HOME

TheInfoList



OR:

Tooth eruption is a process in
tooth development Tooth development or odontogenesis is the complex process by which teeth form from embryonic cells, grow, and erupt into the mouth. For human teeth to have a healthy oral environment, all parts of the tooth must develop during appropriate st ...
in which the
teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, ...
enter the
mouth In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on ...
and become visible. It is currently believed that the
periodontal ligament The periodontal ligament, commonly abbreviated as the PDL, is a group of specialized connective tissue fibers that essentially attach a tooth to the alveolar bone within which it sits. It inserts into root cementum one side and onto alveolar ...
plays an important role in tooth eruption. The first
human teeth The human teeth function to mechanically break down items of food by cutting and crushing them in preparation for swallowing and digesting. As such, they are considered part of the human digestive system. Humans have four types of teeth: inci ...
to appear, the deciduous (primary) teeth (also known as baby or milk teeth), erupt into the mouth from around 6 months until 2 years of age, in a process known as "
teething Teething is the process by which an infant's first teeth (the deciduous teeth, often called "baby teeth" or "milk teeth") appear by emerging through the gums, typically arriving in pairs. The mandibular central incisors are the first primary te ...
". These teeth are the only ones in the mouth until a person is about 6 years old creating the primary dentition stage. At that time, the first permanent tooth erupts and begins a time in which there is a combination of primary and permanent teeth, known as the mixed dentition stage, which lasts until the last primary tooth is lost. Then, the remaining permanent teeth erupt into the mouth during the permanent dentition stage.


Theories

Although researchers agree that tooth eruption is a complex process, there is little agreement on the identity of the mechanism that controls eruption. There have been many theories over time that have been eventually disproven. According to Growth Displacement Theory, the tooth is pushed upward into the mouth by the growth of the tooth's root in opposite direction. Continued Bone Formation Theory advocated that a tooth is pushed upward by the growth of the bone around the tooth. In addition, some believed teeth were pushed upward by vascular pressure or by an anatomic feature called the cushioned hammock. The cushioned hammock theory, first proposed by Harry Sicher, was taught widely from the 1930s to the 1950s. This theory postulated that a
ligament A ligament is the fibrous connective tissue that connects bones to other bones. It is also known as ''articular ligament'', ''articular larua'', ''fibrous ligament'', or ''true ligament''. Other ligaments in the body include the: * Peritoneal l ...
below a tooth, which Sicher observed under a microscope on a histologic slide, was responsible for eruption. Later, the "ligament" Sicher observed was determined to be merely an artifact created in the process of preparing the slide. The most widely held current theory is that while several forces might be involved in eruption, the periodontal ligament provides the main impetus for the process. Theorists hypothesize that the periodontal ligament promotes eruption through the shrinking and cross-linking of their collagen fibers and the contraction of their fibroblasts. There is good evidence from experimental animals that a traction force is unlikely to be involved in tooth eruption: Animals treated with lathyrogens that interfere with
collagen Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whol ...
cross-link formation showed similar eruption rates to control animals, provided occlusal forces were removed. Inherent in most of the theories outlined above is the idea that a force is generated in the periodontal ligament beneath unerupted teeth, and that this force physically drives teeth out through the bone. This idea may have been superseded by a further recent theory. This new theory proposes firstly that areas of tension and compression are generated in the soft tissues surrounding unerupted teeth by the distribution of bite forces through the jaws. These patterns of tension and compression, are further proposed to result in patterns of bone resorption and deposition that lift the tooth into the mouth. This theory is based on Wolff's law, which is the long established idea that bone changes shape in accordance with the forces applied. Significantly, a recent finite element analysis study, analysing the distribution of force through the jaw of an 8 year-old child, observed overall compression in the soft tissues above, and tension in the soft tissues below, unerupted teeth. Because bone resorbs when compressed, and forms under tension, this finite element analysis strongly supports the new theory. Further work is required, however, to confirm this new theory experimentally.


Timeline

Although tooth eruption occurs at different times for different people, a general eruption timeline exists. The tooth buds of baby teeth start to develop around 6 weeks of pregnancy. Adult teeth buds start forming around 4 months of pregnancy. The entire tooth will start to form from the crown down to the root. Typically, humans have 20 primary teeth and 32 permanent teeth. The dentition goes through three stages.Illustrated Dental Embryology, Histology, and Anatomy, Bath-Balogh and Fehrenbach, Elsevier, 2011, page 191-192 The first, known as primary
dentition Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiolo ...
stage, occurs when only primary teeth are visible. Once the first permanent tooth erupts into the mouth, the teeth that are visible are in the mixed (or transitional) dentition stage. After the last primary tooth is shed or exfoliates out of the mouth, the teeth are in the permanent dentition stage. Each patient should be assigned a dentition period to allow for effective dental treatment.


Signs and symptoms of tooth eruption

There are several signs and symptoms associated with the eruption of primary teeth. It is a process that begins with the eruption of the mandibular central incisors at the age of 6 months. A common symptom among young children is a mild rise of temperature, however this is not necessarily classified as a fever. General symptoms during primary tooth eruption include; irritability and drooling being the most common, followed by a decreased appetite, sleeping problems, rhinorrhea, fever, diarrhea, rash and vomiting. Local signs included inflammation of the gums and
Gingival The gums or gingiva (plural: ''gingivae'') consist of the mucosal tissue that lies over the mandible and maxilla inside the mouth. Gum health and disease can have an effect on general health. Structure The gums are part of the soft tissue lini ...
reddening (Hyperemia) most commonly presenting in posterior teeth. A study shows that 70.5% of children between 0–36 months showed signs and symptoms of tooth eruption whether it being a fever, Gingival irrational and/or drooling.


Primary dentition stage

Primary dentition stage starts on the arrival of the mandibular central incisors, typically from around six months, and lasts until the first permanent molars appear in the mouth, usually at six years. There are 20 primary teeth and they typically erupt in the following order: (1) central
incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...
, (2) lateral incisor, (3) first molar, (4)
canine Canine may refer to: Zoology and anatomy * a dog-like Canid animal in the subfamily Caninae ** ''Canis'', a genus including dogs, wolves, coyotes, and jackals ** Dog, the domestic dog * Canine tooth, in mammalian oral anatomy People with the surn ...
, and (5) second molar. As a general rule, four teeth erupt for every six months of life, mandibular teeth erupt before maxillary teeth, and teeth erupt sooner in females than males. During primary dentition, the tooth buds of permanent teeth develop inferior to the primary teeth, close to the palate or tongue.


Mixed dentition stage

Mixed dentition stage starts when the first permanent tooth appears in the mouth, usually at five or six years with the first permanent molar, and lasts until the last primary tooth is lost, usually at ten, eleven, or twelve years. There are 32 permanent teeth and those of the maxillae (on the top) erupt in a different order from permanent mandibular (on the bottom) teeth. Maxillary teeth typically erupt in the following order: (1) first molar (2)
central incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...
, (3)
lateral incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wh ...
, (4)
first premolar The premolars, also called premolar teeth, or bicuspids, are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth ...
, (5) second premolar, (6)
canine Canine may refer to: Zoology and anatomy * a dog-like Canid animal in the subfamily Caninae ** ''Canis'', a genus including dogs, wolves, coyotes, and jackals ** Dog, the domestic dog * Canine tooth, in mammalian oral anatomy People with the surn ...
, (7)
second molar The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone to ...
, and (8) third molar. Mandibular teeth typically erupt in the following order: (1) first molar (2)
central incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...
, (3)
lateral incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wh ...
, (4)
canine Canine may refer to: Zoology and anatomy * a dog-like Canid animal in the subfamily Caninae ** ''Canis'', a genus including dogs, wolves, coyotes, and jackals ** Dog, the domestic dog * Canine tooth, in mammalian oral anatomy People with the surn ...
, (5)
first premolar The premolars, also called premolar teeth, or bicuspids, are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth ...
, (6) second premolar, (7)
second molar The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone to ...
, and (8) third molar. While this is the most common eruption order, variation is common. Since there are no premolars in the primary dentition, the primary molars are replaced by permanent premolars. If any primary teeth are shed or lost before permanent teeth are ready to replace them, some posterior teeth may drift forward and cause space to be lost in the mouth. This may cause crowding and/or misplacement once the permanent teeth erupt, which is usually referred to as
malocclusion In orthodontics, a malocclusion is a misalignment or incorrect relation between the teeth of the upper and lower dental arches when they approach each other as the jaws close. The English-language term dates from 1864; Edward Angle (1855-19 ...
.
Orthodontics Orthodontics is a dentistry specialty that addresses the diagnosis, prevention, management, and correction of mal-positioned teeth and jaws, and misaligned bite patterns. It may also address the modification of facial growth, known as dentofacial ...
may be required in such circumstances for an individual to achieve a functioning and aesthetic dentition.


Permanent dentition stage

The permanent dentition begins when the last primary tooth is lost, usually at 11 to 12 years, and lasts for the rest of a person's life or until all of the teeth are lost ( edentulism). After the adult tooth forms in the bone, it will push through under the baby tooth. The adult tooth will dissolve the baby tooth’s root, making the baby tooth loose until it falls out. During this stage, permanent third molars (also called " wisdom teeth") are frequently
extracted ''Extracted'', also known as ''Extraction'' in the UK, is an independent 2012 American science fiction thriller directed and written by Nir Paniry. Sasha Roiz stars as a scientist whose consciousness becomes trapped in the mind of a convict (Domi ...
because of decay, pain or impactions. The main reasons for tooth loss are decay or
periodontal disease Periodontal disease, also known as gum disease, is a set of inflammatory conditions affecting the tissues surrounding the teeth. In its early stage, called gingivitis, the gums become swollen and red and may bleed. It is considered the main caus ...
.


Active vs. Passive eruption


Active eruption

Active eruption is known as eruption of teeth into the mouth towards the occlusal plane. This is a natural path of eruption of all the teeth as they emerge from gingiva and continue erupting until they make contact with the opposing tooth.


Passive eruption

Passive eruption is known as movement of the gingiva apically or away from the crown of the tooth to the level of Cementoenamel junction (CEJ) after the tooth has erupted completely. Problems in gingival tissue migrating apically can give rise to what is known as altered or delayed passive eruption. In this phenomenon, the gingival tissues fail to move apically and thus lead to shorter clinical crowns with more square-shaped teeth and appearance of what is known as gummy smile.


Coslet classification

Coslet et al. classified delayed passive eruption into two types which related the bone crest of a tooth to the
Mucogingival junction A mucogingival junction is an anatomical feature found on the intraoral mucosa. The mucosa of the cheeks and floor of the mouth are freely moveable and fragile, whereas the mucosa around the teeth and on the palate are firm and keratinized. Wher ...
(MGJ) of that tooth. These two groups were further divided based on the position of the alveolar bone crest to the cementoenamel junction.


Abnormalities

Abnormalities in tooth eruption (timing and sequence) is often caused by genetics and may result in
malocclusion In orthodontics, a malocclusion is a misalignment or incorrect relation between the teeth of the upper and lower dental arches when they approach each other as the jaws close. The English-language term dates from 1864; Edward Angle (1855-19 ...
. In severe cases, such as in
Down syndrome Down syndrome or Down's syndrome, also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is usually associated with physical growth delays, mild to moderate intellectual d ...
, the eruption may be delayed by several years and some teeth may never erupt.


Primary failure of eruption

Primary failure of eruption (PFE) is a rare disease in which tooth eruption does not occur despite space in the arch for eruption. Non-eruption of non-ankylosed teeth occurs due to an eruption mechanism that has failed leading to a posterior unilateral/bilateral open bite. Infra occlusion is the primary hallmark of PFE. Primary teeth are most commonly affected and normally all teeth distal to the most mesially affected tooth will show characteristics of this disease. PFE can be treated by orthodontic treatment, however this is dependant on the patient's age, preference and clinical situation.


Cleidocranial Dysplasia

Cleidocranial Dysplasia (CCD) is a disorder characterised by the identification of a heterozygous pathogenic variant in RUNX2 (CBFA1) and/or various clinical presentations and radiographs. There is a wide range of clinical presentations found in patients with CCD, including patients with a classical presentation of the disorder to patients who have isolated dental anomalies. These will often affect the mechanisms of tooth eruption and result in problems within primary and secondary dentition. Studies have shown that up to 94% of persons with CCD spectrum disorder have dental findings including supernumerary teeth and eruption failure of permanent teeth. The presence of a second permanent molar within primary dentition is the most common at 80% along with wide spacing in the lower incisor area, supernumerary tooth germs (705) and parallel-sided ascending rami. Individuals with a CCD spectrum disorder are also more likely to have an underbite and to have cysts in their gums that usually form around extra teeth. Dental procedures can be carried out for the retention of deciduous teeth and non-eruption of permanent teeth. A combination of surgical and orthodontic work can also be considered for actively erupting teeth.


Cleft lip

Reports have noted that there is late tooth eruption in cleft lip patients when contrasted with non cleft lip patients. The duration of delay is around 0.2 to 0.9 years, with an average of 0.56 years when all types of clefts were accounted for. The
lateral incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wh ...
on the cleft side was typically the most delayed. The type of cleft and the severity of the condition did not affect the duration of tooth eruption. Overall, teeth which were located closer to the cleft lip took a longer time to erupt compared to teeth which were further away.


See also

*
Tooth development Tooth development or odontogenesis is the complex process by which teeth form from embryonic cells, grow, and erupt into the mouth. For human teeth to have a healthy oral environment, all parts of the tooth must develop during appropriate st ...
*
Orthodontics Orthodontics is a dentistry specialty that addresses the diagnosis, prevention, management, and correction of mal-positioned teeth and jaws, and misaligned bite patterns. It may also address the modification of facial growth, known as dentofacial ...
*
Deciduous teeth Deciduous teeth or primary teeth, also informally known as baby teeth, milk teeth, or temporary teeth,Illustrated Dental Embryology, Histology, and Anatomy, Bath-Balogh and Fehrenbach, Elsevier, 2011, page 255 are the first set of teeth in the ...
*
Permanent teeth Permanent teeth or adult teeth are the second set of teeth formed in diphyodont mammals. In humans and old world simians, there are thirty-two permanent teeth, consisting of six maxillary and six mandibular molars, four maxillary and four mand ...
* Schultz's rule * Failure of eruption of teeth *
Teething Teething is the process by which an infant's first teeth (the deciduous teeth, often called "baby teeth" or "milk teeth") appear by emerging through the gums, typically arriving in pairs. The mandibular central incisors are the first primary te ...
*
Dentition Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiolo ...


References

{{Tooth development Tooth development Teeth Pediatrics