A strange phenomenon can happen to patients when tooth structure disappears without decay present. The roots of teeth are the most common area affected. The term resorption is used in such instances. There are two main types of resorption; internal and external. Because internal resorption occurs inside the teeth and external resorption happens mostly on roots, detection without radiographs (x-rays) is difficult. Surprisingly, the process often happens without pain, and most patients are unaware it is happening. The process can result in tooth loss, so early diagnosis and treatment are critical. This post will cover how tooth and root resorption are diagnosed and treated. 

Internal Resorption 

The inside of the tooth is hollow, contains soft tissue and nerve, and is called the root canal. The tissue in the canal can make new tooth structure and remove it. When the tissue inside the tooth removes tooth structure, we call it internal resorption. It is also called internal root resorption or internal granuloma and is more common in the middle of the roots but can happen anywhere inside the tooth within the root canal system. When it happens in the upper reaches of the root canal, it can make the tooth appear dark or pink, which is the one instance where it can be noticed without an x-ray, although x-rays should be taken to verify that it is resorption. It can occur in any tooth but is more common in anterior teeth. The main causes of internal resorption are infection in the tooth's nerve, trauma, and orthodontic movement, but resorption is often seen without any known cause. 

External Resorption 

As the name implies, external resorption happens on the outside of the tooth. Unfortunately, it occurs under the gums, most often on the roots, and goes unnoticed, especially since it is usually asymptomatic. The lesions most often fill with new bone from the surrounding jaw, which gives this type of lesion the name external replacement resorption. When the lesions don't fill with bone, inflammation, and infection are usually involved. Therefore, these lesions are called external inflammatory resorption. They are commonly seen at the tips of roots involving an abscess and are usually mediated by cells in the bone. The root will appear shorter and have an irregular shape. Another type of resorption that happens just below the gums is called external cervical resorption. Its cause is unknown. Since it happens just below the gums, where cavities often form, it can be mistaken for tooth decay. The lesions are hard, however, whereas cavities are soft.  

Diagnosis 

Since resorption is usually symptom-free, it isn't easy to diagnose. It is usually picked up on routine radiographic examinations. The lesions will appear as a hollowing out of the inside of the tooth in the case of internal resorption and a defect in the root in the case of external resorption. In the case of external resorption of roots, the lesions can be missed due to the limitations of standard radiographs. Three-dimensional imaging (CBCT) is now very common in many dental offices and is a much better diagnostic tool for resorption. CBCTs are not routine, so they are usually done after suspected resorption to find the extent and location of the lesion.  

Treatment 

Treatment of internal resorption is done via root canal treatment. Because the tissue inside the tooth is responsible for the resorption, removing it, as is done during root canals, prevents further resorption. If the resorption has already broken through to the tooth's exterior, the prognosis is often diminished; extraction is often the only recourse. In the case of external resorption, external inflammatory resorption can respond to treatment that addresses the underlying infection or inflammation. Treatments include root canal, gum surgery, and surgery on the tip of the root and surrounding bone called an apicoectomy. External replacement resorption is much more difficult to treat, and extraction may be the only recourse. 1 

Orthodontics and Resorption 

 When teeth are moved orthodontically, the pressure, although mild, can exceed the blood pressure in the capillaries in the ligament surrounding the tooth, causing blood flow stoppage. The ligament around the tooth dies. When the ligament dies, it is removed by inflammatory cells in the adjacent bone. The tooth then comes in direct contact with the bone. Bone is constantly being deposited and removed normally. The process is sped up during tooth movement because the bone is taken away toward the direction the tooth is being moved and deposited on the trailing side. The cells in the bone do not differentiate the mineral in the root from the surrounding bone because it is the same. Therefore, root minerals are removed and replaced with bone. The roots will appear shorter and blunter as a result. This process is called orthodontically induced inflammatory root resorption or OIIRR. Since it happens inside the body, bacterial infections are not associated with this strictly inflammatory process. 

The more force placed on teeth to move them, and the duration of treatment are key influences in the process. The process is poorly understood, but we know that anterior teeth are at higher risk, previous trauma does not seem to be a causative factor, root shape is not a factor, and asthma may be a risk factor based on animal studies. Fortunately, most cases do not result in tooth loss, even when the roots are 80% resorbed.  

Conclusion 

Resorption is a sneaky problem that can happen to anyone at any age. Since it usually causes no symptoms until it is too late and happens in places we can't see, resulting in tooth loss, early diagnosis and treatment are critical. Even if you visit the dentist, it is most often missed if no radiographs are taken. As always, we should visit the dentist every six months for a checkup and x-rays taken once a year. 2