Curving Hand Files: When, How and Why?

by Rich Mounce, DDS

Hand files have great value for me in both orthograde root canal therapy and orthograde retreatment. For me, hand files are used primarily as negotiators, patency files and glide path creators to allow subsequent rotary nickel titanium files to be used safely. Pre-curving hand files has become a habit that is second nature and automatic. Said differently, I pre-curve all hand files regardless of how radiographically straight the canal may appear. It must be realized that all canals are curved to some degree, be that in a mesial to distal direction, buccal to lingual or some three dimensional blending of the these two curvatures. Pre-curving hand files allow easier negotiation of canal curvatures in virtually any type of clinical situation, irrespective of whether the given canal has been entered or retreated before or a virgin canal. For bypassing ledges and apical blockages especially, pre-curving a file is essential to allow canal negotiation if it is possible.

A clear distinction must be made of the two most common curves that are placed onto hand files. One is the J-bend at the tip of the hand file (most easily placed by the EndoBender pliers (SybronEndo, Orange, CA, USA) and the other is the broad gentle curve that can be made with one’s fingers. The J-bend encompasses approximately a 3-4mm curve at the tip of the file, while the remaining file length is relatively straight. The curve is never acute enough that the flutes are deformed or kinked. This type of bend is most often used in the aforementioned bypassing of a ledge, canal blockage or to negotiate delicate apical anatomy. Broad wide sloping finger-created file curvatures are usually used in virgin canals and perhaps canals that have no existing iatrogenic event.

Regardless of the given curvature, placement of either of these curvatures, where appropriate, will often allow the curved file to traverse the canal where a straight canal will not. The canal is curved, the file should be curved as well to match it and allow maximum tactile sense and advancement. As an aside, I use a substantial number of hand files in virtually all cases, even if the tooth is relatively simple. I do not sterilize hand files for a second use. Cutting efficiency is reduced and time is lost using an inefficient instrument because it is dull or straight. Hand files will perform with the greatest efficiency possible if used once and disposed of immediately. For an average tooth, I will use at least one pack each of 6-10 K files, all pre-curved before entry into the canal. The efficiency and safety gained from using sharp files far outweighs the costs involved.

I welcome your questions and feedback.

Dr. Richard Mounce is in private endodontic practice in Portland, OR. Dr. Mounce is the author of a comprehensive DVD on cleansing, shaping and packing the root canal system for the general practitioner. The material is also available as audio CD’s and as a web cast pay-per-view.