Paradigms in endodontics: CIE, MIE/RDE, NIE

Writing in Dentistry Today in 2008, L. Stephen Buchanan relates a conversation he had with renowned prosthodontist Carl Reider.¹ Reider is quoted as saying that “he [Reider] would prefer it if the endodontist could just suck the dying pulp out of the tooth without removing any dentin.” Buchanan continues, “He [Reider] made that paradigm-shifting statement to me back in 1990.”

We may look back at this as the earliest beginnings of a sea change in endodontics that started with Buchanan’s realization that “root canal shaping procedures were complex because we were using relatively nontapered instruments to create tapered root canal shapes. What would it be like … to use variably tapered files that possessed the final canal shape on a single instrument?”²

“The logical answer seemed to be that variably tapered shaping instruments would allow ideal predefined canal shapes …”² with a predefined maximum flute diameter that limits coronal enlargement: engineered dentin preservation. These variably tapered instruments such as the GT NiTi File Series were not an outgrowth of the ISO standard steel root canal files with color-coded specified tip sizes, 0.02mm/mm of taper, 16mm of flute length. It was a complete departure from all previous file designs, concepts, and procedural steps of Endodontics 1.0: Conventional Instrumentation Endodontics (CIE).

Up to that time, endodontists primarily operated out of this mindset: “‘The root is mine!’ meaning that the shapes we create in root canals when we treat patients are our business.”² These operator needs trumped the tooth needs, much to the detriment and credibility of our specialty. Buchanan illuminated some questioning of endodontics being a credible treatment modality in dentistry, while others were calling for the end of endodontics as a specialty. Something had to give.

Drs. David Clark, Eric Herbranson, and I extended these concepts of dentin preservation and introduced the Hierarchy of Tooth Needs.³ We also note that the restoratively aware “clinician needs to consider many factors that will affect the outcome. In simple terms, these factors can fall into three categories: the operator needs, the restoration needs, and the tooth needs. The operator needs being conditions the clinician needs to treat the tooth. The restoration needs being the prep dimensions and tooth conditions for optimal strength and longevity. The tooth needs being the biologic and structural limitations for a treated tooth to remain predictably functional.”⁴

So “what would it be like to use variably tapered files” ended up being the question that eventually led to the reversal of the Endodontic Triad’s myopic focus on debridement, disinfection, and destruction of the tooth in the process of fixing it. This reversal placed preservation of the pericervical dentin (PCD) as the primary objective and led to the second paradigm in endodontics: Endodontics 2.0, or minimally invasive, restoratively driven endodontics (MIE/RDE).

Dr. Reider questions, “What would it be like not to use shaping files at all?” We believe the answer to his 30-year-old question leads to the next paradigm in endodontics: non-instrumentation endodontics (NIE). NIE or Endodontics 3.0 is perhaps first defined by what it is not. NIE does not mean “no files are ever used,” but instead, the purpose of files, if they are used, has changed. This leads to a central tenet of NIE: debridement and disinfection of the root canal system is no longer an instrumentation or file-based, chemomechanical procedure. Debridement and disinfection of the root-canal system is done by some other means. Files, if they are used, are not for “shaping,” but instead, for verification of existing anatomy, recovering original anatomy, establishing original anatomy and ensuring … for the time being … an obturatable space.