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 teeth (also known as deciduous, milk, first and baby teeth) and the most commonly affected are the adult second premolars and the upper lateral incisors. It usually occurs as part of a syndrome that involves other abnormalities and requires multidisciplinary treatment. The phenomenon can be subdivided into the following according to the number of teeth concerned:

Hypodontia: one to six missing teeth excluding the third molars
Oligodontia: six or more missing permanent teeth excluding the third molars
Anodontia: complete absence of teeth

Signs and symptoms
Typically, all baby teeth will be present by the age of three. As for all adult teeth, they erupt between the ages 6 to 14, with the exception of the third molar, also known as the wisdom teeth which normally erupt between 17 and 25 years of age. If the tooth has yet to erupt by an appropriate age, panoramic x-rays are taken. Dental features
Microdontia may be present in one or more of the other teeth. This means that the teeth appear smaller than normal, may be observed in both the primary and permanent dentition. This condition can be genetically-linked and in severe cases, may present themselves in the form of ectodermal dysplasia, cleft lip or palate or Down Syndrome.
This risk is especially high in young patients with large pulp chambers. Tooth autotransplantation
Autotransplantation involves the removal of a tooth from one socket and relocating to another socket in the same individual. If done successfully, it is able to ensure stable alveolar bone volume as there is continuous stimulation of the periodontal ligament. Implant supported tooth replacement
Placing dental implants has proven to be a predictable and reliable method of treating hypodontia, along with bringing excellent aesthetic results. Implant placement should be delayed until jaw growth in an individual is complete. One limitation of implant placement would be the need for a sufficient amount of bone volume, which if not met, may affect the positioning of the implant. However, bone grafting can be carried out to overcome this. Epidemiology
Hypodontia is less common in the primary dentition, with reported prevalence rates ranging from 0.5% in the Icelandic population to 2.4% in the Japanese population. In the primary dentition the teeth reported as most likely to be missing are the lateral incisors, both maxillary and mandibular. If a deciduous tooth is missing this will increase the risk of an absent successor.In the permanent dentition third molars are most commonly absent, and one study found prevalence rates of between 20–22%. When third molars are ignored the prevalence rate for each tooth varies from study to study. In Caucasian studies mandibular second premolars and maxillary lateral incisors are most often absent. Several UK studies have found the lower second premolar to be most commonly absent.