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What Is Pulp Necrosis?

Medically Reviewed by Dan Brennan, MD on April 12, 2021

Pulp necrosis is an irreversible condition that occurs when the soft pulp inside of a tooth dies. This is the last stage of a disease called pulpitis.

There is a pulp chamber inside of each of your teeth. The chamber holds blood vessels and nerves that are inside small pieces of flesh. This flesh, or pulp, is protected by the enamel of the tooth. When your tooth is damaged by decay or injury, the pulp can get infected and eventually die off. 

What Are the Symptoms of Pulp Necrosis?

Your teeth have three layers, the enamel, the dentin, and the pulp. The pulp is the innermost layer. It has to have a continuous supply of blood. If something interferes with the blood supply to the tooth, the two main symptoms you will notice are pain and discoloration.

Pain. Discomfort is often the first symptom of a necrotic tooth. The pain can range from mild to extreme. It's caused by the infection and swelling inside of your tooth. This puts pressure on the nerve at the base of the tooth.

Discoloration. The lack of blood supply to the tooth causes it to change color. The tooth may start as yellow, then change to gray, and eventually to black.

You may experience other symptoms as well, including:

  • Bad taste in your mouth from the infection
  • Inflamed sore on the gums, indicating an abscess
  • Bad smell from the tooth
  • Swelling of the periodontal membrane around the tooth

What Causes Pulp Necrosis?

Pulp necrosis is the end-stage of pulpitis, which can be caused by: 

  • Cavities that are untreated and progress deep into the tooth.
  • Trauma to the tooth interfering with the tooth's blood supply.
  • Multiple invasive treatments on a tooth.

The usual order of progression for pulp necrosis is:  

  • A cavity or dental injury occurs.
  • Bacteria enter the pulp through an opening in the tooth.
  • The healthy pulp tries to fight off the bacteria. 
  • The infection causes swelling, which causes pain. 
  • The tooth nerve is deprived of oxygen and nutrition.
  • Blood flow to the tooth is reduced or stopped completely.
  • The pulp dies off.

How Is Pulp Necrosis Diagnosed?

Your dentist will order x-rays and likely perform one of the following pulp sensibility tests to determine if the pulp in your tooth is dead.  

Endo-Ice Test. This test is done by spraying a cold spray onto a Q-tip and holding it against the tooth for 5 to 10 seconds. If there is no response to this test, the tooth is probably nonvital. If there is pain that lasts longer than 10 seconds, there is significant pulpitis. 

The hot test. This is performed by holding a source of heat next to the tooth until you feel the heat. The heat source can be hot water or some other heated compound. 

Electric pulp test (EPT). The EPT measures the vitality of the pulp by sending a gradually increasing electrical current through your tooth to get a response. The EPT records a number from 0 to 80. Any response before 80 indicates live pulp. No response at 80 indicates the pulp is dead. 

How Is Pulp Necrosis Treated?

The necrotic pulp has to be removed. This can be completed in one of two ways.

Root canal. In this procedure, the dentist removes the damaged and infected pulp. Then the pulp chamber is cleaned and treated so that no bacteria can grow. That empty space is filled in and the tooth is covered with a crown. 

Extraction. When a necrotic tooth can't be saved with a root canal, it may have to be removed completely. It can then be replaced with an implant or a bridge. 

What Are the Complications of Pulp Necrosis?

Untreated pulp necrosis can lead to more severe problems, including:  

How Can Pulp Necrosis Be Prevented?

Good dental hygiene, including brushing and flossing, is the key to preventing pulpitis and pulp necrosis. Regular flossing and brushing prevent decay from forming. It's also important that you eat a healthy diet since your teeth need vitamins and minerals to stay healthy.

You can't prevent trauma, but you can act quickly once it occurs. A damaged tooth may be able to be saved if you get to the dentist quickly after an accident. If you play a contact sport, you may want to use a mouthguard to help prevent trauma to your teeth. 

WebMD Medical Reference

Sources

SOURCES:

Absolute Dental: "Causes and Treatments for a Dead Tooth."

Dental Health Society: "Dental Pulp Necrosis." 

Herman Ostrow School of Dentistry of USC: "How to Conduct an Endo-Ice Test to Prove Irreversible Pulpitis."

LANGLEY ENDODONTICS: "Determining Pulpal Status – Electric Pulp Testing," "Determining Pulpal Status – The Hot Test."

MERCK MANUAL: "Pulpitis."

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