Normal and pathological dental eruption

Course outline 

1- Introduction and definitions

2. Physiology of dental eruption
   1. Pre-eruptive movements
   2. Eruption phase
      1. Histological changes
         1. In the tissues overhanging the tooth
         2. In the tissues surrounding the tooth
         3. In the underlying tissues 2.2.2 Mechanism of dental eruption
   3. Post-eruptive phase
3. Chronology and placement of teeth
4. Anomalies of the eruption
   1. Temporary teeth

• Temporary tooth eruption syndrome
• Early eruption of temporary teeth
  • Natal and neonatal teeth
  • Early temporary teeth
• Delayed eruption of temporary teeth
• Inclusion of temporary teeth
• Premature loss of temporary teeth
• Delayed loss of temporary teeth

2. Permanent teeth

• Early eruption of permanent teeth
• Delayed eruption of permanent teeth
• Accidents of permanent tooth eruption
• Inclusion of permanent teeth
• Premature loss of permanent teeth

5- conclusion Bibliography

1 – Introduction

Throughout its development, the dental germ performs a succession of movements which modify its relationships with its tissue environment. We first distinguish pre-eruptive movements, then the pre-functional eruption phase followed by a functional eruption phase and finally a post-eruptive phase.

Mammals are diphyodonts, meaning they have two sets of teeth:

Temporary dentition and permanent dentition.

• Temporary teeth erupt between 6 months and 2.5 years .
• Permanent teeth erupt between the ages of 6 and 12-13 years.
• The third molar or wisdom tooth appears around the ages of 18-30 .

Definitions:

Tooth eruption is a biological process by which a developing tooth emerges through the bone and oral mucosa, to appear in the oral cavity, then to come into contact with its antagonist and allow mastication.

Dentition: corresponds to the phenomena linked to the eruption and evolution of teeth on the arch; (dynamic phenomenon)

The dentition: refers to all the teeth in place on the arch (static state).

2. Physiology of dental eruption

Tooth eruption is a continuous process that ends only with the loss of the tooth. The germ goes through several phases along its path, we distinguish:

1. Pre-eruptive movements

Pre-eruptive movements begin from the beginning of tooth germ formation until the formation of the tooth crown; resulting in bone resorption in the direction of movement and apposition in the opposite direction to accommodate growth of the jaws and face .

• The germs of the anterior permanent teeth remain positioned lingually
• The premolars will be located under the roots of the temporary molars.
• Permanent molars, which have no corresponding primary teeth, develop from the distal extension of the dental lamina
• The upper molars develop into the tuberosities of the maxilla with their occlusal surfaces inclined distally.
• The lower molars develop in the base of the mandibular rami and their occlusal surfaces are inclined mesially.

2. Eruption phase

Ranging from the beginning of root edification and ending when the tooth reaches occlusal contact.

• The prefunctional or intraosseous eruption phase begins from the beginning of root development until emergence into the oral cavity;
• The functional or suprabony eruption phase begins from emergence into the oral cavity to occlusal contact.

The eruption phase takes place according to 4 major events:

• root formation, with proliferation of Hertwig’s epithelial sheath, dental papilla mesenchyme and follicular sac fibers;
• a movement in an occlusal direction through the bony crypt to the oral mucosa; the reduced enamel organ fuses with the oral epithelium; this is the stage where the mucosa becomes white due to the decreased blood supply to the area.
• the upper part of the crown enters the oral cavity through this fused epithelium thus marking the clinically visible stage of eruption
• the erupting tooth continues its occlusal movement until contact with its antagonist.

1. Histological changes
2. In the tissues overhanging the tooth
   • The cells, connective tissue fibers and nerve fibers above the tooth degenerate under the action of enzymes produced by macrophages.

• The number of blood vessels decreases. Creating an area called the eruption path.
• Osteoclasts contribute to bone resorption and formation of the eruption path.

2. In the tissues surrounding the tooth
   • The dental follicle is composed of loose connective tissue, but when eruptive movements begin, the fine fibers parallel to the tooth surface are transformed into bundles of collagen fibers attached to the developing tooth root and extending to the surface of the alveolar bone. These are the first fiber bundles of the periodontal ligament.
   • At the same time, the bony crypt is remodeled to accommodate the root dimensions, which are smaller than those of the crown to accommodate the forming root.

b- in the underlying tissues

– The crown of the tooth, when beginning its eruption, frees up space in the apical zone which allows the lengthening of the root.

2. Mechanism of dental eruption

Tooth eruption is a multifactorial process. Two events are essential:

• Resorption of bone overhanging the crown of the tooth to form an eruption path,
• The movement of the tooth through this path.

Thus, we can observe that:

• Blocking a germ before the eruption phase by ligatures does not prevent the formation of the eruption path (cahill, 1969);
• Removal of the dental follicle prevents eruption (Cahill and Marks, 1980):
• If the tooth is replaced – with preservation of the follicle – by an inert object just before eruption, this inert object erupts (Cahill and Marks, 1984);
• Prior to eruption, there is an influx of monocytes into the coronal zone of the follicle, as well as a quasi-concomitant influx of osteoclasts into the overlying alveolar bone

🡺 The dental follicle is therefore essential for eruption, at least for the intraosseous phase, since circulating monocytes flow into it and fuse to form the osteoclasts necessary for the formation of the eruption path in the alveolar bone.

It has long been thought that root formation plays a role in tooth eruption. However, a tooth without a root is capable of erupting. Root formation is therefore a consequence and not the cause of eruption.

The alveolo-dental ligament would have a role during the supra-osseous phase; but sometimes the alveolo-dental ligament is present at the level of a non-evolved tooth.

Vascularization probably plays a role in tooth eruption. For example, sympathetic nerve resection, which causes vasodilation, results in earlier tooth eruption. Similarly, localized hyperemia, such as in periodontitis, also increases the vascularization of periodontal tissues and accelerates the eruption of adjacent teeth. Other factors that decrease vascularization, such as hypopituitarism, on the contrary delay eruption.

3. Post-eruptive phase

• It begins when the teeth are functional and continues slowly as long as the tooth remains in the arch.
• The alveolar processes will increase in height and root formation continues after the teeth become functional, for approximately 1 to 1.5 years for primary teeth and 2 to 3 years for permanent teeth.
• When root formation is complete, a slow and continuous eruption compensates for the wear of the occlusal surfaces and maintains the vertical dimension of occlusion. It is associated with a phenomenon of apical cementogenesis which compensates for the loss of axial length.

3. Chronology and placement of teeth

• The stable temporary dentition consists of 20 teeth: eight incisors, four canines and eight molars. Temporary teeth erupt on average between the ages of 6 months and 2 and a half years at a rate of one group of teeth every 6 months.
• The eruption sequence usually begins with the mandibular central incisors, more rarely with the maxillary central incisors.
• The stable adult permanent dentition consists of 32 teeth: eight incisors, four canines, eight premolars and 12 molars. The first 28 permanent teeth erupt on average between the ages of 6 and 12 years, regularly at the rate of one group of teeth every year.
• In the temporary dentition, eruption occurs earlier in boys than in girls. In the permanent dentition, on the contrary, eruption in girls precedes that of boys except for the first molars and incisors.
• In general, the mandibular teeth precede the maxillary teeth in the permanent dentition. Only the mandibular central incisors and occasionally the mandibular second molars precede their maxillary counterparts in the temporary dentition.

4. Anomalies of the eruption:
5. Temporary teeth
6. Temporary tooth eruption syndrome

The eruption of temporary teeth is frequently accompanied by local or general signs such as: hypersalivation, fever, stomatitis, loss of appetite, eruption cyst, gingival inflammation and jugal erythema. These eruption accidents generally remain benign.

Exceptionally, they take on a more serious character with high fever, convulsive seizures or respiratory and digestive disorders.

2. Early eruption of temporary teeth

The eruption of a temporary tooth is said to be early when it occurs 1 month (incisor) to 6 months (molar) before the average age of eruption.

Usually, no clinical significance is noted. However, it may be related to congenital hyperthyroidism.

3. Natal and neonatal teeth

The presence of a natal tooth (on the arch at birth) or a neonatal tooth (erupting within the first 30 days of life) is a rare phenomenon that frequently concerns the mandibular central incisor. Generally, the tooth is mobile and has incomplete root formation.

A very superficial position of the germ with a hereditary character would probably be at the origin of this anomaly, but the etiology remains poorly understood.

4. Early temporary teeth

Hereditary or congenital factors, such as hyperthyroidism or dentofacial dysplasia, appear to be the cause of early eruption of temporary teeth. A superficial location of the tooth germ can also cause this type of anomaly.

5. Delayed eruption of temporary teeth

In the primary dentition, eruption delays are generally uncommon.

Children born prematurely more often have a delay in the eruption of temporary teeth, which is however compensated for around the age of 2 and a half years.

Possible etiologies:

• Delayed dental maturation
• An obstacle preventing the tooth from erupting.
• A hereditary origin
• Result from nutritional deficiencies, infections,
• Endocrine hypofunction such as hypothyroidism or pituitary dwarfism
• Associated with Down syndrome (trisomy 21)

6. Inclusion of temporary teeth

It is rare and preferentially affects the second molar and is often due to a malposition, an obstacle placed in the path of eruption (dental crowding, cystic lesion) or even a morphological anomaly of the tooth.

7. Premature loss of temporary teeth

Premature loss of a temporary tooth is due to the early development of the germ of a permanent tooth.

Premature loss of several temporary teeth is generally associated with general pathologies such as:

• Cherubism (failure of permanent teeth to erupt in the affected area)
• Papillon-Lefevre syndrome (mobility of the incisor and molar sectors).
• Type I dentin dysplasia (radicular dysplasia).
• Expulsive folliculitis is an infectious disease characterized by the rapid elimination of temporary teeth. The tooth, formed of a simple shell of enamel and dentin, is expelled in a few days. The fleshy bud left in place involutes and disappears.

8. Delayed loss of temporary teeth

It is generally linked to the absence of the germ of the corresponding permanent tooth or to its malposition. It preferentially concerns the maxillary canines, the maxillary lateral incisor, the second mandibular molar and the temporary mandibular central incisor. The tooth concerned undergoes little resorption and can remain on the arch for several years.

This anomaly affects all temporary teeth in children with cleidocranial dysostosis or anodontia (absence of all permanent tooth germs).

4-2-Permanent teeth:

1. Early eruption of permanent teeth

The early eruption of a single tooth (incisor, canine or premolar) is the result of the premature loss of the temporary tooth that it replaces, due to an infectious pathology, trauma or carious damage.

Early eruption of all permanent teeth is usually associated with general pathologies or syndromes such as Turner syndrome.

2. Delayed eruption of permanent teeth

Late eruption of a single tooth is relatively common. Generally linked to a local factor such as:

• A dental malposition,
• Gingival hyperplasia,
• Closing the gap left by the temporary tooth,
• An occlusion disorder
• An abnormality of alveolar bone morphology

Late eruption of multiple permanent teeth is very rare. It is often linked to:

• A systemic factor such as vitamin A and D deficiency
• An endocrine pathology such as hypothyroidism.
• Associated with certain syndromes such as cleidocranial dysplasia, Gardner syndrome (rectocolic polyposis), Turner syndrome or Down syndrome (trisomy 21).
• calcification of hyperplastic follicles
• fibroodontogenic dysplasia
• gingival fibromatosis

3. Accidents of permanent tooth eruption

Congestive or suppurative pericoronitis due to infection of the pericoronal sac and the overlying fibromucosa is common, particularly for the third mandibular molar, and manifests itself by inflammatory mucosal congestion which may be accompanied by pain, regional signs (cellulitis, trismus, discomfort when chewing, adenopathy, ulcerative stomatitis), or even general signs (fever, deterioration of the general condition).

A disturbed eruption can also be complicated by osteitis, the formation of a dentigerous cyst.

4. Inclusion of permanent teeth

Inclusion particularly concerns the maxillary and then mandibular third molars, the maxillary canines and the mandibular second premolars.

It is usually due to local factors:

-malposition of the germ,

-insufficient space on the arch,

– obstacle on the path of eruption (supernumerary tooth, odontoma, cyst),

-anomaly of germ morphology,

-thick and fibrous gingival mucosa,

– alveolar bone growth abnormality.

Multiple inclusions are rare, they can be related to general pathologies or syndromes such as Cherubism, Gardner’s syndrome, hyperparathyroidism.

5. Premature loss of permanent teeth

It is generally a consequence of the following factors:

• An infectious pathology ,
• A trauma ,
• The evolution of a carious disease.
• Papillon-Lefevre syndrome (palmoplantar hyperkeratosis with periodontal disease)

Conclusion

The existence of many theories concerning dental eruption shows that the pathophysiology of this phenomenon remains poorly understood. Eruption anomalies have many origins. Knowing how to recognize these anomalies will allow the practitioner to remedy them and avoid, in a large number of cases, the need for long and complex orthodontic treatments.

Bibliographic sources

• F. Tilotta, m. Folliguet, s. Seguier. Pathophysiology of dental eruption . Emc

– oral medicine 2013:1-8 [article 28-260-b-10].

• Moulis E, Favre de Thierrens C, Goldsmith MC and Torres JH. Anomalies of the eruption. Encyclmedchir (scientific and medical editions Elsevier SAS, Paris, all rights reserved), stomatology/odontology, 22-032-a-10, 2002, 12 p.
• Béatrice RICHARD, Yves DELBOS, Louis-Frédéric JACQUELIN. Training and Research Unit in Odontology. University of Bordeaux: Dental eruption . 2009.
• Wise age. The biology of tooth eruption. J teeth res. 1998 aug;77(8):1576-9.
• Nanci a. Tencate’s oral histology. 6th ed, 2003; mosby.
• Avery jk. Essentials of oral histology and embryology . 3rd ed, 2006; mosby.

Normal and pathological dental eruption

  Deep cavities may require root canal treatment.
Dental veneers correct chipped or discolored teeth.
Misaligned teeth can cause uneven wear.
Dental implants preserve the bone structure of the jaw.
Fluoride mouthwashes help prevent cavities.
Decayed baby teeth can affect the position of permanent teeth.
An electric toothbrush cleans hard-to-reach areas more effectively.

Normal and pathological dental eruption