#3 partially necrotic tooth with a severe curve greater than 90° in the mesial root. Formed the glide-path with a number 10 hand file and established working length. Then used the EdgeEvolve rotary files. Took a 17/04 filed to work in length. Then took each successive file to the working length 20/04 25/04 30/04 35/04 40/04. Then increased the taper with a 40/06 40/08 40/10. What's obvious is how well the 40/10 was able to negotiated the 90 deg curve in the mesial root. But what's more subtle is how well it kept the apical anatomy in the palatal root and the slight S curve in the distal root. That's innovation!