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Previous issue date: 2012-03-28 === Introduction: This in vitro study evaluated the capacity of centralization of the preparation, as well as the wear, distortion and fracture of three rotary nickel-titanium (Ni-Ti) systems Wizard CD Plus (WP), Wizard Navigator (WN) and BioRace(BR). Methodology: Were used 90 mesiobuccal roots (MV) of first upper molars (MS). The overlap of tomographic images before and after instrumentation was used to evaluate the transport of the preparation, at 2.0, 4.0, 6.0 and 8.0 mm from the apex. The instruments were observed by SEM before and after the third use, at its tip and at 5 mm of it. The data were analyzed by Kruskal-Wallis, complemented by Tukey test (P<0.05). Results: There was transport of the root canal in all groups, with no statistical difference between them (P> 0.05). There was no fracture and distortion at 5mm from the tip of the instruments. The group BR exhibited more distortion at the tip than the group WP (P = 0.011). There was more wear of the instrument in the group WP than in the BR (P <0.001). There was a progressive increase in distortion at the tip (P = 0.026) and of the wear (P <0.001) compared to the use in the group BR, as well as the wear in the group WP (P<0.001). Conclusion: None of the rotary systems employed was able to provide centralized preparation and the progressive use of the instruments did not favor the occurrence of fracture despite having increased the occurrence of distortion and wear === Introdu??o: Este estudo in vitro avaliou a capacidade de centraliza??o do preparo, bem como o desgaste distor??o e a fratura de tr?s tipos de instrumentos rotat?rios de n?quel-tit?nio (Ni-Ti) Wizard CD Plus (WP), Wizard Navigator (WN) e BioRace(BR). Metodologia: Foram utilizadas 90 ra?zes m?sio-vestibulares (MV) de primeiros molares superiores (1?s MS) e 10 conjuntos de cada tipo de instrumento rotat?rio. A sobreposi??o de imagens tomogr?ficas de feixe c?nico pr? e p?s-instrumenta??o avaliaram a capacidade de centraliza??o do preparo, a 2,0, 4,0, 6,0 e 8,0mm do ?pice. Os instrumentos foram avaliados em microscopia eletr?nica de varredura (MEV), antes e ap?s at? o terceiro uso, na sua ponta e a 5mm desta. Os dados foram analisados pelo Teste de Kruskal-Wallis, complementado pelo Teste de Tukey (P<0.05). Resultados: Houve transporte do canal radicular em todos os grupos, n?o havendo diferen?a estat?stica entre os mesmos (P>0.05). N?o houve fratura e distor??o a 5mm da ponta nos instrumentos analisados. O grupo BR apresentou mais distor??o na ponta do instrumento do que o grupo WP (P=0,011). Houve mais desgaste do instrumento no grupo WP do que no BR (P<0,001). Ocorreu aumento progressivo da distor??o na ponta do instrumento e do desgaste em rela??o ao uso no grupo BR (distor??o P=0,026 e desgaste P<0,001), assim como do desgaste no grupo WP (P<0,001). Conclus?o: Nenhum dos sistemas rotat?rios empregados foi capaz de proporcionar preparos centralizados e o uso progressivo dos instrumentos aumenta a ocorr?ncia de distor??o e desgastes em sua topografia.
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