National Center for Advancing and Translational Sciences Genetic and Rare Diseases Information Center, a program of the National Center for Advancing and Translational Sciences

Amelogenesis imperfecta

Amelogenesis imperfecta (AI) (amelogenesis - enamel formation; imperfecta - imperfect) is a disorder that affects the structure and appearance of the enamel of the teeth. This condition causes teeth to be unusually small, discolored, pitted or grooved, and prone to rapid wear and breakage with early tooth decay and loss. These dental problems, which vary among affected individuals, can affect both primary (baby) teeth and permanent teeth. People with this disease my also have problems involving the tissues surrounding teeth (periodontal tissues) such as gums, cementum, ligaments, and alveolar bones in which the tooth root rests. Teeth are also sensitive to either hot or cold exposures, and sometimes both. Severe and continuous pain due to exposed dentin resulting from the enamel defect is present in some cases.[1][2][3]

There are 4 main types of AI that are classified based on the symptoms, X-rays appearance and  type of enamel defect. The main types are: hypoplastic (type I); hypomaturation (type II); hypocalcified (type III); and hypomaturation/hypoplasia/taurodontism (type IV). These 4 types are divided further into 17 or 18 subtypes, which are distinguished by their specific genetic cause and by their pattern of inheritance.[2][3] AI can be inherited in an autosomal dominant, autosomal recessive or X-linked recessive pattern.[1] Treatment may include dentures that cap the teeth (full crown restorations), orthodontic treatment, special toothpaste for the tooth sensitivity, and good oral hygiene.[3]
Last updated: 6/11/2018
In general, both the primary and permanent teeth are affected. The enamel tends to be soft and weak, and the teeth appear yellow and damage easily.[2] 

The defects associated with amelogeneis imperfecta are highly variable and include abnormalities classified as hypoplastic (defects in the amount of enamel), hypomaturation (defect in the final growth and development of the tooth enamel), and hypocalcification (defect in the initial stage of enamel formation followed by defective tooth growth). The enamel in the hypomaturation and hypocalcification types is not mineralized and is thus described as hypomineralized.[2] 

Traditionally, the diagnosis and classification of amelogenesis imperfecta is based on the clinical presentation and the mode of inheritance. There are four principal types based on the defects in the tooth enamel. These types are subdivided into 14 different subtypes based on the clinical presentation and the mode of inheritance.[2] 

Detailed information about the signs and symptoms associated with the four major types of amelogenesis imperfecta is available from the UNC School of Dentistry.
Last updated: 9/17/2015

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Showing of 12 |
Medical Terms Other Names
Learn More:
HPO ID
80%-99% of people have these symptoms
Yellow-brown discoloration of the teeth
Yellow-brown discolored teeth
0006286
30%-79% of people have these symptoms
Anterior open bite 0200095
Fragile teeth 0025124
Hypocalcification of dental enamel
Decreased enamel calcification
Poorly calcified tooth enamel
[ more ] 		0011084
Hypomature dental enamel 0011085
Hypoplasia of dental enamel
Underdeveloped teeth enamel
0006297
Impaired mastication
Chewing difficulties
Chewing difficulty
Difficulty chewing
[ more ] 		0005216
5%-29% of people have these symptoms
Abnormal jaw morphology 0030791
Abnormality of dentin
Abnormal dentin
0010299
Multiple unerupted teeth
Multiple non-erupting teeth
0006283
Taurodontia 0000679
Widely spaced teeth
Wide-spaced teeth
Widely-spaced teeth
[ more ] 		0000687
Showing of 12 |
Last updated: 7/1/2020
Amelogenesis imperfecta is caused by mutations in the AMELX, ENAM, and MMP20 genes. These genes provide instructions for making proteins that are essential for normal tooth development. These proteins are involved in the formation of enamel, which is the hard, calcium-rich material that forms the protective outer layer of each tooth. Mutations in any of these genes alter the structure of these proteins or prevent the genes from making any protein at all. As a result, tooth enamel is abnormally thin or soft and may have a yellow or brown color. Teeth with defective enamel are weak and easily damaged.[1]

In some cases, the genetic cause of amelogenesis imperfecta can not been identified. Researchers are working to find mutations in other genes that are responsible for this disorder.[1]

Click on each gene name to learn more about the role it plays in the development of tooth enamel.

Last updated: 9/17/2015
The different types of amelogenesis imperfecta can have different types of inheritance according to the gene that is altered:[3]

The following types have autosomal dominant inheritance:
  • IA
  • IB
  • IIIA
  • IIIB
  • IV
The types that are inherited in an autosomal recessive manner are:
  • IC
  • IF
  • IG or enamel-renal syndrome type
  • IH
  • IJ
  • IIA1
  • IIA2
  • IIA3
  • IIA4
  • IIA5
  • IIA6
Type 1E is inherited in a dominant pattern linked to the X chromosome.

In autosomal dominant cases, one copy of the altered gene in each cell is sufficient to cause the disorder. Autosomal recessive inheritance means two copies of the gene in each cell have to be altered for the person to have the disease.  A condition is considered X-linked if the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes. In most cases, males with X-linked amelogenesis imperfecta experience more severe dental abnormalities than females with this form of this condition.[1]
Last updated: 6/11/2018
A dentist can identify and diagnose amelogenesis imperfecta on the basis of the patient's family history and the signs and symptoms present in the affected individual.[4]

Extraoral X-rays (X-rays taken outside the mouth) can reveal the presence of teeth that never erupted or that were absorbed. Intraoral X-rays (X-rays taken inside the mouth) show contrast between the enamel and dentin in cases in which mineralization is affected.[4]

Genetic testing is available for the genes AMELX, ENAM, and MMP20. You can visit the Genetic Testing Registry to locate laboratories performing genetic testing for these genes.[1]

The American Academy of Pediatric Dentistry is a source of information to find a pediatric dentist. The National Dental Association can also assist people in locating a dentist.
Last updated: 9/17/2015
Treatment depends on the type of amelogenesis imperfecta, the age of the affected person, and the type and severity  of enamel abnormality.[1891][2] Treatments include preventative measures, various types of crowns, as well as tooth implants or dentures, orthodontic, peirodontal and restorative treatment.[5][4] The social and emotional impact of this condition should also be addressed.[4]

Detailed information on the treatment of amelogenesis imperfecta is available from the UNC School of Dentistry.
Last updated: 8/1/2011

Research helps us better understand diseases and can lead to advances in diagnosis and treatment. This section provides resources to help you learn about medical research and ways to get involved.

Clinical Research Resources

  • The Research Portfolio Online Reporting Tool (RePORT) provides access to reports, data, and analyses of research activities at the National Institutes of Health (NIH), including information on NIH expenditures and the results of NIH-supported research. Although these projects may not conduct studies on humans, you may want to contact the investigators to learn more. To search for studies, enter the disease name in the "Text Search" box. Then click "Submit Query".

Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

Organizations Providing General Support

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • Genetics Home Reference (GHR) contains information on Amelogenesis imperfecta. This website is maintained by the National Library of Medicine.
  • MedlinePlus was designed by the National Library of Medicine to help you research your health questions, and it provides more information about this topic.
  • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

In-Depth Information

  • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
  • Online Mendelian Inheritance in Man (OMIM) lists the subtypes and associated genes for Amelogenesis imperfecta in a table called Phenotypic Series. Each entry in OMIM includes a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine.
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Amelogenesis imperfecta. Click on the link to view a sample search on this topic.

Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know.

  1. Amelogenesis imperfecta. Genetics Home Reference (GHR). May 2015; http://ghr.nlm.nih.gov/condition/amelogenesis-imperfecta.
  2. Wright JT. Amelogenesis Imperfecta. Developmental Defects of the Teeth. https://www.dentistry.unc.edu/dentalprofessionals/resources/defects/ai/.
  3. Amelogenesis Imperfecta. National Organization for Rare Diseases (NORD). 2018; https://rarediseases.org/rare-diseases/amelogenesis-imperfecta/.
  4. Crawford PJM, Aldred M & Bloch-Zupan A. Amelogenesis imperfecta. Orphanet. April, 2007; http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=88661.
  5. Naik M & Bansal S.. Diagnosis, Treatment Planning, and Full-mouth Rehabilitation in a Case of Amelogenesis Imperfecta. Contemporary Clinical Dentistry. 2018; 9(1):1-25. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5863396/.
  6. Leung VW, Low B, Yang Y & Botelho MG. Oral Rehabilitation of Young Adult with Amelogenesis Imperfecta. J Contemp Dent Pract. May 1, 2018; 19(5):599-604. https://www.ncbi.nlm.nih.gov/pubmed/29807973.