a Eurodonto. Concluiu-se que, quando comparados os torques dos fios estéticos e convencionais de mesma marca, não foram encontradas diferenças estatisticamente significativas, exceto o da marca Eurodonto, que apresentou menor torque para os fios convencionais. (AU)

Abstract The purpose of this study was to compare the torque magnitude of aesthetic and conventional nickel titanium (NiTi) rectangular wires subjected to torsion tests. Commercial esthetic and conventional pre-contoured NiTi wires from 4 brands (American Orthodontics, Eurodonto, Orthometric, and TP Orthodontics) with a cross-section of 0.016" x 0.022" were tested. The tests were carried out in a torsion machine with rotation from 0º to 90° and the behavior in deactivation at 20° and at a maximum torque at 90° was analyzed. At 20° in unloading, American Orthodontics esthetic and conventional wires had higher torque, while conventional Eurodonto and TP Orthodontics esthetic wires had lower torque. At maximum torque (90°), the wires that had the highest torque were conventional TP Orthodontics and aesthetic American Orthodontics, and the wires with the lowest torque were conventional Eurodonto and aesthetic Orthometric. No statistically significant differences were found when the aesthetic threads were compared to each other. When comparing aesthetic and conventional wires from the same brand, the only one that showed a statistically significant difference was Eurodonto. It was concluded that, when comparing the torques of the aesthetic and conventional wires of the same brand, no statistically significant differences were found, except for the Eurodonto brand, which presented lower torque for the conventional wires. (AU)

Comparative analysis of torque and apical force to assess the cutting behaviour of ProTaper Next and ProTaper Universal endodontic instruments.

This study assessed the cutting properties of two Nickel Titanium file systems with different designs and manufacturing materials. ProTaper Next X1 and X2 (PTN; Dentsply Sirona) and ProTaper Universal S2 and F1 (PTU; Dentsply Sirona) instruments were employed. The cutting parameters, that is torque and apical forces, were determined using a specially designed bench-testing machine. Dimensional and geometric parameters were considered to evaluate the results. The average maximum torque values showed statistically significant differences (P < 0.05) among all instruments. Apical force for PTN X2 and PTU F1 instruments initially decreased and then experienced a rapid increase in the last 2 mm of the canal. For PTN X1 and PTU S2, apical force increased during the entire test. When compared to PTU files, PTN required higher torque and apical forces during the shaping procedure. The results lead us to conclude that PTN instruments demonstrated a lower cutting efficiency than PTU.

Structural Characteristics and Torsional Resistance Evaluation of WaveOne and WaveOne Gold Instruments after Simulated Clinical Use.

INTRODUCTION: The aim of this study was to compare 2 reciprocating nickel-titanium systems with different manufacturing characteristics and to evaluate the influence of simulated clinical use on their torsional resistance. METHODS: New 25/.08 WaveOne Primary (WO; Dentsply Sirona, York, PA) and 25/.07 WaveOne Gold Primary (Dentsply Sirona) files were used in this study. The diameter and cross-sectional area at 3 mm from the tip were measured using image analyses. The alloy microstructure was evaluated by X-ray diffraction and the phase transformation temperatures by differential scanning calorimetry analyses. Forty files were divided into 4 groups: control group 1 and control group 2, which were submitted to torsion tests until rupture, and experimental group 1 and experimental group 2, in which instruments were used to shape 2 mesial canals of an extracted mandibular molar and then submitted to torsion tests until rupture. RESULTS: WO had higher values of diameter and area at 3 mm from the tip. X-ray diffraction analysis presented R-phase and austenite for both systems. Austenite finish temperatures, determined by differential scanning calorimetry, were above room temperature. WO showed higher values of torque until rupture, and WaveOne Gold showed higher values of angular deflexion (P > .05). No differences were found between the same type of instrument in the control and experimental groups. CONCLUSIONS: The higher torsional resistance of WO can be attributed to geometric characteristics. The use in 1 tooth with curved canals is safe and does not affect the torsional resistance of the instruments analyzed.

Avaliação da superfície de fios ortodônticos de NiTi após utilização de produtos contendo fluoretos / Evaluation of NiTi orthodontic wires surfaces after use of fluoride products

A resistência à abrasão e à corrosão de três fios ortodônticos de níquel titânio (Superelastic, 3M; Turbo Wire, Ormco e Copper NiTi, Ormco) frente ao uso de flúor e escovação foram avaliados através de simulação in vitro. Foram utilizadas a microscopia eletrônica de varredura (MEV) para avaliação da morfologia superficial e espectroscopia por dispersão em energia (EDS) para avaliação da composição química elementar dos fios antes e após os experimentos. Vinte segmentos de cada fio foram obtidos e divididos em dois grupos, contendo dez amostras de cada tipo, sendo que, em um grupo, as amostras foram imersas em solução de fluoreto de sódio 0,05% por tempo equivalente a 1 mês de bochechos diários de 1 minuto. No outro grupo, foram feitas escovações dos fios por período de tempo referente a um mês de 3 escovações diárias com creme dental contendo fluoreto de sódio a 0,24%. As imagens obtidas das superfícies dos fios foram analisadas por comparação observacional descritiva. Todas as amostras usadas no experimento se mostraram susceptíveis a modificações diante da escovação com pasta contendo fluoreto de sódio. Já frente à imersão em solução, os fios que mais apresentaram alterações foram o Superelastic e o Copper NiTi, mostrando aumento de pites de corrosão e aprofundamento de sulcos preexistentes. A composição química elementar dos fios manteve-se inalterada frente aos experimentos. Concluiu-se que a escovação e os fluoretos afetam as superfícies dos fios, podendo aumentar o atrito e o acúmulo de biofilme na superfície durante o tratamento ortodôntico.(AU)

Abrasion and corrosion resistance of three nickel-titanium orthodontic wires (Superelastic, 3M; Turbo Wire, Ormco and Copper NiTi, Ormco) under sodium fluoride usage and tooth brushing were evaluated through in vitro simulation. Scanning electron microscopy (SEM) for morphological surface analysis and energy dispersive spectroscopy (EDS) for elementary chemical composition were used for evaluation of the wires before and after assays. Twenty segments of each wire were obtained and divided in two groups containing ten samples of each type. One group of samples was immersed in sodium fluoride solution 0.05% during equivalent time of one month of daily 1 minute mouthwashes. In the other group the wires were brushed three times daily using a dental cream with sodium fluoride 0.24% during one month. Wire surfaces images obtained were analyzed by means of comparative observational description. All samples exhibited superficial changes under tooth brushing with fluoride dental cream. Considering fluoride solution immersion, Superplastic and Copper NiTi showed increasing in pitches of corrosion and deepening of existing grooves. Elementary chemical composition of wires remained unaltered. Concluding, tooth brushing and fluorides affect the surfaces of NiTi orthodontic wires, which may increase the friction and accumulation of biofilm in the surface during orthodontic treatment. (AU)

Cyclic flexural fatigue resistance of NiTi Controlled Memory and Blue Technology instruments after torsional preloading.

Objective The aim of this study was to evaluate the influence of torsional preloading on the cyclic flexural fatigue resistance of thermally treated NiTi instruments. Material and Methods Ten new instruments New Hyflex CM (HF 30.06; Coltene/Whaladent Inc.), Typhoon CM (TYP 30.06; Clinician's Choice Dental Products) and Vortex Blue (VB 30.06; Dentsply Tulsa Dental) were chosen, based on geometry and specific characteristics of the manufacturing process. The new instruments of each system were tested in a bench device to determine their fatigue resistance through mean value of number of cycles to failure (Nf) (Control Group - CG). Another group of 10 new HF, TYP and VB instruments were submitted to 20 cycles of torsional straining between 0° and 180° (Experimental Group - EG) and then submitted to fatigue until rupture under the same conditions of the CG. Tested instruments were examined by scanning electron microscopy (SEM). Data were analyzed using one-way analysis of variance and post hoc Tukey's test (α=.05). Results Higher fatigue resistance was accomplished by HF instruments, followed by VB and TYP (p<0.05). During the torsional preloading, the lowest mean torque value was observed for TYP instruments (p<0.05). The torsional preload caused a significant reduction in the Nf values (p<0.05) of about 20%, 39% and 45% for instruments HF, VB and TYP, respectively. Longitudinal cracks, generated during the torsional preloading, were present in VB files, but were not observed in the CM instruments (HF and TYP). Conclusions In conclusion, the flexural fatigue resistance of thermally treated instruments is diminished after cyclic torsional loading.

Evaluating the cutting efficiency of NiTi instruments with reciprocating motions / Avaliação da eficiência de corte de instrumentos NiTi com movimento reciprocante

Aim:This study tested a setup for in vitro experimental analysis of axial forces and torque during the preparation of artificial canals using nickel-titanium reciprocating endodontic files.Methods: The cutting efficiency of Reciproc (RC) and WaveOne (WO) reciprocating size 25/.08 instruments (n = 10) was evaluated, taking into account their dimensional and geometrical features. Measurements of the diameter at each millimeter from the tip, pitch length, helical angle, and cross-sectional design and area were assessed. Cutting efficiency tests were carried out on a specific bench device by measuring the torque and axial force required during artificial canal shaping. Statistical analysis was performed using one-way ANOVA (α = 0.05). Results:The WO samples showed larger A3 mean values than did the RC instruments (p < 0.0001), despite having equal diameters at 3mm from the tip (D3) (p = 0.521). The mean values of pitch length were higher for RC than for WO instruments (p< 0.0001), with consequently smaller helical angles (p < 0.0001). For the cutting efficiency tests, the required torque was lower for the RC group when compared to the WO group, but it was significant only in the first stage of insertion in the artificial canals (p = 0.008). Regarding the apical force, the RC instruments reached higher values when compared to the WO instruments (p = 0.04) in the second stage of cutting action. Conclusion: Reciproc instruments demonstrated statistically higher cutting efficiency when compared to WaveOne instruments.

Objetivo: Este estudo testa uma configuração para análise experimental in vitro de forças axiais e torque durante o preparo de canais artificiais usando instrumentos endodônticos reciprocantes de níquel-titânio. Métodos: Foi avaliada a eficiência de corte dos instrumentos reciprocantes tamanho 25 / 0,08 (n = 10) Reciproc (RC) e WaveOne (WO), levando em consideração suas características dimensionais e geométricas. Medidas do diâmetro a cada milímetro a partir da ponta, comprimento de pitch, ângulo helicoidal e desenho da área transversal e área foram avaliados. Testes de eficiência de corte foram realizados em um dispositivo de bancada específico, medindo-se o torque e a força axial exigidos durante a modelagem de canais artificiais. A análise estatística foi feita com ANOVA one-way (α = 0,05). Resultados: As amostras de WO mostraram valores médios A3 maiores do que os instrumentos RC (p <0,0001), apesar de terem diâmetros iguais a 3 mm da ponta (D3) (p = 0,521). Os valores médios do comprimento do pitch foram maiores para o RC do que para os instrumentos do WO (p < 0,0001), com consequentemente menores ângulos helicoidais (p < 0,0001). Para os testes de eficiência de corte, o torque necessário foi menor para o grupo RC em comparação com o grupo WO, mas significativo apenas no primeiro estágio de inserção nos canais artificiais (p = 0,008). Em relação à força apical, os instrumentos RC alcançaram valores maiores em relação aos instrumentos WO (p = 0,04) no segundo estágio de corte. Conclusão: Os instrumentos Reciproc demonstraram uma eficiência de corte estatisticamente superior em comparação com os instrumentos WaveOne.

Influence of Cyclic Flexural Deformation on the Torsional Resistance of Controlled Memory and Conventional Nickel-titanium Instruments.

INTRODUCTION: The aim of this study was to evaluate the influence of cyclic deformation on the torsional resistance of controlled memory (CM) nickel-titanium files in comparison with superelastic (SE) instruments with similar geometric and dimensional characteristics. METHODS: New 30/.06 HyFlex (HF; Coltene/Whaledent, Inc, Cuyahoga Falls, OH), Typhoon (Clinician's Choice Dental Products, New Milford, CT), RaCe (FKG, La-Chaux De Fonds, Switzerland), and ProTaper Universal F2 instruments (F2; Dentsply Maillefer, Ballaigues, Switzerland) were assessed. The diameter and pitch length were measured along the active part of the instruments. The number of cycles to failure (Nf) in flexural fatigue and the torsional resistance were evaluated for new files (n = 10). Ten new instruments of each type were fatigued to 3/4 of their fatigue life and then submitted to torsion until rupture. Data were analyzed using 1-way analysis of variance (α = .05). RESULTS: New CM files had a significantly higher Nf when compared with SE instruments; HF exhibited the highest value (P = .001). The mean torque value for F2 was the highest (P = .001). CM files precycled to 3/4 Nf had a significantly lower torque than the new files (HF: P = .003, Typhoon: P = .001), whereas the SE instruments displayed no significant differences (F2: P = .059, RaCe: P = .079). CONCLUSIONS: Cyclic flexural loading significantly reduced the torsional resistance of CM instruments.

Enhancement of NiTi superelastic endodontic instruments by TiO2 coating.

Rotary nickel-titanium (NiTi) endodontic instruments were coated with a nanometric flexible TiO2 layer through dip-coating sol-gel. Control groups and coated samples of superelastic NiTi instruments model RaCe 25/0.06 (0.25mm tip-diameter, 6% conicity) were comparatively investigated with respect to the cutting efficiency, fatigue life, and corrosion resistance. Results showed an improvement in cutting efficiency for the coated samples and a high resistance to corrosion in NaClO. The coated instruments showed a better performance in fatigue life after corrosion.

The impact of clinical use on the torsional behavior of Reciproc and WaveOne instruments.

OBJECTIVE: The aim of this study was to assess the influence of clinical use, in vivo, on the torsional behavior of Reciproc and WaveOne instruments considering the possibility that they degraded with use. MATERIAL AND METHODS: Diameter at each millimeter, pitch length, and area at 3 mm from the tip were determined for both types of instruments. Twenty-four instruments, size 25, 0.08 taper, of each system were divided into two groups (n=12 each): Control Group (CG), in which new Reciproc (RC) and WaveOne Primary (WO) instruments were tested in torsion until rupture based on ISO 3630-1; and Experimental Group (EG), in which each new instrument was clinically used to clean and shape the root canals of one molar. After clinical use, the instruments were analyzed using optical and scanning electron microscopy and subsequently tested in torsion until fracture. Data were analyzed using one-way analysis of variance at a=.05. RESULTS: WO instruments showed significantly higher mean values of cross-sectional area A3 (P=0.000) and smaller pitch lengths than RC instruments with no statistically significant differences in the diameter at D3 (P=0.521). No significant differences in torsional resistance between the RC and WO new instruments (P=0.134) were found. The clinical use resulted in a tendency of reduction in the maximum torque of the analyzed instruments but no statistically significant difference was observed between them (P=0.327). During the preparation of the root canals, two fractured RC instruments and longitudinal and transversal cracks in RC and WO instruments were observed through SEM analysis. CONCLUSION: After clinical use, no statistically significant reduction in the torsional resistance was observed.

The impact of clinical use on the torsional behavior of Reciproc and WaveOne instruments

ABSTRACT Torsional overload is a fracture representative parameter for instruments in single-file techniques. Objective The aim of this study was to assess the influence of clinical use, in vivo, on the torsional behavior of Reciproc and WaveOne instruments considering the possibility that they degraded with use. Material and Methods Diameter at each millimeter, pitch length, and area at 3 mm from the tip were determined for both types of instruments. Twenty-four instruments, size 25, 0.08 taper, of each system were divided into two groups (n=12 each): Control Group (CG), in which new Reciproc (RC) and WaveOne Primary (WO) instruments were tested in torsion until rupture based on ISO 3630-1; and Experimental Group (EG), in which each new instrument was clinically used to clean and shape the root canals of one molar. After clinical use, the instruments were analyzed using optical and scanning electron microscopy and subsequently tested in torsion until fracture. Data were analyzed using one-way analysis of variance at a=.05. Results WO instruments showed significantly higher mean values of cross-sectional area A3 (P=0.000) and smaller pitch lengths than RC instruments with no statistically significant differences in the diameter at D3 (P=0.521). No significant differences in torsional resistance between the RC and WO new instruments (P=0.134) were found. The clinical use resulted in a tendency of reduction in the maximum torque of the analyzed instruments but no statistically significant difference was observed between them (P=0.327). During the preparation of the root canals, two fractured RC instruments and longitudinal and transversal cracks in RC and WO instruments were observed through SEM analysis. Conclusion After clinical use, no statistically significant reduction in the torsional resistance was observed.

Effects of R-Phase on Mechanical Responses of a Nickel-Titanium Endodontic Instrument: Structural Characterization and Finite Element Analysis.

The effects of the presence of the R-phase in a near-equiatomic NiTi alloy on the mechanical responses of an endodontic instrument were studied by using finite element analysis. The input data for the constitutive model in the simulation were obtained by tensile testing of three NiTi wires: superelastic austenite NiTi, austenite + R-phase NiTi, and fully R-phased NiTi. The wires were also characterized by X-ray diffraction and differential scanning calorimetry. A commercially available endodontic instrument was scanned using microcomputed tomography, and the resulting images were used to build the geometrical model. The numerical analyses were performed in ABAQUS using load and boundary conditions based on the ISO 3630-1 specification for the bending and torsion of endodontic instruments. The modeled instrument containing only R-phase demanded the lowest moment to be bent, followed by the one with mixed austenite + R-phase. The superelastic instrument, containing essentially austenite, required the highest bending moment. During bending, the fully R-phased instrument reached the lowest stress values; however, it also experienced the highest angular deflection when subjected to torsion. In summary, this simulation showed that NiTi endodontic instruments containing only R-phase in their microstructure would show higher flexibility without compromising their performance under torsion.

Constant Insertion Rate Methodology for Measuring Torque and Apical Force in 3 Nickel-Titanium Instruments with Different Cross-sectional Designs.

INTRODUCTION: The aim of this study was to evaluate the cutting characteristics of 3 nickel-titanium instruments with different cross-sectional designs using a recently developed methodology. METHODS: Insertion tests at a constant rate of 5.4 mm/min were performed on a bench test device by measuring the torque and apical force required for penetrating prefabricated acrylic blocks containing an artificial canal preflared with #10 and #15 K-files. Size 20/.06 Mtwo (VDW, Munich, Germany) and RaCe (FKG, La-Chaux De Fonds, Switzerland) instruments, together with ProTaper Universal (PTU) F1 instruments (Dentsply Maillefer, Ballaigues, Switzerland) (10 instruments of each type), were tested using an endodontic motor set at 300 rpm and 5 N·cm. The instruments were characterized with respect to the pitch length, rake angle, and cross-sectional area. Statistical analysis was performed with analysis of variance (α = 0.05). RESULTS: The torque was significantly lower for Mtwo compared with the other 2 groups (P < .05). It was also lower for RaCe in comparison with PTU F1 (P < .05). Regarding the apical force, the RaCe instruments had lower values when compared with the Mtwo and PTU F1 instruments (P < .05). There was no statistically significant difference between the PTU F1 and Mtwo instruments (P > .05). CONCLUSIONS: The methodology allowed the cutting properties of the instruments to be assessed in terms of their different geometric characteristics. The cross-sectional design, especially in Mtwo instruments with 2 sharp edges and great chip removal capability, was a differential factor for their higher cutting action.

Behavior of nickel-titanium instruments manufactured with different thermal treatments.

INTRODUCTION: The purpose of this study was to investigate if nickel-titanium instruments with similar designs manufactured by different thermal treatments would exhibit significantly different in vitro behavior. METHODS: Thirty-six instruments each of ProTaper Universal (PTU F1; Dentsply Maillefer, Ballaigues, Switzerland), ProFile Vortex (PV; Dentsply Tulsa Dental Specialties, Tulsa, OK), Vortex Blue (VB, Dentsply Tulsa Dental Specialties), and TYPHOON Infinite Flex NiTi (TYP; Clinician's Choice Dental Products, New Milford, CT) (all size 25/.06) were evaluated. Bending resistance, torsion at failure, and dynamic torsional tests were performed with the instruments (n = 12). Analysis of variance and Tukey post hoc tests were applied. RESULTS: Flexibility was significantly higher for TYP compared with the other 3 groups (P < .0001). With respect to the maximum torque at failure, PV group showed the highest resistance to twisting (torsional strength) among the analyzed instruments followed by VB, TYP, and PTU. The TYP group exhibited greater angular deflection at failure compared with the other groups (P < .0001). The mean dynamic torque scores during simulated canal preparation were highest for TYP (3.01 ± 0.71 Ncm) and lowest for PV (1.62 ± 0.79 Ncm). However, no significant differences were observed comparing groups PTU with TYP and VB and VB with PV (P > .05). The highest mean forces were recorded with PTU (7.02 ± 2.36 N) and the lowest with TYP (1.22 ± 0.40 N). CONCLUSIONS: TYP instruments were significantly more flexible than the other instruments tested. The PV group had the highest torsional strength and TYP, despite being the most flexible, showed similar torsional moments to the other instruments, whereas its angular deflection was the highest among the groups.

Resistência à fadiga de instrumentos rotatórios ProTaper Universal após o uso com e sem movimento de pressão lateral / Fatigue resistance of rotary ProTaper Universal instruments after use with and without lateral pressure motion

Objetivo: Avaliar a resistência à fadiga de instrumentos rotatórios ProTaper Universal após múltiplos usos clínicos com e sem movimento de pressão lateral. Material e Métodos: Trinta conjuntos de instrumentos ProTaper Universal (PTU) (Dentsply-Maillefer, Ballaigues, Suíça), calibres S1, S2, F1 e F2, em um total de 120 instrumentos, foram analisados e divididos em três grupos: Grupo com Pressão Lateral (PL), com 10 conjuntos de instrumentos, cada conjunto usado clinicamente em cinco molares inferiores e superiores (15 a 20 canais) utilizando os instrumentos de formatação com movimento de pressão lateral; e Grupo Sem Pressão Lateral (SPL), com 10 conjuntos de instrumentos, cada conjunto usado clinicamente em cinco molares inferiores e superiores (15 a 20 canais), utilizando os instrumentos de formatação sem movimento de pressão lateral. Os instrumentos dos grupos PL e SPL foram posteriormente testados em fadiga até a ruptura, juntamente com 10 conjuntos de instrumentos novos do Grupo Controle (GC). Os dados foram analisados por meio de análise de variância (α = 0,05). Resultados: Múltiplos usos clínicos causaram uma redução na vida em fadiga dos instrumentos analisados. Quando o efeito de se utilizar o movimento de pressão lateral com os instrumentos de formatação foi avaliado, houve uma tendência para o consumo da vida em fadiga ser maior para os instrumentos de S1 e S2 em PL e observou-se o mesmo para os instrumentos F1 e F2 no grupo SPL. Conclusão: O uso do movimento de pressão lateral com os instrumentos PTU S1 e S2 durante a formação de canais radiculares curvos tendeu a diminuir o consumo de vida em fadiga dos instrumentos F1 e F2. Descritores: Endodontia. Tratamento do canal radicular. Instrumentos odontológicos.

Impact of heat treatments on the fatigue resistance of different rotary nickel-titanium instruments.

INTRODUCTION: The aim of this study was to assess the influence of M-Wire (Dentsply Tulsa Dental Specialties, Tulsa, OK) and controlled memory technologies on the fatigue resistance of rotary nickel-titanium (NiTi) files by comparing files made using these 2 technologies with conventional NiTi files. METHODS: Files with a similar cross-sectional design and diameter were chosen for the study: new 30/.06 files of the EndoWave (EW; J. Morita Corp, Osaka, Japan), HyFlex (HF; Coltene/Whaledent, Inc, Cuyahoga Falls, OH), ProFile Vortex (PV; Dentsply Tulsa Dental Specialties, Tulsa, OK), and Typhoon (TYP; Clinician's Choice Dental Products, New Milford, CT) systems together with ProTaper Universal F2 instruments (PTU F2; Dentsply Maillefer, Ballaigues, Switzerland). The compositions and transformation temperatures of the instruments were analyzed using x-ray energy-dispersive spectroscopy and differential scanning calorimetry, whereas the mean file diameter values at 3 mm from the tip (D3) were measured using image analysis software. The average number of cycles to failure was determined using a fatigue test device. RESULTS: X-ray energy-dispersive spectroscopy analysis showed that, on average, all the instruments exhibited the same chemical composition, namely, 51% Ni-49% Ti. The PV, TYP, and HF files exhibited increased transformation temperatures. The PTU F2, PV, and TYP files had similar D3 values, which were less than those of the EW and HF files. The average number of cycles to failure values were 150% higher for the TYP files compared with the PV files and 390% higher for the HF files compared with the EW files. CONCLUSIONS: M-Wire and controlled memory technologies increase the fatigue resistance of rotary NiTi files.

Mechanical behavior of three nickel-titanium rotary files: A comparison of numerical simulation with bending and torsion tests.

AIM: To assess the flexibility and torsional stiffness of three nickel-titanium rotary instruments by finite element analysis and compare the numerical results with the experiment. METHODOLOGY: Mtwo (VDW, Munich, Germany) and RaCe (FKG Dentaire, La-Chaux-de-Fonds, Switzerland) size 25, .06 taper (0.25-mm tip diameter, 0.06% conicity) and PTU F1 (Dentsply Maillefer, Ballaigues, Switzerland) instruments were selected for this study. Experimental tests to assess the flexibility and torsional stiffness of the files were performed according to specification ISO 3630-1. Geometric models for finite element analysis were obtained by micro-CT scanning. Boundary conditions for the numerical analysis were based on the specification ISO 3630-1. RESULTS: A good agreement between the simulation and the experiment moment-displacement curves was found for the three types of instruments studied. RaCe exhibited the highest flexibility and PTU presented the highest torsional stiffness. Maximum values of von Mises stress were found for the PTU F1 file (1185MPa) under bending, whereas the values of von Mises stress for the three instruments were quite similar under torsion. The stress patterns proved to be different in Mtwo under bending, according to the displacement orientation. CONCLUSIONS: The favorable agreement found between simulation and experiment for the three types of instruments studied confirmed the potential of the numerical method to assess the mechanical behavior of endodontic instruments. Thus, a methodology is established to predict the failure of the instruments under bending and torsion.

Comparison of the mechanical behavior between controlled memory and superelastic nickel-titanium files via finite element analysis.

INTRODUCTION: The aim of this study was to evaluate the flexibility and torsional stiffness of a controlled memory (CM) nickel-titanium (NiTi) file and compare its mechanical responses with those of a superelastic NiTi file with the same geometry using finite element simulation. METHODS: A commercially available instrument with a tip size of 30 and a 0.06 taper was selected for this study. The geometric model for finite element analysis was generated by micro-computed tomographic scanning, and the data for the constitutive model of controlled memory NiTi were obtained from the literature. The numeric analysis was performed in ABAQUS (SIMULIA, Providence, RI) with boundary conditions that were based on the ISO 3630-1 specification. RESULTS: The CM NiTi file exhibited the least bending moment and maximum stress value (523 MPa) under 45° bending simulation. However, the least torsional stiffness was calculated for this same instrument. CONCLUSIONS: The higher flexibility and potential fatigue resistance of the CM NiTi files were confirmed, indicating that this new technology represents an improvement in the mechanical behavior of the rotary NiTi files.

Cleaning the apical third of curved canals after different irrigation protocols.

This study evaluated the protocols of sonic and vacuum irrigation regarding the capacity of debris removal from root canal systems. Canal preparations were carried out on 30 mandibular first molars using the ProTaper Universal System. Teeth were divided into two experimental groups (n=15): Group 1: sonic irrigation and Group 2: vacuum irrigation protocol. Subsequently, the mesial roots were sectioned and observed by stereomicroscopy and scanning electron microscopy. Three independent examiners evaluated images of the apical thirds according to the following scores: 1= small presence of debris, 2= moderate presence of debris, and 3= dense presence of debris. Data were analyzed with ANOVA and Kruskal-Wallis tests (α=0.05). Comparison among the groups revealed that at the apical third, the root halves of Group 1 had significantly less surface debris (p=0.002) than those of Group 2. However, at 2 mm from the working length, Group 2's specimens showed less remaining debris in approximately 75% of the analyzed root canals. At the whole apical third, the sonic irrigation protocol removed significantly more debris than the vacuum protocol. However, in the region at 2 mm from the working length, the second irrigation method demonstrated a better performance.

An analytical mechanical model to describe the response of NiTi rotary endodontic files in a curved root canal.

AIM: To build a mathematical model describing the mechanical behavior of NiTi rotary files while they are rotating in a root canal. METHODOLOGY: The file was seen as a beam undergoing large transformations. The instrument was assumed to be rotating steadily in the root canal, and the geometry of the canal was considered as a known parameter of the problem. The formulae of large transformations mechanics then allowed the calculation of the Green-Lagrange strain field in the file. The non-linear mechanical behavior of NiTi was modeled as a continuous piecewise linear function, assuming that the material did not reach plastic deformation. Criteria locating the changes of behavior of NiTi were established and the tension field in the file, and the external efforts applied on it were calculated. The unknown variable of torsion was deduced from the equilibrium equation system using a Coulomb contact law which solved the problem on a cycle of rotation. RESULTS: In order to verify that the model described well reality, three-point bending experiments were managed on superelastic NiTi wires, whose results were compared to the theoretical ones. It appeared that the model gave a good mentoring of the empirical results in the range of bending angles that interested us. CONCLUSIONS: Knowing the geometry of the root canal, one is now able to write the equations of the strain and stress fields in the endodontic instrument, and to quantify the impact of each macroscopic parameter of the problem on its response. This should be useful to predict failure of the files under rotating bending fatigue, and to optimize the geometry of the files.

Cleaning the apical third of curved canals after different irrigation protocols

This study evaluated the protocols of sonic and vacuum irrigation regarding the capacity of debris removal from root canal systems. Canal preparations were carried out on 30 mandibular first molars using the ProTaper Universal System. Teeth were divided into two experimental groups (n=15): Group 1: sonic irrigation and Group 2: vacuum irrigation protocol. Subsequently, the mesial roots were sectioned and observed by stereomicroscopy and scanning electron microscopy. Three independent examiners evaluated images of the apical thirds according to the following scores: 1= small presence of debris, 2= moderate presence of debris, and 3= dense presence of debris. Data were analyzed with ANOVA and Kruskal-Wallis tests (α=0.05). Comparison among the groups revealed that at the apical third, the root halves of Group 1 had significantly less surface debris (p=0.002) than those of Group 2. However, at 2 mm from the working length, Group 2's specimens showed less remaining debris in approximately 75% of the analyzed root canals. At the whole apical third, the sonic irrigation protocol removed significantly more debris than the vacuum protocol. However, in the region at 2 mm from the working length, the second irrigation method demonstrated a better performance.

Este estudo avaliou protocolos de irrigação sônica e a vácuo em relação à capacidade de remoção de debris do sistema de canais radiculares. Trinta primeiros molares mandibulares tiveram seus canais radiculares preparados pela utilização do Sistema ProTaper Universal. Os dentes foram divididos em dois grupos experimentais (n=15): Grupo 1: protocolo de irrigação sônica, e Grupo 2: protocolo de irrigação a vácuo. Posteriormente, as raízes mesiais foram seccionadas e observadas em lupa estereoscópica e microscopia eletrônica de varredura. Três examinadores independentes avaliaram as imagens do terço apical de acordo com as seguintes pontuações: 1. pequena presença de debris; 2: moderada presença de debris; e 3. densa presença de debris. Os dados foram analisados pelos testes estatísticos ANOVA e Kruskal-Wallis (α=0,05). A comparação entre os grupos revelou que, no terço apical, as hemissecções radiculares do Grupo 1 apresentaram debris remanescentes de forma significativamente menor (p=0,002) do que as do Grupo 2. No entanto, a 2 mm do comprimento de trabalho, as amostras do Grupo 2 mostraram menos debris remanescentes em aproximadamente 75% dos canais radiculares analisados. Considerando todo o terço apical, o protocolo de irrigação sônica removeu significativamente mais debris do que o protocolo de irrigação a vácuo. No entanto, na região a 2 mm do comprimento de trabalho, o segundo método de irrigação demonstrou um melhor desempenho.