Agenesis
Tooth development disordersTooth developmental disorders may involve tooth enamel, dentine or cementum (a part of the tooth - see the image), or the shape, number and size of teeth. Hypodontia (a reduced number of teeth) is a genetically conditioned orthodontic dental anomaly of tooth number. Agenesis of permanent teeth (a failure to develop permanent teeth) occurs in 2.6% to 11.3% of the population worldwide, varying by gender and continent. A significantly increased occurrence in the agenesis of teeth (a failure to develop teeth) is associated with deviations in the position of the canine teeth. Agenesis of one or more teeth is the most frequent anomaly (deviation) in the development of teeth in humans, resulting from the defective functioning of dental tissue.
Agenesis is the most frequently occurring developmental defect of teeth
Agenesis of a tooth (a failure to develop a tooth) is the most frequently occurring defect of dentition (a part of teeth, see the image), which occurs in approximately 20% of the population according to the Online Mendelian Inheritance in Man (OMIM) database. The agenesis of permanent teeth in the European population is estimated at 5.5%.
Wisdom teeth
As soon as one becomes an adult, the third molars usually begin to cut through. The third molars are the last four teeth that begin to cut through between the 17th and the 25th years of age, which is probably why people tend to call them wisdom teeth.
The question is why the third molars even develop, since they are practically useless. According to one theory, this is a remnant from our ancestors. They often chewed tough, usually uncooked food (meat, nuts and roots) and ate more vegetables and fruit than we do. Therefore, their jaws were bigger, with sufficient space for one extra tooth, which came in quite handy while chewing. The third molars were therefore used much more in the past than they are now. Although this occurs very rarely, some people never develop the third molars. Why is this? This is due to the evolutionary reduction in the size of the facial skeleton and jaws over the last 20,000 years. This theory also appears to be supported by the finding that people from cultures that rely on crop farming have smaller jaws and more often lack the third molars. On the other hand, the descendants of ancient hunters (such as the aboriginal people in Australia) have bigger jaws and faces and almost all of them develop wisdom teeth.
Agenesis (a failure to develop a tooth) is mostly conditioned by a genetic defect. Only a small percentage of agenesis is caused by external factors, mainly by diseases such as rubella (German measles), syphilis, scarlet fever, rickets or nutritional deprivation during pregnancy or childhood. The absence of a tooth may also be caused by radiation of the cranial (skull) section during early development of the body, damage to the mother’s body due to radiation, chemical substances and medication (Thalidomide, cytostatic drugs). The most frequent local causes of agenesis include various types of trauma, tumours and osteomyelitis (inflammation of the bone marrow).
Tooth development
Poor tooth development results from defective functioning of the dentogingival unit. Variations in the number of teeth are divided into various types according to the defect type:
Agenesis - the failure to develop a tooth.
Hypodontia - a reduced number of teeth (fewer than six teeth are missing) - occurs as a result of discontinued tissue growth. The upper incisors, the third molars and the second premolars are most frequently missing.
Oligodontia - numerous teeth fail to develop (six or more teeth are missing).
