Necrotic Immature Permanent Teeth: Apexification or Regenerative Endodontics?

Jump to a section 9

1. Why an open apex changes the endodontic plan
2. What apexification and regenerative endodontics are each trying to achieve
3. Case selection: which immature teeth suit which approach
4. What the evidence says about outcomes
5. The regenerative protocol in outline
6. Follow-up after apexification or a regenerative procedure
7. Risks, alternatives and consent
8. Referring a young patient’s immature tooth to us
9. Common questions

Why an open apex changes the endodontic plan

Conventional root canal treatment assumes a root that has finished forming. When the pulp of a young permanent tooth becomes necrotic before that happens, the canal is wide, the walls are thin and there is no apical constriction to fill against. The AAE’s position statement on regenerative endodontics describes pulp necrosis in an immature tooth, whether from trauma, caries or a dental anomaly, as a distinctive treatment challenge.

Until 2004, the AAE position statement on regenerative endodontics notes, clinicians relied on traditional apexification or an apical barrier. Calcium hydroxide apexification brought its own problem. In a laboratory study on immature sheep incisors, Andreasen, Farik and Munksgaard (2002) found fracture strength fell steadily the longer the canal was dressed with calcium hydroxide, and estimated it would halve in about a year. It was a laboratory study on animal teeth, so it shows a mechanism rather than a clinical fracture rate.

What apexification and regenerative endodontics are each trying to achieve

The table sets the two side by side, from the AAE’s November 2022 considerations and the reviews discussed below.

	MTA apexification (apical plug)	Regenerative endodontic procedure
Main aim	Seal the open apex with a barrier so the canal can be filled and restored	Disinfect without much instrumentation, then let tissue grow into the canal from a blood clot or scaffold
Root development	None expected; the root stays as thin and short as it is	Root wall thickening and lengthening are a secondary goal, not achieved in every case
Visits	Depends on the technique and the clinician	Two or more appointments, one to four weeks apart
Use of the canal later	The canal is filled, so a post remains possible	AAE case selection asks that the pulp space is not needed for a post
Main complications reported	Discolouration from MTA; root fracture, reported after calcium hydroxide apexification	Crown discolouration, persistent infection, no root development
Pooled survival	97.1% (Torabinejad 2017)	97.8% (Torabinejad 2017)

MTA apexification

An apical plug of MTA or another calcium silicate cement gives the obturation something to condense against, and the tooth is then filled and restored as usual. It does not try to change the root. Panda and colleagues’ 2022 meta-analysis found MTA and calcium hydroxide equally effective at forming a calcific barrier, with calcium hydroxide apexification showing lower success than MTA in the studies it pooled.

Regenerative endodontic procedures

Regenerative endodontics, sometimes still called pulp revascularisation, relies on gentle chemical disinfection rather than shaping, followed by bleeding induced into the canal and a coronal seal over the clot. The AAE Clinical Considerations for a Regenerative Procedure set out three levels of success. The primary goal is the elimination of symptoms and evidence of bony healing. The secondary goal is increased root wall thickness or length, which the AAE calls desirable but perhaps not essential. The tertiary goal is a positive response to vitality testing.

Case selection: which immature teeth suit which approach

The European Society of Endodontology position statement on revitalisation (Galler and colleagues, 2016) describes revitalisation as a biologically based alternative to apexification in properly selected cases, written for suitably trained dentists, and it comes with a patient consent form. It also says plainly that controlled clinical trials were lacking and that the protocol would change as evidence emerged.

The AAE’s November 2022 considerations list four selection criteria:

• A tooth with a necrotic pulp and an immature apex.
• A pulp space that is not needed for a post and core in the final restoration.
• A compliant patient and parent, because the procedure takes two or more visits and years of recalls.
• No allergy to the medicaments and antibiotics needed to complete the procedure (ASA 1 or 2).

Factors that point away from a regenerative attempt

The 2025 AAE position statement notes that severe traumatic injuries and large, chronic periapical lesions have been found to reduce success. In Lin and colleagues’ 2017 randomised trial, teeth treated for dens evaginatus gained more root length and thickness after regenerative treatment than teeth treated after trauma. A tooth that needs a post, or a family unlikely to return for two years of review, may be better served by an apical plug.

Factors that favour a regenerative attempt

Panda and colleagues concluded in 2022 that a regenerative procedure should be considered when root development is severely deficient, the dentine is insufficient and the prognosis would be poor even with apexification. That is the tooth with the most to gain from thicker walls, and the one where an apical plug leaves the most fragile root behind.

What the evidence says about outcomes

Three sources carry most of the comparative weight, and all three are clear about their limits.

Survival and healing

Torabinejad and colleagues’ 2017 meta-analysis identified 750 studies and put ten randomised trials into subgroup analyses. Pooled survival was 97.1% for the MTA apical plug and 97.8% for regenerative treatment, and pooled success was 94.6% and 91.3%, with no significant difference in either. Most of the underlying studies were case reports and case series, 72% for the plug and 86% for regenerative treatment, and the authors rated the overall level of evidence as low.

Panda and colleagues’ 2022 systematic review and meta-analysis reached the same place: survival and success were statistically similar, and the authors called the two interventions equally comparable, with moderate certainty.

Root development

This is where the procedures are meant to differ. In Lin and colleagues’ 2017 randomised controlled trial of 118 teeth, 103 were reviewed at 12 months. Every tooth in both groups survived and was symptom free with apical healing, and the regenerative group showed significantly greater increases in root length and thickness on CBCT. Twelve months is a short follow-up for a tooth expected to last decades.

In the Panda meta-analysis (2022), pooled estimates for root length and apical foramen width were not statistically significant, with heterogeneity of 98% that the authors themselves say questions the reliability of the finding. In short, regenerative treatment can produce root development that apexification does not, but not reliably, and long term comparative data are thin.

The regenerative protocol in outline

These steps paraphrase the AAE’s November 2022 considerations, which the AAE describes as one possible source of information in a field that is changing quickly. The ESE protocol differs in its details, so read both before treating a case.

1. First visit. Local anaesthetic, rubber dam and access. Irrigate gently with 20 mL of sodium hypochlorite per canal at a lower concentration, 1.5 to 3% in the AAE’s 2022 document, through a closed ended, side vented needle about 1 mm short of the root end, then saline or EDTA. The lower concentration is meant to spare stem cells in the apical tissues.
2. Medicament. Dry the canal and place calcium hydroxide or a low concentration antibiotic paste kept below the cementoenamel junction, then seal with 3 to 4 mm of temporary material for one to four weeks. Our post on antibiotic use in endodontics covers the paste itself.
3. Second visit. Reassess. If infection persists, the AAE suggests more time with the medicament or a different one. If not, anaesthetise without a vasoconstrictor, irrigate with 20 mL of 17% EDTA (AAE, 2022) and dry the canal.
4. Bleeding and seal. Induce bleeding with a precurved file about 2 mm past the apical foramen so the canal fills towards the cementoenamel junction, leaving room for 3 to 4 mm of capping material. Place a calcium silicate cap over the clot, then glass ionomer and a bonded restoration.

Follow-up after apexification or a regenerative procedure

The AAE recommends clinical and radiographic review at 6, 12 and 24 months, then yearly, and calls CBCT highly recommended for the initial evaluation and the follow-up visits. It also says when each change tends to show.

What to look for	When the AAE says it is often seen
No pain, swelling or sinus tract	Often between the first and second appointments
Resolution of the apical radiolucency	Often 6 to 12 months after treatment
Increased root wall width	Often 12 to 24 months, usually before any visible increase in length
Increased root length	After wall thickening, when it occurs
Positive response to vitality testing	Not always; the AAE treats it as a tertiary goal

Risks, alternatives and consent

Both procedures are invasive and neither can promise a result. Outcomes vary between teeth and between patients, and what follows is what the guidance and the reviews say needs to be in the consent conversation.

• Discolouration. The AAE warns that the antibiotic paste and MTA have both been associated with staining of the crown and root, and suggests alternatives to MTA where appearance matters. If a front tooth darkens later, internal bleaching of a discoloured tooth is one option.
• Persistent or recurrent infection, and pain. Named by the AAE as possible adverse effects. The Panda systematic review (2022) found reinfection reported more often after regenerative treatment, though only one study assessed it.
• No root development. Lin’s 2017 trial found greater gains on average, not in every tooth.
• Fracture of a thin root. One study in the Panda review reported cervical fractures after calcium hydroxide apexification, and the Andreasen laboratory work is the reason long dressings fell out of favour.
• Canal calcification. Pulp canal obliteration was reported after regenerative procedures in the Panda review.

The alternatives

The AAE’s consent list gives the alternatives to a regenerative procedure as MTA apexification, no treatment, and extraction when the tooth is judged unrestorable. A family is always entitled to a second opinion before deciding.

Referring a young patient’s immature tooth to us

Many of these teeth arrive after trauma, and the ESE’s 2021 position statement on traumatised permanent teeth was written to complement the International Association of Dental Traumatology guidelines in choosing the endodontic approach. If a young patient’s tooth has an open apex and a necrotic pulp, or you are unsure whether the pulp is necrotic, we are happy to see them. Our guide to when to refer a root canal covers case difficulty more generally.

Send the case through the online referral form with your radiographs, any CBCT, the history of the injury or the cause, and what has been done so far. We are a group of endodontic specialists in Sydney at Crows Nest, and three of our dentists are registered specialists in endodontics with the Dental Board of Australia. Fees depend on the tooth, the number of visits, whether a regenerative attempt or an apical plug is chosen, and whether sedation is needed, and a written estimate follows the examination.

Common questions

Is regenerative endodontics better than MTA apexification?

Not on survival or healing. Torabinejad’s 2017 meta-analysis and the Panda systematic review (2022) both found no significant difference. Regenerative procedures aim for root development that apexification does not, and Lin’s 2017 trial found more root length and thickness at 12 months, but not in every tooth and over a short follow-up.

Is pulp revascularisation the same as a regenerative endodontic procedure?

In practice, yes. The AAE uses revascularisation and pulpal regeneration as other names for regenerative endodontics, and the ESE calls the same approach revitalisation. All three describe disinfecting an immature necrotic canal and inducing bleeding into it.

How long should the tooth be followed up?

The AAE recommends review at 6, 12 and 24 months, then yearly. Root wall thickening, when it happens, is often seen between 12 and 24 months, so a short recall interval can miss it.

What if the regenerative attempt fails?

The AAE lists MTA apexification as an alternative in its consent items, so an apical plug remains an option after a regenerative attempt that has not worked. Extraction and no treatment are the other alternatives it names.

Why does the antibiotic paste matter for the front teeth?

The AAE notes that triple antibiotic paste has been associated with tooth discolouration, and suggests sealing the pulp chamber with a bonding agent and keeping the paste below the cementoenamel junction. Calcium hydroxide is the other medicament it lists.