Dr. Rich Mounce discusses his guiding philosophy for conserving tooth structure
In dental school, one concept was always considered sacrosanct — conserve tooth structure. In endodontics, we have historically advocated straight-line access and early coronal enlargement to obtain visual and tactile control. In addition, pre-enlargement (opening the coronal third with either Gates Glidden drills or nickel-titanium [NiTi] orifice openers) was considered essential for ease of gaining patency, subsequent shaping, and debris removal. Gates Glidden drills and orifice openers were universally recommended with brushing up and away from the furcation, a motion accentuating dentin removal in the cervical region of the tooth. Posts, in addition to the aforementioned cervical tooth structure removal, are clear risk factors for furcal and vertical root fracture.
Slowly, minimally invasive endodontics has begun to take root (no pun intended!) as a guiding treatment philosophy. Minimally invasive endodontics might be thought of as a mindset to conserve tooth structure and use posts only if absolutely necessary. Tooth structure can be preserved by:
- Using a contracted (smaller) access cavity (not necessarily straight line)
- Avoiding pre-enlargement
- Preparing smaller final prepared canal tapers
Virtually all endodontists in North America use dental operating microscopes. As a result, we have control over our access size with the caveat that many teeth we treat are already coronally debilitated, and ideal access may not be possible. Conceptually though, keeping access as small as possible, while providing visual and tactile control, is critical. Minimizing post placement will unquestionably prevent fracture.
Pre-enlargement was a necessary evil, in large measure because our previous NiTi files are not particularly efficient. We could not take a .06 tapered NiTi file and advance it apically in a one-file technique because no .06 tapered NiTi file could cut efficiently enough to progress apically without pre-enlargement. As a result, we removed tooth structure through pre-enlargement (often using a brushing motion) in order to allow subsequent files to reach the apex. Unfortunately, this potentiated root fracture due to excessive tooth-structure removal, as mentioned previously.
Fortunately, pre-enlargement is a thing of the past, as is the need for larger tapers in endodontic canal preparation. In approximately 90% of all canals, .01/25 tapered controlled-memory ProDesign Logic NiTi Glide Path Files (Easy Endo USA) can prepare the glide path without the use of hand files. Alternatively, clinicians can gain patency with a number 10 hand file and follow it with the .01/25 Logic Glide Path File.
Once the glide path is prepared, a .05/25 tapered controlled memory ProDesign Logic NiTi Shaper File (Easy Endo USA) can predictably reach the apex in four to five pecks eliminating pre-enlargement and/or a brushing motion.
If clinicians want to prepare a larger apical diameter, they can do so using Logic files or any preferred method. The time and cost savings are remarkable because only one file is required after the glide path is prepared. It is a fact, at this time, that no other NiTi system (besides ProDesign Logic) exists in .05 taper that allows a single file minimally invasive preparation of the root canal system allowing canal preparation without pre-enlargement and/or brushing.
The resulting prepared canal (.05/25) is more than large enough to be irrigated, activated, and obturated easily and efficiently — all the while conserving tooth structure, the essence of Minimally Invasive Endodontics. I welcome your feedback.