Root perforation during root canal treatment: can the tooth be saved?

Inside the root of a tooth there are fine canals containing the tooth's nerve and blood vessel tissue. In root canal treatment, these canals are cleaned and widened with fine instruments; if a crown is to be made on a root-filled tooth, part of the canal is sometimes also hollowed out for a post (a pin inside the root). If an instrument strays from the path of the canal during this and goes through the root wall, an opening forms between the canal and the connective tissue and bone surrounding the root. This is called a perforation. A 2022 review writes that perforations can be caused by disease processes (decay, root resorption) or by treatment.

The real danger of a perforation is infection. According to the 1996 classification by Fuss and Trope, perforations were common complications of root canal treatment or post preparation and often ended in extraction; successful treatment depends mainly on sealing the hole straight away and preventing infection. The same article names the three most important factors determining the outcome: when the perforation happened and how soon it was sealed, its size and its position.

The time factor works like this: a hole noticed during treatment and sealed in clean conditions in the same session gives bacteria no chance to settle. In a hole left open for months, on the other hand, inflammation and resorption begin in the surrounding bone. The size factor: sealing a small hole so that it does not leak is easier than sealing a wide tear. The position factor: a hole in the middle of the root or near its tip, within the bone, is expected to do better than a hole close to the gum line that risks opening into the mouth through a gum pocket. This is what the Fuss and Trope classification predicts; in measured data the clearest difference was seen in teeth where the hole was connected with the mouth, while in the Heidelberg study the outcome of repair with MTA did not change significantly with the position of the hole. In molars, holes opening into the area between the roots (the furcation) are also sensitive in this respect.

In the past, perforations were sealed with materials such as amalgam and the results were unpredictable. The 2022 review writes that MTA (mineral trioxide aggregate) and other calcium silicate cements provide an environment favourable to tissue regeneration and have been used successfully in perforation repair, whereas the evidence supporting many of the new materials coming onto the market is still limited.

The most comprehensive data on success rates comes from a 2015 meta-analysis. In the review, which examined 17 studies published between 1950 and 2014, the pooled success rate for perforations repaired without surgery (from inside the tooth) was 72.5%. In studies using MTA the rate rose to 80.9%, but this difference was not statistically significant. Having an area of inflammation around the perforation before treatment lowered the chance of success; upper teeth did markedly better than lower teeth.

Single-centre studies paint a similar picture. In a study at Heidelberg University in Germany following 64 perforations repaired with MTA for 12 to 107 months, 86% of the teeth were assessed as healed, and the authors concluded that MTA gave a good long-term seal wherever in the root the perforation was. In another study, in which 90 teeth were followed for an average of 3.4 years in a practice providing only endodontic treatment, the healing rate was 73.3%. Two factors stood out in this study: pre-existing inflammation around the hole, and the hole being directly connected with the mouth; the lowest success was seen with the latter.

A perforation also affects the overall success of root canal treatment. In the prospective study by the Eastman Dental Institute in London, a perforation made during treatment was among the factors increasing the risk of losing the tooth; in teeth whose root canal treatment was being redone, a pre-existing perforation had the same effect. The absence of a perforation was also positively associated with healing at the root tip, but this association was at the borderline of statistical significance.

The first list covers situations that increase the likelihood of repair giving a good result. The second list shows situations where the chance of success falls or extraction may be more realistic. The final decision comes from the examination and imaging.

The sequence below shows the general course from noticing a perforation to follow-up after repair. The details vary with the position of the hole and when it was noticed.

1. 1

   Emergency signs first

   If there is difficulty breathing, speaking or swallowing, rapidly growing swelling of the face or neck, swelling of the eye, or you cannot open your mouth, call 112 or go to A&E. If there is swelling and a fever, contact your dentist the same day.

2. 2

   Noticing it

   A perforation is most often noticed during treatment through unexpected bleeding, seeing that the instrument tip has strayed from the path of the canal, or on a check-up X-ray. Perforations noticed later may show up as a deepening of the gum pocket at a single point, a discharging bump on the gum, tenderness when biting or a dark area beside the root on the X-ray.

3. 3

   Identifying the position and size

   The dentist assesses where in the root the hole is, whether it is connected with a gum pocket, and its size. A standard X-ray does not always show the hole; a cone beam CT scan and a microscope help at this stage.

4. 4

   Cleaning the area and controlling the bleeding

   The repair material must be placed on a dry, clean surface. The area around the hole is cleaned and the bleeding is brought under control; if the hole is old, the infected tissue inside it is cleaned out.

5. 5

   Sealing the hole

   The hole is sealed from inside the tooth, usually under a microscope, with MTA or another calcium silicate cement. In the first Heidelberg study, all the repairs were done using a microscope. For some holes that cannot be reached from inside the tooth, the root surface can be reached surgically through the gum.

6. 6

   Completing the root canal treatment and the restoration

   Once the hole has been sealed, the root canal treatment is completed and the tooth is closed with a sealed filling or crown. Keeping bacteria in the mouth from getting back inside the tooth is also important for the repair to last.

7. 7

   Follow-up

   In studies, repaired perforations were followed with clinical examinations and X-rays for anything from 1 year to several years. Your dentist will ask for check-up X-rays to see the condition of the bone around the hole.

The options are listed starting with the least invasive. Which one is suitable is determined by the position of the hole, its size, how long it has been open and the general condition of the tooth.

A perforation is an upsetting situation for both patient and dentist. The mistakes below can needlessly reduce the chance of saving the tooth.

The first few days after the repair are similar to those after root canal treatment. Healing of the bone around the hole, however, takes time and is monitored with check-up X-rays.

1. The first few days

   The tooth may be tender and uncomfortable when you bite. The NHS writes that after root canal treatment the area may feel swollen and tender, that this will settle within a few weeks, and that paracetamol or ibuprofen can be taken.

2. Completing the root canal treatment

   The repair is sometimes done in the same session as the root canal treatment and sometimes in a separate session. While the tooth is closed with a temporary filling, try not to bite hard food on that side.

3. Filling or crown

   When the root canal treatment is finished, the tooth is closed with a sealed filling or crown. Not delaying this step protects the durability of the repair.

4. Check-up X-rays

   Your dentist will ask for X-rays at set intervals to see the condition of the bone around the hole. In studies, the results were assessed at between 1 year and several years.

We do not give figures here, because the scope varies greatly with the position of the hole, when it was noticed and the route chosen. The items that determine the price are:

The route of repair

Repair from inside the tooth, surgical repair, root removal, or extraction and an implant in its place are very different procedures.

Imaging and microscope

A CBCT scan to identify the position of the hole, and the repair being done under a microscope, affect the scope.

Repair material

MTA and similar calcium silicate cements are different cost items from older materials.

Where the perforation happened

If the perforation happened during a procedure by the dentist treating you, discuss openly with that dentist how and by whom the repair will be done and how the cost will be shared.