Morphology, histophysiology and pathophysiology of temporary teeth
I/ Introduction:
- The temporary tooth is the best space maintainer in all three dimensions: sagittal, frontal and horizontal.
- Any pathology leading to tooth loss will cause disturbances in the growth of the arches and in the establishment of permanent teeth.
II/ Eruption sequences:
- characteristic of the temporary tooth:
- Width of tubules
- Importance of vascularization.
- Thin dentin.
- Variable pulp physiology.
- Importance of the pulpo-periodontal complex.
- Periodontal pulp communication
- Physiological and pathological resorption.
- Evolutionary root anatomy.
- Relationship with the germ of the permanent tooth.
A. From a morphological point of view
- The thickness of the hard tissues of the temporary tooth is reduced , the pulp is therefore proportionally more voluminous, the pulp horns are longer, more tapered and are not far from the enamel surface.
- The pulp floor has numerous pulpo-periodontal canals communicating with the inter-radicular space, the complex canal anatomy is the main cause of endodontic treatment failures ,
- Root canal shaping is particularly delicate due to the pronounced curvature of the roots and their fineness in the apical zone and the germ of the permanent tooth which can occupy different positions and which evolve according to root resorption.
- Root filling techniques must take this particularity into account.
B. From a histological point of view
- The pulp tissue of temporary teeth is of the same nature as that of permanent teeth with the characteristics of young connective tissue, very highly vascularized , rich in enzymes and strong odontoblastic activity.
III/ the physiological stages of the temporary tooth:
Stage I : the temporary tooth in formation:
- Morphological characteristics : while having the anatomical characteristics specific to the temporary tooth, we observe at the same time roots that are still incompletely formed.
- Physiological characteristics : temporary teeth in formation are affected by caries , but may be the site of trauma . In these cases, the pulp reaction will be inevitable:
- “Repair” type response with preservation of vitality.
- Abnormal stimulation of dentinogenesis with complete closure of the canal lumen.
- Pulp necrosis is often asymptomatic and sometimes only becomes apparent after months or can be diagnosed by abnormal coloring.
At the level of the root structures of traumatized teeth , the cementum and bone reaction can result in ankylosing repair , it is not uncommon to observe a slight delay in the replacement timeline, therefore any trauma occurring at the level of the temporary incisors requires radiological and clinical monitoring.
Stage II : the stable temporary tooth:
- Morphological characteristics:
- Enamel-dentin-pulp relationships:
- The enamel layer is of low importance (1mm) but its repair is very regular, the enamel prisms at the neck are directed towards the grinding face instead of radiating towards the gingival setting, the abrasion of the enamel is faster than that of permanent teeth.
- The total thickness of enamel-dentine is less than that of the permanent tooth, the average thickness is only 2 to 3 μm compared to 6 μm for the permanent tooth with a maximum of 4 μm at some cusps and a minimum of 0.7 μm at the neck constriction, so there is a small amount of dentin tissue to protect the pulp organ, the thickness of the calcified dentine before birth is homogeneous, while the closed portion during childhood shows a more globular calcification. It is less dense and is more easily removed with an excavator.
- The pulp is proportionally much more important , with an exuberant development of the horns which sometimes form real pulp digitations.
- Peridental structures:
- The epithelial attachment of the temporary tooth: temporary teeth have particularly domed crowns, the contact surfaces are located near the coronal third rather than the gingival third, the papilla is clearly more voluminous since it fills the interdental space,
- the free gingiva reaches the crown, the epithelial attachment is located at the level of the enamel and not at the enamel-cementum junction.
- The gingival groove is very slightly marked, the papillary gingiva very rounded.
- Interdental contact areas and septal structures: temporary molars establish their proximal relationships through contact surfaces.
- It is known that a contact point is transformed under the influence of mastication occlusion and compression.
- At the level of the temporary dentition, the contact point is transformed all the more easily into a surface if:
- The thickness of the enamel is thin and therefore fragile.
- The interdental septum is wider .
- Compressive forces are increased upon eruption of permanent molars.
- Ligaments and alveolar areas: these will undergo changes throughout the life of the temporary tooth.
Physiological characteristics : in its stable phase, the temporary tooth has a physiology quite comparable to that of the permanent tooth.
It has the capacity to react to different stimuli, dentinogenesis can be particularly intense and more significant than at the level of the permanent tooth, the quantity of reactive dentin produced in response to the phenomenon of abrasion for example, is the best illustration.
- The pulp also has a structure comparable to that of the permanent tooth,
- Its central region is richly vascularized, its innervation seems to be less than that of the permanent tooth , the cellular and fibrous constituents are represented by fibroblasts, histiocytes, endothelial cells, mesenchymal cells, collagen fibers, all these elements allow the pulp to fulfill its multiple functions (induction, formation, nutrition, protection, defense and repair)
- Its peripheral region or odontogenic region with the odontoblastic layer, the Weill zone which represents the place of mobilization and replacement of odontoblasts, the rich cellular zone containing fibroblasts and undifferentiated mesenchymal cells.
- Like the permanent tooth through the apical zone but also through the accessory pulpo-periodontal canals which constitute multiple communication routes even in stable periods.
Physiopathological characteristics : the stable temporary tooth can respond to an attack by concentrating its defense and repair activities and therefore react actively like the permanent tooth, our therapies can have the same goal and use the same methods.
- Given the low thickness of the enamel-dentine structures that constitute the most effective pulp protection, pulp damage can occur rapidly despite a small loss of substance and a small cavitation . This rapid development is also caused by the lower mineralization of the enamel and by the fact that young dentine is all the more permeable.
Stage 3 : resorption of the temporary tooth
- Physiological resorption is a determining process in the life of the temporary tooth, not only because it modifies the surrounding structures, this resorption results from the activity of multi-nucleated cells, osteoclasts and cementoclasts which appear in the environment of dental structures, their activity is regularly compensated by consolidation and repair but nevertheless results in the destruction of the cementum and dentin and the expulsion of the tooth.
Morphology, histophysiology and pathophysiology of temporary teeth
a* start of root resorption b* loss of the temporary tooth
- It is known that several factors, both local and general, participate in this process and that it is essential to consider these areas in order to explain it. The temporary tooth and its periodontal structures, the presence of the permanent tooth, the alveolar areas adjacent to the two structures that will undergo continual remodeling, the modifications of these areas are very significant in the resorption process under the combined actions of the eruptive forces of the permanent tooth and the masticatory forces exerted on the temporary tooth.
- A change in the connective tissue interposed between the two dental organs is observed in a typical, highly hyperemic granulation tissue of the inflammatory type.
- This granulation tissue with high osteoclastic activity is formed both from the alveolar areas and from the periodontal tissues.
Morphology, histophysiology and pathophysiology of temporary teeth
Sensitive teeth react to hot, cold or sweet.
Sensitive teeth react to hot, cold or sweet.
Ceramic crowns perfectly imitate the appearance of natural teeth.
Regular dental care reduces the risk of serious problems.
Impacted teeth can cause pain and require intervention.
Antiseptic mouthwashes help reduce plaque.
Fractured teeth can be repaired with modern techniques.
A balanced diet promotes healthy teeth and gums.