Updated 29th of January 2023
Hypodontia, or tooth agenesis, is a condition where a person has one or more missing teeth that have never developed. It’s the most common dental anomaly, occurring in about 2.2 to 10 % of the general population. This condition can have negative impact on the mouth’s function, as well as on the smile’s appearance.
Hypodontia is an inherited condition and people sometimes refer to it as congenitally missing teeth. It is more common in girls than in boys, with a ratio of 3:2. The most affected teeth are the second premolars and the upper lateral incisors. The absence of third molars (wisdom teeth) is considered to be a normal variation and does not classify as being hypodontia.
The phenomenon of congenitally missing teeth is subdivided into categories depending on the number of absent teeth:
- Hypodontia refers to less thank 6 missing teeth, excluding wisdom teeth.
- Oligodontia is when 6 or more teeth are absent.
- Anodontia refers to a rare condition where all the teeth are missing.
A child should have all his baby teeth erupted by the age of three. A teenager should have all her adult teeth out by the age of 14, except for wisdom teeth. If missing teeth are suspected, a panoramic x-ray can confirm it.
Hypodontia affects adult teeth mostly, and it’s very rare in the primary dentition. But almost half of the children who have missing primary teeth will also have missing adult teeth.
Oral features that may be present with congenitally missing teeth:
- Microdontia where teeth appear smaller than normal.
- Misplaced positioning of adult teeth, because of the absence of neighbouring teeth acting as a guide during eruption.
- Retrognathic maxilla and prognathic mandible, also called underbite, where the lower jaw looks more advanced than normal.
- Significant mandibular angle and a flatter chin, which might happen when more than one tooth is missing.
Causes of hypodontia
Although hypodontia is mainly hereditary caused by genetics, environmental factors can lead to having missing teeth during dental development.
The most accepted theory of hypodontia is a problem at the level of the dental lamina, an area of tissue under the gums where teeth form. Heredity is the most common cause, where the mutation of specific genes prevents the dental lamina of performing its function.
Other factors that may affect having missing teeth:
- Cleft lip / cleft palate often happens in conjunction with hypodontia.
- Down Syndrome (a condition in which a person has an extra chromosome).
- Ectodermal Dysplasia (a group of conditions in which there is abnormal development of the skin, hair, nails, teeth, or sweat glands).
- Environmental causes such as radiation, allergies, chemotherapy, toxic epidermal necrolysis, or exposure to polychlorinated biphenyls (PCBs).
- Low birth weight, especially in twins.
- Maternal smoking during pregnancy.
- Some infectious illnesses such as rubella or candidiasis.
Treatments of hypodontia
Treating hypodontia depends on the location and the number of missing teeth.
Orthodontics can move teeth to either close a space of a missing tooth or create a space big enough to have the missing tooth replaced by either a bridge or a dental implant.
Maryland bridges are a good treatment option to replace lateral incisors. This is often combined with orthodontic treatment.
Partial dentures may be used to replace several missing teeth.
Dental implants are a good option to replace missing teeth, for people who want a fixed and stable treatment.
- Vahid Rakhshan1. (Congenitally missing teeth (hypodontia): A review of the literature concerning the etiology, prevalence, risk factors, patterns and treatment). Dent Res J (Isfahan). 2015 Jan-Feb; 12(1): 1–13.
- ScienceDirect, ( Hypodontia ).
- Wikipedia, (Hypodontia).