Avaliação e comparação de instrumentos endodônticos rotatórios de NiTi antes e após o uso clínico

摘要

The objective of this study was to evaluate and to compare rotatory instruments of NiTi before and after the clinical use. Twenty-four groups of rotatory instruments of NiTi of the ProTaper system (Dentsply-Maillefer, Ballaigues, Switzerland) were divided in two groups in a random way. The instruments of the group 1 (n=12) were stored for subsequent accomplishment of the mechanical tests. The instruments of the group 2 (n=12) were directed to a single endodontist, who used each group in the preparation of ten radicular canals. After the collection of the instruments, all the S1, S2 and F1 alloys from the two groups, were tested related to the resistance to the cyclical fatigue. For this test a simulator of curved canal of stainless steel was used with 1,5mm of internal diameter, angle of 90 degrees and ray of 6mm where the instruments were introduced with speed of 350 rotations per minute (RPM) until happening the fracture of the same ones. The passed time to the fracture happened was analyzed and transformed in RPM. The size of the fragments was also analyzed. The data were analyzed using the normality test of Kolmogorov-Smirnov at the level of significance of 1% and they were analyzed with ANOVA of two factors (RPM and size of the fragment), following by the Tukey test at the level of significance of 5%.The obtained results showed significant difference for the factor RPM (p=0. 008), but not significant for the factor of the fragment (p=0. 12). Average values of RPM were from 641 to the new instrument S1 (±127, 92); 476 to the used instrument S1 (± 182, 92); 545 to new instrument S2 (±66, 61); 504 to used instrument S2 (±150. 01); 453 to new instrument F1 (±53, 18) and 433 to used instrument F1 (±153, 43). The average values of the fragments (mm) recorded were 6, 41 (new S1); 7, 46 (used S1); 6, 95 (new S2); 7, 35 (used S2); 7, 30 (new F1) and 7, 09 (used F1). All the instruments were analyzed in a lateral view and in the fracture surface in electronic microscopy of scintiscan (EMS) to qualitative analysis of the fractured instruments.