James L. Gutmann, DDS, FACD, FICD, FADI
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The advent of NiTi instruments for cleaning and shaping of the root canal system has been a tremendous boon to the delivery of quality, predictable, endodontic treatment. The developments seen in these instruments, such as the metallurgy, the helical angles, and dynamic cross sections, have been dramatic in enabling clinicians to achieve their goals; however, before these instruments can be applied in any given root canal system, a pathway or glide path must be created.
The need for a pathway as it relates to the application of rotary NiTi instruments has been verified. Previously, clinicians were limited to small stainless steel K-files (.06 to 15 or 20) for this purpose. This process often resulted in canal blockage, deviation into the canal wall (ledging or false canal), apical zipping or tearing, or a separated instrument.
This occurred because the stainless steel file tended to deviate from the canal confines based on clinician use and the impact of remaining tissue and/or calcifications in the uncharted canal space.
NiTi welcomes PathFile
Today, the family of NiTi instruments welcomes PathFile™ (DENTSPLY Tulsa Dental Specialties). PathFile has virtually eliminated the problems encountered when trying to create an acceptable and predictable pathway prior to the use of larger or variably tapered NiTi instruments.
Designed and fabricated on NiTi technology, which uses strength, flexibility, and memory, this new file embraces the value of a minimally tapered instrument (.02) in a rotary manner, while it glides through the canal space to create the desired pathway in an effortless, safe manner.
Its smaller taper gives it increased flexibility and more resistance to cyclic fatigue. This means less canal transportation, more flexibility, and faster instrumentation time. The benefits include preservation of the original canal anatomy, no transportation of the apical foramen, and no ledges if they are used short of the desired working length.
The instruments are available in three sizes at a .02 taper — sizes 0.13, 0.16, and 0.19. They are used at a constant speed of 300 rpm with light pressure and gentle movement until the desired apical position is achieved. If resistance is felt, the instrument is removed and a small K-file is inserted to ensure patency. This may occur if pulp tissue is blocking the canal or if a pulp stone has been loosened from the canal wall. Subsequently, the canal is irrigated and the original pathway with the small K-file is verified prior to returning to the use of the PathFile.
The basic sequence of application in teethwith small and/or curved canals is as follows:
- Establish an initial pathway with a very small K-file prior to using the PathFile. Use a .06 to .10 depending on the original size of the canal. Use in a gentle, teasing manner concomitant with copious irrigation.
- Establish the working length with a No. 10 K-file using an Apex Locator or radiographs.
- Apply the PathFile 0.13 to the working length; use copious irrigation.
- Apply the PathFile 0.16 to the working length; use copious irrigation.
- Apply the PathFile 0.19 to the working length; use copious irrigation.
- Confirm the working length with a No. 15 K-file, an Apex Locator, or quality radiograph.
- Any NiTi rotary system can now be used to clean and shape the canal in a safe manner.
For teeth that have larger or straighter canals, establish a pathway by determining the working length with a No. 15 K-file, then applying the 0.16 and 0.19 PathFiles, or even going directly from the working length, when the No. 15 K-file is loose in the canal, to the 0.19 PathFile.
If a size No. 20 K-file can go easily to the desired apical position, then the use of a PathFile will not be indicated. In teeth with larger canals, the PathFile may not be of value in the coronal two-thirds, but may very well help the clinician open the delicate and challenging apical third of the canal in a safe manner.
The ability to establish a pathway in the root canal in a safe and straightforward manner is available to all clinicians through the use of the PathFile. Using the PathFile for those difficult-to-manage canals opens up a whole new world of successful applications of NiTi technology.
James L. Gutmann, DDS, FACD, FICD, FADI, is Professor Emeritus in Restorative Sciences, Baylor College of Dentistry, Texas A&M University Health Science Center in Dallas. He is a Diplomate of the American Board of Endodontics and past president of the American Association of Endodontists. He is presently in private practice limited to endodontics in Dallas. Reach him at firstname.lastname@example.org.