"Resistência à fadiga cíclica flexural de instrumentos rotatórios de Ni-Ti em razão do uso e do torque" / Flexural cyclic fatigue resistance of NiTi rotatory instruments due to number of users and torque.
AUTOR(ES)
Dirce Akemi Sacaguti Kawakami
DATA DE PUBLICAÇÃO
2007
RESUMO
The aim of the present study was to evaluate the flexural cyclic fatigue resistance of nickel-titanium rotary instruments, number 25, taper 0,04, and length of 25mm (K3, SybronEndo), when submitted to several torque values and number of uses in simulated canal blocks, by using devices appropriated for dynamic tests. It was tried to detect whether, in addition to the factor number of uses, there would be an influence related to torque, or even the possibility of an interaction between number of uses and torque. The data was collected from 320 simulated canals that were prepared, driven by an electrical motor at 300 rpm, using 80 instruments divided in 4 groups of 20 sample each, based on torque values (0,5 Ncm, 1,0 Ncm, 2,0 Ncm e 6,0 Ncm). Each group was randomly divided in 4 subgroups of 5 samples each, according to the number of uses (1, 3, 5 and 7 cycles). All files were submitted to flexural cyclic fatigue test realized in a device that allows the instrument to freely rotate, reproducing the movement of an instrument rotating in a curved canal (40º angle and 5 mm of radius), simulating the pecking movement, where the instrument slide over the groove created in the hardened steel. An electric motor hand-piece was used with a contra-angle 16:1 reduction set at 300 rpm and torque value identical to that used during preparation of simulated canals. The fracture of the instrument was easily detected at moment which the counter and the timer were immediately stopped. Data collected by the counter and the timer were converted in seconds and analysed by ANOVA and t Student test (p<0.01). In regards to the number of uses factor, there was not a statistically significant difference, while comparisons made with torque value set at 6,0 Ncm showed t values significantly high, with p<0.01. It was not seen any interaction between both variables, number of uses and torque. Based on the results of this investigation, it can be concluded that torque affected the resistance to flexural cyclic fatigue of nickel-titanium rotary instruments, being low on those tested at high torque value; while the factor number of uses up to 7 times did not affect the results.
ASSUNTO(S)
fratura fadiga clínica cyclic fatigue flexural fatigue níquek-titanium fatigue nickel-titanium instrumento rotatório rotatory instruments fadiga fracture torque fadiga flexural torque
Documentos Relacionados
- Influência da fadiga cíclica de instrumentos rotatórios de NiTi em canal curvo simulado
- Analise de falhas de instrumentos endodonticos rotatorios de Ni-Ti em odontologia
- Cyclic Fatigue Resistance of Rotary NiTi Instruments after Simulated Clinical Use in Curved Root Canals
- Avaliação da vida restante em fadiga de instrumentos rotatórios de NiTi ProTaper após uso clínico múltiplo
- Avaliação das características superficiais de instrumentos rotatórios de NiTi antes e após o uso