3.1 Prevalence and Incidence
Various defects (anomalies/malformations) can develop in the tooth structures depending on the causative agent and its relationship to the stage of the tooth formation and calcification. The incidence of defects differs based on race, geographic region, and sex, and these variations have been reported on different tooth parts as well as tooth supporting structures. In one study, enamel defects were reported in 33% of the population (Masumo et al. 2013).
The frequency of defects is common, so it is important for the dentist to have the knowledge to inform the parents appropriately. Accordingly, this topic should be adequately covered in the dental undergraduate teaching curriculum.
3.2 Diagnosis and Classification of Defects in Teeth
The classification of defects in teeth varies and is based on the different structures involved. When each part of the tooth is affected, it is classified as a “structural defect.” This may affect the quantity of the tooth substance produced, causing shape and size variation, and, in certain circumstances, the absence of teeth or the formation of extra teeth. Tooth color is also affected in certain defects, causing abnormal appearance. Apart from these variations in classification, the causative source of the defect may also be considered as a tool for the classification of dental defects. The following sections discuss the most common classifications used by dental professionals and scientists.
3.2.1 Cause of Disturbance
- Genetic: Tooth shape and structural content can be influenced by genome dictation. There may be a wide range of disturbances as part of a much larger clinical manifestation, such as a syndrome involving several body organs as well as the teeth, including those in ectodermal dysplasia; or, alternatively, only teeth may be involved, such as the case in amelogenesis imperfecta.
- Congenital: There are instances when a child’s tooth development is affected by events during pregnancy or at birth. This is known as congenital, and there is no faulty gene involved, an example of which is enamel hypoplasia caused by maternal dehydration or viral infection during pregnancy.
- Acquired: These cases are affected by environmental factors – for example, fluorosis defects caused by water fluoride content or isolated enamel, and dentine hypoplasias in permanent teeth caused by infections involving primary antecedent teeth, such as in Turner’s hypoplasia.
3.2.2 Extent of Involvement of the Dentition
Defects can either involve part or all of the teeth. They may also affect one tooth, a few teeth, or the full dentition. It is important to classify them on the level of involvement of the teeth:
3.2.3 The Structure Involved
18.104.22.168 Enamel Defects
- Enamel hypoplasia: This condition accounts for 15.8% of all enamel defects – for example, molar incisor hypoplasia (MIH) (Gurrusquieta et al. 2017). Localized cases are more frequent than those with more generalized involvement.
- Amelogenesis imperfecta