root canal preparation is performed with the use of endodontic instruments and auxiliary chemical substances , seeking to achieve cleaning , shaping , and disinfection , in order to fill the root canal later . the use of rotary nickel  titanium ( niti ) instruments has increased considerably due to their safe use , when used in accordance with the recommendations of their manufacturers , enabling the canal to be prepared more quickly , when compared with manual instruments , and even with better quality , in case of canals with severe curvatures . cutting dentin is an important step during root canal preparation , as it is necessary to remove contaminated dentin and shape the canal to create conditions for it to be filled . due to elasticity , one could suppose that the cutting efficiency of niti instruments would be lower than that of steel instruments , because they undergo deflection or bend during contact with the dentinal surface . however , studies have shown that niti instruments have a more efficient cutting capacity when compared with steel instruments . although there have been significant advancements in rotary instrumentation , the influence of the rotary cutting instrument blade design is still controversial , with respect to the efficiency of their cleaning capacity . their cutting capacity results from a complex inter - relationship between different parameters , such as , the sectional design of the instrument , radial lands or active cutting blades , metallurgical properties,[911 ] and treatment of instrument surfaces with the incorporation of ions . the aim of this study is to evaluate the cutting efficiency of different rotary niti instruments ; that is , k3 , niti tee , profile , and quantec . forty instruments with taper size .04/25 were tested and divided into groups according to their brands ( n = 10 ) : k3 ( sybron - endo , orange county , ca , usa ) , niti tee ( sjding sendoline , kista , sweden ) , profile ( dentsply maillefer , ballaigues , switzerland ) , and quantec ( analytic endodontics , mexico ) . the characteristic of each instrument is shown in table 1 . different instrument designs forty acrylic resin blocks ( dentsply maillefer , petrpolis , rj , brazil ) , with simulated canals were used in this study , and for each block , a rotary instrument was used . the canals initially had a diameter of a caliber 10 instrument , having been manually prepared in this manner , up to a caliber 20 instrument , to their full extent , using the crown - down technique , under irrigation with 5 ml distilled and deionized water , at every change of instrument . before any intervention , the blocks were washed in an ultrasonic vat , with distilled water and detergent solution , in the proportion of 10 : 1 for 20 minutes , dried with air jets , and placed in an oven at 60c for 48 hours . instrumentation of each block with the analyzed instruments was performed by the same operator using a tc 3.000 engine ( nouvag , tcm endo , goldach , switzerland ) at a constant speed of 300 rpm . the instruments were introduced into the canal , inundated with 5 ml distilled and deionized water , until the working length was reached , which was 0.5 mm short of the total working length of the simulated canal . each instrument remained at the working length for 5 seconds , and was then removed , while it was still running . the procedure of washing and drying the acrylic resin blocks was performed before the instruments were used , was repeated after instrumentation , to determine the final weight ( fw ) , and also performed before the use of 04/25 instruments . the cutting efficiency of each instrument was measured by means of measuring the acrylic resin block mass before and after using the .04/25 instruments ( fw - iw ) , with the aid of a precision digital analytic balance ( bel engineering , italy ) , which was due to the quantity of material removed by instrumentation . after obtaining the results , having verified the normality of the sample , the analysis of variance ( p < 0.05 ) was performed . forty instruments with taper size .04/25 were tested and divided into groups according to their brands ( n = 10 ) : k3 ( sybron - endo , orange county , ca , usa ) , niti tee ( sjding sendoline , kista , sweden ) , profile ( dentsply maillefer , ballaigues , switzerland ) , and quantec ( analytic endodontics , mexico ) . the characteristic of each instrument is shown in table 1 . forty acrylic resin blocks ( dentsply maillefer , petrpolis , rj , brazil ) , with simulated canals were used in this study , and for each block , a rotary instrument was used . the canals initially had a diameter of a caliber 10 instrument , having been manually prepared in this manner , up to a caliber 20 instrument , to their full extent , using the crown - down technique , under irrigation with 5 ml distilled and deionized water , at every change of instrument . before any intervention , the blocks were washed in an ultrasonic vat , with distilled water and detergent solution , in the proportion of 10 : 1 for 20 minutes , dried with air jets , and placed in an oven at 60c for 48 hours . instrumentation of each block with the analyzed instruments was performed by the same operator using a tc 3.000 engine ( nouvag , tcm endo , goldach , switzerland ) at a constant speed of 300 rpm . the instruments were introduced into the canal , inundated with 5 ml distilled and deionized water , until the working length was reached , which was 0.5 mm short of the total working length of the simulated canal . each instrument remained at the working length for 5 seconds , and was then removed , while it was still running . the procedure of washing and drying the acrylic resin blocks was performed before the instruments were used , was repeated after instrumentation , to determine the final weight ( fw ) , and also performed before the use of 04/25 instruments . the cutting efficiency of each instrument was measured by means of measuring the acrylic resin block mass before and after using the .04/25 instruments ( fw - iw ) , with the aid of a precision digital analytic balance ( bel engineering , italy ) , which was due to the quantity of material removed by instrumentation . after obtaining the results , having verified the normality of the sample , the analysis of variance ( p < 0.05 ) was performed . the means and standard deviations of mass loss from the acrylic resin blocks during instrumentation are shown in table 2 . the results test showed that the acrylic resin blocks prepared with k3 , niti tee , and profile instruments presented the greatest mass loss , showing no statistically significant difference among them ( p < 0.05 ) . the lowest mass loss was found in the blocks prepared with quantec instruments ( p < 0.05 ) . biomechanical techniques for preparing root canals have evolved from manual methods to rotary techniques employing nickel - titanium instruments . using niti rotary instruments for root canal instrumentation has enabled clinicians to create consistently tapered preparations more predictably and efficiently , while minimizing procedural mishaps , especially in curved canals . the greater cutting capacity of k3 instruments , as compared to quantec , is possibly due to the unique cross - section design of k3 , which has a positive angle of inclination for greater cutting efficiencies and ample radial lands and relief at the posterior extremity of the blade , to reduce friction . unlike quantec , which has two cutting blades thus , the k3 instruments present excellent cutting capacity , as the debris resulting from its cutting action is easily displaced from the working area , and removed by the unique helical angle of this file . schafer and florek conducted a study in which they compared the efficiency of the k3 system and k - flexofile files for smear layer removal . the authors obtained excellent results with the k3 system , although complete root canal cleaning had not been obtained . the niti tee instruments showed a cutting efficiency similar to that of the k3 and profile instruments , and superior to that of the quantec instruments . these instruments had a rounded , non - cutting tip and a positive cutting angle , without the presence of radial land . in addition , they had two 90 cutting blades that caused grooves ( scratches ) on the canal wall , which allowed the removal ( drainage ) of dentin scrapings and other debris resulting from instrumentation . jodway and hlsmann , comparing k3 and niti tee instruments , observed that they were safe as regards their use , and had similar root canal cleaning and shaping capacities . the good cutting capacity of profile instruments could be attributed to the u - shaped , cross - sectional design , with radial lands and central parallel core . with a neutral and negative angle of inclination thus , the debris is transported up to the coronal portion and effectively removed from the root canals . some studies have indicated that the positive cutting angle improves the cutting efficiency of the instrument . nevertheless , this is not the only determining factor for the cutting capacity of instruments , as the profile instruments , which have a negative cutting angle , presented the same efficiency as the k3 and niti tee instruments and greater efficiency than the quantec instruments , fitted with a positive cutting angle . quantec instruments have two cutting blades and a helical angle combined with spaces created in the instrument , which progressively increase as they withdraw from the cutting edge , creating a larger area of escape and allowing rapid debris removal from the canal . thus , when activated , the instrument does not make a thread ; therefore it does not stick to the canal walls , diminishing the risk of instrument fracture , because it has a less aggressive cut , which possibly reduces its cutting power , as it presents the lowest cutting efficiency among the studied instruments . the cutting capacity of endodontic instruments is an important factor to evaluate , as the preparation of dentinal walls , by eliminating contamination and shaping endodontic space , is an important step in successful endodontic therapy . however , after debridement , in some oval and flattened root canals , the walls may not be prepared , irrespective of the debridement technique , leaving a smear layer , debris , and unprepared root canal walls . this complex anatomy may be considered as one of the main challenges in controlling the root canal infection , because the pulp tissue as well as the root dentin may conceal toxins and microorganisms , compromising the final result of endodontic treatment . the use of endodontic irrigant solutions and ultrasound agitation , or even the association of endodontic instruments are ways that may improve the cleaning of roots that have a complex anatomy . from the results of the present study it can be concluded that k3 , niti tee , and profile instruments present a better cutting efficiency than the quantec instruments .