What Is a Coronectomy?
A coronectomy is a surgical procedure in which the crown of a lower wisdom tooth is removed while the roots are intentionally left in place. It is an alternative procedure to full wisdom tooth removal.
It is most commonly performed when a lower wisdom tooth lies very close to the inferior alveolar nerve (IAN), the nerve that provides sensation to the lower lip, chin, and lower teeth.
The aim is to treat the problematic part of the tooth whilst reducing the risk of nerve injury.
Why Might a Coronectomy Be Recommended?
Most wisdom teeth can be removed completely. However, in some patients, X-rays or CT scans show that the roots are closely related to the inferior alveolar nerve.
In these circumstances, complete removal carries an increased risk of:
- Numbness of the lower lip and chin
- Tingling or altered sensation
- Rarely, permanent sensory disturbance
A coronectomy may be recommended if:
- The tooth requires treatment
- The roots are very close to the nerve
- The roots are healthy and not infected
- Reducing the risk of nerve injury is a priority
How Is a Coronectomy Performed?
The procedure is similar to a conventional wisdom tooth removal.
After the gum is lifted:
- Bone is removed around the tooth if required
- The crown is separated from the roots
- The crown is removed
- The remaining roots are trimmed below the surrounding bone level. If the roots become mobile at this point, the coronectomy procedure must be abandoned and a conventional extraction performed.
- The area is cleaned and closed with stitches
The retained roots are left undisturbed to minimise trauma to the adjacent nerve.
What Are the Benefits of Coronectomy?
Potential benefits include:
- Reduced risk of inferior alveolar nerve injury and permanent altered sensation
- Treatment of the wisdom tooth without exposing the nerve to unnecessary risk
What Are the Disadvantages of Coronectomy?
Coronectomy is not suitable for every patient.
Potential disadvantages include:
- Roots remain within the jaw, with a risk of infection or cyst formation
- Postoperative infection may require a several-day hospital admission for removal of the roots and drainage of infection (approximately 1% incidence)
- Similar postoperative recovery to conventional wisdom tooth surgery
- Further monitoring may be required
- The retained roots can migrate over time
- A second procedure may occasionally be required if the roots become exposed or symptomatic
Most retained roots remain symptom-free and require no further treatment.
What Happens to the Roots Afterwards?
Following coronectomy, the roots often move slightly within the bone during healing. This process is known as root migration.
In most patients:
- Migration occurs during the first 1-2 years
- The roots remain buried beneath the gum
- No additional treatment is required
Occasionally the roots migrate towards the surface of the gum. If this occurs and symptoms develop, removal of the roots may be recommended. By this stage, the roots have usually moved away from the nerve, making later removal safer.
Risks and Complications
All surgical procedures carry risks.
Common
- Pain, swelling, bruising, and jaw stiffness
- Bleeding
- Temporary difficulty opening the mouth
- Food trapping around the healing site
Uncommon
- Infection
- Dry socket (alveolar osteitis)
- Delayed healing
- Failure of the retained roots to remain buried
Rare
- Injury to the inferior alveolar nerve resulting in numbness, tingling, or altered sensation of the lip and chin
- Injury to the lingual nerve causing altered sensation of the tongue
- Root exposure requiring further treatment
- Need for later root removal
Although coronectomy substantially reduces the risk of nerve injury, it does not eliminate it completely.
Key Points
- Coronectomy involves removal of the crown while leaving the roots behind.
- It is primarily used when wisdom tooth roots lie close to the inferior alveolar nerve.
- The aim is to reduce the risk of numbness of the lower lip and chin.
- Recovery is similar to conventional wisdom tooth surgery.
- Most retained roots remain symptom-free.
- A small number of patients require multi-day hospital admission because of postoperative infection.
- A small number of patients require later treatment because of root migration or root exposure.