[Single file endodontic treatment: a new era?]

Root canal shaping is one of the key stages of endodontic treatment, when performed properly, it is a predictive factor for the outcome of the treatment. It is critical for an adequate disinfection, which is more effective at the completion of a proper shaping procedure. The introduction of NiTi instruments into endodontic greatly improved the root canal shaping and decreased the time required for a full mechanical preparation. Over the last 2 decades, numerous attempts have been made to further improve the procedure with a wide range of rotary NiTi endodontic file systems. All these systems require several subsequent files. Recently, three different concepts of single-file systems have been introduced: 1. The single file reciprocating working motion: it consists of a reciprocating counterclockwise and a clockwise motion. This reciprocal motion reduces torsional loads thus, allows safer instrumentation with less working time. 2. Single-file instrumentation using full 360 degrees rotational movement to be used in a full clockwise rotation. Some of these files also have an Anti Breakage Control (ABC) which protects from catastrophic procedural malfunction by unwinding of these file before breakage. 3. The Self-Adjusting File (SAF) which is a thin-walled, pointed cylinder, hollow nickel-titanium endodontic file that is elastically compressible into a root canal that has been previously negotiated using a #20 hand file and can widened inside it, facilitating removal of debris and dentin from the canal wall. The file conforms to the canal shape and permits irrigant flow through the file. The SAF works in a combined vibrating and partial rotational motions, and circumferentially simultaneously enlarging and irrigating the canal. The objectives of these new approaches is to reduce the working time and cost and improve safety of the shaping procedure, and suggest to have a lower procedural errors incidents. Few studies, conducted in the recent years, using these new instruments demonstrated an excellent shaping and centering ability of these new systems. They produce smooth tapered canal preparations with reproducible results, even when performed by less experienced practitioners. As mentioned above, these new techniques appeared to be promising, but further fundamental clinical and laboratory studies are needed to confirm their abilities.