Apexification and regenerative treatment: how is a dead tooth with an immature root saved?

When a permanent tooth appears in the mouth, its root is not yet complete. The lengthening of the root, the thickening of its walls and the narrowing of its tip continue over the following years thanks to the tooth's living nerve. If during this period a knock to a front tooth or deep decay in a molar kills the nerve, this development stops. What remains is a root with a wide open tip, thin walls and a short length. The tooth may look sound in the mouth; the problem is usually noticed on an X-ray, through a colour change, or from a draining opening (fistula) appearing on the gum.

In a tooth whose nerve is alive but damaged, the aim is different: to protect the part of the nerve that is still alive so that the root develops naturally. This is called apexogenesis. Apexification and regenerative treatment, on the other hand, are for teeth whose nerve is no longer alive, that is, where necrosis has developed. The dentist determines which picture you are in with sensitivity tests, X-rays and symptoms.

For years, classic apexification was done by placing calcium hydroxide inside the canal, renewing it for months, and waiting for hard tissue to form at the root tip. This method is thought to have a cost: in a laboratory study published in Dental Traumatology, the fracture resistance of dentine in long-term contact with calcium hydroxide decreased markedly over time in sheep teeth, halving in about a year. This is a study of animal teeth, but it is consistent with the fractures often reported in thin-walled roots.

That is why apexification today is mostly done with MTA. After the canal has been cleaned and medicated for a short time, a plug of MTA a few millimetres thick is placed at the root tip, and the root filling and tooth restoration are done on top of the plug. In a 2024 overview looking at 31 systematic reviews together, MTA was found to form the barrier at the root tip faster than calcium hydroxide, while overall success rates were similar. The same overview notes that colour change in the tooth can be seen with MTA.

Regenerative endodontics (also called revascularisation or revitalisation) works on a different logic. According to the clinical considerations of the American Association of Endodontists (AAE), at the first session the canal is gently rinsed with a low-concentration disinfectant and calcium hydroxide or a low-concentration antibiotic paste is placed inside it. At the second session 1–4 weeks later, the area beyond the root tip is lightly stimulated with a fine instrument so that the canal fills with blood, MTA or another bioceramic cement is placed over the clot that forms, and the tooth is sealed. The AAE writes that products prepared from the patient's own blood, such as PRP or PRF, can also be used instead of a blood clot.

The answer to the question of which method is better is nuanced. In a 2025 umbrella review looking at 12 systematic reviews comparing these two treatments, the success rates and the rates at which the tooth stayed in the mouth were above 85 per cent in every area and similar for the two methods; regenerative treatment was superior in terms of the thickening of the root walls and the lengthening of the root. However, the authors stress that the evidence is weak and that most of the reviews are of low or critically low quality. Another meta-analysis from 2022 recommends that regenerative treatment be preferred in teeth where root development is very insufficient and the dentine has stayed very thin.

Regenerative treatment is not suitable for every tooth. The AAE's patient selection criteria are: a tooth whose nerve has died and whose root tip is open, no need for a post in the canal for the final restoration, a patient and family who will comply with follow-up, and no allergy to the medicines and antibiotics to be used. The AAE also recommends explaining to the patient in advance that there may be no response to treatment, that colour change in the crown and root, pain or infection may develop, and that the alternatives are MTA apexification, no treatment, or extraction if the tooth cannot be saved.

Success is not assessed with a single measure. The AAE defines three goals in regenerative treatment: the primary goal is the resolution of symptoms and evidence of healing in the bone; the secondary goal is the thickening of the root walls or the lengthening of the root, which is a desirable but perhaps not essential result; the tertiary goal is the tooth responding to vitality testing. So even if the root does not lengthen on the X-ray, if the tooth stays in the mouth without pain, without inflammation and with healed bone, the treatment is considered to have achieved its basic aim.

The first list gives situations where apexification or regenerative treatment comes into it. The second list gives situations where these treatments may not be suitable or where another route comes first. The decision is made by your dentist or a root canal specialist (endodontist) after an examination.

The sequence below describes the AAE's recommendations for regenerative treatment and the usual stages of MTA apexification. The details vary with the tooth and the dentist.

1. 1

   Diagnosis

   The dentist assesses the tooth's vitality with tests, and the level of root development and the inflammation at the root tip with X-rays. For regenerative treatment, the AAE regards a three-dimensional scan (CBCT) as a highly recommended tool in the initial assessment and follow-up.

2. 2

   Information and consent

   According to the AAE, the patient and family should be told that two or more sessions will be needed, that antimicrobial medicines will be used, about possible adverse outcomes such as colour change, no response to treatment, pain and infection, and about the alternatives.

3. 3

   First session: cleaning and medication

   The tooth is numbed and isolated with a rubber sheet (rubber dam). The canal is rinsed generously and gently with low-concentration sodium hypochlorite, dried, and calcium hydroxide or a low-concentration triple antibiotic paste is placed inside it. The tooth is sealed with a temporary filling.

4. 4

   Second session (1–4 weeks later)

   If the symptoms have resolved, the canal is rinsed again. In regenerative treatment, the area beyond the root tip is lightly stimulated so that the canal fills with blood, and MTA or a bioceramic cement is placed over the clot. In apexification, an MTA plug is placed at the root tip instead. If signs of infection continue, the AAE recommends extending or changing the medication.

5. 5

   Sealing the tooth

   A permanent filling is placed over the cement layer. To reduce colour change in front teeth, the AAE recommends using materials that do not stain.

6. 6

   Follow-up

   The AAE recommends clinical and X-ray check-ups at 6, 12 and 24 months, and once a year after the first two years. In regenerative treatment, the inflammation at the root tip mostly resolves within 6 to 12 months, while thickening of the root walls is mostly seen within 12–24 months.

These are the alternatives the AAE recommends explaining to the patient, and the other routes discussed in practice.

The following are the known adverse outcomes of these treatments and the wrong decisions families often make.

With these treatments, healing is measured not in days but in months. The sequence below is the usual course described by the AAE.

1. Between sessions (1–4 weeks)

   The AAE writes that pain, swelling or the draining opening on the gum (fistula) usually resolve between the first and second sessions. If the temporary filling falls out, tell your dentist straight away.

2. 6–12 months

   The resolution of the inflammation at the root tip on X-rays is mostly seen during this period.

3. 12–24 months

   In regenerative treatment, thickening of the root walls is mostly seen during this period, before a marked increase in root length.

4. After the second year

   The AAE recommends a check-up once a year. It is possible for the tooth to respond to vitality testing again, but it is not always an expected result.

We do not give a figure here; the scope of these treatments varies with the tooth and the course of healing. The main factors that determine the scope:

The method chosen

Classic apexification with calcium hydroxide needs many sessions; MTA apexification and regenerative treatment usually need two sessions.

Imaging

Assessment and follow-up with a scan change the scope.

Length of follow-up

Regular check-ups and X-rays are needed for at least two years.

Additional procedures

Dealing with colour change, repairing a fracture, or a second method if there is no response to treatment are separate procedures.