Anodontia is a rare

genetic disorder A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality. Although polygenic disorders ...

characterized by the congenital absence of all primary or permanent

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, t ...

. It is divided into two subsections, complete absence of teeth or only some absence of teeth. It is associated with the group of

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different de ...

and nerve

syndrome A syndrome is a set of medical signs and symptoms which are correlated with each other and often associated with a particular disease or disorder. The word derives from the Greek language, Greek σύνδρομον, meaning "concurrence". When a sy ...

s called the

ectodermal dysplasia Ectodermal dysplasia (ED) is a group of genetic syndromes all deriving from abnormalities of the ectodermal structures.James, William; Berger, Timothy; Elston, Dirk (2005). ''Andrews' Diseases of the Skin: Clinical Dermatology''. (10th ed.). S ...

s. Anodontia is usually part of a syndrome and seldom occurs as an isolated entity. There is usually no exact cause for anodontia. The defect results in the

dental lamina The dental lamina is a band of epithelial tissue seen in histologic sections of a developing tooth. The dental lamina is first evidence of tooth development and begins (in humans) at the sixth week in utero or three weeks after the rupture of th ...

obstruction during embryogenesis due to local, systemic and genetic factors. Congenital absence of permanent teeth can present as

hypodontia Hypodontia is defined as the developmental absence of one or more teeth excluding the third molars. It is one of the most common dental anomalies, and can have a negative impact on function, and also appearance. It rarely occurs in primary teet ...

, usually missing one or two

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 ...

, or

oligodontia Hypodontia is defined as the developmental absence of one or more teeth excluding the third molars. It is one of the most common dental anomalies, and can have a negative impact on function, and also appearance. It rarely occurs in primary teet ...

that is the congenital absence of six or more teeth. Congenital absence of all

wisdom teeth A third molar, commonly called wisdom tooth, is one of the three molars per quadrant of the human dentition. It is the most posterior of the three. The age at which wisdom teeth come through ( erupt) is variable, but this generally occurs betw ...

, or third

molars 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 ...

, is relatively common. Anodontia is the congenital absence of teeth and can occur in some or all teeth; whereas partial anodontia (or

), involves two dentitions or only teeth of the permanent dentition (Dorland's 1998). Approximately 1% of the population has oligodontia. Many denominations are attributed to this anomaly: partial anodontia, hypodontia, oligodontia, the congenital absence, anodontia, bilateral

aplasia Aplasia (; from Greek ''a'', "not", "no" + ''plasis'', "formation") is a birth defect where an organ or tissue is wholly or largely absent. It is caused by a defect in a developmental process. Aplastic anemia is the failure of the body to produc ...

. Anodontia being the term used in controlled vocabulary Medical Subject Headings (MeSH) from

MEDLINE MEDLINE (Medical Literature Analysis and Retrieval System Online, or MEDLARS Online) is a bibliographic database of life sciences and biomedical information. It includes bibliographic information for articles from academic journals covering medic ...

which was developed by the

United States National Library of Medicine The United States National Library of Medicine (NLM), operated by the United States federal government, is the world's largest medical library. Located in Bethesda, Maryland, the NLM is an institute within the National Institutes of Health. Its ...

. The congenital absence of at least one permanent tooth is the most common dental anomaly and may contribute to masticator dysfunction, speech impairment, aesthetic problems, and malocclusion (Shapiro and Farrington 1983). Absence of lateral incisors represents a major stereotype. Individuals with this condition are perceived as socially most aggressive compared with people without anodontia (Shaw 1981). The occurrence of anodontia is less so than hypodontia which has a

prevalence In epidemiology, prevalence is the proportion of a particular population found to be affected by a medical condition (typically a disease or a risk factor such as smoking or seatbelt use) at a specific time. It is derived by comparing the number o ...

of 0.1-0.7% in primary teeth and 3–7.5% in permanent teeth.

Signs and symptoms

The main sign of anodontia is when a child has not developed any of their permanent teeth by the age of 12. Another sign of anodontia can include the absence of

baby 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 ...

when the baby has reached 12 to 13 months. Symptoms that are associated with anodontia include:

alopecia Hair loss, also known as alopecia or baldness, refers to a loss of hair from part of the head or body. Typically at least the head is involved. The severity of hair loss can vary from a small area to the entire body. Inflammation or scar ...

, lack of sweat glands,

cleft lip A cleft lip contains an opening in the upper lip that may extend into the nose. The opening may be on one side, both sides, or in the middle. A cleft palate occurs when the palate (the roof of the mouth) contains an opening into the nose. The te ...

palate The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly separ ...

, and missing fingernails. Typically, these symptoms are seen because anodontia is typically associated with

. In the rare case that ectodermal dysplasia is not present, anodontia will be caused from an unknown genetic mutation.

Cause

Anodontia typically occurs with the presence of ectodermal dysplasia, which is a group of disorders where two or more ectodermally derived structures will have abnormal development. In the rare case that ectodermal dysplasia is not associated or present, anodontia will be caused by an unknown genetic mutation. Although no specific gene has been identified, there have been many different genes found to be associated with anodontia including

EDA EDA or Eda may refer to: Computing * Electronic design automation * Enterprise Desktop Alliance, a computer technology consortium * Enterprise digital assistant * Estimation of distribution algorithm * Event-driven architecture * Exploratory ...

, EDAR, and EDARADD genes. Other genes such as

MSX1 Homeobox protein MSX-1, is a protein that in humans is encoded by the ''MSX1'' gene. MSX1 transcripts are not only found in thyrotrope-derived TSH cells, but also in the TtT97 thyrotropic tumor, which is a well differentiated hyperplastic tissue ...

PAX9 Paired box gene 9, also known as PAX9, is a protein which in humans is encoded by the ''PAX9'' gene. It is also found in other mammals. Expression and function This gene is a member of the Pax genes, paired box (PAX) family of transcription f ...

IRF6 Interferon regulatory factor 6 also known as IRF6 is a protein that in humans is encoded by the ''IRF6'' gene. Function This gene encodes a member of the interferon regulatory transcription factor (IRF) family. Family members share a highly c ...

, GREM2,

AXIN2 Axin-2 also known as axin-like protein (Axil) or axis inhibition protein 2 (AXIN2) or conductin is a protein that in humans is encoded by the ''AXIN2'' gene. Function The Axin-related protein, Axin2, presumably plays an important role in the r ...

LRP6 Low-density lipoprotein receptor-related protein 6 is a protein that in humans is encoded by the ''LRP6'' gene. LRP6 is a key component of the LRP5/LRP6/Frizzled co-receptor group that is involved in canonical Wnt pathway. Structure LRP6 is a t ...

, SMOC2, LTBP3,

PITX2 Paired-like homeodomain transcription factor 2 also known as pituitary homeobox 2 is a protein that in humans is encoded by the ''PITX2'' gene. Function This gene encodes a member of the RIEG/PITX homeobox family, which is in the bicoid clas ...

, and

WNT10B Protein Wnt-10b (formerly Wnt12) is a protein that in humans is encoded by the ''WNT10B'' gene. The WNT gene family consists of structurally related genes that encode secreted signaling proteins. These proteins have been implicated in oncogenesis ...

. The WNT10A gene is considered to be the major gene involved in hypodontia and oligodontia. These genes are involved in hypodontia and oligodontia. If Anodontia is present in the maternal or paternal side, the chances of this being inherited are increased.

Mechanisms and Pathophysiology

Anodontia is a genetic disorder that is typically occurs in result of another syndrome. Different results can occur depending on which gene is inherited. It remains unclear which specific gene is the direct cause but it is known that several genes can play a role when inherited. Many genes are involved with this and other relating disorders. The main genes involved include: EDA, EDAR, and EDARADD genes. One working gene and one non-working gene are inherited, one from an affected parent and one from a non-affected parent, which then result in a 50% chance of the child inheriting the

. Anodontia alone will not have an effect on any other body part besides teeth being missing.

Associated syndromes

Hypodontia and anodontia are frequently associated with a multitude of genetic disorders and syndromes, approximately 70. Syndromes particularly involved with ectodermal involvement are a prime circumstance for anodontia to occur, some examples of these are: Rieger's, Robinson's and focal dermal hypoplasia. Three syndromes which classically have signs of anodontia are oculomandibulodyscephaly, mesoectodermal dysplasia and ectodermal dysplasia. In cases of oculomandibulodyscephaly there are no permanent teeth but there are deciduous teeth present. In mesoectodermal dysplasia the symptoms are anodontia and hypodontia. In cases of ectodermal dysplasia oligodontia is also present. Other symptoms associated with anodontia include: Alopecia, loss of sweat glands, cleft lip or palate, or missing finger nails.

Diagnosis

Anodontia can be diagnosed when a baby does not begin to develop teeth around the age of 12 to 13 months or when a child does not develop their

by the age of 10. The dentist can use a special X-ray, such as a panoramic image, to check if there are any teeth developing. There is also a higher risk for a child to develop anodontia if their parent has this disorder as well. In the absence of all permanent teeth, anodontia will be diagnosed. If between one to five teeth are missing, this will be diagnosed as hypodontia. In the absence of six or more teeth, this will be diagnosed as oligodontia.

Complications

The complications associated with anodontia can vary but the majority results in problems with aesthetic appearance, speaking, and masticatory function. Complications may occur with the placement of the dental implant. Although it is rare, some complications may include the screw of the implant becoming loose or sore spots.

Prevention and Treatment

Anodontia cannot be prevented due to it being a genetic disorder.

Prosthetic In medicine, a prosthesis (plural: prostheses; from grc, πρόσθεσις, prósthesis, addition, application, attachment), or a prosthetic implant, is an artificial device that replaces a missing body part, which may be lost through trau ...

replacement of missing teeth is possible using

dental implant A dental implant (also known as an endosseous implant or fixture) is a prosthesis that interfaces with the bone of the jaw or skull to support a dental prosthesis such as a crown, bridge, denture, or facial prosthesis or to act as an orthodo ...

technology or

dentures Dentures (also known as false teeth) are prosthetic devices constructed to replace missing teeth, and are supported by the surrounding soft and hard tissues of the oral cavity. Conventional dentures are removable ( removable partial denture o ...

. This treatment can be successful in giving patients with anodontia a more aesthetically pleasing appearance. The use of an implant prosthesis in the lower jaw could be recommended for younger patients as it is shown to significantly improve the craniofacial growth, social development and self-image. The study associated with this evidence worked with individuals who had

of varying age groups of up to 11, 11 to 18 and more than 18 years. It was noted that the risk of implant failure was significantly higher in patients younger than 18 years, but there is significant reason to use this methodology of treatment in those older. Overall the use of an implant-prosthesis has a considerable functional, aesthetic and psychological advantage when compared to a conventional denture, in the patients.

Prognosis

Patients diagnosed with anodontia are expected to have a normal life expectancy. Once anodontia is diagnosed, dental implants or dentures will need to worn in order to treat this disorder. There is an 88.5% to 100% chance for dental implants in patients with ectodermal dysplasia or tooth agenesis to be successful when placed after the age of 18.

Epidemiology

The

of anodontia is unknown but it is a very rare disorder. Anodontia occurs in less than 2-8% of the general population in regards to

and 0.1-0.7% in primary teeth. Gender and ethnicity do not play a role in anodontia.

Research

A recent study in 2019 by R. Constance Wiener and Christopher water looked at anodontia, hypodontia, and oligodontia in children West Virginia. There is a high prevalence of children with missing permanent teeth in West Virginia compared to the rest of the nation. During this study, 500 panoramic images were taken of children between the ages of 6 to 11. Out of the 500 images taken, 60 children had at least one or more missing permanent teeth. The results showed that more females had one or more missing permanent teeth than males. From the 60 children who had missing permanent teeth, 15.5% were female and 8.8% were males. A case study conducted in 2016 of a 6 year old boy presented with anodontia. There was no family history of anodontia and the patient did not present any other symptoms for ectodermal dysplasia. It was observed the hypodontia was present in the maxillary arch and the only teeth present were the left primary first molar and the bilateral primary second molars. It was also observed that the

buccal mucosa The oral mucosa is the mucous membrane lining the inside of the mouth. It comprises stratified squamous epithelium, termed "oral epithelium", and an underlying connective tissue termed '' lamina propria''. The oral cavity has sometimes been des ...

, and floor of the mouth were considered normal. The patient proceeded with oral rehabilitation and give removable denture to wear. The patient struggled in the beginning to keep wearing the denture until gradually learning to adjust to it. The family reported no problems with retention and began a monthly recall visit in order to monitor any eruptions of teeth or adjustments that needed to be made. Improvements in speech skills, communication, and self esteem were also observed after placement of the denture. Another case study in 2013 of an eight year old boy who reported missing teeth, difficulty chewing, and difficulty speaking was seen to have other symptoms of ectodermal dysplasia. The father confirmed there is a family history of missing teeth. The patient also had sensitivity to heat, absence of sweating, dry skin, absent eyebrows and eyelashes, hyper pigmentation, and many other ectodermal dysplasia symptoms. After a full examination, the patient was diagnosed with complete anodontia. The patient was treated with a complete set of removable dentures. After the dentures were given, the patient's facial presentation and expressions improved. The patient was also set up for recall follow ups every six months. Drastic improvement was seen with improvements with chewing and speech.

References

External links

{{Tooth disease Developmental tooth pathology