Apical healing
Introduction :
The periapex constitutes a functional unit in constant remodeling where all the components are linked by fibers, vessels and where the BLACK space, nourishing center, ensures the metabolism of the hard tissues which surround it. The cementum on one side and the alveolar bone on the other.
This region is able to cope with endodontic irritations and heal itself.
1) Definition:
1.1/ healing:
It is a repair phenomenon which is the final stage of inflammation, this healing results in connective tissue which replaces the destroyed tissue.
The structure of the connective tissue will change gradually and slowly.
1.2/ BLACK space:
Limited by the end of the root, capped with cellular and acellular cement, and by the cortex of the bottom of the alveolar cavity. It contains:
* the apical orifice or foramen.
* the innervation and vascularization pedicle.
* the ligamentous bundles uniting the apical cementum to the alveolar bone cortex. Black’s space is made up of a richly vascularized and innervated fibrous connective tissue, which contributes with the rest of the alveolo-dental ligament, or desmodontium, to the attachment. From the dental root to the alveolar bone.
2) Anatomy of the apical region:
2.1/ Definition: It is a crossroads region that contains the alveolo-dental ligament and connective tissue rich in cells. Due to its anatomical and physiological characteristics, it offers an access route to microorganisms. This region is richly vascularized by the dental artery and its anastomoses with the interdental arteries.
According to (KUTTLER), the apical region is formed by the joining of two cones:
– one dentin has its summit at the cemento-dentin junction.
– the other purely cemental one is inverted with respect to the first, its summit is located at the cemonto-dentin junction at the point of narrowing of the dentin cone and its base is at the apical foramen.
The height of the cementum portion is 0.5 mm in young adults and 0.7 mm in elderly subjects.
The set of two cones can be compared to an hourglass whose two compartments are
disproportionate.
*The apical foramen
It is also called the apical “hole”, it is the space limited by the cementum walls starting at the apical constriction and opening into the periodontium. It has an irregular funnel shape which changes as a result of physiological (cementum apposition) or pathological (resorption) processes.
*The periapex
It is a widely vascularized area and constitutes the site of cellular and immunological reactions which allow apical healing after the aggression of this area following pathological processes of which the endodontium is the seat.
These reactions allow, depending on the severity of the aggression:
– cementogenesis leading to the closure of the foramina by the development of neocementum in cases of pulpitis.
– osteocementogenesis in the case of pulp gangrene or desmodontitis.
*Apical constriction
It is located at the cemento-dentin junction below the apical foramen. It has a diameter ranging from 210 to 224 microns and varies according to age. The distance usually separating the apical constriction from the anatomical apex can be estimated at 0.5 or even 2 mm. It increases with age and is greater in posterior teeth than in anterior teeth.
3) Histology of the apical region:
The periapex is made up of a set of histologically different elements:
a) Cement:
acellular cementum: the collagen fibers from the neighboring connective tissue are included in the cementum layer, thus constituting the SHARPEY fibers, thus giving the acellular or fibrillar cementum. It constitutes 2/3 of the cementum tissue.
Cellular cementum: cementoblasts will deposit on the acellular cementum to produce cellular cementum.
NB: For SELTZER, there is a third type of cement at the cemento-dentin junction: this is the intermediate cementum.
b) Desmodont:
It is a connective tissue formed:
– fibrillar elements: collagen, elastic or reticulin fibers.
– cellular elements: fibroblasts and histiocytes.
– a fundamental substance: formed of water retained by macromolecules of proteins and mucopolysaccharides.
The desmodont is richly vascularized (vessels of the pulp artery, anastomosing vessels of the gingiva).
c) Alveolar bone:
It is a connective tissue composed of fibrillar and cellular elements. It is formed of three layers:
An external layer in continuity with the compact bone of the jaws, it is in contact with the periosteum.
An intermediate layer with a trabeculated appearance due to the presence of bony trabeculae within it.
An inner layer called the lamina dura or cribriform plate or alveolar bone proper.
There is perpetually at the level of the alveolar bone, a formative activity and a destructive activity alternating by the intermediary of the osteoblasts and the osteoclasts.
4) Physiology of the apical region:
After pulp eviction, the dentinogenic function of the latter is cancelled; but there remain at the apex, living elements such as cementum, bone which are the supports of the periapical repair.
a) Cement:
It is an element in perpetual rearrangement throughout life. The fibroblasts are arranged in a single row on the root dentin surface then differentiate into cementoblasts and will secrete the precement. The latter will calcify to give the cement while the second layer of the precement is affixed to the surface. Its thickness increases with age, but the appositions are more or less regular which indicates calcification by thrust.
However, in the extent of healthy cementum, we note small isolated areas of resorption without relation to any pathology, whether periapical or periodontal. The deep calcified layers contain few or no cementoblasts; we then speak of acellular or fibrillar cementum.
From the primary cementum come ligamentous fibers called SHARPEY fibers which will be enclosed during the calcification of this primary cementum.
We must therefore always, after root canal treatment, restore the tooth’s function as quickly as possible, which will stimulate periapical repair.
We therefore have slow cementogenesis throughout life which will suddenly become active when there is a stimulus, until the moment when a new balance is found and cementogenesis will then become slow again.
b) Alveolar bone:
The alveolar bone is the site of continuous remodeling; by coordination of destructive and formative activities (apposition, resorption) by cells such as osteoblasts and osteoclasts, the phenomena of osteogenesis and osteoclasis follow one another. Pressure causes resorption while traction causes apposition. Similarly, bone congested by the presence of a canal infection during or after pulp gangrene is resorbed, and in its place, the fundamental connective tissue framework reappears.
c) The cellular components of the periapex:
Synthetic cells
They characterize the specialized connective tissues that are the periodontal ligament and the pulp. These cells actively participate in the repair process.
– Fibroblasts and fibrocytes
They are the most numerous and are concentrated in the central zone of the desmodont. Electron microscopy reveals numerous and developed organelles, a sign of strong synthesis activity.
Fibrocytes are older fibroblasts but with fewer organelles and much slower functions.
– Cementoblasts
They are arranged in front along the cementum and appear either isolated or grouped by 4 or 5 opposite the dentin or the cementum already formed.
– Osteoblasts
They are aligned along the bone surfaces under construction. Many organelles are described as in any cell with high synthesis activity.
– Odontoblasts
Responsible for the formation of dentin, they contain numerous highly developed organelles and possess, in addition, a very marked synthetic power.
Cementoclastic and osteoclastic cells
These cells are responsible for the resorption phenomena.
Quiescent cells or cells incorporated into hard tissues:
It is essentially the cementocytes and the osteocytes that have the same origin. Indeed, the cementoblasts and osteoblasts are arranged on the edge of the desmodont, each cell type developing according to its specificity an organic matrix which is secondarily mineralized. Caught in a mineral matrix, cementoblasts and osteoblasts take the name of cementocytes for the former and osteocytes for the latter.
5) Reparative potential of the apical region:
The periapex has a strong potential for regeneration (defense, synthesis, resorption, quiescent cells, BLACK space) that endodontic treatment, through root canal obturation, should stimulate, leading to apical healing.
Apical healing
6) Apical healing
– When the pulp disappears, a biological relay unit is formed in the periapical region, consisting of bone, cementum and ligament, provided that the preparation technique has respected the anatomical requirements.
-Any endodontic therapy causes an inflammatory reaction at the apical level which will result in a reduction in synthetic activity and an increase in osteoclastic and cementoclastic phenomena.
-Once the preliminary inflammatory phase is controlled by the defense cells, the biological desmodontal, cementum and bone repair disappears and can begin after having established a fibrous connective tissue.
a) Desmodontal repair:
– increase in the differentiation and activity of fibroblasts which will ensure the remodeling of desmodontal fibers by the synthesis and secretion of collagen precursors which then undergo maturation.
b) Cement repair:
– Cementoblasts create resorption areas called cementoclasies which are spontaneously repaired by new cement formation.
– The gaps are filled or lined with a thin layer of cementum which allows the reattachment of the newly formed desmodontal fibers.
Two fibrillar frameworks are thus formed. One perpendicular to the tooth called the “extrinsic framework”, produced by the desmodont and represented by the insertion of SHARPEY’s fibers, the other parallel to the bone surface called the “intrinsic framework”, and produced by the cementoblasts. The SHARPEY’s fibers mineralize secondarily.
The cementum also reconstituted covers the apex of the tooth by lining the internal walls of the foramen. Many authors observe a closure of the apex in devitalized teeth. This healing is of course linked to the apical anatomy but also to the limit of preparation and canal obturation.
The repair cementum always appears cellular with few fibers. The structure is not related to the location or nature of the repaired tissue. It is less radiopaque, therefore less mineralized than the surrounding tissue.
c) Bone repair:
During bone repair, there may be either formation of granulation tissue and healing or isolation by a fibrous bundle.
The steps of tissue repair are as follows:
After organization of the clot, there is formation of granulation tissue, opening of new circulation pathways and formation of numerous anastomoses.
Fibroblasts grow along the fibrin filaments and help in the formation of a protein matrix by depositing collagen fibers. Then fibroblasts and capillaries become less numerous and avascular fibrous tissue or scar tissue is formed.
The repair always proceeds from the periphery to the center. After treatment, an area of rarefaction can be found where histology demonstrates the presence of dense avascular fibrous connective tissue: this is healthy healing tissue.
7) Apical remodeling after root canal treatment:
Healing after root canal treatment is accompanied by a more or less significant remodeling of the calcified tissues.
The bone resorption area occupied by the apical lesion transforms into alveolar bone, with normal trabecular orientation immediately after healing or later, after a period of remodeling.
Cementum must line the root apex to allow reattachment of the newly formed periodontal ligament.
In order to allow this reattachment, the areas of resorption, large and small gaps, must be filled (so-called anatomical healing) or lined with new cementum (physiological healing).
Cement apposition also continues along the dentinal walls, sometimes up to the apex. Some authors believe that this process ends with the complete and “hermetic” obturation of the apical foramen by the cementum.
This internal apposition must be preceded by the proliferation of connective tissue after the inflammation has disappeared. The success of a root canal treatment results in a restitution of the radiological apical structures.
8) Healing factors:
General factors and local factors are cited.
***General factors of healing
- Age.
- General health.
- Hormonal disorders.
- Vitamin disorders.
- Nutrition.
***Local factors of healing
- Persistent infection.
- Hemorrhage.
- Tissue laceration.
- Presence of foreign body.
- Presence of accessory canals.
Apical healing
9) Healing criteria:
***Clinical criteria
- Absence of symptoms.
- Disappearance of the fistula, of a swelling.
- Non-painful percussion.
***Radiological criteria
- Disappearance of the radiolucent image.
- Regular ligament not enlarged.
Apical healing
Conclusion :
After pulp eviction, the dentinogenic function of the latter is cancelled, the apex thanks to these living elements such as cementum, bone which will be the support of periapical healing.
Any endodontic therapy must respect the limits of preparation and obturation represented by the cemento-dentin constriction in order to preserve the reparative potential of the apical region. This reparative potential includes fibrogenesis, cementogenesis and osteogenesis.
Untreated cavities can damage the pulp.
Orthodontics aligns teeth and jaws.
Implants replace missing teeth permanently.
Dental floss removes debris between teeth.
A visit to the dentist every 6 months is recommended.
Fixed bridges replace one or more missing teeth.