Block Management: Clinical Technique

I would like to welcome each of you to another blog session.  As many of you might anticipate, I receive an enormous number of emails per week.  It’s in the hundreds and hundreds, and my staff can fortunately answer many of these, but I am left, Cliff Ruddle, to answer the more technical ones. 

Some of the email questions aren’t very conducive to email answers.  This is because within each question, sometimes there are multiple sub-questions.  So, an email is restrictive; it doesn’t allow for a dialogue.  So, some of these email questions are best answered by Cliff blogging the answers.  So, I am going to take a single question that came in from a colleague in India and he has been a good, good friend and, I mean by friend, I met him in India and I know he’s doing an enormous amount to make a difference for Indian endodontics.  He’s very sincere and he emails me on a regular ongoing basis.  Sometimes I can answer his questions in a response email but in this particular instance, I’ve already emailed this colleague and promised that I would get back to him with a blog.  

Here we go.  When I answer his question, I’ll paraphrase his questions because sometimes we have to be respectful of colleagues in other countries because their English isn’t as proficient as perhaps I’m accustomed to, just like when I go to their countries, my Indian is woefully lacking and non-existent.  So, I’ll try to paraphrase the question, but it will be the spirit that it was asked.

The colleague’s first question was… He’s concerned about block management and ledges, and that’s another whole issue, but his main question is that there could be a collagenous stump of tissue in the narrowing cross-sectional diameters of the canal apically and what would be the best way to get through this obstruction?  This impediment?

Well, I have taught nonsurgical retreatment for many, many years.  Many have taught it as well, around the world.  Perhaps I’ve been identified a little bit more than most in that I have made the only, still to this day, DVD series that deals with all facets of nonsurgical retreatment.  I have contributed many chapters in textbooks around the world and given many lectures at congresses and so, by default, I kind of get a lot of retreatment questions.  As a perspective, even by the year 1990, over 90% of my practice was focused on nonsurgical retreatment. 

Let me be more specific.  Out of every 1,000 people that came and saw Cliff Ruddle, 900 had had previous endodontics.  So, even going back several decades, retreatment was the normal fare and I’ve learned a lot from retreatment.  Some of it was discoveries, very little of it was read in textbooks, or seen in other lectures.  And of course, as the field’s evolved, much of this has been recorded and written, and now it’s available to virtually anyone. 

So, let’s get started on the block.  I have taught for many, many years that one of the most important things about a block is after you regain access and remove the provisional, you irrigate with sodium hypochlorite, full strength, and then see if you can slide a 10 file to the working length, because obviously somebody has already been in the canal.  There’s some presumption of previous enlargement in the body, so there wouldn’t be the usual emphasis on access, although I’ll say as a side bar, it’s important to have straightline access to each orifice.  By that I mean, we should have the orifice flared, we should have the internal triangles of dentin removed, and we should have emphasized intentionally relocating the coronal aspect of a canal in furcated teeth away from furcal side concavities.  So, this is part and parcel to radicular access where allegedly or presumably there’s this collagenous block. 

OK.  So, we want to have great access, but presumably somebody’s already been in the canal, so we should see if a 10 file will slide to the full working length.  If it doesn’t slide to the full working length, then I would like you to take the file out and put a little bit more curvature towards it’s terminal extent.  Let’s go back in with a pre-curved file.  It would help, if necessary, to pre-enlarge the canal further to gain better, radicular access deep, and now the pre-curved file can be passed through the pre-enlarged canal and would arrive in the curvature, if it’s there, pre-curved.

I would like you to use unidirectional stops on your files.  Most manufacturers provide this.  But the file should be curved and the rubber stop torqued so that its unidirectional line is oriented with the curvature on the file.  This means when the file has been seated and it’s deep in the canal, one simply looks at the rubber stop and you can tell whether you’re going distal.  If you want to get a little different vector disto-lingual, move the file a little bit to the distal-buccal.  But, we can more or less try north, south, east and west, and what we’re looking for is to slide the file to length.  And, presumably, the rubber stop is short of the anticipated full working length, implying a block.

So, by trying to move the instrument in little gentle strokes, little gentle 1/2 mm vertical amplitude strokes, we’re trying to discover the physiologic terminal extent of that canal.  If this happens, then we happily move forward by sliding the instrument to length and once you’re at length, the file should be moved deliberately in up-and-down, vertical, 1 mm amplitude strokes until the file is loose.  Did everybody hear that part?  Loose.  This means you might have your favorite assistant count to 50 as you take 50 little, short vertical strokes.  You might say, “Can you count to 25 backwards?”  If you have the right patient, you might say, “I’m too tired to count today; would you count?”  But, in many instances, once that file is to length the common error is to remove the file, and to move on to the next instrument, which means you might never re-enter the canal ever again.

So, the reason I’m emphasizing so much, the loose file, is that we like this instrument to have a chance to repeatedly go back along the slide path to the full length.  So, don’t take the file out until it’s completely loose. 

If, on the other hand, the instrument after some effort, and it’s pre-curved, cannot be carried to the working length, then, in fact, we need another idea.  In this instance, I would vacuum with suction all the reagent in the canal; presumably it was 6% sodium hypochlorite, and then top off the pulp chamber with a viscous chelator.  A viscous chelator could be RC Prep, it could be Glide, it could be ProLube… To me, they’re all more or less exactly the same.  It’s ethylenediaminetetraacetic acid in a methylcellulose suspension and this gives us a superior lubricant.  It’s an emulsifying agent and this means it prevents the re-adherence of collagenous, which is glue-like sticky, tissue to itself, and finally, the debris that we are generating with the instrument is more effectively held-up in suspension.  So, we always speak of lubrication, emulsification and floatation as the hallmark features of a viscous chelator. 

Again, I would carry the file back into a canal filled a viscous chelator and do the same things I’ve just repeated.  Try little short 1/2 mm strokes with a pre-curved file and try working a little bit east, or northeast, or southeast… whatever vector it is.  Look carefully at your radiographs because if it was a necrotic tooth, or a tooth that was previously treated and failing, there’s usually a lesion of endodontic origin.  And, these lesions always form adjacent to the portals of exit.  So, it is fundamental to associate that the lesions form adjacent to the portals of exit.  They’re not germane to the bone, nor do they arise from the bone.  So, you’re trying to direct your file to the lesion because that’s to appreciate the interrelationships between root canal systems, pulpal breakdown, and lesions of endodontic origin.  And of course, the disease flow is along the anatomy and exits through what we call, or Schilder defined years and years ago, portals of exit. 

So, try to work the instrument to a lesion.  If it was a vital case and there has not been osteolytic breakdown and you cannot see a discernible lesion radiographically, it doesn’t mean there isn’t a lesion.  It just means you don’t know exactly how to direct your file.  Then, it helps to somehow remember some of the micro CTs… remember some of the work that Hess did… to have a greater appreciation for root canal system anatomy and some of the various proclivities of anatomy that we would find in the various roots of human teeth. 

I would continue in this manner, picking in short vertical strokes with a pre-curved file, because oftentimes, the end of the file will begin to engage.  If you took your ring finger and hit the handle on the file, it would begin to oscillate rapidly.  I call that handle flutter.  Handle flutter just means the tip of the file is engaged.  This can give you an indication that you could begin to watch-wind the handle, but I’m talking 5 degrees clockwise / 5 degrees counterclockwise to see if the file can get pulled on down towards length. 

Again, if you can get to length, leave the file in place and work in short linear, vertical amplitude strokes, repeatedly, until the instrument is completely loose.  So, that would represent, in a more or less quick fashion, a description how to negotiate blocked canals when there has been an iatrogenic event.  Remember, the canal was never blocked prior to the dentist going into the tooth, because there was always an apical foramen, or foramina, and tissue would enter these foramina and move on up through the root.  So, there was always an open patent canal.  It just happened to be open and patent before man enters the tooth, and it is man, or woman, who obstructs root canal system anatomy. 

So, that would be a little way you could start to try, my friend, and see if you could then carry your instruments to the full working length.  When you have accomplished this, you will be thrilled with the result and you will have learned a lesson in patience and determination and perseverance. 

Thank you very much.  I’ll answer the rest of your questions in a separate blog.