The number of individuals with amelogenesis imperfecta depends on the geographic location. In the U.S., about 1 in 14,000-16,000 children are born with AI, while in northern Sweden about 1 in 700 children are born with AI. The average global prevalence is slightly less than 1 in every 200 individuals. Within the 4 main types, hypoplastic is the most common form, followed by hypomaturation making up about 20-40% of cases, then hypocalcified makes up about 7% of cases, and hypomaturation/hypoplasia/taurodontism is the most rare form. Depending on the subtype of AI, there are different inheritance patterns of the genetic mutation. In X-linked dominant inherited forms of AI, children born genetically male are twice as likely than those born genetically female to develop the subtype. In X-linked recessive inherited forms of AI, only children born genetically male can develop the subtype. To read more about genetic inheritance patterns, refer to our  RareShare Guide on Genetic Inheritance.

There are 4 main types of amelogenesis imperfecta (AI), and each of the 4 main types can be categorized into 20 subtypes total. Each subtype is caused by a unique genetic mutation inherited in a specific pattern. To read more about genetic inheritance patterns, refer to our  RareShare Guide on Genetic Inheritance. The subtypes, the main type they fall under, and their known causes are tabulated below:

The genes AMELX, ENAM, and MMP20 especially and other genes listed above all express proteins necessary for normal tooth development: enamelin, ameloblastin, amelotin, tuftelin, amelogenin, dentine sialophosphoprotein, kallikrein, and matrix metalloproteinase. These proteins are essential for the development of enamel, which is the hard outer surface of the teeth made of mostly calcium that protects the tooth from degradation. Most of the known genetic mutations associated with development of amelogenesis imperfecta cause abnormal or reduced protein production of enamel-forming proteins, and this leads to symptoms of cracked or missing enamel in individuals with AI. 

Individuals with amelogenesis imperfecta experience a multitude of tooth problems, including cosmetic, physical pain, and complications. Some of the problems associated with loss or lack of tooth enamel include cracked teeth, early decay, loss of teeth, heat and cold sensitivity in teeth, and extreme pain when nerves are exposed. Thin enamel exposes the dentin layer underneath where the nerves of the teeth are located, and exposure of this area can lead to severe pain, sometimes continuously. 

Characteristic physical features of the teeth include discoloration, unevenly spaced teeth, chipping, mottled, and an open bite where the upper and lower teeth and jaws do not align when the mouth is closed. Not only will these features cause problems with chewing food, they can be uncomfortable and embarrassing. 

The thin enamel characteristic of AI will also cause issues in areas surrounding the teeth (periodontal). The gums can become inflamed or infected, the cementum that covers the root of the tooth can become damaged and loosen teeth, and the alveolar bones where the tooth root is can also be affected. These complications can cause further mouth problems such as gingivitis or gum disease.

A diagnosis of amelogenesis imperfecta is usually conducted by a dentist or orthodontist, usually upon visual inspection of the teeth and an examination of the family history of genetic AI.

A dental examination may involve an X-ray analysis of the teeth and roots. A special dental tool is used to distinguish between different types of AI to assess the quality of the enamel and how it breaks down. A radiographic exam can also be performed to assess the contrast between tooth enamel and dentin to examine density of the tooth enamel to determine the best type of treatment.

Since there are so many forms of amelogenesis imperfecta, treatment plans are developed to fit the needs of each individual to alleviate stress on the mouth when chewing, talking, or even closing. AI often requires expensive and continuous repair of the mouth, with orthodontia (alignment of teeth and jaw) and periodontia (treatment of gums and supporting structures). Some of the strategies used by dentists and orthodontists to restore normal function and appearance of teeth include:

• Crowns - tooth-shaped cap placed over the existing tooth to improve shape and size (used in hypocalcified and hypomaturation types where enamel is too weake for bonding)

• Bonding - high quality plastics fill in gaps in the teeth

• Orthodontia - braces or other appliances to straighten teeth or improve bite

• Dentures overlaying the tops of affected teeth correct open bite - can be removed

Additionally, using a desensitizing toothpaste can help prevent heat and cold sensitivity. 

Maintenance of good oral hygiene with a low sugar diet and regular brushing can also help lower the breakdown of tooth enamel and prevent painful symptoms of amelogenesis imperfecta.

Early diagnosis and treatment of amelogenesis imperfecta leads to improved outcomes. The sooner an individuals teeth can be protected from damage and decay, the less wear and tear on the teeth and the less likely they will develop painful symptoms or side effects. Preventing breakage of tooth enamel prevents pain and other complications such as cavities and gingivitis from occurring. In many cases of AI, a person’s teeth can be restored to appear and function normally for their lifetime with proper maintenance and care. 

1. https://rarediseases.org/rare-diseases/amelogenesis-imperfecta/ 

2. https://medlineplus.gov/genetics/condition/amelogenesis-imperfecta/#synonyms 

3. https://www.verywellhealth.com/amelogenesis-imperfecta-4783760 

4. https://www.healthline.com/health/amelogenesis-imperfecta#symptoms 

5. https://www.nature.com/articles/sj.bdj.2012.314

6. https://rarediseases.info.nih.gov/diseases/5791/amelogenesis-imperfecta