Separated files, busted files, broken files, and my all time favorite "Disarticulated files" (Do files actually "articulate"?!) all mean the same thing - part of the instrument has fractured off in the canal space. If you do endodontics, you know the feeling. You remove that last file and all of a sudden it is shorter than it was when it was inserted. Your heart races, your stomach churns and the perspiration starts. You pick up the endo ruler and gingerly measure just how much of the instrument has been "eaten" by the canal. You shake your head. You may even curse (under your breath). All the while, you try to formulate a way to tell you patient that things haven't gone "exactly as planned". This month's EndoFiles Fax deals with the anxiety of "file separation". Don't panic, things are not always as bad as they first appear.
File breakage is a fact of life. Are you going to break the tips of .06s .08s and an occasional .10? Yes. And if anyone says they don't, they're lying, they don't do much endo or they've never tried to negotiate into multiple foramina or lateral canals - especially on molars and in elderly patients. Those small fragments don't usually cause too much of a problem, it's the bigger fragments that cause most of the headaches. Ni Ti rotary files have been engineered with greater flexibility than stainless steel but they can break too - even at $10 a piece. Bu they need to be used wet. NEVER use them dry. Always use them with NaOCL in combination with a lubricant. Many preparations are available: RC Prep, Slide, Glide, File-Eze, ProLube are all examples that can be purchased through suppliers. These files should also be cleaned often and not allowed to accumulate debris in the flutes that increases friction. There is no such thing as too much irrigation.
Manufacturer's defects are also a factor that must be considered. Instrument technology has produced some remarkably flexible instruments but these defects do occur and some clinicians have suggested that they play a much greater role in file breakage than we may have initially thought. When you think about it, how much can you expect from a stainless steel file that costs about $1 or 2 US each to purchase? Microfractures created during the manufacturing process can propagate when the file is put under stress and can cause file breakage, even in a brand new file. When you consider purchasing the "El cheapo", gray market or No Name brand of file, remember: You get what you pay for. Is it worth it when you're working on that critical abutment?
OK the file just broke in the canal - Now what do you do?
1. Where is the fragment?
Locate the file fragment visually and/or on a radiograph. What is the position of the file? Can you see it from the access? Files located in the straight or cervical portions of canals can often be seen visually and have a reasonable chance of being removed without compromising the root dentin. Files broken past curves of the root often cannot be seen visually (even with a scope) and frequently cannot be removed because of lack of direct vision.
2. Risks vs. Benefits
Whenever we consider whether to attempt removal of a broken file, we always have to keep in mind that there will likely be compromise of root dentin (at least to some extent) during removal attempts and possibility of perforation or eventual root fracture. This is especially true with thin or very curved roots (eg./ mandibular molars.) The cost/benefit ratio has to be constantly kept in mind. Is a surgical alternative more feasible or desirable? (Especially in anterior teeth) In the case of a tooth with easy surgical access to the apex (a very curved s shaped maxillary lateral incisor, for example), it may be better to treat the case surgically. The canal is treated conventionally to the point of the file breakage and then a minimal surgical resection and retrofill is performed to ensure apical seal. Once the apex is resected, the file fragment can often be removed during ultrasonic retropreparation (from the apex). It is sometimes a better choice to sacrifice a bit of resected apical dentin rather than risk strip perforation or dentin compromise during attempted instrument removal in a conventional manner. This is especially true with critical abutments and thin roots.
3. Do You have enough magnification?
File removal requires high levels of magnification -most often with a surgical operating microscope. Using engine driven instruments blind is a sure way to ruin your chances of salvaging the tooth. I cannot emphasize this too strongly; loupes are NOT enough magnification - in all but the easiest cases. You have to be able to see what you are doing deep inside the tooth - and that most often means a scope. Ultrasonics have revolutionized our ability to work very far into the canal space- almost to the apex in many cases. Small, Titanium tips of varying lengths (Such the CPR (Spartan) and ProUltra (Tulsa) series) allow us to see along side the ultrasonic instrument while we remove small amounts of dentin and/or attempt to dislodge the broken file. That is not possible when using a contra-angle handpiece because the handpiece blocks our view (even when using surgical length or Mueller burs). In this situation, a good Ultrasonic unit, high magnification and VERY high levels of canal illumination are absolutely essential. Headlamps are often not enough, especially when using a mirror to see the canal.
4. Vital or Non-vital case
Surprisingly little research has been performed on the effects of leaving file fragments in the canal space. The minimal research that has been performed suggests that it does not affect the prognosis in many cases. (Crump and Natkin JADA 1970). More recent in vitro dye study research (Saunders, Eleazer et al JOE 30:3: 177-179 March 2004) suggested that: (a) separated instruments do not play a large role in sealing ability of the obturation material and (b) success might be more affected by lack of coronal seal and residual apical irritants present beyond the level of the broken instrument. But this was an "in vitro" study and it might not be clinically relevant. The general consensus appears to be that file breakage in vital cases seems to result in better outcomes than in non-vital cases but this empirical opinion is not supported by any published research, to my knowledge. Obviously, if there is sterile tissue apical to the file, it is reasonable to assume that there is less of chance that the case will become symptomatic compared to those cases with infected, bacteria filled canals. The determining factor (as with all endodontic cases) appears to be the critical "threshold" of bacterial reduction. If enough of the canal has been cleaned then perhaps the bacteria level has been reduced to the point where a few mms of unfilled canal might not matter- IF the file fragment and rest of the canal seal the coronal aspect of the canal system. (Emphasis mine- ed.) However, we all have cases that appear to be well cleaned and filled (radiographically) yet, fail to heal or go on to develop lesions. (We also see apparently poorly done endodontics that shows no pathology and is asymptomatic!) While there may be some question as to when to attempt remove broken files, there is no doubt that optimal results are best obtained when they can be removed with minimal damage to the tooth. This allow for optimal canal cleaning, shaping and obturation.
5. Bypass vs. Remove
One strategy of dealing with broken files is not to attempt to remove them at all; it involves bypassing the broken fragment and incorporating the broken file into the canal obturation. This is the strategy that I used for many years before getting a scope. It can work very well, especially when the file that is broken has large spaces between the flutes that can be bypassed with a small .06 or .08 file. But this process is very time-consuming and requires a lot of patience. You must never become frustrated and never rush. You can easily go through dozens of .06 or .08 files before regaining patency. At that point the rest of the case is also done with hand files, mostly with a "pull out/reaming" motion. (Never try to use one Ni-Ti rotary file to remove another broken file!) Carefully examine the path of file insertion before placing the next file. Be careful not to place larger size hand files directly over the file fragment - you can easily jam the embedded file deeper into the canal, plugging the canal again. At that point you will have to try to regain patency and go through the entire file series again. (Frustration!!). Perseverance and determination are necessary. END PART 1