Dental arches are only harmonious and fully functional if they are intact. Anodontia is the congenital absence of dental units. It may involve one or more teeth, single tooth, group or total anodontia. The lack of continuity of the arches, through the spaces created by the absence of teeth, poses serious aesthetic and functional problems. Variants of anodontia are oligodontia, when a maximum of 6 teeth are missing, and hypodontia, when the number of missing teeth exceeds 6.
Prevalence of anodontia
Theoretically, anodontia can involve any tooth unit but cases where the arch is completely edentulous are rare. The most common missing teeth are the wisdom molars (about 30% of cases), lateral incisors and lower premolars.
Causes of anodontia
Maternal pathology – during pregnancy, some of the mother’s problems can affect the baby’s teeth.
Child trauma – in the child’s first year of life, minor accidents affecting the oral region can impact the development of the tooth buds and consequently the normal growth of the teeth.
Natural process – some tooth buds may be missing without any other pathology being involved.
Anodontia usually occurs in ectodermal dysplasia, which is a group of anomalies where 2 or more derived ectodermal structures have abnormal development. When anodontia is not associated with this syndrome, it is caused by an unknown genetic mutation, but although no specific gene has been identified, several different genes are thought to be associated with anodontia, including EDA, EDAR, EDARADD, MSX1, PAX9, IRF6, GREM2, AXIN2, LRP6, SMOC2, LTBP3, PITX2 and WNT10B. The last gene is considered to have a major impact in the development of hypodontia or oligodontia. If anodontia is present on the maternal or paternal side, the chances of it being inherited are higher.
The problem of missing teeth
Oral rehabilitation in the case of anodontia depends on the number of missing teeth and their location. You can opt for orthodontic treatment to close the gaps or prosthetic treatment.
Prosthodontic treatment – replacement of missing teeth is carried out when the gaps are large enough to allow this procedure. The dentist may design a dental bridge supported on the remaining teeth or use implants inserted into the edentulous bone.
Orthodontic treatment – if the spaces are not very large and the teeth have migrated towards edentulousness, the dentist may indicate orthodontic treatment. This method can be combined with prosthetic treatment for satisfactory results.
Absence of upper lateral incisors
This situation where one or both upper lateral incisors are missing is a complex one, as it concerns an aesthetically important area. It creates asymmetry and migrations that mainly affect the aesthetic function. Also, the lateral incisors are located in the vicinity of the canines, with particular importance in functional guidance. Once this guidance is affected, a disharmony of the arches in the functional movements occurs, which is transmitted to the temporomandibular joint, causing pain and limiting mouth opening.
Absence of lower premolars
Not as much of a challenge as the previous situation because the premolars are not in an area of particular aesthetic importance. The spaces can be braced or orthodontically closed. In most cases, when only one premolar is missing, the space closes itself by migrating the posterior teeth without affecting the occlusion.
Absence of wisdom molars
Not a dental problem. They are not in an aesthetically important area and sometimes their presence causes crowding in the front areas, especially in narrow arches.
The dentist can identify the absence of teeth clinically by directly viewing the existing spaces and will ask the patient if there has been a previous extraction. He will correlate the clinical result with the radiographic result to detect if there is an impacted tooth. He will design a treatment plan tailored to the situation in the oral cavity.
The gaps created by missing teeth can jeopardize the function of the arches, so treatment should be instituted as soon as possible..
Anodontia is a rare genetic anomaly characterized by the congenital absence of all temporary or permanent teeth. It is divided into 2 subsections, complete absence of teeth or only of one tooth. It is associated with a series of skin or nerve syndromes called ectodermal dysplasia. Anodontia is usually part of a syndrome and rarely occurs as an isolated entity. There is no exact cause of anodontias. The defect results in obstruction of the dental lamina during embryogenesis due to local, systemic and genetic factors.
Congenital absence of permanent teeth may present as hypodontia, when 1 or 2 permanent teeth are missing, or oligodontia when 6 or more teeth are missing. Congenital absence of all wisdom molars (3rd molar) is relatively common.
Anodontia is the congenital absence of teeth and can occur in some or all teeth, while partial anodontia (or hypodontia), involves both or only the permanent dentition. About 1% of the population has oligodontia. Several names are attributed to this anomaly such as: partial anodontia, hypodontia, oligodontia, congenital absence, anodontia, bilateral flattening.
Congenital absence of at least one permanent tooth is one of the most common dental anomalies and can contribute to masticatory dysfunction, speech defects, aesthetic problems and malocclusion. The absence of lateral incisors is a major stereotype. People with this condition are socially perceived as being the most aggressive compared to those without. The occurrence of anodontia is lower than hypodontia which has a prevalence of 0.1-0.7% in temporary teeth and 3-7.5% in permanent teeth.
Signs and symptoms
The main sign of anodontia is when a child does not erupt any permanent teeth until the age of 12. Other signs of anodontia may include the absence of temporary teeth when the child reaches 12 to 13 months of age.
Symptoms that are associated with anodontia include: alopecia, lack of sweat glands, cleft lip or palate and missing nails. Most of the time, these symptoms are seen because anodontia is usually associated with ectodermal dysplasia. In the rare case where ectodermal dysplasia is not present, anodontia will be caused by an unknown genetic mutation.
Mechanisms and Pathophysiology
Anodontia is a genetic abnormality that usually occurs as a result of another syndrome. Different outcomes can occur depending on the gene that is involved. It remains unclear which specific gene is the direct cause, but several genes are known that may be related to this anomaly. The main genes involved include: the EDA, EDAR and EDARADD genes.
If a functional and a non-functional gene are inherited, one from an affected parent and one from an unaffected parent, it can lead to a 50% chance of the child inheriting the genetic disorder. Individual anodontia will have no effect on any other part of the body apart from missing teeth.
Hypodontia and anodontia are frequently associated with a multitude of syndromes and genetic abnormalities, about 70. Syndromes primarily involved with ectodermal participation are a prime circumstance for anodontia to occur, some examples being Rieger’s disease, Robinson’s and focal dermal hypoplasia.
Three syndromes with classic signs of anodontia are Mandibulo-oculo-facial dyscephaly, mesoectodermal dysplasia and ectodermal dysplasia. In cases of Mandibulo-oculo-facial dyscephaly, permanent teeth are not present, but temporary teeth are. In mesoectodermal dysplasia the symptoms are anodontia and hypodontia. In ectodermal dysplasia, oligodontia is also present. Other symptoms associated with anodontia include alopecia, lack of sweat glands, cleft palate or lip and missing nails.
Anodontia can be diagnosed when the child does not start developing teeth around 12-13 months of age or by the age of 10 years on permanent teeth. The dentist may use X-rays, such as panoramic X-rays, to check for developing teeth. There is also a higher risk for a child to develop anodontia if the parents have this abnormality. In the absence of all permanent teeth, anodontia will be the diagnosis. If 1 to 5 teeth are missing, the diagnosis will be hypodontia, and if 6 or more teeth are missing, oligodontia.
Complications associated with anodontia can vary, but most result in problems related to aesthetic, phonatory and masticatory function. Complications can occur with the application of a dental implant. Although rare, some complications may relate to loosening of the implanted screw or the development of painful lesions.
Prevention and treatment
Anodontia cannot be prevented due to the fact that it is a genetic abnormality. Prosthetic replacement of missing teeth is possible through the use of dental implants or dentures. This treatment can successfully give patients with anodontia a more aesthetically pleasing appearance. The use of implant prosthodontics in the jaw may be recommended in young patients due to the expected improvement in craniofacial growth, social development and self-image. The study associated with this evidence was conducted in individuals with ectodermal dysplasia in various age groups up to 11 years, between 11 and 18 and older than 18 years.
It was noted that the risk of implant failure was significantly higher in patients younger than 18 years, but there are significant reasons to use this treatment methodology in older patients. Overall, the use of an implant prosthesis has a considerable functional, aesthetic and psychological advantage in patients compared to a conventional prosthesis.
Patients diagnosed with anodontia are expected to have a normal life span. Once anodontia is diagnosed, dental implants or dentures are required to treat the condition. There is an 88.5% to 100% chance that dental implants in patients with ectodermal dysplasia or hyperostosis will be successfully inserted after the age of 18.
The prevalence of anodontia is unknown, but it is a very rare anomaly. Anodontia occurs in less than 2-8% of the general population in permanent teeth and 0.1-0.7% in temporary teeth. Gender and ethnicity do not play a role in the occurrence of anodontia.
A recent 2019 study by R. Constance Wiener and Christopher Water looked at anodontia, hypodontia, and oligodontia in West Virginia children. There is a high prevalence of missing permanent teeth in children 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 and 11. Of the 500 images taken, 60 children had at least one or more missing permanent teeth. The results showed that more girls were missing one or more permanent teeth than boys. Of the 60 children with missing permanent teeth, 15.5% were girls and 8.8% were boys.
A case study was conducted in 2016 on a 6-year-old boy who had anodontia. There was no family history of anodontia and the patient had no other symptoms characteristic of ectodermal dysplasia. It was noted that hypodontia was present in the maxillary arch and the only teeth present were the left first temporary molar and bilateral second temporary molar.
It was also noted that the buccal mucosa, palate and oral floor were considered normal. The patient continued with oral rehabilitation and was fitted with a removable denture. The patient had some discomfort at first wearing the denture until he gradually learned to adjust with it. The family reported no retention problems and continued to come in for monthly checkups for the dentist to monitor any tooth eruptions or adjustments that needed to be made. Improvements in speech, communication and self-esteem skills were also noted after the application of dentures.
Another case study in 2013 was conducted on an eight-year-old boy who reported missing teeth, difficulty chewing and phonation, and was noted to have other symptoms of ectodermal dysplasia.
The father confirmed that there was a family history of anodontia. The patient also had heat sensitivity, absence of sweating, dry skin, absent eyebrows and eyelashes, hyperpigmentation and many other symptoms of ectodermal dysplasia. After a complete examination, the patient was diagnosed with complete anodontia. The patient was treated by fabricating and fitting of removable dentures, both in the jaw and the mandible. After the dentures were fitted, the patient’s facial appearance and expressions improved. The patient was also recalled every six months. A drastic improvement in chewing and phonation was observed.