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Contextualizing with history here is kinda important. As many of the old timers are calling it quits, it may be of benefit to put this down for the next generation of pulp slaying tooth fixers. The story goes like this. There was an observation that failing endodontics was associated with poorly root filled teeth. The following Schilder inference follows, namely: “Inadequate obturation of the root canal invites failure.” So the focus laser beamed on the fill and it’s associated process centered outcome. In order to employ the warm gutta percha technique, the root canal must be shaped so that a continuously tapering funnel is created with its narrowest diameter at the periodontal ligament and its widest diameter at the coronal opening or access cavity.

Back then they were doing this shaping by hand with reamers. And they had these stainless heat pluggers that looked like a spreader that they heated to a “cherry” red before “sheparding’ the gutta percha into the canals with graded stainless pluggers. So in order to get the pluggers to fit, they had to shape the canal to fit the graded pluggers. “Whala”, the continuous taper was unleashed and the rotary revolution followed suit. “Deep shape” became a thing and a lot of root dentin went down the drain. Observationally, we saw some of these break and wondered if maybe all that shape was necessary. Not to mention the strip perf’s. The first to make a change was Buchannan with GT files which at least had a maximum flute diameter. SSW under the direction of Khademi made the biggest leap a decade ago with variable taper instruments. That made things soooo much easier.

Out went shaping, deep shape and in came dentin conservation. Because, well, did you ever find anything that got stronger by whittling on it? Me neither. And yet we still had length control and root filling to contend with and accomplish. That led to the idea of rootform appropriate instrumentation. The balance of not hogging the tooth, and still accomplishing what was necessary. The apical taper kept the fillings from going long and the variable taper kept from too much coronal hogging. Using imaging and knowledge of root anatomy to guide the instrumentation was central to this approach. Using a thoughtful approach to balancing necessary and sufficient notions of root dentin removal achieve the desired process centered outcomes of the operator is the grounding principle behind root-form appropriate instrumentation., Generally speaking as long as the teeth were of average length and didn’t have extreme curves the following could be somewhat prescriptive as long as the prior principle is kept in the forefront of one’s mind and the driver doesn’t fall asleep at the wheel.

So prescription wise there are a number of great instruments out there. What I kinda landed on were three different instruments of different tips and tapers. Namely 17.04V (grey) , 20.06V (yellow), and 20.07V (blue) the V standing for variable taper as none of these are continuous taper instruments. The 17.04 and 20.06 I use are heat treated SSWhite instruments the 20.7 is the F1 by Tulsa which can be obtained in heat treated as well in their gold line. There are lots of F1 substitutes out there if your not a Tulsa fan. The colors here refer to the final file used. Longer roots than the average will typically mean dropping back a size.

This was all a decade ago, before tech. What’s necessary for tech? Probably less; hopefully less, maybe even none one day. There’s some evidence that the move to lose some weight from the continuous taper days has had some benefit in outcomes at longer time frames ie less breaking failures. Are there diminishing returns for losing additional weight, and whittling even less? Harder to tell. Maybe. Harder to root fill? Definitely. The instrumentation appears to approach some conservative silver point preps from the age before rubber or even smaller, considerably smaller with tech ended instrumentation.

The left image is presented with permission from a Shilder trained endodontist. The right was what I was trying to accomplish at the time highlighting root-form appropriate instrumentation as a pillar of Restoratively Driven Endodontics a decade ago. There are still tons of continuous taper rotary systems being employed today, pleasing the dopamine release centers of those enamored with “the look”. Countering those emotions are our own visceral response when we see extraction pending teeth that were given the deep shape death sentence.