In dentistry, endodontic therapy is designed to eliminate bacteria from the infected root canal which prevent reinfection of the tooth . Root canal instrumentation is achieved by the use of endodontic instruments and irrigating solutions under aseptic working conditions. It may be accomplished by using hand-held or engine-driven (rotary) instruments. Traditionally, the shaping of root canals was achieved by the use of 0.02 tapered stainless steel hand files. In modern endodontic practice various advances in the instruments such as changes involving metallurgy, instrument taper, and the way files are used in the root canals. A new generation of endodontic instruments made from nickel-titanium has added a new dimension to the practice of endodontics.The aim of this book is bring about the understanding of different new rotary files metallurgy, design features and direction to use to achieve mechanical and biological objectives of the root canal treatment.