The development of teeth starts at approximately 6 to 7 weeks after conception. Tooth development is a continuous process which takes place in many stages.
Each tooth develops through three successive stages
- Bud stage
- Cap stage
- Bell stage
During the early stages, the tooth germs grow and expand and the cells that are to form the hard tissues of the teeth differentiate. This leads to the formation of enamel and dentine. As the crowns of the tooth begin to form and mineralize, the root formation begins. After the roots calcify, the formation of the supporting tissues begin. These supporting tissues are cementum, periodontium and the alveolar bone. Subsequently the completed tooth crown erupts in the oral cavity. Root formation continues until the supporting tissues are fully developed.
Developmentally, missing permanent teeth is usually a result of genetic abnormality. When fewer than 6 teeth is missing in the oral cavity it is termed as hypodontia. When more than 6 teeth are missing it is known as oligodontia.
The primary dentition is made up of central incisors, lateral incisors, canines, first molars and second molars. There is one of a kind in each quadrant making a total of 5 in each quadrant. Hence totally there are 20 primary teeth. All of these are gradually replaced by a permanent counterpart except the primary first and second molars. They are replaced by the premolars. The replacement of the primary teeth starts at about 6 years of age when the permanent first molar develops. This results in mixed dentition. The process of shedding primary teeth and replacing by permanent teeth is called as exfoliation.
