Evaluating apical deviation and abrasion on K3 and ProTaper files

Objectives: Apical deviation and abrasion were evaluated after simulation of clinical usage. Methods: Twenty-six mesovestibular roots from recently extracted human upper first molars, with a mean angulation of 40°, were divided into two groups, A (K3) and B (Protaper). Instruments were analyzed by scanning electron microscope (SEM) before instrumentation, after seven and 13 uses. Root were pepared according to factory instructions, and apical deviation evaluated by double radiographic exposure,the distace between inictal and final positions of the files having been meansured by means of Imagetool. Results: Mean deviation for groups A and B were 0.248mm and 0.158mm respectively, no statistical difference (p<0.5) having been detected by the Student-Newman-Keuls test. The following criteria were used for the evaluation of abrasion: defets (lengthening, shortening and reversion of spires, presence os craters), cracks and fractures. Under SEM, metalic slivers were often observed on spire crests, in addition to slanted grooves, in both groups before application. After seven applications, in the K3 system,files 25/08 and 25/10 showed cracks in the body os the active portion, leading to a ductile frature on the latter after the eighth aplication. In the Protaper system, after sevem applications, cutting edge angle defects and cracks were present in all instrumens, with a rupture fracture in F3 at the 13th application. In the end, craters were observed along tghe active portions of both systems. Conclusions: Ahead of the data, one concludes that both the systems suffer apical deviation and abrasion, being most of the defects found in the Protaper system.