Fatigue Life of Reciproc and Mtwo instruments subjected to static and dynamic tests.

INTRODUCTION: This study evaluated the influence of flexibility and reciprocating movement on the fatigue life of endodontic instruments subjected to static and dynamic tests. METHODS: The rotary nickel-titanium instruments used in this study were Reciproc and Mtwo. The instruments were initially subjected to a cantilever-bending test and then to static and dynamic fatigue tests. Reciproc instruments were operated in reciprocating movement, whereas Mtwo instruments were worked in continuous rotation. RESULTS: The means of bending resistance (maximum load in grams) of the instruments were 274.9 for Reciproc and 429 for Mtwo. The mean times (in seconds) to fracture of the instruments subjected to static and dynamic tests were 214.5 (static) and 286.3 (dynamic) for Reciproc and 38.9 (static) and 99 (dynamic) for Mtwo. The Student's t test revealed significant differences in all tests (P < .05). CONCLUSIONS: The results of the present study showed longer fatigue life for instruments with higher flexibility, driven by reciprocating movement, and in the dynamic testing model. These findings reinforce the assumption that use of reciprocating movement is a means to prolong the fatigue life of rotary nickel-titanium endodontic instruments during instrumentation of curved canals.

Buckling resistance of pathfinding endodontic instruments.

INTRODUCTION: This study compared the buckling resistance of the following endodontic pathfinding instruments: C-Pilot file (VDW, Munich, Germany), C+ file (Maillefer/Dentsply, Ballaigues, Switzerland), and PathFile (Maillefer/Dentsply). METHODS: The test instruments were subjected to a devised buckling resistance test, which consisted of the application of an increasing load in the axial direction of the instrument by using a universal testing machine. The maximum load required to generate a lateral elastic displacement of 1 mm was recorded for each instrument. RESULTS: The results indicated that the buckling resistance decreased in the following order: C+ file > C-Pilot file > PathFile. The difference was statistically significant (P < .05). CONCLUSIONS: The stainless steel instruments (C+ and C-Pilot) were more resistant to buckling than the nickel-titanium instrument (PathFile). Considering that buckling resistance may influence the performance of instruments during the negotiation of constricted canals, the C+ files showed significantly better results than the other instruments tested.

Mechanical behavior of pathfinding endodontic instruments.

INTRODUCTION: This study compared the mechanical properties of 3 pathfinding endodontic instruments. METHODS: The test instruments were subjected to mechanical tests to evaluate resistance to bending (flexibility), buckling, cyclic fatigue, and torsional load in clockwise rotation. Data were statistically evaluated by analysis of variance and the Student-Newman-Keuls test for multiple comparisons. RESULTS: In the buckling resistance test, the highest values were observed for C-Pilot files (VDW, Munich, Germany) and the lowest for Scout RaCe (FKG Dentaire, La Chaux-de-Fonds, Switzerland) instruments. In the bending resistance test, the lowest flexibility was observed for the C-Pilot instrument, and no significant difference was observed between Scout RaCe and PathFile (Maillefer/Dentsply, Ballaigues, Switzerland) instruments. The ranking in the fatigue resistance test was the following: PathFile > Scout RaCe > C-Pilot, with statistically significant differences observed in the number of cycles to fracture between all the instruments. In the torsional assay, the angular deflection to fracture decreased in the following order: Scout RaCe > PathFile > C-Pilot. As for the maximum torque values, the ranking was as follows: C-Pilot > PathFile > Scout RaCe. CONCLUSIONS: Findings revealed that the stainless-steel C-Pilot instrument showed increased resistance to buckling but decreased flexibility and cyclic fatigue resistance when compared with nickel-titanium pathfinding instruments. PathFile instruments showed the highest resistance to cyclic fatigue, and Scout RaCe files exhibited the highest angular deflection to fracture. The different mechanical behavior of the instruments indicates that the combined use of stainless steel hand instruments and rotary nickel-titanium instruments during the exploration of narrow curved canals may be necessary to exploit the best performance of each pathfinding instrument.

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.

Torsional properties of pathfinding instruments.

INTRODUCTION: This study compared the torsional properties of 2 stainless steel endodontic pathfinding instruments: C-Pilot (VDW, Munich, Germany) and C(+) files (Maillefer/Dentsply, Ballaigues, Switzerland). Stainless steel conventional K-type instruments (KCC(+), VDW) were used as controls. METHODS: File sizes 10 were subjected to a torsional assay in clockwise rotation. The 2 parameters evaluated were maximum torque and angular deflection at failure. The fractured surfaces and the helical shafts of the fractured instruments were then examined by scanning electron microscopy (SEM). RESULTS: The results indicated that the angular deflection to fracture decreased in the following order: KCC(+) > C-Pilot > C(+). As for the maximum torque values, the results revealed the following descending order: C(+) > KCC(+) > C-Pilot. SEM analysis revealed that plastic deformation occurred along the helical shaft of the fractured instruments and that the fractured surfaces were of the ductile type. CONCLUSIONS: The instruments tested showed different torsional behavior depending on the parameter evaluated. Considering that high angular deflection values may serve as a safety factor for instruments used as pathfinders, the conventional K file showed significantly better results than both C-Pilot and C(+) files.

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.

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.

Resistência à flambagem de instrumentos endodônticos empregados no cateterismo de canais radiculares atresiados / Resistence to buckling of the endodontic instruments used in the catherism of the partially calcified root canals

Este estudo analisa a forma de trabalho, as dimensões e a resistência à flambagem de instrumentos endodônticos empregados no caterismo de canais radiculares etresiados. Foram analisados instrumentos C+File, Colorinox e Nitiflex da Dentisply-Maillefer, CC Cord da Antaeos e HI da Miltex. As dimensões foram determinadas no projetor de perfil. As formas foram obtidas no MEV. A resistência à flambagem foi quantificada pela aplicação de uma força na direção axial dos instrumentos. Concluiu-se que os instrumentos C+File apresentaram formas e dimensões diferentes. Os instrumentos C-File apresentam maior resistência à flambagem seguidos pelo CC Cord.

Instrumentos endodônticos de NiTi de diferentes conicidades. Fratura por torção em flexão / Torsion in bending fracture with differently tapered rotary endodontic instruments

No presente trabalho, avaliou-se a resistência à fratura de instrumentos endodôntios de NiTi acionados a motor quando submetidos ao ensaio de torção e flexão. As características morfológicas da superfície de fratura foram analisadas por microscopia eletrônica de varredura (MEV). Foram utilizados instrumentos de número 25, de conicidades nominais 0,02-0,04 e 0,06 mm/mm com comprimentos de 25 mm das marcas comerciais Hero (Micromega, França) e Race (FKG, Alemanha). Os resultados obtidos indicaram que os instrumentos Hero quando comparados aos Race apresentaram maior resistência mecânica quanto ao torque máximo de fratura, enquanto a avaliação no MEV indicou fratura do tipo dúctil

Geometria da haste helicoidal de instrumentos endodônticos de NiTi acionados a motor. Estudo crítico / Geometry of the helical shaft of NiTi engine-driven endodontic instruments. A critic review

A geometria da haste helicoidal dos instrumentos endodônticos de NiTi acionados a motor apresenta uma variação acentuada de formas e dimensões oriundas do processo de fabricação. A geometria da haste helicoidal é uma característica importante no desenho do instrumento, que pode interferir na instrumentação de canais radiculares. O objetivo deste trabalho foi realizar um estudo crítico da geometria (formas e dimensões) das hastes helicoidas de instrumentos endodônticos de NiTi acionados a motor. A conclusão deste trabalho mostrou que os instrumentos endodônticos de NiTi acionados a motor apresentam: hastes helicoidais com valores variáveis em relação à geometria, seções retas transversais com diferentes formas e áreas, e ângulos de ataques negativos.

Estudo comparativo da flexibilidade de instrumentos endodônticos de NiTi acionados a motor / Comparative study of flexibility of engine-driven NiTi instruments

No presente trabalho, avaliou-se a carga necessária elástica (deslocamento) de instrumentos de NiTi acionados a motor de mesmo número (diâmetro nominal) de três marcas comerciais. Nos ensaios mecânicos de flexão, as amostras foram fixadas em uma das extremidades (cantilever) e a carga aplicada na extremidade oposta na direção perpendicular ao eixo do instrumento. Os resultados obtidos indicaram que os instrumentos da marca comercial ProTaper são mais rígidos (menos flexíveis) do que os ProFile e K³ em todos os números (diâmetros nominais) ensaiados