November 1, 2006
by Richard Mounce, DDS
Recently, I was on a technical scuba diving training dive where a serious accident occurred. The situation was caused by a lack of communication and a faulty dive plan. It was completely preventable. While not potentially fatal, in an endodontic context, the vast majority of problems that bedevil clinicians are also, very fortunately, completely preventable.
Prevention begins with case assessment, one aspect of which is a determination of the degree of difficulty from a technical standpoint as well as the patient’s cooperation. Technical determination of the degree of difficulty is multifactorial. Technical challenges include: location of the tooth in the mouth, presence and type of coronal restorations, degree of bone support, tissue contours, calcification, number of roots, length of roots, curvature at all canal levels, visibility of the pulp chamber radiographically, limitations to opening, complexity canal configuration, amongst other such factors.
Determination of the presence of these various factors requires excellent visualization of the tooth through radiographs, most often from multiple angles: mesial, distal and straight on. Digital radiography facilitates such radiographic evaluation easily and practically. The author is a strong advocate of the DEXIS sensor and platform (DEXIS, Alpharetta, GA) due to image clarity, ease of use and system reliability. Via digital radiography, the ability to take multiple radiographic angles rapidly and efficiently and manipulate these images with software is a quantum leap in capability relative to paper film.
Assessing potential risks such as those above should be done by intention every time a tooth is considered for treatment. If the degree of difficulty is found to be significant and requires more time, equipment, skills, visualization, etc than the clinician has at that moment in time, the patient should be referred.
Once the potential risks are assessed, it becomes necessary to plan and sequence the treatment to avoid the problem. Each separate potential iatrogenic event should be thought through to its complete solution. Again, in a diving context, technical divers anticipate all the known variables on any given dive and develop a solution, which is usually written down and carried throughout the dive. For example, if ones dive computer goes out into a dive, having a back up decompression schedule can go far to bringing the diver back alive and unharmed, the reverse is true. Dives are never started with known variables unaccounted for.
Managing various potential iatrogenic events not only require this comprehensive degree of forward thinking but that also the clinician should be open minded to allow the possibility that circumstances might change once the tooth is opened. For example, after access, it might be found unexpectedly that, at the orifice level, the canals exit the pulpal floor at an acute angle making initial negotiation difficult.
Having the ideal visualization through a surgical operating microscope (SOM) has significant value to deal with such clinical conditions. The author uses the Global SOM (Global Surgical, St. Louis, MO) due to its superior visualization, lighting and magnification.
The vast majority of iatrogenic problems can be avoided by maintaining canal patency, the reverse is true. Rotary nickel titanium (RNT) files, for example, generate a great deal of dentin chips which can be pushed apically if they are not irrigated away and held in suspension. If the tooth is vital, ideally a viscous EDTA gel (File-Eze, Ultradent, South Jordan, UT) should be placed in the chamber to hold the pulp and such dentin chips in suspension while they are irrigated. Failure to use such a gel can easily lead to blockage of the canal, as pulp might otherwise be pushed apically. Having a lubricating and emulsifying gel like File-Eze in the chamber, while negotiating the orifice of a calcified canal, can go far toward avoiding canal blockage.
Next, and importantly, using small K files first such as 6’s, 8’s and 10’s to gain a minimal canal diameter and make certain the canal is open and negotiable early in the management of any given canal third has significant value, especially if the canal is not wide open and easily traversed. Rushing into a canal with RNT files without first negotiating the canal with small K files that are precurved can easily accentuate blockages and other iatrogenic issues. An ideal instrument for creating such a small J bend in a hand file is the EndoBender pliers (SybronEndo, Orange, CA). The small files can be used in several ways. First, they can function as scouting files and negotiators. Second, they can act to create a glide path that can open the canal to at least a size 15-hand K file before using RNT files. Finally, they can be used to recapitulate the canal. Recapitulation refers to the ability to pass a small hand K file back through the canal at any given moment in preparation to assure that the canal is open and negotiable.
After the canal is open and negotiable to at least a 15K file, RNT files can be used, most ideally in a crown down manner. Crown down in this context means files are used from larger tapers to smaller and from larger tip sizes to smaller. In such a sequence, each successive file is introduced slightly more apical to the last. If the touch of insertion is gentle, slow and passive during insertion and only 1-2mm of the canal wall is engaged for cutting at any given time, chances for fracture are remote.
In a clinical example, if an orifice is narrow and calcified or the canal exits the pulpal floor at an acute angle, gaining a glide path to the coronal and middle third of the canal first and then introducing orifice openers can have value in the prevention of all types of iatrogenic RNT outcomes. In other words, after a glide path is created, then and only then is it safe and advisable to use a RNT orifice opener such as the K3 Shaper files (SybronEndo, Orange, CA). The Shaper should be entered gently, passively and only as far as it can be inserted without putting more pressure on the file than would be used with a #2 lead pencil. Canal dependent, generally, insertion progresses from larger tapers to smaller and from larger tip sizes to smaller. Shaper insertion, if progressing from .12 taper to .10 to .08, may, in a significant curvature coronally, require multiple insertions to remove the cervical dentinal triangle, shape the coronal third, allow adequate access to the middle third and provide enough physical space for irrigating solutions to reach the middle third of the root.
In all of these insertions, the shapers should only be advanced as far as they can without being forced to any arbitrary position. Pushing the Shaper, or any RNT file forward where it does not want to go easily, is the harbinger of a transported canal and/or possibly a separated file.
In summary, the prevailing concept though is that the clinician should clearly see the potential problem before it exists if possible and have a clearly defined strategy so as to avoid an otherwise preventable problem. As in scuba diving, anticipating the problem and preventing its emergence is always preferable to having to treat the aftermath of its occurrence.
Dr. Mounce lectures globally and is widely published. He is in private practice in endodontics in Portland, Oregon, USA. Amongst other appointments, he is the endodontic consultant for the Belau National Hospital Dental Clinic in the Republic of Palau. Korror, Palau (Micronesia). Dr. Mounce can be contacted at Lineker@aol.com.
Dr Mounce has no commercial interest in any of the products mentioned in this article.