The Changing Look of Clinical Endodontics

Regenerative endodontics involves the performance of biologically-based procedures that are designed to physiologically replace damaged tooth structures, including dentin, root structures, and the pulp-dentin complex.¹ It should be noted that in the endodontic literature, the terms regeneration, revascularization, and revitalization are often used synonymously and interchangeably.² Clinically, a regenerative endodontic procedure is one that is performed on an immature permanent tooth with necrotic pulp to obtain root-end closure with the goal of obtaining continued development of the root and thickening of the canal walls (Figure 1).³ Historically, the clinical treatment for apexification on these types of teeth is performed by placing calcium hydroxide over a period of several months or delivering a single-step treatment with mineral trioxide aggregate.³ Based on outcomes, these apexification treatments have demonstrated the ability to obtain root closure but not continued root development and wall thickening.⁴

Clinical treatment of an immature permanent tooth with necrotic pulp using regenerative endodontics usually involves two treatment appointments. At the initial appointment, after local anesthesia is administered and isolation is achieved with a rubber dam, minimal canal instrumentation is performed (due to the thin dentinal walls) in conjunction with irrigation using 1.5% sodium hypochlorite (NaOCl). This lower concentration is used to limit the killing of stem cells. After preparing the canal, it is irrigated with sterile saline and dried, then calcium hydroxide or a triple antibiotic paste is placed in the canal to serve as an antimicrobial medication between treatments. Following this, the canal access is temporized with a sterile cotton pellet or sponge and a temporary material (eg, Cavit^™ Temporary Filling Material, 3M; IRM^® Immediate Restorative Material, Dentsply Sirona), and the patient is asked to return in 1 to 4 weeks for the final treatment appointment.^3,5

At the second regenerative endodontic treatment appointment, a 3% solution of mepivacaine HCL without an added vasoconstrictor is used to achieve local anesthesia. In regenerative endodontic procedures, the induction of periapical bleeding into the canal space is necessary, and the absence of a vasoconstrictor will help facilitate this process. A rubber dam is placed, and after the tooth is accessed, 17% ethylenediaminetetraacetic acid (EDTA) is used to irrigate the canal. Next, the canal is dried, and bleeding is induced 1 to 2 mm beyond the apical foramen with a hand file. The blood should fill the canal to around the level of the cementoenamel junction (Figure 2). This induced bleeding brings with it scaffolding, stem cells, and additional blood-derived bioactive growth factors to complement those that were released by the dentinal matrix when the 17% EDTA was irrigated into the canal.³ The triad of stem cells, scaffolding, and growth factors is what enables tissue regeneration to occur.⁶

After a resorbable collagen matrix is placed over the blood clot, a bioceramic material is placed directly over the collagen matrix, and a glass ionomer is placed over the bioceramic material (Figure 3). A final composite restoration is then placed over the glass ionomer, and a final radiograph is taken (Figure 4). The patient should be put on a 6-month recall schedule for as long as 3 years, dictated by the process of healing.⁷

Recently, there have been reports in the literature that describe the use of regenerative endodontic procedures not only on immature permanent teeth with necrotic pulps but also on mature permanent teeth with necrotic pulps, teeth with persistent apical periodontitis following conventional endodontic treatment, traumatized teeth with external inflammatory resorption, teeth with horizontal fractures, and avulsed teeth.^8-10 One reason for the increase in the use of regenerative endodontics for cases other than those involving immature permanent teeth with necrotic pulps is the belief that obturating a disinfected canal with the host's vital tissue may be better than using foreign materials (eg, gutta-percha and sealers). The tissues generated in canals after a regenerative endodontics procedure are similar to those of the cementum, bone, and periodontal ligament and contain blood vessels and nerves. Although none of these tissues are true pulpal tissue, they are the host's own vital tissues; thus, they are inherited with immune defense mechanisms to protect against infection.^7,11

One problem in clinical practice is that many clinicians are not familiar with regenerative endodontics. When they view a radiograph of a patient who has had this procedure, their initial thought is that the root canal treatment was not completed. They often proceed to either extract the tooth or access it and perform conventional endodontic re-treatment, consequently destroying the bioactive obturation.

Although the use of calcium hydroxide for vital pulp therapy was first reported in the literature more than 79 years ago,¹² during the last couple of years, there has been a paradigm shift in vital pulp therapy. This shift has included the replacement of calcium hydroxide with bioceramic materials, sodium hypochlorite with EDTA, and temporary fillings with a composite or amalgam restoration.¹³

In addition to this paradigm shift, another recent advancement in vital pulp therapy is cryotherapy.¹⁴ The goal of cryotherapy is to lower the temperature of the tissue.¹⁵ Lowering the temperature of human tissue has been shown to decrease nerve conduction velocity as well as reduce hemorrhage, edema, and inflammation.¹⁶ Cryotherapy has also been shown to reduce the number of leukocytes that adhere to the endothelial walls of the capillaries, which limits the migration of these types of cells to the affected tissue, reducing endothelial dysfunction and further reducing inflammation.¹⁷ In addition, cryotherapy can diminish the clinical need for pharmacologic intervention via narcotics or local anesthesia.¹⁸

Vital pulp cryotherapy is a new technique that involves the placement of sterile shaved ice on vital pulpal tissue that has been directly or indirectly exposed by a carious lesion (Figure 5). For endodontic treatment, it is used in conjunction with 17% EDTA, bioceramic pulp capping materials, and restorative materials. Vital pulp cryotherapy has been shown to reduce postoperative tooth pain.¹⁴

This procedure can be performed on teeth with a pretreatment pulpal diagnosis of normal, reversible pulpitis or symptomatic, irreversible pulpitis as well as on teeth with a pretreatment periradicular diagnosis of normal or symptomatic apical periodontitis (ie, by percussion and/or palpation tests without radiographic evidence or by a periapical radiograph and/or a cone-beam computed tomography scan indicating a periradicular radiolucency [lesion]). It is important to note that the performance of vital pulp cryotherapy necessitates that the tooth be restored with a composite or amalgam restoration immediately following the procedure. It is contraindicated to place a temporary filling or prepare a tooth for a crown after a vital pulp cryotherapy procedure.¹⁴

After the definitive restoration is placed, the final radiograph taken demonstrates a similar appearance to the final radiograph taken after a regenerative endodontic treatment (Figure 6). When comparing the final radiograph of a vital pulp cryotherapy treatment with one taken after vital pulp therapy with calcium hydroxide, the vital pulp cryotherapy radiograph exhibits increased radiopacity and can demonstrate deeper material placement on the coronal portion of the pulp.

Unlike the distinctively different radiographic appearance of teeth that have been treated with conventional endodontic treatment and teeth that have been treated with vital pulp therapy, the radiographic appearance of a regenerative endodontic procedure is quite similar to that of a vital pulp cryotherapy procedure. The future direction of endodontic treatment is moving toward a more biologic approach to treating inflammation and infection of the pulpal tissue, and the procedures of regenerative endodontics and vital pulp cryotherapy demonstrate a better clinical ability to do this than the traditional methodology.^3,14 This change in conventional endodontic treatment has made it more about function than form (ie, bioactive obturation vs gutta-percha and sealer obturation).

As with any change in healthcare technology and treatment protocols, there is a "technology adoption life cycle." This life cycle is a bell curve that divides clinicians into the categories of early, early majority, late majority, and laggards regarding the adoption of new technology.¹⁹ The clinical adoption of regenerative endodontics and changes in vital pulp therapy techniques by dentists is no different. There will be early adopters who immediately embrace the potential benefits, those who will wait until these bioactive endodontic techniques have been proven with more evidence-based research, and those who will not change their current endodontic treatment protocols at all. Wherever endodontists may fall on this spectrum, it is imperative that all clinicians understand and appreciate the shift toward more bioactive treatment in endodontics. This awareness, coupled with the ability to identify these treatments radiographically, will prevent unnecessary future treatment or the need for re-treatment and optimize restoration.

James Bahcall, DMD, MS
Clinical Professor
Department of Endodontics
University of Illinois at Chicago
College of Dentistry
Chicago, Illinois

Qian Xie, DDS, PHD
Assistant Professor
Department of Endodontics
University of Illinois at Chicago
College of Dentistry
Chicago, Illinois

Mark Baker, DDS
Clinical Associate Professor
Department of Endodontics
University of Illinois at Chicago
College of Dentistry
Chicago, Illinois

Steve Weeks, DDS
Clinical Assistant Professor
Department of Endodontics
University of Illinois at Chicago
College of Dentistry
Chicago, Illinois

Vikash Huliyar, DDS
Second Year Endodontic Resident
University of Illinois at Chicago
College of Dentistry
Chicago, Illinois