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Working length and patency are so interrelated they must be discussed together. The breakthrough to apical one-third finishing procedures is canal patency. And it's performed by gently pushing small highly flexible files to the radiographic terminus.
In this Just-in-Time segment, topics include
Root canal system anatomy
Negotiating the apical one-third
Determining working length
Confirming patency
Securing the glide path
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this show is going to deal primarily with working length and patency into a lesser extent the glidepath needle one-third the assumption for all my friends internationally is that the access has been cut the triangles of dentin have been eliminated and we've done the pre enlargement in the coronal 2/3 of all the systems clearly the anatomy is most difficult nickel 1/3 so we'd always want to use clinically of viscous ki later with a small sized hand file we're using little back-and-forth reciprocating motions but when that stop gets about one millimeter off the reference point I personally don't like to reciprocate anymore I like to slide instruments to length oftentimes students have been taught to work to the physiologic terminus which would be defined as the minor constriction or the semental dentinal Junction this is a very arbitrary point that varies from tooth to tooth from root to root on multi routed teeth and from wall to wall within each single canal what I've just really said is it's kind of ludicrous for us to think we can work to a landmark that can range sometimes as much as two or three millimeters in its vertical extent so for me it is much wiser as a teacher to have students direct files intentionally that are small and flexible right to the radiographic terminus we can all agree on this landmark internationally it's not ambiguous and we should recognize the file is minutely long we should get over this concern of the instrument touching the tissue in the attachment apparatus because at this point in time we're advocating a picot ectomy procedures and surgical procedures to do corrective measures we're also sticking implants in bone that are all types of diameters in length and it's simply irrelevant to be concerned and needlessly over worried about placing a an 8 or a 10 or a 15 to the RT oftentimes colleagues like to talk about working to the radiographic apex but as you can see in this animation that they're obviously not always coinciding canals frequently exit routes other than at the radiographic apex so it's more appropriate to speak of instrumenting to the radiographic terminus the radiographic terminus then would be my working length it's very important to keep the canals open this means patency files are repeatedly and deliberately passed through the foramen like you can see clinically on this first mandibular molar with a full veneer crown notice how gentle the instrument is being used and by using it frequently in this
manner we're transitioning the canal to a little larger diameter we're smoothing and refining the walls and at some point we can now decide do we have a smooth reproducible glide path a secret that I've learned that will help you know whether you should carry rotary files to length or prepare these apical thirds manually is to take a 15 file and progressively pull it back one or two millimeters then three or four millimeters then four or five millimeters and if you can pull this instrument back and without reciprocating the handle always slide the instrument to the full working length you have a wonderful glide path and rotary will typically follow in this animation because there's a decreasing radius curvature we must though even with a well-prepared glide path we might have to be concerned about cyclic fatigue and we still might want to finish the more difficult highly curved ones manually so you can see in this mandibular molar on the post-op film the distal route trifer Cates in the last couple millimeters the rotary file is not going to know which branch to take and it'll typically roll over and can be predisposed to fracture in this mandibular second bicuspid you can see an asymmetrical lesion the importance of carrying the small size files too and minutely through the foramen cannot be overemphasized because we want our reagents to come off that shaped canal so that those irrigants can penetrate circulate and clean into a myriad of lateral canals we see on that second bicuspid notice in fact the first bicuspid has three apical portals of exit I've always said that
