ICD-9 Code 521.01

Dental caries limited to enamel

Not Valid for Submission

521.01 is a legacy non-billable code used to specify a medical diagnosis of dental caries limited to enamel. This code was replaced on September 30, 2015 by its ICD-10 equivalent.

ICD-9: 521.01
Short Description:Dental caries - enamel
Long Description:Dental caries limited to enamel

Convert 521.01 to ICD-10

The following crosswalk between ICD-9 to ICD-10 is based based on the General Equivalence Mappings (GEMS) information:

  • K02.61 - Dental caries on smooth surface limited to enamel

Code Classification

  • Diseases of the digestive system (520–579)
    • Diseases of oral cavity, salivary glands, and jaws (520-529)
      • 521 Diseases of hard tissues of teeth

Information for Medical Professionals

Index to Diseases and Injuries

References found for the code 521.01 in the Index of Diseases and Injuries:


Information for Patients


Tooth Decay

What is tooth decay?

Tooth decay is damage to a tooth's surface, or enamel. It happens when bacteria in your mouth make acids that attack the enamel. Tooth decay can lead to cavities (dental caries), which are holes in your teeth. If tooth decay is not treated, it can cause pain, infection, and even tooth loss.

What causes tooth decay?

Our mouths are full of bacteria. Some bacteria are helpful. But some can be harmful, including the ones that play a role in tooth decay. These bacteria combine with food to form a soft, sticky film called plaque. The bacteria in plaque use the sugar and starch in what you eat and drink to make acids. The acids begin to eat away at the minerals on your enamel. Over time, the plaque can harden into tartar. Besides damaging your teeth, plaque and tartar can also irritate your gums and cause gum disease.

You get fluoride from toothpaste, water, and other sources. This fluoride, along with your salvia, helps the enamel repair itself by replacing the minerals. Your teeth go through this natural process of losing minerals and regaining minerals all day long. But if you don't take care of your teeth and/or you eat and drink lots of sugary or starchy things, your enamel will keep losing minerals. This leads to tooth decay.

A white spot may appear where minerals have been lost. This is an early sign of tooth decay. You may be able to stop or reverse the decay at this point. Your enamel can still repair itself, if you take better care of your teeth and limit sugary/starchy foods and drinks.

But if the tooth decay process continues, more minerals are lost. Over time, the enamel is weakened and destroyed, forming a cavity. A cavity is a hole in your tooth. It is permanent damage that a dentist has to repair with a filling.

Who is at risk for tooth decay?

The main risk factors for tooth decay are not taking care of your teeth and having too many sugary or starchy foods and drinks.

Some people have a higher risk of tooth decay, including people who:

  • Don't have enough saliva, because of medicines, certain diseases, or some cancer treatments
  • Don't get enough fluoride
  • Are very young. Babies and toddlers who drink from bottles are at risk, especially if they are given juice or get bottles at bedtime. This exposes their teeth to sugars for long periods of time.
  • Are older. Many older adults have receding gums and more wear on their teeth. These raise the risk of decay on the exposed root surfaces of their teeth.

What are the symptoms of tooth decay and cavities?

In early tooth decay, you usually don't have symptoms. As tooth decay gets worse, it can cause:

  • A toothache (tooth pain)
  • Tooth sensitivity to sweets, hot, or cold
  • White or brown stains on the surface of a tooth
  • A cavity
  • An infection, which can lead to an abscess (pocket of pus) forming. The abscess can cause pain, facial swelling, and fever.

How are tooth decay and cavities diagnosed?

Dentists usually find tooth decay and cavities by looking at your teeth and probing them with dental instruments. Your dentist will also ask if you have any symptoms. Sometimes you may need a dental x-ray.

What are the treatments for tooth decay and cavities?

There are several treatments for tooth decay and cavities. Which treatment you get depends on how bad the problem is:

  • Fluoride treatments. If you have early tooth decay, a fluoride treatment can help the enamel to repair itself.
  • Fillings. If you have a typical cavity, your dentist will remove the decayed tooth tissue and then restore the tooth by filling it with a filling material.
  • Root canal. If the damage to the tooth and/or an infection spreads to the pulp (inside of the tooth), you might need a root canal. Your dentist will remove the decayed pulp and clean inside the tooth and root. The next step is to fill the tooth with a temporary filling. Then you will need to come back to get a permanent filling or a crown (a cover on the tooth).
  • Extraction (pulling the tooth). In the most severe cases, when the damage to the pulp cannot be fixed, your dentist may pull the tooth. Your dentist will suggest that you get a bridge or implant to replace the missing tooth. Otherwise, the teeth next to the gap may move over and change your bite.

Can tooth decay be prevented?

There are steps that you can take to prevent tooth decay:

  • Make sure that you get enough fluoride by
    • Brushing with a fluoride toothpaste
    • Drinking tap water with fluoride. Most bottled water does not contain fluoride.
    • Using fluoride mouth rinse
  • Practice good oral health by brushing your teeth twice a day with a fluoride toothpaste and regularly flossing your teeth
  • Make smart food choices by limiting foods and drinks that are high in sugars and starches. Eat nutritious, balanced meals and limit snacking.
  • Do not use tobacco products, including smokeless tobacco. If you currently use tobacco, consider quitting.
  • See a dentist for regular check-ups and professional cleanings
  • Make sure that your children get sealants on their teeth. Dental sealants are thin plastic coatings that protect the chewing surfaces of the back teeth. Children should get sealants on their back teeth as soon as they come in, before decay can attack the teeth.

NIH: National Institute of Dental and Craniofacial Research


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ICD-9 Footnotes

General Equivalence Map Definitions
The ICD-9 and ICD-10 GEMs are used to facilitate linking between the diagnosis codes in ICD-9-CM and the new ICD-10-CM code set. The GEMs are the raw material from which providers, health information vendors and payers can derive specific applied mappings to meet their needs.

  • Approximate Flag - The approximate flag is on, indicating that the relationship between the code in the source system and the code in the target system is an approximate equivalent.
  • No Map Flag - The no map flag indicates that a code in the source system is not linked to any code in the target system.
  • Combination Flag - The combination flag indicates that more than one code in the target system is required to satisfy the full equivalent meaning of a code in the source system.

Index of Diseases and Injuries Definitions

  • And - The word "and" should be interpreted to mean either "and" or "or" when it appears in a title.
  • Code also note - A "code also" note instructs that two codes may be required to fully describe a condition, but this note does not provide sequencing direction.
  • Code first - Certain conditions have both an underlying etiology and multiple body system manifestations due to the underlying etiology. For such conditions, the ICD-10-CM has a coding convention that requires the underlying condition be sequenced first followed by the manifestation. Wherever such a combination exists, there is a "use additional code" note at the etiology code, and a "code first" note at the manifestation code. These instructional notes indicate the proper sequencing order of the codes, etiology followed by manifestation.
  • Type 1 Excludes Notes - A type 1 Excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
  • Type 2 Excludes Notes - A type 2 Excludes note represents "Not included here". An excludes2 note indicates that the condition excluded is not part of the condition represented by the code, but a patient may have both conditions at the same time. When an Excludes2 note appears under a code, it is acceptable to use both the code and the excluded code together, when appropriate.
  • Includes Notes - This note appears immediately under a three character code title to further define, or give examples of, the content of the category.
  • Inclusion terms - List of terms is included under some codes. These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
  • NEC "Not elsewhere classifiable" - This abbreviation in the Alphabetic Index represents "other specified". When a specific code is not available for a condition, the Alphabetic Index directs the coder to the "other specified” code in the Tabular List.
  • NOS "Not otherwise specified" - This abbreviation is the equivalent of unspecified.
  • See - The "see" instruction following a main term in the Alphabetic Index indicates that another term should be referenced. It is necessary to go to the main term referenced with the "see" note to locate the correct code.
  • See Also - A "see also" instruction following a main term in the Alphabetic Index instructs that there is another main term that may also be referenced that may provide additional Alphabetic Index entries that may be useful. It is not necessary to follow the "see also" note when the original main term provides the necessary code.
  • 7th Characters - Certain ICD-10-CM categories have applicable 7th characters. The applicable 7th character is required for all codes within the category, or as the notes in the Tabular List instruct. The 7th character must always be the 7th character in the data field. If a code that requires a 7th character is not 6 characters, a placeholder X must be used to fill in the empty characters.
  • With - The word "with" should be interpreted to mean "associated with" or "due to" when it appears in a code title, the Alphabetic Index, or an instructional note in the Tabular List. The word "with" in the Alphabetic Index is sequenced immediately following the main term, not in alphabetical order.