Reciprocating History
Canal curvature has always introduced complexity into canal preparation. The “balanced force
concept”, i.e. small clockwise and counter-clockwise movements, was developed over a period
of twelve years, and proposed in 1985 by Roane as a means of overcoming the curvature influence. Using the balanced force technique, it is possible to shape curved canals with larger diameter hand instruments. The use of stainless steel hand instruments, however, is time-consuming and strenuous, and there is a high frequency of preparation errors.
The development of continuous rotary preparation with nickel-titanium instruments solved some
of these issues, although it is still necessary to use several hand and rotary files in different steps,
and there may be a lengthy learning curve before proficiency can be achieved.
Inspired to find a simpler and more convenient safe way to successfully prepare a root canal,
Prof. Ghassan Yared, who was at that time Professor of the Endodontic Undergraduate and
Graduate Programmes at the University of Toronto, started researching and testing mechanical reciprocation with nickel-titanium instruments.
In 2008, he published a clinical article on canal preparation using only one NiTi engine-driven instrument and joined together with to develop RECIPROK, a system specifically for use in reciprocation.