Materials for retrograde filling in root canal therapy

Honglin Li, Zhiyong Guo, Chunjie Li, Xiangyu Ma, Yan Wang, Xuedong Zhou, Trevor M. Johnson, Dingming Huang

Key messages

- Due to a lack of robust evidence, the benefits and risks of different materials used for retrograde filling in root canal therapy are unclear.

- The evidence is not robust enough to determine which material is best to use in retrograde filling.

- We need future studies to strengthen the evidence.

What is retrograde filling in root canal therapy?

The living part of the tooth, also known as the tooth pulp, can become permanently swollen because of damage or bacterial infection due to tooth decay. To deal with this problem, the dentist has to drill a hole on the top of the crown of the tooth to access the inner space of the tooth, the root canal system. The dentist will then remove the infected tissue and bacteria by a combination of mechanical cleaning and irrigation.

After this is done, the dentist fills the space with an inactive packing material and seals the opening. This treatment is known as root canal therapy. Although results are generally good, a small number of failures can happen. This can be because the root canal system is complex and it is not always easy to completely eliminate all bacteria. These can spread and the infection around the root can last indefinitely.

When root canal therapy fails, a retreatment called retrograde filling is a good alternative to save the tooth. During retrograde filling the dentist cuts a flap in the gum and creates a hole in the bone to get access to the bottom tip of the root of the tooth. After cutting off the tip, followed by thorough preparation, the apex is sealed (the apical seal), and the hole made by the dentist filled with a dental material. This sealing process is considered the most important factor in achieving success in a retrograde root filling.

What materials can be used for retrograde filling?

Many materials have been developed to seal the root tip, for example, mineral trioxide aggregate (MTA), intermediate restorative material (IRM), super ethoxybenzoic acid (Super-EBA), dentine-bonded resin composite, glass ionomer cement, amalgam, and root repair material (RRM). However, there is no agreement on which material is best.

What did we want to find out?

We wanted to find out which material works better for retrograde filling in root canal therapy, and whether they are associated with any unwanted (adverse) effects.

What did we do?

We searched for studies that compared different materials used for retrograde filling in root canal therapy. We compared and summarised the results of the studies and rated our confidence in the evidence, based on factors such as study methods and sizes.

What did we find?

We found eight studies with a minimum duration of 12 months that involved 1399 people (1471 teeth) over 17 years of age undergoing retrograde filling using different types of filling material.

The evidence:

- is not robust enough to determine which material is best to use in retrograde filling.

No studies investigated the unwanted effects of any of the materials.

What are the limitations of the evidence?

The main limitations of the evidence are that studies:

- were very small;

- were conducted in ways that may have introduced errors into their results; and

- there were not enough studies to be certain about the results.

Due to these limitations, we have little confidence in the evidence.

How up to date is this evidence?

The evidence is up to date to April 2021.

Read the full review.

Li  H, Guo  Z, Li  C, Ma  X, Wang  Y, Zhou  X, Johnson  TM, Huang  D. Materials for retrograde filling in root canal therapy. Cochrane Database of Systematic Reviews 2021, Issue 10. Art. No.: CD005517. DOI: 10.1002/14651858.CD005517.pub3. Accessed 14 October 2021.