Surface finishing of unused rotary endodontic instruments: a SEM study

Abstract

During endodontic therapy, cleaning of root canals is performed using endodontic files and auxiliary chemical substances, and it is important that the endodontist be familiar with the instruments used in daily practice. This study evaluated, under scanning electron microscopy (SEM), the quality of the surface finishing of unused rotary endodontic instruments. Fifty sizes 20, 25 and 30 rotary files from different commercial brands (ProFile, Protaper, Race, Hero and K3 Endo) were removed directly from their packages and had their final 3 mm examined with a scanning electron microscope at x190 magnification with no previous preparation. The images were evaluated by 3 skillful, calibrated, blinded observers according to the following criteria: cutting edge, debris, grooves, microcavities, tip shape, tip position, scraping and transition angle. Data were recorded in worksheets designed for the study. Irregular edges were observed in 50-100% of the files. Except for ProFile, all commercial brands presented surface debris in 100% of samples. Only Race files showed no grooves or microcavities. K3 Endo files presented the best tip centralization. Excetp for ProTaper files, all commercial brands presented blunt-cutting edges in 100% of samples. All types of files presented surface scraping. K3 Endo files and Protaper had a high percentage of transition angle. Based on the evaluation criteria used in the present study, most samples presented a minimum of 2 alterations and a maximum of 7 alterations per instrument. Under the tested conditions, the quality of the surface finishing of the examined instruments was not as expected, given that no instrument was free of imperfections and most of them presented at least 2 and up to 7 types of surface defects. These results suggest that the manufacturing process and the packaging conditions of rotary endodontic instruments are far from ideal.

Translated abstract

Durante a terapia endodôntica, a ação de limpeza é realizada com os instrumentos endodônticos auxiliada por substâncias químicas. Sendo assim, é importante que o endodontista conheça como são os instrumentos. Este trabalho visou avaliar a qualidade do acabamento de superfície de instrumentos endodônticos rotatórios por meio de microscopia eletrônica de varredura. Foram selecionados, 50 instrumentos endodônticos rotatórios nos números de 20, 25 e 30, das marcas Profile, Protaper, Race, Hero e K3 Endo, da forma como são encontradas no mercado e sem nenhum preparo prévio. Os instrumentos tiveram seus 3 milímetros finais fotomicrografados em microscópio eletrônico de varredura com ampliação de x190. As imagens foram avaliadas por três profissionais especialistas, e os resultados anotados em planilhas. A metodologia aplicada permitiu concluir que todos os instrumentos das marcas comerciais avaliadas apresentaram inadequações no acabamento da superfície. Cabe aclarar que, observando os critérios selecionados utilizados para avaliação a maioria das amostras apresentaram o mínimo de duas alterações e o máximo de sete por instrumento avaliado.