Pulp Revascularization

Pulp Revascularization of Immature Permanent Teeth

Tissue engineering is a growing field.

In the near future, it will probably be possible to generate a complete vital tooth from a single stem cell. Stem cells are in fact totipotent cells, which have the capacity to proliferate and to produce cells, which are capable of differentiating into specialized cells.

Two types of stem cells exist: embryonic stem cells and adult stem cells (or postnatal cells) . Concerning pulp revascularization, mature stem cells are rather of interest. These cells are found in many sites of the dental element: in the pulp, in the apical papilla, and in the periodontal ligament . These clonogenic cells, rapidly differentiating, have the capacity of inducing dentin-pulp regeneration if differentiating into appropriate cells. In addition, the pulp, which is a product from migration of the neural crest, would probably be a very good candidate to allow nerve regeneration . Regarding the daily practice, it is imperative to find ways to save as much as possible the vitality of stem cells from the dental element and induce their differentiation.

Pulp revascularization is dependent on the ability of residual pulp and apical and periodontal stem cells to differentiate . These cells have the ability to generate a highly vascularized and a conjunctive rich living tissue. This one is able to colonize the available pulp space. Subsequently, these stem cells will differentiate into newly formed odontoblasts that will induce an apposition of hard tissue. The nature of this latter is unknown yet .

Revascularization is a new treatment method for immature necrotic permanent teeth. Indeed, it would provide, after treatment, a vital tooth that would be able to complete its root maturation. Up to now, apexification procedures were applied for these teeth:

using calcium dihydroxide to induce the formation of an apical calcified barrier;

using mineral trioxide aggregate (MTA) to produce an artificial apical barrier.

Both methods have shown to be effective regarding the narrowing of the apical foramen of an immature tooth. However, the pulp revascularization allows also the stimulation of the apical development and the root maturation of immature teeth (root growth and thickening of dentinal walls and natural apexification).

Indications for treatment of pulp revascularization are the presence of deep caries or trauma inducing a stop in the development of root canal of an immature tooth. It is important to keep in mind that an endodontic treatment on an immature tooth, often necessary up to now, involves a root canal treatment on an open apex tooth with thin and fragile walls. This will involve the persistence of a weakened tooth with often a reserved long-term prognosis due to the remaining of an intrinsic fragility and to the difficulty to obtain a good sealing of an open apex. Revascularization technique would allow the growth of root and thus avoiding the remaining of thin and fragile walls. It will reduce the risk of root fracture . This is not the case with apexification treatment.

Immature teeth with a large open apex and short roots seem to be more conducive to the successful treatment of pulp revascularization.

A great importance is given to maintaining the vitality of a tooth in order to keep a possibility of “alert” signal in case of pathogenic stimuli. Losing its innervation and vascularization, a tooth is more vulnerable to any lesion. The maintaining of dental vitality allows better defenses in case of future possible infections.

This pulp revascularization is used for necrotic immature permanent teeth. Even if pulp has lost its vitality, residual pulp stem cells are able to survive. Apical papilla stem cells can also survive to an apical lesion thanks to an abundant blood supply

Conventional endodontic treatment consists in the development and application of techniques designed to accomplish the chemical-mechanical preparation of root canals in order to eliminate an infection, many times difficult to combat due to the complexity of the root canal system. However, this process may become even more complicated in cases of immature teeth with open apexes, whose root walls are fragile due to the thin thickness of the root canal dentin, along with the intense activity and anatomy of an open apex, making it difficult to accomplish the complete obturation of the canal, and with the real risk of solid and plastic material overflow into the periapex. The incomplete root development may be caused by trauma or infections powerful enough to halt mineral deposition by the destruction of blood flow, impeding the root to complete its formation

One way to treat open apex teeth is the apexification technique that is made in pulpless teeth and which promotes apical closure, and can be obtained with the insertion of a MTA (Mineral Trioxide Aggregate) barrier or with periodical exchanges of calcium hydroxide, enhancing further obturation. This process is named apexogenesis and its goal targets at the preservation of vital pulp tissue so that the continued root development with apical closure may occur . Nevertheless, some studies have shown that this protocol can also be used in non-vital teeth. The procedure is named pulp revascularization and is directed by disinfection protocols concerning the root canals, being indicated the use of sodium hypochlorite irrigation (NaOCl) followed by a combination of ciprofloxacin, metronidazole and minocycline antibiotics to be used as intracanal medication