Pulp with age:
- reduce collagen fiber
- Increase cellular in pulp
- decrease pulp chamber size.***
Internal dental anatomy:
A. Topographic anatomy of the constituent tissues of the dental organ:
The internal anatomy is constantly evolving throughout the life of the tooth on the arch, the reader will refer to the notions of chapter 1 on the histological constitution of the tooth, the notions of growth of the dental organ (growth and exfoliation) and aging of chapter 3 and finally to the notions of biomechanics of chapter 4 complementary to this internal topographic anatomy and tissue distribution of the dental organ.
1- Enamel:
The thickness of the enamel is maximum compared to the incisal edges and cusp peaks. It can reach 2.5 mm vertically above the cuspal peaks of permanent molars (see Fig. 1.10, page 9) and gradually decreases towards the neck where it ends in a few microns. The enamel has folds corresponding to the external reliefs of the crown: cingulate of the incisors and canines, furrows of the premolars and molars. The enamel of temporary teeth is halved compared to that of permanent teeth. Since enamel is an acellular structure, it is not subjected to rearrangements that aim to compensate for its wear or loss due to trauma or carious damage.
2- The dentine:
Dentin is the tissue that constitutes the majority of the dental organ in the form of a large corono-radicular dentinal nucleus.
The external contours (enamel and cementum) of the dentinal nucleus, closely related to the deepest layer of enamel and cementum, are definitively fixed during odontogenesis. At its border with the enamel, the dentine reproduces very coarsely and in a very frustrating way, the coronary reliefs (cusp, incisal edge, cingulum, axial contours).
At the level of the collar, there is practically no break in direction between the axial coronal and root contours.
The dental pulp contained in the pulp cavity dug in the heart of the dentinal nucleus is responsible for the centripetal dentin edification. Unlike its external contours, the internal contours, pulp, of the dentinal nucleus are the seat of a permanent activity. As long as the pulp is alive, the dentine constantly remodels by apposition / resorption processes, thus modifying the internal contours of the pulp cavity. These reworkings can be physiological or respond to traumatic, pathological or therapeutic phenomena.
The physiological apposition of secondary dentin has the effect of gradually reducing the pulp volume, while the apposition of reactive dentin is done against the causative agent (caries, for example).
Dentin resorption phenomena may have an internal origin and affect the surface of the peripulpal dentin in response to chronic inflammation of the pulp, or, following trauma, have an external origin in the form of a lysis osteoclastic type tissue that affects the root surface.
3- The cement:
The thickness of the cementum is approximately 20 to 50 μm at the cervical level. It increases progressively apically up to 50 to 200 μm.
The cementation reshaping correspond to processes of apposition / resorption which are manifested in response to local solicitations of dental or periodontal origin.
The cementum physiologically affixes throughout the life of the tooth on the arch, whether the pulp is alive or not. This apposition is minimal at the cervical level and increases towards the apex. It compensates for the occlusal wear of the crown.
4- The enamel / cement junction:
At the level of the collar, the junction between the enamel and cementum can be done in several ways:
- Enamel and cement clash through an end-to-end contact.
- Enamel and cement do not meet, exposing the dentinal tissue and thus constituting a factor of hyperesthesia and vulnerability to carious attack
- The cement covers the enamel, creating a heterogeneity of the tooth surface and susceptibility to the retention of plaque. These three configurations can be found on the same tooth.
B- Anatomy of the pulp cavity:
The pulp is a connective tissue, consisting in particular of the cellular and vasculonervous elements of the tooth; it occupies the pulp cavity which is an extended dentinal cavity in the crown and in the root.
1- Coronal pulp cavity:
In the crown, the pulp cavity takes the name of pulp chamber and contains the coronary pulp. The pulp chamber, like the crown, presents four axial walls: vestibular, lingual, mesial and distal. The wall parallel to the occlusal surface of the tooth is the pulp ceiling. It is limited by the pulp horn or horns that point towards the cuspal peaks or the incisal edge. There are usually as many pulp horns as cusps or eminences.
For example, the pulpal chamber of a maxillary central incisor of a young subject has three pulpal horns facing the three lobes of the incisal edge.
The general shape of the pulp chamber in occlusal view is modeled on that of the occlusal contour: triangular for the incisors and canines, oval for the premolars and quadrangular for the molars.
For molars, the pulp chamber is perfectly defined. It is roughly cuboid with a ceiling, four axial walls and a cervical wall, the pulpal floor. The ceiling carries the pulp horns facing the Cuspian peaks and the floor opens to the entrance openings of the channels.
2- Root pulp cavity:
In the root, the pulp canal contains the root pulp. At the end of the root, the pulp cavity communicates with the periapical periodontium by the apical foramen which delivers passage to the vasculoneural elements of the tooth (Fig. 2.21).
There are several types of pulpal channels:
the main channels: they leave the pulp chamber and end in the apical region;
the lateral channels: they leave the main channel and end at a distance from the apical region. For the molars, they can exist at the level of the furcation: they then connect the cameral pulp to the inter-radicular region. These are the lateral inter-root canal;
the terminal (or apical) channels: they leave the main channel and end in the apical region. They are found only at the apical third of the root.
C- Constitution of the pulp cavity:
1- Simple pulp cavity:
It is a single cavity that extends from the crown to the root, with no other delimitation between the chamber and the pulp canal than a projection of the level of the cervical line. It has only one main channel that goes from the chamber to the apical foramen.
The shape of the contours of the main canal is homothetic to that of the external contours of the root.
In axial section, the canal can present seven configurations: round, oval, triangular, rectilinear, in keel, in beans (in C) or in hourglass (in 8). Different section shapes can coexist within a single root.
Simple pulp cavities are more common on monoradiculate teeth and more rare on premolars and molars.
2- Complex pulp cavity:
It is a pulp cavity whose main channels can branch, divide and join each other throughout their journey to the apical foramen. It is usually present on the multiradicular teeth, but sometimes it is found on certain monoradiculated teeth.
Traditionally, it is considered that the complex pulp cavity can adopt four configurations:
- type I: a single main canal from the pulp chamber to the apical foramen;
- type II: two main canals that separate from the pulp chamber and confluence to form a single main canal near the apical foramen;
- type III: two main channels that separate from the pulp chamber and remain separated to end with two apical foramina;
- type IV: a single main canal that starts from the pulp chamber and divides into two main channels ending in two apical foramina.
This classification remains rather caricatured compared to clinical realities and other more complex and unusual variations can be observed.
3- Variability of the pulp cavity:
The morphology of the pulp cavity is homothetic to that of the external contours of the tooth, but since dentin and pulp are tissues that react by physiological or non-physiological modifications, these reactions can cause variations in its shape and volume.
Internal dental anatomy:
A. Topographic anatomy of the constituent tissues of the dental organ:
The internal anatomy is constantly evolving throughout the life of the tooth on the arch, the reader will refer to the notions of chapter 1 on the histological constitution of the tooth, the notions of growth of the dental organ (growth and exfoliation) and aging of chapter 3 and finally to the notions of biomechanics of chapter 4 complementary to this internal topographic anatomy and tissue distribution of the dental organ.
1- Enamel:
The thickness of the enamel is maximum compared to the incisal edges and cusp peaks. It can reach 2.5 mm vertically above the cuspal peaks of permanent molars (see Fig. 1.10, page 9) and gradually decreases towards the neck where it ends in a few microns. The enamel has folds corresponding to the external reliefs of the crown: cingulate of the incisors and canines, furrows of the premolars and molars. The enamel of temporary teeth is halved compared to that of permanent teeth. Since enamel is an acellular structure, it is not subjected to rearrangements that aim to compensate for its wear or loss due to trauma or carious damage.
2- The dentine:
Dentin is the tissue that constitutes the majority of the dental organ in the form of a large corono-radicular dentinal nucleus.
The external contours (enamel and cementum) of the dentinal nucleus, closely related to the deepest layer of enamel and cementum, are definitively fixed during odontogenesis. At its border with the enamel, the dentine reproduces very coarsely and in a very frustrating way, the coronary reliefs (cusp, incisal edge, cingulum, axial contours).
At the level of the collar, there is practically no break in direction between the axial coronal and root contours.
The dental pulp contained in the pulp cavity dug in the heart of the dentinal nucleus is responsible for the centripetal dentin edification. Unlike its external contours, the internal contours, pulp, of the dentinal nucleus are the seat of a permanent activity. As long as the pulp is alive, the dentine constantly remodels by apposition / resorption processes, thus modifying the internal contours of the pulp cavity. These reworkings can be physiological or respond to traumatic, pathological or therapeutic phenomena.
The physiological apposition of secondary dentin has the effect of gradually reducing the pulp volume, while the apposition of reactive dentin is done against the causative agent (caries, for example).
Dentin resorption phenomena may have an internal origin and affect the surface of the peripulpal dentin in response to chronic inflammation of the pulp, or, following trauma, have an external origin in the form of a lysis osteoclastic type tissue that affects the root surface.
3- The cement:
The thickness of the cementum is approximately 20 to 50 μm at the cervical level. It increases progressively apically up to 50 to 200 μm.
The cementation reshaping correspond to processes of apposition / resorption which are manifested in response to local solicitations of dental or periodontal origin.
The cementum physiologically affixes throughout the life of the tooth on the arch, whether the pulp is alive or not. This apposition is minimal at the cervical level and increases towards the apex. It compensates for the occlusal wear of the crown.
4- The enamel / cement junction:
At the level of the collar, the junction between the enamel and cementum can be done in several ways:
- Enamel and cement clash through an end-to-end contact.
- Enamel and cement do not meet, exposing the dentinal tissue and thus constituting a factor of hyperesthesia and vulnerability to carious attack
- The cement covers the enamel, creating a heterogeneity of the tooth surface and susceptibility to the retention of plaque. These three configurations can be found on the same tooth.
B- Anatomy of the pulp cavity:
The pulp is a connective tissue, consisting in particular of the cellular and vasculonervous elements of the tooth; it occupies the pulp cavity which is an extended dentinal cavity in the crown and in the root.
1- Coronal pulp cavity:
In the crown, the pulp cavity takes the name of pulp chamber and contains the coronary pulp. The pulp chamber, like the crown, presents four axial walls: vestibular, lingual, mesial and distal. The wall parallel to the occlusal surface of the tooth is the pulp ceiling. It is limited by the pulp horn or horns that point towards the cuspal peaks or the incisal edge. There are usually as many pulp horns as cusps or eminences.
For example, the pulpal chamber of a maxillary central incisor of a young subject has three pulpal horns facing the three lobes of the incisal edge.
The general shape of the pulp chamber in occlusal view is modeled on that of the occlusal contour: triangular for the incisors and canines, oval for the premolars and quadrangular for the molars.
For molars, the pulp chamber is perfectly defined. It is roughly cuboid with a ceiling, four axial walls and a cervical wall, the pulpal floor. The ceiling carries the pulp horns facing the Cuspian peaks and the floor opens to the entrance openings of the channels.
2- Root pulp cavity:
In the root, the pulp canal contains the root pulp. At the end of the root, the pulp cavity communicates with the periapical periodontium by the apical foramen which delivers passage to the vasculoneural elements of the tooth (Fig. 2.21).
There are several types of pulpal channels:
the main channels: they leave the pulp chamber and end in the apical region;
the lateral channels: they leave the main channel and end at a distance from the apical region. For the molars, they can exist at the level of the furcation: they then connect the cameral pulp to the inter-radicular region. These are the lateral inter-root canal;
the terminal (or apical) channels: they leave the main channel and end in the apical region. They are found only at the apical third of the root.
C- Constitution of the pulp cavity:
1- Simple pulp cavity:
It is a single cavity that extends from the crown to the root, with no other delimitation between the chamber and the pulp canal than a projection of the level of the cervical line. It has only one main channel that goes from the chamber to the apical foramen.
The shape of the contours of the main canal is homothetic to that of the external contours of the root.
In axial section, the canal can present seven configurations: round, oval, triangular, rectilinear, in keel, in beans (in C) or in hourglass (in 8). Different section shapes can coexist within a single root.
Simple pulp cavities are more common on monoradiculate teeth and more rare on premolars and molars.
2- Complex pulp cavity:
It is a pulp cavity whose main channels can branch, divide and join each other throughout their journey to the apical foramen. It is usually present on the multiradicular teeth, but sometimes it is found on certain monoradiculated teeth.
Traditionally, it is considered that the complex pulp cavity can adopt four configurations:
- type I: a single main canal from the pulp chamber to the apical foramen;
- type II: two main canals that separate from the pulp chamber and confluence to form a single main canal near the apical foramen;
- type III: two main channels that separate from the pulp chamber and remain separated to end with two apical foramina;
- type IV: a single main canal that starts from the pulp chamber and divides into two main channels ending in two apical foramina.
This classification remains rather caricatured compared to clinical realities and other more complex and unusual variations can be observed.
3- Variability of the pulp cavity:
The morphology of the pulp cavity is homothetic to that of the external contours of the tooth, but since dentin and pulp are tissues that react by physiological or non-physiological modifications, these reactions can cause variations in its shape and volume.
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