The last decade has been witness to phenomenal growth in endodontic technology. The introduction of these new technologies has resulted in endodontics becoming easier, faster and most importantly, better. NiTi alloys overall are softer than stainless steel, are not heat treatable, have a low modulus of elasticity (about one fourth to one fifth that ofstainless steel) but a greater strength, are tougher and more resilient, andshow shape memory and superelasticity. The latter two properties arethe main reasons why NiTi alloys have succeeded in endodontics. Thepurpose of this article is to review the design features of different rotary instruments used for pulp space preparation. Important mechanical features include thevariability of taper, rake angle, cross-sectional geometry, tip configuration, design of blades, helical angle and pitch. These design features influence flexibility, cutting efficiency and safety. In this review, design features of commonlyused NiTi rotary systems are summarized.
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