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Tooth Resorption, Internal and External: Causes, Symptoms & Treatment

Medically reviewed by
Dr. Sarah Abbas
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What is tooth resorption? In short, it occurs when some of the body's cells start eating away at part of the tooth structure. If you have just been told you have tooth or root resorption, you likely have a lot of questions.

  • What exactly is this condition?
  • Will you need a tooth extraction?
  • Will this problem spread to other teeth and affect your overall oral health?
  • Is it even possible to treat dental resorption?

Tooth resorption is quite uncommon in adults, and many people have not even heard of it until their dentist diagnoses the condition. So, in this article, we will explain exactly what tooth resorption means, the different forms it can take, and how it can be treated.

What is tooth resorption?

What causes tooth resorption?
X-ray of a resorbed tooth

The term ‘resorption' refers to a process in which one part of your body draws in or absorbs another part. It may occur in different tissues located in various areas of the body.

Tooth resorption, including root resorption, involves parts of the tooth being broken down by cells called osteoclasts.

This process can occur internally, in the tooth pulp, or externally, affecting the cementum or less commonly enamel. The latter is more common. Occasionally, external root resorption may occur alongside internal resorption.

Tooth resorption often begins on the external surface of the tooth and may gradually move inwards. In addition to losing part of a tooth, or ending up with a dead tooth, you may also develop gum inflammation and other symptoms characteristic of this condition.

Here are some other quick facts about tooth resorption before we look at it in more detail:

  • People with resorption usually feel no pain and are asymptomatic.
  • External resorption can be misdiagnosed; a second opinion may be necessary.
  • Root canal therapy may help treat internal resorption, but if there is a large defect, the tooth may fracture or break and fail to function.

Types of tooth resorption

Depending on the exact area affected, resorption of the tooth is divided into two main classifications: internal tooth resorption and external tooth resorption.

Internal tooth resorption

As indicated by the name, internal resorption affects the insides of the teeth. It is relatively uncommon compared to external resorption and occurs in men more often than in women.

Internal resorption is also more prevalent in people who have recently experienced dental trauma or undergone extensive oral surgery. For example, tooth autotransplantation (repositioning of an erupted or impacted tooth in another location to replace a missing tooth in the same person).

Most patients suffering from internal resorption are unaware of this problem because it's hard to see from the outside. Therefore, most cases of internal resorption are normally detected via X-rays performed as a part of a routine dental examination.

On an X-ray, an internally resorbing tooth will show a larger pulp chamber or canals replacing the surrounding dentin, in comparison with neighbouring teeth.

External tooth resorption

This problem is more common than internal resorption and can affect any part of the tooth. When it begins with the cementum around the root, it may be called external root resorption.

External resorption may appear on the outer surface of the tooth in the form of deep chips or holes. Resorption that extends to the roots of the tooth can be seen in an x-ray report as a flattening of the root tips as well as a reduction in their length.

resorption tooth definition
Tooth root resorption occurs in a number of ways

External resorption is further classified into several types:


External inflammatory resorption is normally caused by a prolonged trauma of the tooth ultimately giving rise to pathological resorption.

Some of the most common causes of this type of resorption include the drying of the root surface after a trauma, previous surgery, injury to the periodontal ligament (PDL), pressure, or complete exposure of the dentine tubules.


This type of resorption normally is usually not too severe and is often diagnosed after an incidental finding on an x-ray. Also known as transient inflammatory resorption. It is caused by the presence of pressure, such as an impacted tooth or cyst. it normally heals upon removal of the cause and only requires proper monitoring.

The common causes of this condition include a limited, localised injury to the root of the tooth or the surrounding area. Following injury, the affected area undergoes osteoclastic activity (the eating away of bone by cells) for two to three weeks before healing begins.

If the problem is only limited to the cementum or enamel, it is possible to achieve complete healing. However, if the problem involves dentine, re-contouring will be needed.


External cervical resorption refers to a localised lesion in the cervical region of the tooth, just above where the root begins. The problem rarely extends to the pulp and is often caused by prolonged trauma leading to a horizontal and vertical growth of the lesion following periodontal treatment, trauma, or tooth whitening.


This type of root resorption involves the resorption of the tooth tissue followed by a complete replacement with bone. This leads to the elimination of the periodontal ligament space around the tooth and complete fusion between the tooth and surrounding bone.

The reason why this happens is not well understood. However, most orthodontic and dental experts believe that the process begins soon after the obliteration of the PDL and the close approximation between the tooth and the bone.

The damage to the PDL disrupts the release of the protective regulator that helps prevent root resorption. This encourages the osteoclasts (bone-destroying cells) to completely resorb the tooth tissue and replace it with bone.

Learn more about tooth resorption types in this video:

What causes tooth resorption?

There are several factors that may lead to resorption of teeth. The most common cause of external resorption is trauma or pressure on the teeth.

For example, prolonged tooth grinding, using excessive pressure by orthodontic appliances like braces for a long time or the presence of an impacted tooth or cyst. In some cases, the resorption can occur without a known cause (Idiopathic resorption).

In the case of internal resorption, the most common cause is trauma to the teeth following an untreated dental cavity or tooth abscess.

Are there any complications?

Without proper treatment, resorption may lead to a number of complications which include:

  • Infection
  • Discolouration and weakening of teeth
  • Difficulty in extracting the involved tooth due to fusion with bone
  • Crooked teeth
  • Chipping
  • Cavity-like holes
  • Gum recession
  • Complete loss of teeth
  • Toothache

Symptoms of tooth resorption

internal resorption tooth
Symptoms from tooth resorption can include pain, redness and swelling

When it comes to root resorption, there is no clear set of symptoms. In some cases, the patient may not notice the problem for years. However, the symptoms soon begin to appear as the resorption worsens.

The most common symptoms of tooth resorption include:

  • Pain beginning from the crown, root, or the inside of the tooth
  • Redness and swelling of the gums
  • Unequal spacing between the teeth
  • Brittle teeth
  • Development of holes in the teeth
  • Pink spots on the enamel


The diagnosis of root resorption basically depends on the part of the tooth affected. In the case of internal resorption, the dentist may notice dark spots inside the tooth on an X-ray. This is normally followed by a detailed dental history to confirm any past injuries or dental procedures that might have led to this problem.

A dentist may also perform a physical inspection of the tooth. This normally includes taking x-rays and touching the affected teeth with cold and heat in order to assess the condition of the pulp and the extent of resorption.

External absorption can be seen with the naked eye if it occurs in the crown or cervical part of the tooth. X-rays are needed in case of root resorption, in which the external anatomy of the root is altered ranging from small indentations on the root surface to apex resorption and shortening of the root. Also, root fusion with the surrounding bone may be seen.

The steps of diagnosis are similar to those of internal absorption.

Tooth resorption treatment

Treatment for root resorption varies according to the particulars of each case. The first step is the removal of the cause such as the pressure of an impacted tooth or the adjustment of orthodontic force.

If minor resorption has occurred, the dentist will monitor the tooth over a period of time and you may not require any further dental care. However, if more of the tooth structure has been affected, a filling or root canal therapy might be the treatment of choice.

In the case of internal resorption, root canal therapy and crown coverage should be performed in order to stop the progression of the resorption and protect the remaining tooth structure.

The treatment of apical resorption (where the root apex is resorbed) requires root canal treatment and “Apicectomy”, which is an endodontic surgery performed to remove the apical portion of the root in cases of infection-induced root resorption.

In the case of widespread damage, it may be necessary to extract the affected teeth.

root resorption treatment
Various dental techniques can help restore your smile


Root resorption in adults is usually indicative of an underlying tooth injury or infection that may cause long-lasting damage or even lead to the complete loss of the affected tooth.

Resorption is usually discovered during routine dental examinations. Timely diagnosis and prompt treatment play a major role in saving the affected tooth.

It is possible to miss the symptoms of dental resorption until the disease has progressed to a more serious stage.

Routine dental examinations are recommended for the timely diagnosis and prompt treatment of the problem.


Does tooth resorption cause pain?

Every case is different. In many cases, it doesn't cause pain. Yet, there is a possibility for patients to develop resorption pain, especially in advanced cases or in cases of internal resorption.

How common is root resorption?

Root resorption normally affects 5 to 10% of the general population who have never undergone any type of orthodontic treatment. It is one of the most common causes of tooth loss in people.

Can tooth resorption be reversed?

It is not possible to reverse the effects of resorption on teeth. Often, damage can be repaired but not reversed. Your dentist will advise you based on your condition.

Is tooth resorption an autoimmune disease?

Idiopathic root resorption is a type of root resorption that is autoimmune in nature. It commonly occurs in people suffering from scleroderma and is often diagnosed in dental X-ray reports.

What is normal dental resorption?

Dental resorption is a normal process that occurs in baby teeth. However, it's important to distinguish between normal dental resorption and a severe form of tooth decay known as bottle rot.

Tooth Resorption, Internal and External: Causes, Symptoms & Treatment
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Dental Press Journal of Orthodontics: Extreme root resorption associated with induced tooth movement: a protocol for clinical management. Consulted 19 February 2023.

The Medical Journal, Armed Forces India: Internal resorption: an unusual form of tooth resorption. Consulted 19 February 2023.

Dental Press Journal of Orthodontics: External cervical resorption: diagnostic and treatment tips. Consulted 19 February 2023.

Australian Dental Journal: Management of tooth resorption. Consulted 14th July 2023.