Dental Professionals

Revascularization of necrotic, immature permanent teeth

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5Dental trauma and deep carious lesions can often lead to pulpal necrosis in children and young adults. Injuries may result in avulsion, intrusion, extrusion or lateral displacement. Caries may cause bacterial invasion into the young pulp space. Unfortunately, many of these teeth will become necrotic prior to completing root development.

Treatment of necrotic permanent, immature teeth can present a difficult clinical situation.
A young patient may present with pain and swelling requiring calm and deliberate confidence on the dentist’s part. The child and parent may have already seen other
dental/medical providers that day to deal with their troubles.

Extraction and replacement with implants or fixed bridges are often contraindicated due to incomplete skeletal growth. Historically, immature apical development has been managed with root-end closure through apexification. However, this procedure presents several
challenges. Cleaning, shaping, disinfection and obturation are often incomplete in a
very large, blunderbuss canal.

These immature teeth tend to be short, with thin lateral root walls. Even if apexification closure is successful, the long-term future is suspect due to eventual root fracture. An alternative approach to treating the immature necrotic permanent tooth is to revascularize, or regenerate pulpal tissue, allowing for continued root formation. In 2004, Drs. Francisco Banchs and Martin Trope demonstrated the advantages of this treatment modality, resulting in continued maturation of the entire root, versus formation of an apical calcific-barrier through apexification.

The advantage of this treatment is continued root lengthening and reinforcement of lateral dentinal walls with deposition of new hard tissue. Revascularization, regeneration and revitalization are commonly used terms to describe the re-growth of vital connective
tissue within the root canal space. The goal is to stimulate restoration of the pulp-dentin complex, leading to deposition of dentin along the root canal walls.

Three vital components are necessary to achieve this goal:

  • Stem cells
  • Growth factors
  • A 3-dimensional physical scaffold

The undifferentiated mesenchymal stem cells arise primarily from the apical papilla. Dentin or platelet derived growth factors act as signaling molecules or “cues” to stimulate proliferation, differentiation and organization of the undifferentiated stem cells. A scaffold is then necessary to act as a matrix for the attachment of these stem cells, with subsequent growth of new tissue into the pulp space.

Scaffolds can be fabricated with a blood clot from the apical blood supply, PRP (platelet-rich plasma) harvested from the same patient, or yet-to-be Food and Drug Administration-approved hydrogels. Current procedural guidelines to be followed include coronal access, disinfection of the canal space and placement of a subcoronal seal,  followed by placement of a well-sealed coronal restoration. Access is made into the large coronal pulp space. Pulp tissue may be carefully removed with a broach or ultrasonic flushing, but filing against canal walls is contraindicated. Gentle irrigation with sodium hypochlorite and ethylenediaminetetraacetic acid as disinfecting irrigants is accomplished, followed by placement of a bi-or tri antibiotic mixture that disinfects, but allows apical stem cells to remain viable.

Recent investigations have yielded positive outcomes from a low concentration antibiotic mixture of ciprofloxacin, minocycline and metronidazole. Minocycline should be avoided in anterior teeth due to potential staining concerns. Calcium hydroxide pastes and  chlorhexidine gels have also shown promise as low toxicity antimicrobials. Two to three weeks are allowed for disinfection and resolution of prior signs and symptoms. The second visit includes gentle flushing with irrigants, laceration of apical tissues with an endodontic file to induce intracanal bleeding and the placement of an appropriate subcoronal collagen matrix (Collaplug, Zimmer Dental) against which a MTA plug can be placed.

Permanent coronal access closure is then achieved. These teeth should be followed for several years. Anterior and posterior teeth will respond favorably to this treatment (Figures 1-4). Molars will often have multiple roots present with varying degrees of apical maturation, leading to revascularization and conventional treatments within the same tooth
(Figure 5, recently initiated).

Revascularization may also become a predictable option in the future to treat horizontal root fractures, without invading the point of fracture in an attempt at sealing the coronal canal and junction between root segments (Figures 6 and 7). The “open apex” at the inferior border of the coronal root segment can act as the pathway for stem cells and growth factors to enter the canal.

Regenerative procedures have allowed many children to retain compromised teeth. Signs and symptoms of pathology have predictably resolved, with significant continuation of root development. Clinical studies have demonstrated ingrowth of a vascularized, innervated connective tissue. The newly formed mineralized tissue formed along dentinal walls, and as islands within the pulp space, have been found to be histologically similar to cementum and osteodentin.

The eventual goal and current focus of study is to develop strategies to stimulate stem cells within the apical papilla to contribute to the formation of an intact pulpdentin complex capable of regenerating pulp connective tissue and dentin similar to that found in healthy, untreated teeth. Unfortunately, even successfully treated teeth may be subject to future endodontic issues due to trauma, caries and restorative issues, as are all other teeth.
However, with a fully developed crownroot complex, conventional endodontic treatment would be straightforward and predictable.

The field of regenerative endodontics is young, exciting and a quickly changing work in progress. New information is being accumulated as clinical researchers conducting laboratory studies and clinical trials publish their results. Thus far, the results are encouraging. Expanding clinical trials to include potential stem cell repair of vertical root fractures, is being considered.

Additional studies in bioengineering applications regarding the interdependent triad of stem cells, growth factors and scaffolds are necessary to further advance the field.

Dental Professionals