clinical report _ shaping system I as the plane of motion, then the carpenter would be scratching the wood, not cutting it. The same applies to planing an internal root surface. In addition to engaging the walls of the canal less and cutting dentine more efficiently, the K-reamer is more flexible than the K-file because the fewer number of flutes produces a less work 1. even greater flexibility because of its thinner cross-sectional diameter; 2. less engagement along length; 3. the inclusion of two vertical columns of chisels that cut effectively in both clockwise and counterclockwise motion; 4. the inclusion of a cutting tip; and 5. a space for dentinal debris. Fig. 3 Fig. 4 Fig. 5 hardened instrument. Greater flexibility, less engagement and more efficient planing of the canal walls give the dentist an improved tactile perception, providing the ability to distinguish between a tight canal and the encountering of a solid wall. This is all very well, but the problem is that the vast majority of dentists are still being taught to use K-files if not for the entire preparation of the canal at least for the glide path so that rotary NiTi can be used with greater safety. The K-file, an instrument not well designed for its function makes glide-path creation a challenge. It also motivates dentists to use these instruments for as short a period as possible so the more efficient rotary NiTi instruments can be used. There is a bit of a conundrum here. Inefficient K-files are being used so that the more efficient rotary NiTi can be safely employed. If instruments far more efficient than K-files could be employed, the need to switch to rotary NiTi would be reduced. Furthermore, rotary NiTi has its own problems, including unpredictable separation, the need for single usage and great expense. The way to solve this conundrum is through relieved reamers used either with a tight watch-winding motion or in a 30° reciprocating handpiece. This brings a vast improvement and nullifies the need for rotary NiTi. While K-reamers are vastly superior to K-files in the shaping of canals, relieved K-reamers, otherwise known as SafeSiders, are measurably superior to nonrelieved K-reamers. The reasons for this superiority include the following: These factors produce an even better tactile perception, giving the dentists precise knowledge regarding not only when a solid wall is being encountered, but also whether the canal is round or oval. Why is the dentist better off using an instrument that clearly tells him when he/she is encountering a wall? The more precisely the instrument tells the dentist what the tip of the instrument is encountering, the easier it is for the dentist to know when to bend the instrument at the tip to negotiate around any blockage that he/she comes upon. If a dentist doesn’t know a wall has been encountered, he/she is more likely to keep applying increasing vertical force as the instrument is twisted. The result is often an artificially made canal with the original canal with tissue in it untouched or at best inadequately cleansed. Once the dentist has negotiated around the blockage manually, he/she may reattach the relieved K-reamer to the reciprocating handpiece for quick and effective apical negotiation. It usually takes no more than a few seconds to achieve apical length when the canal is patent. The relieved reamers have two requirements to achieve rapid non-distorted shaping. First patency must be maintained. The way to do this is by extending the instrumentation 0.5 mm beyond the constriction through a #25. As long as this is done, patency will be maintained and distortion will not occur. The other requirement is either the use of a tight watch-winding motion or use in a 30° reciprocating handpiece. This particular roots 4 _ 2009 I 13