Tips & Tricks – Access

As we celebrate Canadian New Year’s (Labour day) by heading back to school, I was reminded by my UBC students about the intricacies of access cavity preparation. While textbooks teach the generalized shape of preparations and roughly how many canals we should be looking for, a very common question I will encounter is, “So what burs should I use?” followed closely by, “I really don’t want to perforate.”

Good bur selection and a well-designed access can do so much more than prevent perforations. We can also see the benefits of locating all the anatomy through good visualization while improving our speed and efficiency. Additionally, in this age of minimally invasive dentistry and increased concern over root fractures, good bur selection will allow us to conserve the most crucial area of the tooth; the coronal third.

Following pretreatment, or removal of all decay and temporizing to establish 4 walls, three is always the temptation to reach for a long-shank (surgical) round bur. It makes sense, we are doing Endo, therefore, we need to access deeper so we will need a longer bur. The first of two dilemmas with this logic is that a surgical length bur is capable of going much further than we need. So if there is a moment of disorientation, disaster can occur in the form of an iatrogenic communication with the alveolar crest. The second problem occurs due to the length of the bur. A subtle change in angle results in a large arc of movement for the cutting end. The result is a very small access in enamel which translates into poor visualization and future straight line access, in addition to over-removal of the coronal third of dentin thereby weakening the tooth.

I had an excellent Endodontics instructor that would frequently say, “When you can ‘pulp-out’ with a short shank, why use anything else?” Unable to answer this question, and to avoid the aforementioned consequences, I prefer a non-end cutting short shank bur like a 330. My tip for students is to use the bur that makes the best occlusal amalgam preparations in their hands.

Once your preparation reaches the chamber, taking a few minutes to smooth the walls gives the advantage of improving your straight-line access as well as making instrument introduction into the canals much easier. The efficiency you will gain when you consider how many instruments will enter each canal is phenomenal. This is perhaps the single greatest time saver, and for it, I like to use a safe-ended Endo-Z bur.

In the cases where you’ve cut an ideal access to a few millimetres above the cementoenamel junction and it happens to be more calcified than you anticipated, or you may be looking for the edges of a pulp stone, visualizing where you are drilling is of paramount importance. This is when a long shank will be beneficial as you will be able to see around the head of the handpiece to exactly where the head of the bur is working. Use of the slow-speed is beneficial as it allows for disruption of the disorganized calcified tissues preferentially over the organized primary and secondary dentin. With a steady stream of air allowing you to see exactly where you are going and what is being removed, you can proceed with confidence without being blocked by a stream of water or scorching the dentin with a high-speed.

 

Dr. Jason Conn

Dr, Jason Conn, DMD, CAGS, FRCD(C)

ABOUT Dr. JASON CONN, DMD, CAGS, FRCD(C) – LANGLEY ENDODONTICS

Dr. Conn was born and raised in Langley. He completed a Bachelors in Chemistry at Simon Fraser University before receiving his DMD and Certificate of Advanced Graduate Study in Endodontics at Boston University where he wrote a thesis in clinical decision making and another in odontogenic stem cell differentiation.

Dr. Conn has maintained an active practice alongside Dr. Bittner since 2012 while teaching as a part-time clinical assistant professor at the University of British Columbia.

In his free time, Dr. Conn is a Cub Scout leader, long distance runner, back-country hiker, snowboarder and yogi-in-training.

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On September 20, 2016, posted in: News for Doctors by