Periapical healing Healing and repair of periapical lesions The biological relay unit
- Definitions
We owe to Melcher the distinction between healing and reparation.
- Healing, or regeneration , is the return of tissues to their previous state after treatment, which occurs most of the time.
- Repair is the filling of the lesion with a tissue different from the original tissue, that is to say with healing tissue (Grossmann).
- Conditions for regeneration
No regeneration will occur until:
- irritants located in the canal system will not have been eliminated by canal shaping,
- and as long as this system has not been sequestered from the rest of the organism by the sealing of the endodontium.
Three types of treatments can be used for this purpose:
– Endodontic treatment by exclusive root canal route
– Endodontic treatment associated with surgical excision of the lesion and curettage of the root end, or apical resection with retro obturation;
– Endodontic treatment associated with periodontal treatment when the lesions are combined.
- Regeneration Mechanisms “The Biological Relay Unit”
After the pulp has disappeared, three tissues capable of repair form the “biological relay unit” at the periapex: bone, cementum and periodontal ligament.
After the inflammation has disappeared , vascular and cellular mechanisms will allow bone and cement regeneration, by apposition of new tissue formations, and the reconstitution of the periodontium, will indicate complete healing when the regular periradicular radiolucent space reappears on the X-ray, which represents a healthy periodontium; it can only be or become so again, if the bone and cement physiologies have returned to normal.
The regeneration mechanism differs depending on the treatment:
– If classical endodontic treatment is chosen, the inflammatory tissue filling the lesion is left in place, and must first be transformed into newly formed connective tissue free of any inflammation.
– In the case of surgical endodontics, the lesion void created must first be filled with young connective tissue which brings into play a completely different potential: bone, cementum and periodontium will quickly emerge from this young connective tissue.
From this neoformation of connective tissue the mechanisms are the same, apart from the exceptional formation in the case of conventional endodontic treatment, more common in the case of endodontic surgery , of a scar repair tissue made of dense collagenous connective tissue.
The sequence of regenerative mechanisms begins with:
- a phase of new bone formation after differentiation of blast cells (osteoblasts or deep mesenchymal cells). Bone trabeculation extends from the periphery towards the center, as the newly formed connective tissue appears, the trabeculae thicken and reposition themselves to achieve the normal arrangement of alveolar bone . This regeneration phenomenon is comparable to that of filling an alveolus after extraction.
- A phase of neoformation of cement The neoformed connective tissue then being in contact with the root, a second blast differentiation occurs: the cementoblasts ensure cellular repair and successive layers of neoformed cement can cover the root and the filling material at the level of the foramen if it does not exceed. (Coolidge and Tagger).
- Formation of the desmodont We then witness between the newly formed bone and cement tissues the organization and then the attachment of a new periodontal fibrous complex which reconstitutes the desmodont and signals the complete regeneration of the biological relay unit, provided that the biocompatible replacement unit does not hinder the operation of these mechanisms, in which case, we would only obtain a partial but clinically acceptable cure.
Periapical healing Healing and repair of periapical lesions
- Clinical and radiographic signs of healing of priapical lesions
- Clinical silence after treatment is only a random sign of healing. If clinical signs, diffuse pain, frank periodontitis, or even abscesses, occur after ten days of treatment, it is obvious that the treatment was not successful and that it must be resumed. On the other hand, the absence of clinical signs does not mean that healing is underway; CAP can develop without the slightest symptom.
- Only systematic control X-rays are acceptable as elements of assessment. Apart from immediate controls, images will be taken after 1 month, to ensure that the lesion does not continue to grow, then every 3 months until complete regeneration : this will be indicated by the disappearance of the loss of substance and by the appearance of a regular and radio-transparent periradicular space proving the reorganization of the desmodont.
Periapical healing Healing and repair of periapical lesions
