Desgaste dos instrumentos K3 e Protaper após simulação de uso clinico em canais curvos / Wear of K3 and ProTaper files after simulated clinical use in curved canals

Objetivo : Avaliar o desgaste, apos simulacao de uso clinico, de instrumentos K3 (SybronEndo, Orange, CA, EUA) e ProTaper (Dentsply-Maillefer, Tulsa, Oklahoma, EUA) em 46 raizes mesiovestibulares de primeiros molares superiores humanos, recem-extraidos e com angulacao media de 40°. Metodos : Os dentes foram divididos em: A) K3 (SybronEndo, Orange, CA, EUA) (com bandas radiais) e B) ProTaper (Dentsply-Maillefer, Tulsa, Oklahoma, EUA) (sem bandas radiais). Os instrumentos foram avaliados em microscopia eletronica de varredura antes do primeiro uso, para visualizacao de defeitos de fabricacao, apos sete e 13 ciclos de instrumentacao nos canais. A instrumentacao foi realizada de acordo com as recomendacoes do fabricante, sendo K3 (SybronEndo, Orange, CA, EUA) e Protaper (Dentsply-Maillefer, Tulsa, Oklahoma, EUA). Os criterios para avaliacao de desgaste foram: defeitos (estiramento, encurtamento/ inversao das espiras, presenca de crateras), trincas obliquas e fratura. Apos a avaliacao em MEV antes do uso, foram constatadas em todos os instrumentos, farpas metalicas na crista das espiras e ranhuras obliquas provenientes do processo de usinagem. Resultados : Apos sete usos, no sistema K3 (SybronEndo, Orange, CA, EUA), todos os instrumentos apresentaram defeitos nos ângulos de corte e, 25/08 e 25/10 apresentaram trincas obliquas no corpo da parte ativa levando a fratura ductil desta ultima apos o oitavo uso. No sistema ProTaper (Dentsply-Maillefer, Tulsa, Oklahoma, EUA), em sete usos, alem de defeitos nos ângulos de corte, os instrumentos tambem apresentaram trincas, e a fratura ruptil ocorreu em F3 no 13o uso. Ao final do preparo foram observadas crateras ao longo da parte ativa dos instrumentos. Conclusao : Na analise final, foi evidenciado que os sistemas se equivalem quanto aos defeitos encontrados, independentemente do desenho da parte ativa, sendo proporcionais a quantidade de ciclos de uso, e que estes defeitos podem funcionar como pontos de maior fragilidade, propiciando a fratura. Termos de indexacao : microscopia eletronica de varredura; endodontia; instrumentacao; dente molar. Abstract Objective : To assess wear, after simulated clinical use of K3 (SybronEndo, Orange, CA, EUA) and ProTaper files (Dentsply-Maillefer, Tulsa, Oklahoma, EUA) in 46 mesiovestibular roots of human maxillary first molars, recently extracted and with mean angulation of 40°. Methods : The teeth were divided as follows: a) K3 (SybronEndo, Orange, CA, EUA) (with radial bands) and b) ProTaper (Dentsply-Maillefer, Tulsa, Oklahoma, EUA) (without radial bands). The files were assessed by scanning electronic microscopy before first use to visualize fabrication defects, and after 7 and 13 cycles of debridement in the canals. Debridement with files K3 (SybronEndo, Orange, CA, EUA) and ProTaper (Dentsply-Maillefer, Tulsa, Oklahoma, EUA) was performed in accordance with the manufacturers’ recommendations. The criteria for wear assessment were: defects (stretching, shortening/spiral inversion, presence of craters), oblique cracks and fracture. After assessment by SEM and before they were used, metal barbs on the crest of the spirals and oblique scratches due to the machining process were found in all the files. Results : In the K3 system (SybronEndo, Orange, CA, USA), after being used seven times, all the instruments showed cutting angle defects, and 25/08 and 25/10 had oblique cracks in the body of the active part leading to ductile fracture after being used for the eighth time. In the ProTaper system (Dentsply-Maillefer, Tulsa, Oklahoma, USA), after being used seven times, in addition to cutting angle defects, the files also presented cracks, and ruptile fracture occurred in F3 during use for the thirteenth time. At the end of preparation, craters were seen along the active part of the files. Conclusion : In the final analysis, it was seen that the system are equivalent with regard to the defects found, irrespective of the active part design, being proportional to the number of cycles of use, and these defects could act as points of greater fragility, favoring fracture. Indexing terms : microscopy electron scanning; endodontics; instrumentation; molar.