MORPHOLOGY, HISTOPHYSIOLOGY AND PHYSIOPATHOLOGY OF TEMPORARY TEETH

MORPHOLOGY, HISTOPHYSIOLOGY AND PHYSIOPATHOLOGY OF TEMPORARY TEETH

Temporary teeth are called baby teeth, primary teeth or milk teeth, deciduous teeth. Decidual comes from the Latin ‘deciduus’ meaning ‘that falls out’ or ‘that lasts only one season’. There are 20 baby teeth: 8 incisors, 4 canines and 8 molars. Calcification of the milk teeth begins between the 13th and 16th week of intrauterine life and their eruption takes place between the 6th and 24th postnatal month.

I – PARTICULARITIES OF TEMPORARY TEETH:

Due to their morphological and physiological characteristics, temporary teeth are particularly sensitive to dental caries and its complications.

Morphological characteristics:
- AT THE CORONARY LEVEL: Temporary teeth are generally a third smaller than permanent teeth and have a globular appearance.

the cusps are more pointed.
Shade: the tooth has a characteristic milky appearance (the enamel is more opaque and thinner.

AT THE ROOT LEVEL:

The roots are divergent, the thinness of their apex and the asymmetric physiological root resorption make it difficult to determine the working length and accentuate the

difficulty in canal shaping and obturation.

The roots are much more curved and especially divergent, because the germ of the permanent tooth is located between them.
They diverge from the crown and do not have a common trunk; their separation occurs near the cervical line.
THE ENDODONTIC:
- The pulp chamber is large, explaining the rapidity of pulp damage;
- The horns are tapered, long, and therefore close to the enamel surface;
- the mesial horns of the molars are much longer.
- Pulp involvement due to carious or traumatic attacks is therefore frequent and rapid.
- The pulp ceiling has a strong central depression, which in slow-developing caries can promote a near-separation of the mesial and distal parts of the pulp chamber, due to the formation of reaction dentin.
- The pulp floor has numerous pulpo-periodontal canals

communicating with the interradicular space, quickly promoting damage to the furcation.

AT THE ROOT LEVEL:
- The canal anatomy is complex, the numerous accessory canals make it impossible to completely eliminate the infected pulp parenchyma and necrotic debris, which is the cause of endodontic treatment failures.
- Root perforations during instrumentation are possible.
- Accentuated curvature of the channels which have flattened shapes, their section resembles a bean making shaping delicate.
- The apical foramina can be multiple and occupy different locations.
- The inter-radicular pulpo-periodontal canals are numerous and their number increases with physiological root resorption.
- Physiological resorption of the DT leads to a modification of the foramen which becomes increasingly enlarged.

Histological characteristics:

The enamel:

The thickness of the enamel layer is thinner than on permanent teeth.
When the tooth emerges from the arch, the enamel is immature.
Enamel maturation occurs during the first year.
Generally speaking, it has a lower degree of mineralization than the permanent tooth (its demineralization will be rapid as will pulp damage);
The distribution of the enamel is regular despite the low thickness.
The enamel prisms at the neck are directed toward the occlusal surface instead of radiating toward the neck of the tooth.

Its abrasion is therefore faster.
The interprismatic spaces are more numerous and larger, but the surface layer is often aprismatic.

Dentin:

The thickness of the dentin layer is approximately half that of permanent teeth.
The dentin tubules are wide.
The dentin of temporary teeth has mineralization defects.

The low thickness of the hard tissues (enamel and dentin) makes the pulp volume large;

Similarly, the large diameter of the dentin tubules promotes bacterial penetration.

Physiological characteristics:

Pulp physiology:

The pulp tissue of temporary teeth is similar to that of permanent teeth.

It is a young, highly vascularized connective tissue with high enzymatic activity, which explains its hyperplastic reactions.

According to Kopel, the pulp of temporary teeth develops reactive dentin more readily in response to pulpal aggression than permanent teeth. This defensive reaction, however, is only observed in temporary teeth in stages 1 and 2.
The innervation is not as dense as for permanent teeth, explaining why temporary teeth appear less sensitive.

This reduced sensitivity may also be due to physiological resorption which would result in nerve degeneration.
But it is not proven that the temporary tooth is less sensitive than the permanent tooth and any pulp treatment indicates the use of anesthesia.
The reparative potential of the pulp observed in stage 2 temporary teeth is most often manifested by the significant apposition of reaction dentin, which constitutes a barrier preventing the spread of the attack to the pulp.

III- EVOLUTION OF THE TOOTH:

Eruption refers to the movement of the developing tooth in the axial direction from its original position in the bone mass to its functional position in the oral cavity. We distinguish:
- The intraosseous pre-eruptive phase.
- The pre-functional eruptive phase.
- The functional eruptive phase.
Rhizalysis is a succession of active resorption phases and repair phases.

Root resorption of temporary teeth or rhizalysis is a multi-factorial, complex phenomenon involving numerous osteoclast and osteoblast cells whose activity is regulated by numerous local factors.

This process of physiological root resorption occurs under the effect of the growth of the definitive germ and leads to the bloodless loss of the temporary tooth.

Chronology of tooth eruption:

Sequence of eruption of temporary teeth:

Schematically, temporary teeth erupt between the 6th ^and 30th ^month , at a rate of one group of teeth every 6 months.

Maxilla: i1, i2, m1, c, m2
Mandible: i1, i2, m1, c, m2

	*Eruption*	*Completed root (after eruption)*	*Start of rhizalysis*	*Exfoliation*
*Incisors*	7-8 months	2 years: 2 and a half years	4 years central / 5 years lateral	6-8 years old
*Canines*	16-20 months	3 years	8 years old	11-12 years old
*1st* *^molar*	12-18 months	2 1/2 years	6 years old	10 years
*2nd* *^molar*	20-30 months	3 years	7 years old	11-12 years old

PHYSIOLOGICAL CONDITIONS:

From emergence in the oral cavity until exfoliation, the temporary tooth follows a particular maturation cycle which is schematically broken down into three stages: formation (stage 1), stability (stage 2), resorption or rhizalysis (stage 3).

Different biological processes will mark this evolution during which we distinguish 3 periods or MSR states or stages 1, 2, 3 which are defined in relation to the anatomical aspect of the root, but which are also marked by other characteristics.

Stage 1 or state of maturation (M): From the emergence of the tooth on the arch to the end of root formation

Stage 2 or stability state (S): From the end of root development to the start of rhizalysis.

Stage 3 or Rhizalysis–Involution (R) state: From the start of Rhizalysis to exfoliation of the tooth.

Physiology of temporary teeth:

STAGE 1	Growth and root development phase: duration 2 years.
STAGE 2	Stability phase: duration 3 years ± 6 months
STAGE 3	Resorption phase: duration 4 years.

DENTINOPULPARY PHYSIOPATHOLOGY OF TEMPORARY TEETH:

The division of the life of the temporary tooth has been made into 3 stages:

Stage 1 or state M:

The tissue immaturity of hard tissues and pulp parenchyma, the open apices highlight the paradoxical aspects of the pathophysiology of young tissues: ease and speed of initial lesions, very early, rapid and effective dentino-pulp defense reactions.
The characteristic carious lesions of this stage are baby bottle caries, “baby bottle syndrome” currently called early childhood caries (ECC).

If the extension of carious lesions can be rapid and very destructive, the dentinopulpal response is active and will contain the carious invasion in depth by the classic double mechanism: formation of a layer of sclerosed dentin facing the caries and reaction dentin reducing the pulp volume by odontoblastic hyperactivity, alone at first then odontoblastic and fibroblastic.

Carious extension occurs mainly laterally through the enamel-dentin seal and the ramifications and communications of the dentin tubules.
The enamel “undermined” from below is weakened and eliminated by occlusal and masticatory pressures, coronal destruction appears very significant.
Sclerodentin and dentin isolate the pulp, which can become healthy again, but sometimes present degenerative histological alterations. The evolution of these lesions depends on whether or not harmful eating habits and brushing are present.
The progression of these lesions will be slow and can be stopped. The dentin is colored, from light brown to deep black.
The dentin surfaces are flat and smooth and retain little plaque.

Rapidly progressive caries is rare at stage 1. It is possible when the poor conditions defined by the Kohen scheme are met to the highest degree.
If the dentinopulpal defenses are high at stage 1, the pulp will offer maximum resistance to necrosis.
The importance of pulp-periodontal communications and wide apical openings, as well as the immaturity of the immune system, explain the frequency of acute infections, which can become chronic, without pulp necrosis.
This pathology of the furcation without necrosis is very characteristic of the temporary tooth.
Complications range from a simple parulic abscess indicating damage to the furcation through pulpo-desmodontal communications, acute or chronic, to cellulitis, which is common in children under 5 years of age.
In cases of periodontal infection without prior pulp necrosis, the progression may be towards necrosis, most often but sometimes towards a hyperplastic reaction, budding of the exposed pulp.
- Stage 2 or S state: The teeth are in a period of stability.

– The apices are built, the activity of the dentino-pulp organ is less intense, but the potential for reaction and defense remains very high.

The cavities will most often be located on the proximal surfaces and in the grooves: the first ^will be rapid cavities, the second will be slow-growing.
The dentinopulpal pathophysiology is similar to that of stage 1.
- Stage 3 or state R: This phase is marked by the start of physiological rhizalysis.
Rhizalysis occurs with alternating resorption and repair; the apices and pulp-periodontal communications may be in a phase of wide opening or return to normal. From the beginning of rhizalysis, the number of nerve fibers decreases in the pulp where mineralization islands may appear. In the late stage, the pulp presents the appearance of inflammatory granulation tissue and participates in the final dentin resorption.

Pathophysiology of the temporary tooth (according to Fortier et al 1987)

Stadium	Physiology Pathology Therapeutics
*1: immaturity*	Repair of cavities (rare) Conservation always possible Trauma to pulp vitality
*2: stability*	Repair Very rapid pulp damage Conservation possible Frequent periodontal damage to the tooth
3: resorption	Oriented towards Irreversible conserve or replacement extract

Conclusion :

The preservation of temporary teeth until their physiological loss is essential; in addition to their role in maintaining space for the placement of permanent teeth, they also maintain the vertical dimension, and play a role in the

phonetic and social development of the child.

IV-CONSEQUENCES ON PATHOLOGY AND THERAPY CONCLUSION

Introduction :

The permanent tooth is considered immature (IPD) when its root is still developing and apical closure is not complete.

The apposition of secondary dentin in the pulp chamber and along the root is a continuous physiological process.

When the tooth is immature, its low thickness results in a large pulp volume, which explains the very sensitive behavior of the young tooth to attacks.

PARTICULARITIES OF THE IMMATURE PERMANENT TOOTH :

The immature permanent tooth is that from its eruptive beginnings in the oral cavity until the end of its root, enamel, pulpodentin and periodontal maturation.

HISTOLOGICAL PARTICULARITIES:
1. The enamel:

During the eruptive period, the enamel is immature . It is porous. This immature enamel presents a greater susceptibility to caries

Enamel proteins are still present in large quantities in post-eruptive enamel. The enamel prism sheath, the interface between the prism and the interprismatic substance, constitutes a significant gap. These proteins disappear as the mineral load increases: this enamel maturation process is estimated to last 2 to 3 years. At the same time, the enamel surface gradually wears away. Thus, surface porosity will decrease.

The pulp-dentin organ:

The root and coronal dentin is thin and the dentin tubules are very wide, facilitating rapid bacterial invasion. On the other hand, the wide apical diameter allows for perfect vascularization and excellent reparative potential.

2 – ANATOMICAL FEATURES:

– Absence of root edification (absence of JCD),

-The apex is widely open in the shape of a funnel or blunderbuss,

-the root canal is wide,

-The dentin walls, thin and fragile, appear divergent, parallel or convergent depending on the stage of root formation.

-The highly vascularized apical region has significant repair potential and actively participates in root building.

3- PHYSIOLOGICAL PARTICULARITIES:

Once the crown is fully formed, root formation begins with epithelial proliferation in the underlying connective tissues, which constitute the Hertwig epithelial sheath. It will disintegrate when the root has reached its final length.

We classically distinguish between primary cementum, which covers the root along its entire length, and secondary cementum or osteo-cementum which covers, among other things, in the apical part of the root, the layer of primary cementum.

Even when the root has reached its final length, the apex remains gaping for about two years. The apical funnel is filled with connective tissue. Along with this maturation, which we will call dental, we observe changes in the structures surrounding the tooth. The lamina dura marks the formation of a true cortex in the form of alveoli and the ligament fibers, which represent the attachment system between the tooth and the bone,

continue to organize themselves until they form the alveolo-dental ligaments of the mature tooth.

Different stages of root development:

According to Nolla, root development takes place in ten stages : From the 1st ^to the 6th ^, formation of the crown; From the 7th ^to the 10th ^, formation of the root.
Nolla in 1960 defined the stages of tooth development as follows:

: absence of the crypt
: presence of the crypt
: initial calcification
: 1/3 of the crown built
: 2/3 of the crown built
: the crown is almost finished
: the crown is finished
: 1/3 of the root built
: 2/3 of the root built, divergent root walls
: root almost at its final length and cylindrical walls

10: cementodentin junction in place and root end completed.

CONSEQUENCES ON PATHOLOGY AND THERAPY:

The very rapid progression of caries in immature permanent teeth is explained by the histo-morphological characteristics of the young dental organ.
At the time of eruption into the oral cavity, the tooth is considered immature. Amelogenesis is complete, but the surface and subsurface layers of the post-eruptive enamel are porous and irregular and therefore highly sensitive to chemical and bacterial aggressions in the oral environment. Enamel maturation is completed over the years.
This post-eruptive maturation will occur gradually, giving the dental surface resistance to the carious process.
If a first molar erupts into an oral cavity with many cavities, it will be confronted with a cariogenic bacterial environment.
Therapeutics should be focused on preserving pulp vitality in order to allow physiological closure of the apex or

“Apexogenesis”.

In cases of pulp necrosis, tooth preservation can be achieved by performing “Apexification” treatments. However, the fragility of the root walls reduces the prognosis for preservation.
Maintaining the tooth as long as possible helps maintain the integrity of the arch length and the development of the alveolar bone during the growth period.

CONCLUSION :

The morphological and physiological characteristics of the pulp tissue of immature permanent teeth make pediatric endodontics complex.

Current clinical techniques in use produce excellent results, but they are not evidence-based (Naudin 2003).

A more biological approach to pulp therapy will aim to regenerate damaged pulp or dentin tissue (Machtou 2010).

MORPHOLOGY, HISTOPHYSIOLOGY AND PHYSIOPATHOLOGY OF TEMPORARY TEETH

Untreated cavities can cause painful abscesses.
Untreated cavities can cause painful abscesses.
Dental veneers camouflage imperfections such as stains or spaces.
Misaligned teeth can cause digestive problems.
Dental implants restore chewing function and smile aesthetics.
Fluoride mouthwashes strengthen enamel and prevent cavities.
Decayed baby teeth can affect the health of permanent teeth.
A soft-bristled toothbrush protects enamel and sensitive gums.

MORPHOLOGY, HISTOPHYSIOLOGY AND PHYSIOPATHOLOGY OF TEMPORARY TEETHMORPHOLOGY, HISTOPHYSIOLOGY AND PHYSIOPATHOLOGY OF TEMPORARY TEETH

I – PARTICULARITIES OF TEMPORARY TEETH:

Due to their morphological and physiological characteristics, temporary teeth are particularly sensitive to dental caries and its complications.

Morphological characteristics:
- AT THE CORONARY LEVEL: Temporary teeth are generally a third smaller than permanent teeth and have a globular appearance.

the cusps are more pointed.
Shade: the tooth has a characteristic milky appearance (the enamel is more opaque and thinner.

AT THE ROOT LEVEL:

The roots are divergent, the thinness of their apex and the asymmetric physiological root resorption make it difficult to determine the working length and accentuate the

difficulty in canal shaping and obturation.

The roots are much more curved and especially divergent, because the germ of the permanent tooth is located between them.
They diverge from the crown and do not have a common trunk; their separation occurs near the cervical line.
THE ENDODONTIC:
- The pulp chamber is large, explaining the rapidity of pulp damage;
- The horns are tapered, long, and therefore close to the enamel surface;
- the mesial horns of the molars are much longer.
- Pulp involvement due to carious or traumatic attacks is therefore frequent and rapid.
- The pulp ceiling has a strong central depression, which in slow-developing caries can promote a near-separation of the mesial and distal parts of the pulp chamber, due to the formation of reaction dentin.
- The pulp floor has numerous pulpo-periodontal canals

communicating with the interradicular space, quickly promoting damage to the furcation.

AT THE ROOT LEVEL:
- The canal anatomy is complex, the numerous accessory canals make it impossible to completely eliminate the infected pulp parenchyma and necrotic debris, which is the cause of endodontic treatment failures.
- Root perforations during instrumentation are possible.
- Accentuated curvature of the channels which have flattened shapes, their section resembles a bean making shaping delicate.
- The apical foramina can be multiple and occupy different locations.
- The inter-radicular pulpo-periodontal canals are numerous and their number increases with physiological root resorption.
- Physiological resorption of the DT leads to a modification of the foramen which becomes increasingly enlarged.

Histological characteristics:

The enamel:

The thickness of the enamel layer is thinner than on permanent teeth.
When the tooth emerges from the arch, the enamel is immature.
Enamel maturation occurs during the first year.
Generally speaking, it has a lower degree of mineralization than the permanent tooth (its demineralization will be rapid as will pulp damage);
The distribution of the enamel is regular despite the low thickness.
The enamel prisms at the neck are directed toward the occlusal surface instead of radiating toward the neck of the tooth.

Its abrasion is therefore faster.
The interprismatic spaces are more numerous and larger, but the surface layer is often aprismatic.

Dentin:

The thickness of the dentin layer is approximately half that of permanent teeth.
The dentin tubules are wide.
The dentin of temporary teeth has mineralization defects.

The low thickness of the hard tissues (enamel and dentin) makes the pulp volume large;

Similarly, the large diameter of the dentin tubules promotes bacterial penetration.

Physiological characteristics:

Pulp physiology:

The pulp tissue of temporary teeth is similar to that of permanent teeth.

It is a young, highly vascularized connective tissue with high enzymatic activity, which explains its hyperplastic reactions.

According to Kopel, the pulp of temporary teeth develops reactive dentin more readily in response to pulpal aggression than permanent teeth. This defensive reaction, however, is only observed in temporary teeth in stages 1 and 2.
The innervation is not as dense as for permanent teeth, explaining why temporary teeth appear less sensitive.

This reduced sensitivity may also be due to physiological resorption which would result in nerve degeneration.
But it is not proven that the temporary tooth is less sensitive than the permanent tooth and any pulp treatment indicates the use of anesthesia.
The reparative potential of the pulp observed in stage 2 temporary teeth is most often manifested by the significant apposition of reaction dentin, which constitutes a barrier preventing the spread of the attack to the pulp.

III- EVOLUTION OF THE TOOTH:

Eruption refers to the movement of the developing tooth in the axial direction from its original position in the bone mass to its functional position in the oral cavity. We distinguish:
- The intraosseous pre-eruptive phase.
- The pre-functional eruptive phase.
- The functional eruptive phase.
Rhizalysis is a succession of active resorption phases and repair phases.

Root resorption of temporary teeth or rhizalysis is a multi-factorial, complex phenomenon involving numerous osteoclast and osteoblast cells whose activity is regulated by numerous local factors.

This process of physiological root resorption occurs under the effect of the growth of the definitive germ and leads to the bloodless loss of the temporary tooth.

Chronology of tooth eruption:

Sequence of eruption of temporary teeth:

Schematically, temporary teeth erupt between the 6th ^and 30th ^month , at a rate of one group of teeth every 6 months.

Maxilla: i1, i2, m1, c, m2
Mandible: i1, i2, m1, c, m2

	*Eruption*	*Completed root (after eruption)*	*Start of rhizalysis*	*Exfoliation*
*Incisors*	7-8 months	2 years: 2 and a half years	4 years central / 5 years lateral	6-8 years old
*Canines*	16-20 months	3 years	8 years old	11-12 years old
*1st* *^molar*	12-18 months	2 1/2 years	6 years old	10 years
*2nd* *^molar*	20-30 months	3 years	7 years old	11-12 years old

PHYSIOLOGICAL CONDITIONS:

Stage 1 or state of maturation (M): From the emergence of the tooth on the arch to the end of root formation

Stage 2 or stability state (S): From the end of root development to the start of rhizalysis.

Stage 3 or Rhizalysis–Involution (R) state: From the start of Rhizalysis to exfoliation of the tooth.

Physiology of temporary teeth:

STAGE 1	Growth and root development phase: duration 2 years.
STAGE 2	Stability phase: duration 3 years ± 6 months
STAGE 3	Resorption phase: duration 4 years.

DENTINOPULPARY PHYSIOPATHOLOGY OF TEMPORARY TEETH:

The division of the life of the temporary tooth has been made into 3 stages:

Stage 1 or state M:

The tissue immaturity of hard tissues and pulp parenchyma, the open apices highlight the paradoxical aspects of the pathophysiology of young tissues: ease and speed of initial lesions, very early, rapid and effective dentino-pulp defense reactions.
The characteristic carious lesions of this stage are baby bottle caries, “baby bottle syndrome” currently called early childhood caries (ECC).

Carious extension occurs mainly laterally through the enamel-dentin seal and the ramifications and communications of the dentin tubules.
The enamel “undermined” from below is weakened and eliminated by occlusal and masticatory pressures, coronal destruction appears very significant.
Sclerodentin and dentin isolate the pulp, which can become healthy again, but sometimes present degenerative histological alterations. The evolution of these lesions depends on whether or not harmful eating habits and brushing are present.
The progression of these lesions will be slow and can be stopped. The dentin is colored, from light brown to deep black.
The dentin surfaces are flat and smooth and retain little plaque.

Rapidly progressive caries is rare at stage 1. It is possible when the poor conditions defined by the Kohen scheme are met to the highest degree.
If the dentinopulpal defenses are high at stage 1, the pulp will offer maximum resistance to necrosis.
The importance of pulp-periodontal communications and wide apical openings, as well as the immaturity of the immune system, explain the frequency of acute infections, which can become chronic, without pulp necrosis.
This pathology of the furcation without necrosis is very characteristic of the temporary tooth.
Complications range from a simple parulic abscess indicating damage to the furcation through pulpo-desmodontal communications, acute or chronic, to cellulitis, which is common in children under 5 years of age.
In cases of periodontal infection without prior pulp necrosis, the progression may be towards necrosis, most often but sometimes towards a hyperplastic reaction, budding of the exposed pulp.
- Stage 2 or S state: The teeth are in a period of stability.

– The apices are built, the activity of the dentino-pulp organ is less intense, but the potential for reaction and defense remains very high.

The cavities will most often be located on the proximal surfaces and in the grooves: the first ^will be rapid cavities, the second will be slow-growing.
The dentinopulpal pathophysiology is similar to that of stage 1.
- Stage 3 or state R: This phase is marked by the start of physiological rhizalysis.
Rhizalysis occurs with alternating resorption and repair; the apices and pulp-periodontal communications may be in a phase of wide opening or return to normal. From the beginning of rhizalysis, the number of nerve fibers decreases in the pulp where mineralization islands may appear. In the late stage, the pulp presents the appearance of inflammatory granulation tissue and participates in the final dentin resorption.

Pathophysiology of the temporary tooth (according to Fortier et al 1987)

Stadium	Physiology Pathology Therapeutics
*1: immaturity*	Repair of cavities (rare) Conservation always possible Trauma to pulp vitality
*2: stability*	Repair Very rapid pulp damage Conservation possible Frequent periodontal damage to the tooth
3: resorption	Oriented towards Irreversible conserve or replacement extract

Conclusion :

The preservation of temporary teeth until their physiological loss is essential; in addition to their role in maintaining space for the placement of permanent teeth, they also maintain the vertical dimension, and play a role in the

phonetic and social development of the child.

IV-CONSEQUENCES ON PATHOLOGY AND THERAPY CONCLUSION

Introduction :

The permanent tooth is considered immature (IPD) when its root is still developing and apical closure is not complete.

The apposition of secondary dentin in the pulp chamber and along the root is a continuous physiological process.

When the tooth is immature, its low thickness results in a large pulp volume, which explains the very sensitive behavior of the young tooth to attacks.

PARTICULARITIES OF THE IMMATURE PERMANENT TOOTH :

The immature permanent tooth is that from its eruptive beginnings in the oral cavity until the end of its root, enamel, pulpodentin and periodontal maturation.

HISTOLOGICAL PARTICULARITIES:
1. The enamel:

During the eruptive period, the enamel is immature . It is porous. This immature enamel presents a greater susceptibility to caries

The pulp-dentin organ:

2 – ANATOMICAL FEATURES:

– Absence of root edification (absence of JCD),

-The apex is widely open in the shape of a funnel or blunderbuss,

-the root canal is wide,

-The dentin walls, thin and fragile, appear divergent, parallel or convergent depending on the stage of root formation.

-The highly vascularized apical region has significant repair potential and actively participates in root building.

3- PHYSIOLOGICAL PARTICULARITIES:

continue to organize themselves until they form the alveolo-dental ligaments of the mature tooth.

Different stages of root development:

According to Nolla, root development takes place in ten stages : From the 1st ^to the 6th ^, formation of the crown; From the 7th ^to the 10th ^, formation of the root.
Nolla in 1960 defined the stages of tooth development as follows:

: absence of the crypt
: presence of the crypt
: initial calcification
: 1/3 of the crown built
: 2/3 of the crown built
: the crown is almost finished
: the crown is finished
: 1/3 of the root built
: 2/3 of the root built, divergent root walls
: root almost at its final length and cylindrical walls

10: cementodentin junction in place and root end completed.

CONSEQUENCES ON PATHOLOGY AND THERAPY:

The very rapid progression of caries in immature permanent teeth is explained by the histo-morphological characteristics of the young dental organ.
At the time of eruption into the oral cavity, the tooth is considered immature. Amelogenesis is complete, but the surface and subsurface layers of the post-eruptive enamel are porous and irregular and therefore highly sensitive to chemical and bacterial aggressions in the oral environment. Enamel maturation is completed over the years.
This post-eruptive maturation will occur gradually, giving the dental surface resistance to the carious process.
If a first molar erupts into an oral cavity with many cavities, it will be confronted with a cariogenic bacterial environment.
Therapeutics should be focused on preserving pulp vitality in order to allow physiological closure of the apex or

“Apexogenesis”.

In cases of pulp necrosis, tooth preservation can be achieved by performing “Apexification” treatments. However, the fragility of the root walls reduces the prognosis for preservation.
Maintaining the tooth as long as possible helps maintain the integrity of the arch length and the development of the alveolar bone during the growth period.

CONCLUSION :

The morphological and physiological characteristics of the pulp tissue of immature permanent teeth make pediatric endodontics complex.

Current clinical techniques in use produce excellent results, but they are not evidence-based (Naudin 2003).

A more biological approach to pulp therapy will aim to regenerate damaged pulp or dentin tissue (Machtou 2010).

MORPHOLOGY, HISTOPHYSIOLOGY AND PHYSIOPATHOLOGY OF TEMPORARY TEETH

MORPHOLOGY, HISTOPHYSIOLOGY AND PHYSIOPATHOLOGY OF TEMPORARY TEETH

I – PARTICULARITIES OF TEMPORARY TEETH:

Dentin:

III- EVOLUTION OF THE TOOTH:

Sequence of eruption of temporary teeth:

2 – ANATOMICAL FEATURES:

3- PHYSIOLOGICAL PARTICULARITIES:

CONCLUSION :

MORPHOLOGY, HISTOPHYSIOLOGY AND PHYSIOPATHOLOGY OF TEMPORARY TEETHMORPHOLOGY, HISTOPHYSIOLOGY AND PHYSIOPATHOLOGY OF TEMPORARY TEETH

I – PARTICULARITIES OF TEMPORARY TEETH:

Dentin:

III- EVOLUTION OF THE TOOTH:

Sequence of eruption of temporary teeth:

2 – ANATOMICAL FEATURES:

3- PHYSIOLOGICAL PARTICULARITIES:

CONCLUSION :

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