Figure 4

Representative SEM examination of fractured instruments. Left column (a-e) shows original, and right column (f-j) shows counterfeit products of rotary files. First and second line shows low and high magnification of lateral view of instruments respectively. The remaining three lines shows fracture surfaces of the test instruments. Despite the similarities between instruments, differences in cross sectional design, and morphology characteristics of fracture surface could be observed from the SEM images. The characteristic surface pattern with dimples, and cones produced by ductile rupture are observed at the fracture plane with (e) the ProTaper Universal and (j) the counterfeit one. Figure e/d comparison shows the fracture surface of a counterfeit instrument with much shallower dimples, which indicate less plastic deformation. Absence of circular abrasion marks indicates the flexural fatigue failure.