SEM analysis of endodontic instruments from a Ni-Ti rotary system was assessed, before and after using them, considering their defects and deformations. Twenty Twisted File®, BioRąCe®, Mtwo®, and EndoWave® instruments were micrographed at 190× magnification. The files were washed and micrographed again to view alterations as to the presence or absence of irregular edges, grooves, microcavities, and scraping. Simulated root canal preparations were performed using these instruments. The instruments were cleaned and received a microscopic analysis after being used five times. After analysis tests were tested using Fisher's exact test and Kappa to evaluate the concordance among examiners. There was a statistically significant difference with respect to deformations between Twisted File® and other instruments (p < 0.05). There was no statistically significant difference in strains between the other groups (p > 0.05). All Twisted File® instruments showed the same defects; however damage were lower than those found in BioRace® and Mtwo®. The Endowave® did not show the same defects. In accordance with the data we conclude that the presence of defects was higher in Twisted File® instruments as the instruments and BioRace® Mtwo® brand, the defect rate was smaller and Endowave® instruments had no defects. Regarding the presence of wear after five uses among the groups all instruments showed changes in their cutting blades.

RESUMOIntrodução: A secagem do canal radicular após o preparo químico-cirúrgico com cones de papel absorvente é importante, pois, é imprescindível a obtenção de uma superfície sem umidade. O objetivo desta pesquisa é comparar os pesos de dentes humanos extraídos, considerando dentes úmidos, secos com papel absorvente e estufa. Método: Utilizaram-se 30 dentes humanos extraídos nos quais se executaram o acesso à câmara pulpar, à odontometria e o preparo químico-cirúrgico e, em seguida, foram mergulhados em frascos individuais contendo água destilada, por uma semana. Após isso os dentes foram pesados em balança analítica digital com os dentes umedecidos (Pu), a segunda os dentes secos com cones de papel absorvente (Pa) e depois secagem dos dentes na estufa durante 12 horas a 50 0 C (Pe) e pesagem. Resultados e conclusões: Ao fazer a comparação entre dentes secos com papel absorvente e secos na estufa, o teste "t" de Student mostrou que os pesos em grama dos dentes secos na estufa são menores do que os secos com papel absorvente ("t" = 6,3992) com P=0,0001. Concluiu-se que os dentes apresentaram ordem decrescente de peso: dentes umedecidos, dentes secos com cones de papel absorvente e dentes secos em estufa e, portanto, a secagem dos dentes em estufa mostra-se como de suma importância para a remoção maior de líquidos do sistema de canais radiculares.Descritores: Endodontia • Preparo de canal radicular • Absorção. ABSTRACT Introduction:The drying of the root canal after chemical-surgical preparation with absorbent paper cones is important because it is essential to obtain a surface free of moisture. The aim of this study is to compare the weights of extracted human teeth, whereas teeth wet, dry on paper towels and oven. Method: Were used thirty extracted human teeth which were carried out access to the pulp chamber odontometry and chemical-surgical preparation, and then were immersed in individual bottles containing distilled water for one week. After that teeth were weighed on an analytical balance with digital teeth moistened (Pu), the second teeth dry with absorbent paper cones (Pa) and then drying the teeth in the oven for 12 hours at 50 0 C (Pe) and weighing. Results and conclusion: In making the comparison between teeth dry with absorbent paper and dried in the oven, the "t" Student test showed that the weights in grams of dry teeth in emissions are lower than those dried with absorbent paper ("t" = 6.3992 ) with P = 0.0001.It was concluded that the teeth, in descending order of weight of wet teeth, teeth dried with absorbent paper cones teeth and dried in an oven, and therefore the drying kiln of the teeth of the utmost importance to remove most of the root canal fluid system.