by Richard Mounce, DDS
Recently, I treated a lower bicuspid that was 25 mm long. While that might not be Mt. Everest in dental terms, it’s Himalayan. Tooth length has a number of ramifications with regard to a tooth’s clinical management and difficulty level. Teeth longer than 23 mm are more challenging than their 18 to 23 mm counterparts. Those shorter than 18 mm also have a similar but slightly different set of challenges.
Long teeth can be challenging in that 1) length determination and cone fit may not be straightforward; 2) instrumentation needs change relative to shorter teeth; 3) preventing debris blockage during instrumentation is harder; and 4) maintaining apical patency and providing adequate irrigation into the apical third is vital and can be problematic.
Working in long roots underscores the importance of working a canal slowly rather than rushing to the apex. Rapidly and forcefully driving rotary nickel titanium instruments down a canal will encourage apical debris blockage, separated files, ledges, elbow formation, loss of patency, and - ultimately - defects in final prepared canal shape. Instrumenting the coronal third first, the middle third second, and the apical third last has real value. If each successive third is completely instrumented first, the more apical third is far more predictable. The converse is also true.
I use the K3 RNT system from SybronEndo (Orange, Calif.) for its tactile control, flexibility, fracture resistance, and cutting efficiency. I only use 25 mm K3’s as I perform endodontic treatment under the surgical operating microscope. The Global Microscope (Global Surgical, St. Louis, Mo.) has been my microscope of choice for many years.
Under the scope, reading the laser markings on the K3 is easy and straightforward, if referenced against one of the remaining canal walls. The files are introduced gently, passively, and only 1 to 2 mm of dentin is engaged at any given insertion. Moving down the canal in this manner with recapitulation and adequate irrigation between RNT insertions prevents apical propulsion of the debris that could become the genesis of a future iatrogenic problem or loss of length. I use K3 from larger tip sizes to smaller and from larger tapers to smaller. This sequence is inherently “crown down” as described above. If done so with the right touch, instrumentation can be passive and progressive and diminish some of the significance of a tooth’s length.
Having an idea of the tooth’s length before access is important. Before entering a file into any canal, the clinician should determine the estimated working length. The EWL is an educated guess of the length based on the radiograph. Once a clinician gets the first rotary file to length, or the first hand file (for example, a No. 15 or 20) to the EWL, an electronic apex locator can be used. This locator can affirm the accuracy of the initial EWL. Having a clear understanding of the tooth’s length can go far toward making certain that the apical third is treated and not simply left untouched.
Many problems related to treating teeth of longer length arise from a lack of adequate radiographic evaluation. Use of digital radiography can give an accurate and adequate visualization of the whole length of the tooth. I am an advocate of the DEXIS system (DEXIS digital radiography, Alpharetta, Ga.). Errors in obtaining a diagnostic and accurate representation of the tooth can quickly exacerbate. I like DEXIS for its clarity of image, ease of use, and tools that can aid in diagnosis.
Several strategies for working with teeth of longer than normal anatomical length (greater than 23 mm) have been presented. Accurate radiographic evaluation, crown down instrumentation, copious irrigation, recapitulation, and use of a file (like the 25 mm K3 RNT system) - blended with a preoperative risk assessment of the curvature and anatomical challenges a root presents - can go far toward the efficient management of these challenging clinical entities.
Dr. Richard Mounce lectures globally and is widely published. He is in private practice in endodontics in Portland, Ore. Among other appointments, he is the endodontic consultant for the Belau National Hospital Dental Clinic in the Republic of Palau, Korror, Palau (Micronesia). He can be reached at Lineker@aol.com.