An Overview of Amelogenesis Imperfecta

Amelogenesis imperfecta is a heritable dental disease that affects 1 in 14,000 in the U.S. Children with amelogenesis imperfecta do not produce functional proteins that are required to create and lay down effective enamel. As a result, their teeth can be discolored, misshapen, or fragile, and most cases require dental work to preserve or replace teeth.

Symptoms

Amelogenesis imperfecta can cause specific symptoms affecting the teeth and bite, including:

• Yellow, brown, grey, or white (snow-capping) discoloration of teeth
• Thin, soft, or brittle enamel
• Unusual tooth growth
• Uneven, lumpy, or ridged teeth
• Extreme tooth sensitivity
• Open bite (misaligned jaws)

Some of the additional risks and complications associated with amelogenesis imperfecta include:

• Dental cavities (caries)
• Tooth wear, cracking, and chipping
• Excess tartar build-up
• Large or swollen gums (gingival hyperplasia)
• Tooth rot
• Infection of the tissues and bone surrounding teeth

Causes

A gene is like a blueprint that is used to create proteins and, ultimately, larger structures within the body. When genetic mutations or other chromosomal defects change the information in a gene, the protein created may not function properly. Amelogenesis imperfecta affects proteins that the body normally uses to produce tooth enamel.

There are several proteins that are necessary to correctly make enamel. These include: 

• Enamelin
• Ameloblastin
• Amelotin
• Tuftelin
• Amelogenin
• Dentine sialophosphoprotein
• Kallikrein 4
• Matrix metalloproteinase 20
• Others

There are at least 10 genes known to be necessary for enamel growth, and when mutations in these genes are present, they prevent enamel from being formed correctly during tooth development.

Diagnosis

The diagnosis of amelogenesis imperfecta is based on both a careful family history and assessment of dental characteristics. Genetic testing may be used to understand the cause and heritability of the condition. X-ray imaging may be useful to classify the disorder by type. These classification systems have changed over time, and some favor physical characteristics of teeth to classify, while others use the heritability and underlying genetic cause as primary or secondary diagnostic labels.

The four types defined by physical characteristics, as diagnosed with X-ray imaging, are based on differences in enamel density between the types. These are the types:

• Type 1 (hypoplastic): The crowns of teeth may be smaller than normal with grooves and pits in the enamel of the tooth. The teeth are often discolored and an open bite prevents the teeth from meeting.
• Type 2 (hypomaturation): The enamel of the teeth is often discolored with a rough, pitted texture but normal thickness. The enamel may be especially soft or brittle and prone to damage and sensitivity. An open bite tends to be present.
• Type 3 (hypocalcified): Similar to characteristics present in Type 2, but the enamel appears more chalky and tartar can build up quickly. The enamel is soft and can be quickly damaged.
• Type 4 (hypomaturation-hypoplasia with taurodontism): Teeth are often smaller and discolored with spotting. The enamel is thinner than normal and pits are present. Taurodontism is when the pulp chamber, a space in the root of the tooth, is larger than normal.

Different forms of amelogenesis imperfecta can be inherited dominantly, recessively, or with abnormalities present on the X chromosome. Some gene mutations are known to follow one specific inheritance pattern, while others have been known to be inherited in multiple ways—particularly the ENAM gene.

Differential Diagnosis

When considering a diagnosis of amelogenesis imperfecta, it may be necessary to rule out other potential causes that may lead to similar symptoms and signs. Some of these include:

• Dental fluorosis: The most common alternative explanation of enamel problems is dental fluorosis. Some enamel is present at birth, but the rest is produced at different times throughout the first year of life. If large amounts of fluoride are consumed by a child—often from eating fluoride toothpaste or drinking water high in fluoride content—the stages of enamel development may be disrupted. In moderate to severe cases, this can leave some teeth stained, malformed, or brittle while other teeth that finish developing at a different time may be unaffected.
• Excessive acidity: Acidity may also affect how enamel is preserved. Chronic vomiting during the first year of life can also weaken enamel development, causing symptoms similar to amelogenesis imperfecta.
• Molar-incisor hypomineralisation (MIH): This is a condition in which the enamel of the incisors and first molars lack enamel and are discolored.

There are also several syndromes that may be related to the condition and may be considered.

Tricho-dento-osseous syndrome (TDO) is a condition that may have similar symptoms to amelogenesis imperfecta, notably with taurodontism, and it is unclear whether their underlying causes are related.

Kohlschutter syndrome, platyspondyly, nephrocalcinosis, and cone rod dystrophy can co-occur with amelogenesis imperfecta.

Treatment

The goals of treatment for amelogenesis imperfecta are to optimize both function and cosmetic appearance of teeth, and are meant to: 

• Relieve pain associated with the condition 
• Preserve teeth and enamel 
• Preserve or restore dental function
• Address psychosocial concerns, including cosmetic appearance

Early treatment of amelogenesis imperfecta involves dental work to protect an infant’s baby teeth as they come in. Normal development should be promoted as much as possible.

As part of early development, metal crowns are fitted on teeth in the back of the mouth and polycarbonate crowns or composite fillings are fitted on the front teeth. Local anesthetics are usually used, but a general anesthetic may be necessary for the procedure. Depending on the timing of this dental work, especially if a delay has occurred, some decayed teeth may need to be removed.

Around the age of 6, as permanent adult teeth begin to come in, treatment considerations will depend on the type of amelogenesis imperfecta that is present. Cases where the enamel of the teeth is hard and thin may be effectively protected with composite/porcelain crowns or veneers. 

Other forms of amelogenesis imperfecta may result in adult teeth that are extremely sensitive or weak, making them less able to be preserved. Implants or dentures may be necessary to replace damaged teeth.

In most cases, good oral hygiene will help to preserve teeth over the long term, and dietary avoidance of hard and acidic foods can help avoid additional damage that may weaken enamel. Toothpaste for sensitive teeth can decrease the tooth pain associated with amelogenesis imperfecta.

Children growing up with amelogenesis imperfecta may be distressed by the appearance of their teeth and this may impact how they relate to their peers. This social distress may lead to hiding the appearance of the teeth when smiling, for example. This may impact self-esteem. Early restoration may lead to healthy peer relationships at an important time in social development.

Genetic Counseling

The genetic causes of amelogenesis imperfecta are becoming more clear. Researchers have identified several patterns of inheritance and the specific genes involved. Genetic tests are increasingly available to determine the causes of distinct forms of the condition.

A family history and physical examination, including dental X-rays, may be sufficient to lead to the diagnosis. Further genetic testing may identify specific causes. If needed, genetic counselors may help future parents make informed family planning decisions and identify the potential risk to subsequent generations.

A Word From Verywell

Beyond the altered appearance, problems with the enamel of teeth can lead to significant discomfort, increased sensitivity, and damage that may ultimately cause tooth loss. The social impacts may also be significant. Early identification of these issues may allow for some preventive measures, starting even in childhood, and early restoration to preserve long-term well-being. The costs associated with extensive dental work may be a barrier. If you are concerned about how this condition may affect you, seek out evaluation by a dentist familiar with the syndrome and how it might be effectively treated. You deserve a thoughtful evaluation and treatment plan for your teeth, for all the long-term benefits that come from optimal dental health.