The present invention relates to a reamer with improved blade for Ni—Ti instruments for endodontic use, said reamer comprising a not active tip (3, 13, 113) and at least one blade (2a, 2b 12a, 12b, 12c 112a, 112b) having, at least partially, a substantially spiral development and comprising a crest (4a, 4b 14a, 14b, 14c 114a, 114b) where a plurality of undulations (5a, 5b 15a, 15b, 15c 115a, 115b) is formed, such that said plurality of undulations (5a, 5b 15a, 15b, 15c 115a, 115b) causes a deceleration or an interruption during advancing motion of said reamer when using said reamer for enlarging a channel.
