Influência da orientação das ranhuras superficiais na flexão rotativa de fios de níquel-titânio / Influence of surface grooves orientation on the cyclic fatigue resistance of NiTi wire

Objetivo: Testar a hipótese nula de que a orientação das ranhuras superficiais não influencia na vida em fadiga de fios de níquel-titânio (NiTi). Material e Métodos: Segmentos de fio de NiTi (Moreli, Sorocaba/SP, Brasil) medindo 30mm e com diâmetro de 0,40mm foram utilizados. As ranhuras foram criadas em relação à direção longitudinal, em 45 e 90 graus. O fio foi analisado sob microscopia eletrônica de varredura e a rugosidade, quantificada por interferometria. O número de ciclos para a fratura (NCF) foi determinado pelo teste de flexão rotativa. Resultados: A rugosidade entre os grupos de 45 e 90 graus apresentou diferenças estatisticamente significativas (p<0,05). O grupo sem ranhuras apresentou o maior NCF (p<0,05). O grupo com ranhuras em 45 graus apresentou maior NCF, em comparação ao grupo com 90 graus (p<0,05). Conclusões: A direção das ranhuras possui influência na vida em fadiga dos fios de NiTi. O NCF aumenta com a redução do ângulo das ranhuras em relação ao longo eixo do fio, independentemente da profundidade das ranhuras (AU).

Objective: this study tested the null hypothesis that the surface grooves orientation does not influence the NiTi wire cyclic fatigue. Material and methods: Segments of NiTi wire (Moreli, Sorocaba, Brazil) measuring 30mm and with a 0.40mm of diameter were used. Grooves were created in the longitudinal direction, at 45 degrees and 90 degrees. The wire was analyzed with SEM and the roughness was quantified by interferometry. The number of cycles until fracture (NCF) was determined by the cyclic fatigue test. Results: the roughness between 45 and 90 degrees groups presented differences (p<0.05). The group without grooves presented the highest NCF (p<0.05). The group with 45 degrees grooves presented better NCF in comparison to the group with 90 degrees (p<0.05). Conclusions: the direction of the grooves influences the fatigue life. The NCF increases with the reduction of the angle of the grooves in relation to the long axis, regardless of the depth of the grooves (AU).

The impact of using a pneumatic contra-angle device on the lifespan of M-Wire- and Blue-treated instruments.

OBJECTIVES: To evaluate the cyclic fatigue resistance of Reciproc M-Wire R25 (VDW, Munich, Germany) and Reciproc R25 Blue instruments (VDW) driven by Direct® (VDW) contra-angle connected to an ordinary an air-driven motor or an electric motor and compare the results with those obtained by the Reciproc M-Wire R25 or Reciproc Blue R25 instruments driven by an electric torque-controlled motor using "RECIPROC ALL" preset program. MATERIALS AND METHODS: Thirty Reciproc M-Wire R25 (25/0.08v) and 30 Reciproc Blue R25 (25/0.08v) instruments were used. Cyclic fatigue resistance was tested measuring the time to fracture and the number of cycles to fracture in an artificial stainless-steel canal with a 60° angle and a 5-mm radius of curvature. The Reciproc M-Wire and Reciproc Blue instruments were activated with a 6:1 reduction handpiece powered by a torque-controlled motor using "RECIPROC ALL" preset program, with Reciproc Direct® contra-angle powered by an ordinary air-driven motor or with Direct® contra-angle powered by an electric motor (n = 10). The fracture surface of all fragments was examined with a scanning electron microscope. The results were statistically analyzed using Student's t test and one-way ANOVA at a significance level of P < 0.05. RESULTS: Cyclic fatigue life and number of cycles to fracture were significantly higher for Reciproc Blue instruments than for Reciproc M-Wire instruments regardless of the activation mode (P < 0.05). Instruments driven by Direct® contra-angle powered by an electric or by an ordinary air-driven motor revealed significantly longer cyclic fatigue life and number of cycles to fracture than instruments driven by an electric torque-controlled motor using "RECIPROC ALL" preset program (P < 0.05). CONCLUSIONS: Reciproc Blue instruments showed improved performance regarding fatigue resistance when compared to Reciproc M-Wire instruments. Instruments driven by Reciproc Direct® contra-angle showed higher cyclic fatigue life and number of cycles to fracture than instruments driven by an electric torque-controlled motor. CLINICAL RELEVANCE: Recently, Reciproc Direct®, the world's first contra-angle handpiece with integrated reciprocating motion, has been launched in endodontic market. The present study showed improved cyclic fatigue life of endodontic instruments when activated by Reciproc Direct®.

The internal anatomy of danger zone of mandibular molars: A cone-beam computed tomography study.

AIM: The aim of this study was the assessment of the anatomical thickness of danger zone in the cervical third of mesial canals of mandibular molars. MATERIALS AND METHODS: Fifty mandibular molars were selected and scanned with cone-beam computed tomography. Data were compared using a length tool provided by scanner software. The measured areas were the mesial and distal walls of the cervical third of the mesial roots, which correspond to the safety and danger zones, respectively. In addition, dentin thickness at the furcation was evaluated. RESULTS: Dentin thicknesses of the safety zone were higher than in the danger zone in all teeth examined. The thinnest dentin of the safety zone was found at a point located 4 mm below the canal orifice, with a mean value of 1.03 mm; conversely, in the danger zone, the thinnest point was located 3 mm below the orifice, with a mean value of 0.81 mm. As for the distance from the pulp chamber floor to the furcation, the average value was 2.23 mm. CONCLUSION: These results show that mean thicknesses at the danger zone of mandibular molar mesial roots were <1.0 mm. These data reinforce the importance of understanding anatomy and the need for conservative preparations when assessing and instrumenting these root canals.

Mechanical Properties of Anatomic Finishing Files: XP-Endo Finisher and XP-Clean.

The aim of the present study was to evaluate the cyclic fatigue of two anatomic finishing files: XP-Endo Finisher and XP-Clean. Roughness pattern and the micro-hardness of the files were also assessed. Instruments were subjected to cyclic fatigue resistance measuring the time to fracture in an artificial stainless-steel canal with a 60° angle and a 5-mm radius of curvature. The fracture surface of all fragments was examined with a scanning electron microscope. The roughness of the working parts was quantified by using a profilometer and the micro-hardness test was carried out using a Vickers hardness tester. Results were statistically analyzed using a student´s t-test at a significance level of P < 0.05. Weibull analysis was also performed. XP-Endo Finisher presented significantly longer cyclic fatigue life than XP-Clean instruments (P<0.05). XP-Endo Finisher was able to withstand 1000% more cycles to fracture when compared to XP-Clean instruments. SEM visual inspection of the fracture surfaces revealed fractographic characteristics of ductile fracture in all tested instruments; wide-ranging forms of dimples were identified and no plastic deformation in the helical shaft of the fractured instruments was observed. When mean life was compared XP-Endo Finisher lasted longer than XP-Clean with a probability of 99.9%. XP-Endo Finisher instruments also exhibited significantly lower roughness than XP-Clean instruments (P<0.05). No differences in the micro-hardness was observed between the files (P>0.05). It can be concluded that XP-Endo Finisher instruments showed improved performance when compared with XP-Clean instruments, demonstrating higher cyclic fatigue resistance and lower roughness.

Fatigue resistance of endodontic instruments manufactured in NiTi CM Wire and in conventional NiTi alloy with eletrochemical treatment / Resistência à fadiga de instrumentos endodônticos fabricados em NiTi CM Wire e em niti convencional com tratamento eletroquìmico

ABSTRACT Objective: This study compared the fatigue behavior of endodontic instruments manufactured with conventional NiTi alloy electropolishing, RaCe (FKG Dentaire, LaChauxdeFonds, Switzerland), with instruments manufactured with NiTi CM ​​Wire subjected to thermomechanical treatment, in the manufacturing process, HyFlex CM (Coltène Whaledent, Cuyahoga Falls, Ohio, USA), both with similar geometry and dimensions in order to determine the influence of the manufacturing process in the fatigue resistance. Methods: The methodoly consisted of twenty HyFlex CM and RaCe instruments with D0 0.25 mm, taper 0.06 mm / mm, 25 mm length, both with triangular cross section. The fracture resistance was evaluated by static fatigue test, using a stainless artificial canal with 5mm of radius (86°), recording the time and calculating the number of cycles until fracture occurs (NCF). For statistical analysis the Student t test was used The fractured instruments surface was analyzed by SEM. Results: The NCF was significantly higher for HyFlex CM instruments in comparison with RaCe files (P˂0.05) being 1336% more resistant to fatigue. The analysis of the fractured surface by SEM showed ductile-kind morphological characteristics for both instruments and the absence of plastic deformation. Conclusion: HyFlex CM instruments present higher values ​​of NCF. Thus, it can be concluded that the thermal treatment to which these instruments with CM Wire alloy are submitted makes them more resistant to fracture than Race instruments manufactured with conventional NiTi alloy electropolishing.

RESUMO Objetivo: Este estudo comparou a vida em fadiga de instrumentos endodônticos fabricados com a liga de NiTi convencional com eletropolimento de superfície, RaCe (FKG Dentaire, LaChauxdeFonds, Suiça), com instrumentos fabricados com a liga de NiTi CM Wire, submetidos a tratamento termomecânico, no processo de fabricação, HyFlex CM (Coltene Whaledent, Cuyahoga Falls, Ohio, EUA), ambos com geometria e dimensões semelhantes, visando determinar a influência do processo de fabricação das ligas e do acabamento superficial na resistência à fadiga. Métodos: Foram utilizados vinte instrumentos HyFlex CM e RaCe com D0 0,25mm, conicidade 0,06mm/mm, 25mm de comprimento, ambos com seção transversal triangular. A resistência à fratura foi avaliada através de teste estático de fadiga ciclica, utilizando um canal artificial em aço-inoxidável com 5mm de raio (86°), sendo registrado o tempo e calculado o número de ciclos para ocorrer a fratura (NCF). Para análise estatística empregou-se o teste t de Student. As superfícies de fratura dos instrumentos foram analisadas em MEV. Resultados: O NCF foi significativamente maior para os instrumentos HyFlex CM em comparação com as limas RaCe (p˂0,05), sendo 1336% mais resistentes à fadiga. A análise das superfícies fraturadas em MEV revelou características morfológicas do tipo dúctil para ambos os instrumentos e ausência de deformação plástica. Conclusão: Os instrumentos HyFlex CM apresentaram valores mais elevados de NCF. Deste modo, pode-se concluir que o tratamento térmico a qual estes instrumentos com a liga CM Wire foram submetidos os torna mais resistentes à fratura do que os instrumentos Race, fabricados com a liga de NiTi convencional com eletropolimento.

Influência da conicidade e do ponto de imobilização na flexibilidade dos instrumentos de níquel-titânio rotatórios RaCe / Influence of taper and immobilization point on the flexibility of RaCe nickel-titanium rotary instruments

Objetivo: esse estudo comparou a flexibilidade de instrumentos de níquel-titânio rotatórios com diferentes conicidades, em diferentes diâmetros da haste helicoidal cônica (D3 e D6). Métodos: trinta instrumentos RaCe (FKG, La Chaux-de Fonds, Suíça), #40 (D0 = 40), com 25 mm de comprimento, foram divididos em três grupos (n = 10), de acordo com sua conicidade. No teste de flexão em cantiléver (45 graus), foram realizadas duas avaliações, com cargas aplicadas, em D3 e D6, para cada grupo. Resultados: a comparação das cargas aplicadas em D3 e D6 nos instrumentos RaCe com diferentes conicidades mostrou valores de carga máxima significativamente diferentes para flexionar os instrumentos: D3 < D6, com a flexibilidade em D3 maior do que em D6. A comparação das cargas aplicadas em D3 nos três grupos revelou diferenças significativas entre os grupos (p < 0,0001), enquanto o teste Student-Newman-Keuls (SNK) mostrou diferenças de flexibilidade entre os três grupos: 0,06 < 0,04 < 0,02mm/mm. O mesmo resultado foi encontrado na comparação da força aplicada em D6. Conclusões: a flexibilidade do instrumento aumenta com a redução da conicidade (p < 0,05) e diminui com o aumento no diâmetro do eixo helicoidal (p < 0,05).

Mechanical properties of anatomic finishing files: xp-endo finisher and xp-clean

Abstract The aim of the present study was to evaluate the cyclic fatigue of two anatomic finishing files: XP-Endo Finisher and XP-Clean. Roughness pattern and the micro-hardness of the files were also assessed. Instruments were subjected to cyclic fatigue resistance measuring the time to fracture in an artificial stainless-steel canal with a 60° angle and a 5-mm radius of curvature. The fracture surface of all fragments was examined with a scanning electron microscope. The roughness of the working parts was quantified by using a profilometer and the micro-hardness test was carried out using a Vickers hardness tester. Results were statistically analyzed using a student´s t-test at a significance level of P < 0.05. Weibull analysis was also performed. XP-Endo Finisher presented significantly longer cyclic fatigue life than XP-Clean instruments (P<0.05). XP-Endo Finisher was able to withstand 1000% more cycles to fracture when compared to XP-Clean instruments. SEM visual inspection of the fracture surfaces revealed fractographic characteristics of ductile fracture in all tested instruments; wide-ranging forms of dimples were identified and no plastic deformation in the helical shaft of the fractured instruments was observed. When mean life was compared XP-Endo Finisher lasted longer than XP-Clean with a probability of 99.9%. XP-Endo Finisher instruments also exhibited significantly lower roughness than XP-Clean instruments (P<0.05). No differences in the micro-hardness was observed between the files (P>0.05). It can be concluded that XP-Endo Finisher instruments showed improved performance when compared with XP-Clean instruments, demonstrating higher cyclic fatigue resistance and lower roughness.

Resumo O objetivo do presente estudo foi avaliar a fadiga cíclica de dois instrumentos finalizadores anatômicos: XP-Endo Finisher e XP-Clean. O padrão de rugosidade e a micro dureza dos instrumentos também foram avaliados. Os instrumentos foram submetidos à resistência à fadiga cíclica, medindo o tempo de fratura em um canal artificial de aço inoxidável com um ângulo de 60 ° e um raio de curvatura de 5 mm. A superfície de fratura de todos os fragmentos foi examinada com um microscópio eletrônico de varredura. A rugosidade dos instrumentos foi quantificada usando um perfilômetro e o teste de micro dureza foi realizado usando um testador de dureza Vickers. Os resultados foram analisados ​​estatisticamente usando o teste t de student em um nível de significância de p<0,05. A análise Weibull também foi realizada. XP-Endo Finisher apresentou vida de fadiga cíclica significativamente mais longa do que os instrumentos XP-Clean (p<0,05). XP-Endo Finisher foi capaz de suportar 1000% mais ciclos para fratura quando comparado aos instrumentos XP-Clean. A inspeção visual em microscópio eletrônico de varredura das superfícies de fratura revelou características fractográficas da fratura dúctil em todos os instrumentos testados. Não foi observada deformação plástica no eixo helicoidal dos instrumentos fraturados. Quando o tempo para a fratura foi comparado entre os instrumentos, o XP-Endo Finisher durou mais do que o XP-Clean com uma probabilidade de 99,9%. Os instrumentos XP-Endo Finisher também exibiram uma rugosidade significativamente menor do que os instrumentos XP-Clean (p<0,05). Não foram observadas diferenças na micro dureza entre os arquivos (p>0,05). Pode-se concluir que os instrumentos XP-Endo Finisher apresentaram desempenho melhorado em comparação com os instrumentos XP-Clean, demonstrando maior resistência à fadiga cíclica e menor rugosidade.

Physico-chemical and Biological Properties of a New Portland Cement-based Root Repair Material.

OBJECTIVE: To propose bismuth carbonate, a radiopacifying agent, as a new endodontic root repair material that was added to Portland cement (PC) at 2 wt%, 5 wt%, 10 wt% and 15 wt%, and physicochemical and biological properties of each formulation were evaluated in comparison to MTA-Angelus. METHODS: Mixed and powder samples were analysed by scanning electron microscopy (SEM) and X-ray power diffraction (XRD), and the semiquantitative constitution of the powder was determined by energy-dispersive spectrometer (EDS). Setting time was evaluated by Vicat needle and radiopacity analysed with digital X-ray. The pH of all tested materials was observed after immersion in water for 3, 24, 48, 72 and 168 h (or 7 days). Solubility and calcium release were measured after immersion in water for 24 h. A multiparametric assay XTT-NR-CVDE was used to evaluate the cytotoxicity of the materials in human periodontal ligament (HPDL) fibroblasts. HPDL fibroblasts were exposed to PC 15% and mineral trioxide aggregate (MTA), and the expression of proinflammatory cytokines (IL1A, IL6, IL8, TNF) and bone formation genes (ALP, COL1, RUNX2) was evaluated by real-time PCR. Mineralisation of HPDL fibroblasts cocultured with PC, PC 15% and MTA was evaluated with Von Kossa staining. RESULTS: PC-based groups presented more irregular and larger particles than MTA. PC and MTA showed similarities as observed by XRD and EDS. Setting time of PC-based groups was increased with the addition of bismuth carbonate. All tested materials were alkaline, and pH tended to reduce over time. All cements had solubility lower than recommended, with no difference between them (P>0.05) and showed calcium release. PC 15% had similar radiopacity when compared with MTA (P>0.05). Cell viability was higher for the tested materials than the positive control (P<0.001), but there was no difference when they were compared with negative control (P>0.05). Gene expression levels were similar for all tested groups (P>0.05). Analysed cements had positive Von Kossa staining. CONCLUSION: Overall, the addition of 15% of bismuth carbonate did not result in significant changes to its physicochemical and biological properties when compared with MTA, except for the setting time, and may be considered a potential substitute for MTA.

Comportamento mecânico de instrumentos WaveOne e ProTaper em relação à torção, dureza e tenacidade / Mechanical properties of WaveOne and ProTaper instruments in relation to torsion, hardness and toughness

Objetivo: esse estudo teve como objetivo avaliar a resistência à fratura por torção de duas marcas de instrumentos mecanizados de NiTi, com formas geométricas distintas e produzidas por ligas metálicas diferentes. Métodos: quinze instrumentos WaveOne Large e quinze ProTaper F4 foram selecionados e submetidos aos ensaios mecânicos de torção, microdureza Vickers e tenacidade. No ensaio de torção, foram avaliados a deformação angular até a fratura e o torque máximo. As superfícies fraturadas e as hastes helicoidais dos instrumentos foram analisadas por meio de microscopia eletrônica de varredura (MEV). Resultados: os valores do ângulo máximo em torção foram maiores para o ProTaper, enquanto o torque máximo em torção (N/cm) foi maior para o WaveOne. Os valores de microdureza Vickers foram maiores para a liga NiTi M-Wire, enquanto o grupo controle apresentou maior tenacidade. O teste t de Student demonstrou diferença significativa nos ensaios de torção (p < 0,05), tenacidade e microdureza Vickers. A análise do MEV revelou deformação plástica ao longo das hélices helicoidais de todos os instrumentos fraturados e fratura tipo dúctil. Conclusão: os instrumentos fabricados em NiTi M-Wire apresentaram maior resistência à fratura por torção e maior microdureza, em comparação aos de NiTi convencional. Devido ao maior ângulo de torção do ProTaper e à maior deformação até a fratura, esses parâmetros tornam esse instrumento mais seguro do ponto de vista clínico.

The dentin thickness remaining in the risk zone of mandibular molars after cervical preflaring with four methods / A espessura da dentina remanescente na zona de perigo após o pré-alargamento com quatro métodos

Introduction: Cervical preflaring is an important step of the canal system instrumentation, but can lead to excessive enlargement or root perforation. Objective: Evaluate the remaining dentin thickness in the mandibular molars of mesial roots using cone beam computed tomography: Gates-Glidden (crown-down); Gates-Glidden (step-back); LA Axxess and Easy Pro-Design. Material and method: Were selected 40 lower molars mesial roots, which were scanned in a cone beam CT scanner before and after preparation. Were obtained five sections of the CT images with an interval of 1 mm from the furcation, and measured the thickness variation between the root canal to the root external portion in analysis software. Result: The evaluation of the different levels showed no significance within the same group for the Gates-Glidden group. On the other hand, were observed difference for LA Axxess (p=0.002) and Easy Pro-Design (p=0.005). In the intergroup analysis, were observed difference in all levels, especially for Gates-Glidden in the ascendant order (ANOVA and Tukey). Conclusion: Within the limitations of these study, is possible to conclude that the protocol with greater wear in the cervical risk area was the Gates-Glidden in step-back sequence, as the other groups were equivalent (p>0.05).

Introdução: O preparo cervical é uma etapa importante da instrumentação do sistema de canais, mas pode levar ao alargamento excessivo ou rasgo da raiz. Objetivo: Avaliar, em tomografia computadorizada cone beam, da espessura remanescente de dentina cervical da raiz mesial de molares inferiores, após o preparo com diferentes técnicas: Gates-Glidden (ordem crescente); Gates-Glidden (ordem decrescente); LA Axxess e Easy Pro-Design. Material e método: Foram selecionadas 40 raízes mesiais de molares inferiores, que foram escaneadas em tomógrafo cone beam antes e após o preparo. Das imagens tomográficas foram obtidos cinco cortes com intervalo de 1 mm a partir da furca e, então, mensurada a variação da espessura entre o canal radicular até a porção externa da raiz em software de análise. Resultado: Avaliação dos diferentes níveis demonstraram ausência de significância dentro do mesmo grupo para o grupo das Gates-Glidden. Por outro lado, foi notada diferença para LA Axxess (p=0,002) e para Easy Pro-Design (p=0,005). Na avaliação entre os grupos, foi observada diferença em todos os níveis, sobretudo, para Gates-Glidden na ordem crescente (ANOVA e Tukey). Conclusão: Considerando as limitações desse estudo, concluiu-se que o protocolo que apresentou maior desgaste da área de perigo cervical foi o da Gates-Glidden em ordem crescente, sendo que os demais grupos foram equivalentes (p>0,05).

Bending Resistance and Cyclic Fatigue Life of Reciproc, Unicone, and WaveOne Reciprocating Instruments.

INTRODUCTION: This study evaluated the bending resistance and cyclic fatigue life of a new single-file reciprocating instrument (Unicone; Medin, Nové Mesto na Morave, Czech Republic). Reciproc (VDW, Munich, Germany) and WaveOne (Dentsply Maillefer) instruments were used as references for comparison. METHODS: Flexibility was determined by 45° bending tests using a universal testing machine. The cyclic fatigue test was performed using a custom-made device. For this test, an artificial canal with a 60° angle and a 5-mm radius of curvature was used. Scanning electron microscopic analysis was performed to determine the mode of fracture and possible deformations at the helical shaft. Statistical analysis for the bending resistance test was performed using parametric methods (ie, 1-way analysis of variance). Post hoc pair-wise comparisons were performed using the Tukey test for multiple comparisons (P < .05). Weibull analysis was used to calculate the mean life, beta, and eta parameters. RESULTS: Reciproc presented significantly lower bending resistance than the other tested systems (P < .05), whereas no differences were observed between WaveOne and Unicone (P > .05). When mean life was compared among the brands, Reciproc lasted longer than WaveOne with a probability of 99.9%, longer than Unicone in the "RECIPROC ALL" mode with a probability of 99.9%, and longer than Unicone in the "WAVEONE ALL" mode with a probability of 99.9% (all statistically significant). Moreover, WaveOne lasted longer than Unicone in the "RECIPROC ALL" mode with a probability of 98.5% and longer than Unicone in the "WAVEONE ALL" mode with a probability of 99.8% (all statistically significant). Finally, Unicone in the "RECIPROC ALL" mode lasted longer than Unicone in the "WAVEONE ALL" mode with a probability of 95.3% (statistically significant). CONCLUSIONS: The new reciprocating instrument Unicone showed lower cyclic fatigue resistance compared with Reciproc R25 and WaveOne Primary files.

Bending resistance and cyclic fatigue of a new heat-treated reciprocating instrument.

The current study aimed to evaluate the bending resistance and the cyclic fatigue life of a new heat-treated reciprocating instrument (ProDesign R). Untreated ProDesign R, Reciproc R25, and WaveOne Primary instruments were used as reference instruments for comparison. The bending resistance was performed in ten instruments of each system by using a universal testing machine and a proper apparatus. The cyclic fatigue resistance was tested measuring the number of cycles to failure in an artificial stainless steel canal. Scanning electron microscopy analysis was performed to determine the mode of fracture and possible deformations at the helical shaft. Statistical analysis was performed by using parametric methods; one-way analysis of variance plus post hoc pair-wise Tukey test for multiple comparisons (p < 0.05). Untreated ProDesign R presented significantly higher bending resistance than the other tested systems (p < 0.05). No differences were observed between ProDesign R and Reciproc files regarding the bending resistance (p > 0.05). Moreover, ProDesign R revealed a significantly longer cyclic fatigue life (p < 0.05). In contrast, Untreated ProDesign R and WaveOne instruments presented significantly lower cyclic fatigue life than Reciproc (p < 0.05). The new heat-treated reciprocating instrument ProDesign R have higher cyclic fatigue resistance than Untreated ProDesign R, Reciproc, and WaveOne instruments. ProDesign R and Reciproc were significantly more flexible than Untreated ProDesign R and WaveOne files. SCANNING 38:837-841, 2016. © 2016 Wiley Periodicals, Inc.

Bending Resistance and Cyclic Fatigue Life of a new Single-File Reciprocating Instrument Waveone Gold.

OBJECTIVE: The present study aimed to evaluate the bending resistance and cyclic fatigue fracture resistance of a new single-file reciprocating instrument called WaveOne Gold. Reciproc and WaveOne instruments were used as references for comparison. METHODS: Sixty 25-mm NiTi instruments (Reciproc R25, WaveOne Primary and WaveOne Gold Primary) were tested. Flexibility was determined by applying 45° bending tests using a universal testing machine (n=10). A custom-made device was used during cyclic fatigue test (n=10), comprising a stainless steel artificial canal measuring 1.4 mm in diameter, 19 mm in total length with an 86° angle and 6 mm radius of curvature. Possible deformations at the helical shaft and mode of fracture were evaluated using scanning electron microscopy analysis. Statistical analysis was performed using one-way analysis of variance. Post hoc pair-wise comparisons were performed using Tukey's test for multiple comparisons (P<0.05). RESULTS: WaveOne presented significantly higher bending resistance than the other tested systems (P<0.05), whereas Reciproc presented the lowest bending resistance (P<0.05). Reciproc revealed a significantly longer cyclic fatigue fracture resistance than the other systems (P<0.05). CONCLUSION: Although WaveOne Gold presented higher flexibility than WaveOne, no differences in the resistance to fatigue were observed between both systems. The Reciproc files were more flexible and resistant to fatigue for the angle of curvature of 86° and 6 mm radius than WaveOne and WaveOne Gold files.

Flexibilidade e fadiga cíclica de instrumentos fabricados com métodos diferentes / Flexibility and resistance to cyclic fatigue of instruments manufactured by different methods

Objetivo: o presente estudo comparou o comportamento mecânico de instrumentos de níquel-titânio que apresentavam forma geométrica semelhante, porem, produzidos por métodos de fabricação diferentes. Métodos: foram usados, para o teste de flexibilidade e de flexão rotativa, vinte instrumentos 25/0,06 RaCe (FKG Dentaire, La Chaux-de-Fonds, Suíça), com 25 mm de comprimento, produzidos por fio de NiTi convencional (usinados); 20 instrumentos endodônticos especiais 25/0,06 Twisted File (TF) (SybronEndo, Orange, EUA), com 27 mm de comprimento, fabricados por torção; e 20 instrumentos endodonticos 25/0,06 ProFile Vortex (Dentsply Tulsa Dental, Tulsa, EUA), com 25mm de comprimento, feitos com liga M-Wire. Cada grupo dos respectivos ensaios teve 10 instrumentos de cada fabricante. Resultados: o teste paramétrico ANOVA mostrou que houve diferença significativa entre os valores de carga máxima, na seguinte ordem decrescente: ProFile Vortex > RaCe > TF (p < 0,01). Com o ensaio de flexão rotativa, o teste paramétrico ANOVA, com nível de significância de 1%, mostrou que os instrumentos RaCe tiveram uma diferença significativa menor para a fratura do que os instrumentos Pro-File Vortex, que foram significativamente inferiores aos instrumentos TF, com relação ao tempo e ao numero de ciclos (p < 0,01). Conclusão: os instrumentos TF foram mais flexiveis do que os instrumentos RaCe, que foram menos resistentes a flexão do que os instrumentos ProFile Vortex. Considerando-se o ensaio de flexão rotativa, os instrumentos TF apresentaram um desempenho significativamente superior com relação ao tempo e ao numero de ciclos para a fratura (NCF) do que os outros instrumentos testados.

Comparison of the efficacy of nickel-titanium rotary systems with or without the retreatment instruments in the removal of gutta-percha in the apical third.

BACKGROUND: The purpose of this study was to compare the efficacy of nickel-titanium rotary systems with or without the retreatment instruments in the removal of gutta-percha from the apical third. METHODS: The systems compared were as follows: ProTaper Universal (PT), ProTaper Universal Retreatment (PTr), Mtwo (M2) and Mtwo Retreatment (M2r). Sixty extracted mandibular incisors were treated with a crown-down technique and filled with gutta-percha and sealer. The apical diameter was standardized in 0.30 mm, 1 mm from the apex. The teeth were distributed into 4 experimental groups: PT, PTr, M2 and M2r. In PTr and M2r groups, filling materials were removed by PTr/M2r followed by root canals preparation up to a PT F4/M2 40; in groups PT/M2, the filling materials were removed and the root canals were prepared by PT up to a PT F4/M2 up to a M2 40. The roots were split and photomicrographing. The percentage of clean area in the apical 5 mm was calculated using software. Data were analyzed with the Kruskal-Wallis test. RESULTS: Remaining material was found in all hemisections and there was no statistically significant difference between the groups (p = 0.09). Considering the surface of the canal walls of all teeth, the mean of the percentage of clean area was 54%. CONCLUSIONS: Considering the applied methodology, remaining filling material was found in all hemisections, regardless of the retreatment technique and PT or M2 were as effective as PTr/PT or M2r/M2.

Comparação da flexibilidade e da resistência torsional de instrumentos automatizados de níquel-titânio

Introdução: esse estudo comparou a flexibilidade e a resistência a torção de dois instrumentos fabricados com ligas de niquel-titânio (NiTi) especiais, com um instrumento fabricado com liga convencional. Métodos: instrumentos Twisted File (TF) de liga de NiTi, contendo a fase R (SybronEndo, Orange, EUA) e instrumentos ProFile Vortex (Dentsply Tulsa Dental, Tulsa, OK, EUA) fabricados com a liga NiTi M-Wire foram comparados aos instrumentos RaCe (FKG Dentaire, La Chaux-de-Fonds, Suíça), produzidos por fio de NiTi convencional. Foram realizados ensaios de flexibilidade e torção. Um total de 20 instrumentos de cada fabricante foi testado, todos de 25/0,06. A análise estatística foi realizada utilizando ANOVA. Resultados: houve diferença significativa na resistência mecânica entre os instrumentos testados.Os instrumentos TF foram os mais flexíveis, seguidos pelos RaCe e ProFile Vortex (p < 0,01). No ensaio de torção, os instrumentos ProFile Vortex suportaram maiores valores de força máxima e torque máximo antes da fratura, seguidos pelos RaCe e TF (p < 0,01). Os instrumentos RaCe e TF não apresentaram diferença estatística significativa na resistência a torção (p = 0,061). Conclusão: pode-se observar que existe uma relação entre a flexibilidade com a resistência à torção (torque máximo e ângulo máximo). O instrumento mais flexível (TF) foi o menos resistente à torção. O instrumento mais resistente à torção (ProFile Vortex) foi o menos flexível. O instrumento RaCe apresentou um resultado intermediário tanto para a flexibilidade quanto para a resistência à torção.

Influência de diferentes métodos de fabricação no comportamento mecânico de instrumentos endodônticos de níquel-titânio / Influence of different manufacturing methods on the mechanical behavior of nickel-titanium endodontic instruments

Objetivo: Avaliar o comportamento mecânico de instrumentos endodônticos de NiTi K3 (Sybron Endo,Orange, CA), fabricados convencionalmente e K3XF(Sybron Endo, Orange, CA), submetidos a tratamento térmico na fabricaçÆo.Métodos: Foram utilizados 20 instrumentos K3 e K3XF com D0 0,25 mm, conicidade 0,06 mm/mm e 25 mm de comprimento. Para estandardizaçÆo, dez instrumentos de cada tipo foram examinados sob estereomicroscópio e dois instrumentos (K3 e K3XF) tiveram suas secçães transversais analisadas em microscópio eletrônico de varredura (MEV). A flexibilidade e resistência à fratura foram avaliadas em ensaio de flexÆo em 45° e em teste estático de fadiga, respectivamente. Dez instrumentos K3 e K3XF foram utilizados em cada teste, registrando-se os valores da carga flexural e o número de ciclos para ocorrer a fratura (NCF). Para análise estatística empregou-se o teste t de Student. Os instrumentos fraturados foram analisados em MEV. Resultados: A carga flexural foi significativamente maior para as limas K3 do que para as K3XF (p˂0,05), apresentando, respectivamente, os valores de 713,5 g e 536,4 g. O NCF foi significativamente maior para os instrumentos K3XF em comparaçÆo com as limas K3 (p˂0,05). A análise das superfícies fraturadas em MEV revelou características morfológicas do tipo dúctil para ambos os instrumentos e ausência de deformaçÆo plástica. ConclusÆo: Os instrumentos de NiTi submetidos a tratamento térmico apresentaram os menores valores de força para serem flexionados em 45° e os mais elevado valores de NCF. Desse modo, pode-se inferir que os instrumentos submetidos ao tratamento térmico diferenciado (K3XF) sÆo mais flexíveis e mais resistentes à fratura por fadiga do que os instrumentos K3, fabricados convencionalmente...

Objective: To evaluate the mechanical behavior of K3 NiTi endodontic instruments (Sybron Endo, Orange, CA, USA) with conventional manufacturing or subjected to a thermal treatment during manufacturing (K3XF instruments; Sybron Endo). Methods: Twenty K3 and K3XF instruments with D0 0.25 mm, 0.06 mm/mm taper and 25 mm length were used. For standardizing purposes, 10 instruments of each type were examined by a stereomicroscope and two instruments (K3 and K3FX) had their cross-sections analyzed by scanning electron microscopy (SEM). Flexibility and fracture strength were evaluated by 45° bending test and static fatigue test, respectively. Ten K3 and K3FX instruments were used for each test, obtaining the flexural load values and the number of cycles to failure (NCF). Student?s t test was used for statistical analysis. The fractured instruments were examined by SEM. Results: The flexural load was significantly greater for the K3 than for the K3FX (p<0.05) instruments, 713.3 g and 536.4 g, respectively. The NCF was significantly greater for the K3FX than for the K3 instruments (p<0.05). SEM analysis of the fractured surfaces revealed ductile-type morphological characteristics for both types of instruments and absence of plastic deformity.Conclusion: NiTi instruments subjected to thermal treatment presented lower flexural strength values when subjected to 45º bending and greater NCF values. It may be assumed that the instruments subjected to a special thermal treatment during the manufacturing process (K3FX) are more flexible and more resistant to fatigue fracture than the conventional K3 instruments...

Resistência em flexão de instrumentos endodônticos obtidos de fios metálicos de NiTi convencional e M-wire. Estudo comparativo / Bending resistance of conventional NiTi and M-wire endodontic instruments. A comparative study

Esse estudo avaliou e comparou a resistência em flexão de instrumentos endodônticos mecanizados obtidos de fios metálicos de níquel-titânio (NiTi) convencional e M-wire. Para avaliar a resistência em flexão empregou-se o ensaio mecânico de flexão em cantilever. A flexibilidade em flexão de um instrumento endodôntico depende da composição química e do tratamento termomecânico da liga metálica, assim como, da geometria da seção reta transversal da haste cônica helicoidal do instrumento endodôntico. Os resultados obtidos revelaram que os instrumentos Profile Vortex, fabricados a partir de fios metálicos de NiTi denominados M-wire, apresentaram a maior resistência em flexão (menor flexibilidade). Os instrumentos RaCe, produzidos a partir de fios metálicos de NiTi convencional, apresentaram a menor resistência em flexão (maior flexibilidade).

This study evaluated and compared the bending resistance of rotary endodontic instruments made of conventional nickel-titanium (NiTi) and M-wire by means of cantilever bending test. The flexibility of an endodontic instrument depends on its chemical composition and the thermo mechanical treatment of the alloy, as well as on its cross-sectional geometry on the helical shaft of the endodontic instrument. The results showed that the Profile Vortex instruments, made from NiTi wires called M-wire, had the greatest bending resistance (lowest flexibility), while RaCe instruments, produced from conventional NiTi wires showed the lowest bending resistance (greatest flexibility) among the instruments tested.

Princípios biológicos do tratamento endodôntico de dentes com polpa necrosada e lesão perirradicular / Biological principles of endodontic treatment of teeth with pulp necrosis and apical lesions

O profissional que pratica a Endodontia se depara rotineiramente com três condições básicas que requerem tratamento endodôntico: polpas vitais, polpas necrosadas e casos de retratamento. O sucesso do tratamento endodôntico depende do reconhecimento das idiossincrasias de cada uma destas três condições. Canais radiculares contendo polpa necrosada e lesão perirradicular representam um problema infeccioso e devem ser tratados de forma diferenciada dos dentes com polpa viva (sem infecção). O sucesso do tratamento endodôntico nestes casos vai depender do controle da infecção exercido pelo preparo químico-mecânico, medicação intracanal e obturação. Este artigo revisa os princípios biológicos do tratamento de dentes com polpa necrosada e infectada, visando fornecer ao clínico as condições para a melhora no resultado do tratamento endodôntico destes casos.

The clinician who practices endodontics routinely faces three conditions that require treatment: vital pulps, necrotic pulps and retreatment cases. The successful treatment of these three conditions depends on the recognition of their respective idiosyncrasies. Canals of necrotic teeth associated with apical periodontitis represent an infectious problem and should be treated differently from vital teeth (non-infected). The success of the endodontic treatment will depend on effective infection control promoted by chemomechanical preparation, intracanal medication and obturation. This paper reviews the biologic principles of the endodontic treatment of teeth with necrotic pulps and apical periodontitis, with the purpose to provide the clinician with better conditions to improve the treatment outcome.

Influência dos comprimentos dos arcos de um canal na fratura por fadiga de instrumentos de níquel-titânio mecanizados

Objetivo: o objetivo desse estudo foi avaliar a influência do comprimento do arco de um canal artificial no número de ciclos necessários para induzir a fratura por fadiga de um instrumento endodôntico de níquel-titânio(NiTi) mecanizado. Métodos: os instrumentos usados nesse trabalho foram os Mtwo de diâmetro em D0 de0,35mm, de conicidade 0,02mm/mm e comprimento de 25mm. Os instrumentos foram utilizados em dois canais artificiais metálicos com segmentos curvos, sob velocidade de 300rpm. As curvaturas estavam localizadas nas extremidades dos canais e possuíam diferentes comprimentos de arcos. O dispositivo usado para o teste de flexão rotativa dos instrumentos endodônticos selecionados foi o descrito previamente por Lopes et al. Resultados: o número de ciclos necessários para causar a fratura por fadiga foi influenciado pelo comprimento do arco do canal artificial. Conclusão: o número de ciclos necessários para induzir a fratura por fadiga nos instrumentos usados em flexão rotativa em canais artificiais de mesmo comprimento de raio diminuiu com o aumento do comprimento do arco