Apexification Vs Apexogenesis| Pulp Thrapy of immature permanant teeth
Endodontic treatment of an immature permanent tooth is problematic, mainly for technical reasons. Because basically, the objectives to be achieved are always the same.
Apexogenesis, Apexification, revascularization… so many operating techniques often cited to treat immature teeth. But what is it exactly?
Below we will explain two of such procedures, apexogenesis and apexification.
Confusion is often made between Apexogenesis and Apexification. Yet they have nothing to do with it.
Apexification is a method of inducing a calcified barrier at the apex of a nonvital tooth with incomplete root formation. Apexogenesis refers to a vital pulp therapy procedure performed to encourage physiological development and formation of the root end.
Apexogenesis can be used when the pulp is injured but not necrotic, leaving the apical one-third of the dental pulp in the tooth, allowing the root to complete formation. Apexification stimulates cells in the periapical area of the tooth to form a dentin-like substance over the apex.
Both apexogenesis and apexification procedures are performed for young immature teeth. However, there is a major difference in the two. Apexogenesis aims to preserve pulp vitality and to promote the further development and strengthening of the roots. On the other hand,apexification is carried out when the pulp is necrotic and there is no possibility of further development of the root structure. It aims to close the open apex with the development of a calcific barrier. Therefore careful assessment of pulp vitality is necessary to choose the correct mode of treatment.
Apexogenesis is a biological process that is responsible for the formation of the apex of the tooth. Apex…. Genesis. It is therefore a biological, physiological, ie normal, process of the initial development of the tooth.
This apexogenesis is carried out by stem cells in the pulp which differentiate (in other words, transform) into odontoblasts to make dentin.
The root building continues for a certain length. Then, this length reached, an inflection takes place to proceed to the apical closure of the root. It is this process that is called APEXOGENESIS. We can therefore see that this has nothing to do with therapy.
Unlike APEXIFICATION, To operate, the pulp must be alive. In the presence of a caries pathology or a traumatic exposure, partial or total pulpotomy (or cervical) can be implemented in order to keep the living pulp, and thus allow apexogenesis to take place. this is why we should speak in the absolute, "allowing therapeutic apexogenesis" and not processing apexogenesis which semantically does not mean much.
At a more advanced stage of pathologies, the pulp can necrosis. There are therefore no more cells capable of continuing the development of the tooth. The root therefore remains in an “immature” state - short root, thin walls and above all foraminal diameter (if one can speak of a foramen at this stage) very large. And because this foramen is very large, conventional procedures used in endodontics are not applicable. It is well understood in a case like this that obtaining a taper is illusory and that the vertical compaction of gutta percha is impossible.
It is in these cases that an apexification procedure is implemented. The goal is to close the canal in its apical third other than with gutta percha.
This barrier can be obtained in two ways:
Either by inducing a mineralized biological closure
Or by creating an apical plug with an appropriate material.
For the first solution, the objective is to stimulate periodontal cells to form a mineralized barrier by placing and renewing calcium hydroxide in the canal of the tooth to be treated. After several months and several renewals every three months, we obtain, in the most favorable cases, a closure of the canal with a more or less thick barrier. Once the channel is “closed”, it is filled with gutta percha, either by compaction or by injection with dedicated equipment.
This procedure gives very good results when done well. But it has two drawbacks:
It is long and requires patient compliance - which sometimes is not easy
The fragility of the tooth - for two reasons. On the one hand, the walls are thin and the tooth is short. On the other hand, it has been shown that prolonged exposure of dentin to calcium hydroxide has the consequence of weakening the dentin, and this, in an intrinsic way.
Those who have practiced this technique or who still practice it know that the risk of fracture of the root before the end of treatment is far from negligible.
Subject to the viability of the pulp and the need to ensure further apexogenesis, the amputation method (pulpotomy) of getting rid of pulpitis is used. Apexogenesis is a procedure that stimulates further root development, as it promotes pulp healing.
The damaged soft tissues are covered with a special preparation to stimulate further root growth.
The apex continues to close and the canal walls thicken
If the pulp recovers, further treatment may not be needed.
The more developed the root becomes, the more chances that the tooth will be able to be preserved.
However, apexogenesis is not always successful.
The Second approach is to create an apical plug with a dedicated material. Indeed, once the apical part is closed, it becomes simple to fill the rest of the canal with gutta percha. The advantage is that instead of waiting several weeks for the canal to be closed, the treatment can be carried out in two stages over a period of 24 or 48 hours. The risks of weakening the dentin by the application of calcium hydroxide over the long term are therefore eliminated. And by filling the tooth quickly, somewhere, you are probably already strengthening it?
A manuscript described, a few years ago, the use of calcium sulphate (the famous plaster of Paris) to create this plug (Harbert, 1996). The idea was excellent, but apart from this case report, to my knowledge, there is no follow-up given to this protocol. Maybe because of the material.
Achievement of successful apexification is carried out in two ways: multi-step and one-step.
Multi-step. In this case, the treated canals are obturated with pastes based on calcium hydroxide, which are delivered to the treatment area using a plugger, canal filler, syringe, amalgam tregger and other instruments. Beforehand, the cavities are thoroughly dried with paper points. After filling the canals, the crown is sealed with glass ionomer or zinc oxide-eugenol cement. After 30 days, the calcium hydroxide is replaced. After about 3-6 months, an X-ray examination is performed, with the help of which the presence or absence of a dense barrier bridge in the apical part of the tooth is determined.
One-time. This method of apexification involves obturation of the apical zone of the root canal with MTA preparations. Within a few hours, the material completely hardens, after which a permanent filling of the tooth is performed. This method is used in case of endoparadontal lesions, inability to prolong treatment, insufficient effectiveness of other drugs for apexification, as well as when it is impossible to ensure reliable sealing of a temporary filling and in other cases.
Regardless of the condition of the tooth and the selected treatment technology, permanent root canal filling can be performed only after the complete formation of a dense and durable apical barrier in the root apex area.
The marketing of Mineral Trioxide Aggregate a few years later, on the other hand, made it possible to review the concept and develop it.
The idea is to deposit the MTA directly in the apical third and to form a plug of approximately 5 millimeters to obtain an optimal seal. In a second session, after having checked that the material has taken hold, the canal is filled with gutta percha. We thus obtain an almost conventional root canal filling, with however a technique that is not.
Several studies have made it possible to validate the concept and the technique. In 2007, we published a clinical study which showed a success rate of 82% on about fifty treated cases (Simon et al., 2007).
As MTA is a bioactive material, it is able to induce as a second intention the formation of a mineralized barrier on contact. A bit like the famous mineralized bridge when the material is placed directly in contact with the pulp.
Can we imagine reducing the number of sessions to just one? The solution is in the material used. One of the disadvantages of MTA is that it takes a long time to take and takes several days. It is difficult to envisage the two phases (stopper and rise) in the same session - even if, between us it is said, this is what is commonly done in daily practice.
Biodentine or other bioceramics have much shorter setting times. About 10 minutes for Biodentine. It then becomes entirely possible to carry out the two stages of the obturation in the same session.
One of the disadvantages of Biodentine is its low radiopacity. It is difficult on postoperative radiographs to discern the limits of the filling and the dentinal walls.
Apexification gives excellent results. The procedure is not necessarily very simple and requires learning and a little practice.
The use of an operating microscope greatly facilitates the implementation, without a doubt.
In recent years, new concepts based on tissue engineering have been applied in endodontics. Revascularization or revitalization techniques have developed and make it possible to treat these immature teeth with a technique that is much simpler technically but which requires a different conception of dentistry.