Endodontic Experts Retire ‘Dilaceration’ in New Root Canal Glossary

Root canal anatomy has a vocabulary problem, and an international panel of endodontists has tried to fix it. Their consensus glossary defines 15 terms that dentists and researchers have long used in different ways. It was first published in the International Endodontic Journal on August 26, 2026, and started gaining endodontists' attention around World Endodontic Day on October 16.

TL;DR

• An international panel agreed on standard definitions for 15 root and canal anatomy terms.

• Some familiar terms are out, including pulp chamber roof and root dilaceration.

• Canal isthmus and transverse canal anastomosis are now defined as two different things.

• The glossary is a recommendation, and its impact depends on whether people adopt it.

International Experts Establish New Root Canal Anatomy Glossary

The paper, A Consensus-Based Glossary for Controversial Terminology in Root and Canal Anatomy, is led by Hany Mohamed Aly Ahmed of Universiti Malaya in Malaysia. His co-authors include Henry Duncan of Trinity College Dublin, Ove Peters of the University of Queensland, and Paul Dummer of Cardiff University, along with a wider Delphi group of endodontists from around the world.

The problem they set out to solve is a familiar one. Anyone who reads endodontic research has seen the same structure called different things, or the same word used for different structures. A 2024 review by the same group found inconsistent use of terms for accessory canals, isthmuses, and pulp chamber anatomy. That makes it hard to compare studies, and it can confuse students learning anatomy for the first time.

The glossary covers 15 terms across three areas: the roots themselves, the pulp chamber, and the canals. It's a reference for how to describe anatomy. It doesn't change how root canals are treated.

Which Root Canal Anatomy Terms Have Changed?

Most of the 15 terms kept their names and simply got tighter definitions. A handful were renamed or split apart. These are the changes clinicians are most likely to notice:

Some of the reasoning is about plain English. A roof is the outside of a building, while a ceiling is the inside surface, which is what the pulp chamber has.

Other changes matter more. Dilaceration comes from a Latin word meaning "to tear apart," which doesn't describe most curved roots. It has also been defined as anything from a 20° bend to a 90° bend, which helps explain why studies report such different rates. Setting the bar at 90° gives everyone the same cutoff.

The apical terms touch daily practice. Many clinicians aim to finish instrumentation at the narrowest point near the apex. The authors note that the narrowest point on a 2D X-ray often isn't the narrowest point in 3D. Calling it a foramen, not a diameter, separates the anatomical landmark from a measurement.

The isthmus split is the most practical change. An isthmus is a real flattened channel, common in roots such as the mesial root of lower molars. A transverse anastomosis is a smaller, thread-like link. Both can hold bacteria, but they're different structures. The full glossary is free to read and includes all 15 definitions with micro-CT images.

Why Does Standardized Root Canal Anatomy Terminology Matter?

Words shape what the next clinician expects to find. Picture a general dentist referring a lower molar after spotting what looks like a connection between the two mesial canals on CBCT. Calling it an isthmus tells the endodontist to expect a flattened channel that needs shaping and cleaning. Calling it an anastomosis suggests something much finer. Those two descriptions lead to different expectations about time, difficulty, and the risk of leaving tissue behind.

Missed or poorly cleaned anatomy is one known reason for root canal treatment failure. Isthmuses in particular are hard to reach with files, which is why so much effort goes into root canal irrigation and activation methods, including dental lasers.

Clear terms also make records more useful. When anatomy is described consistently in notes, referral letters, and imaging reports, it feeds into a more accurate dental treatment plan. The glossary doesn't add any new imaging requirements. It just gives everyone the same words for what CBCT and micro-CT show.

How Did Researchers Reach Agreement on the 15 Terms?

The team used a Delphi process, a common way to get a group of experts to agree without one loud voice taking over. A seven-member working group drafted the 15 terms and definitions. They invited 55 experts, and 32 completed an anonymous online survey rating each one.

A term passed if at least 70% of the panel scored it 7 or higher out of 9. Fourteen terms cleared that bar in the first round. The furcation canal term only reached 69%, as several panelists felt it overlapped with chamber accessory canals. It was reworded and renamed "accessory furcation canal," then passed with 88% in a second round.

Nineteen panelists then met online to discuss the results, and the working group made final tweaks. This is expert agreement, not clinical evidence. It reflects what experienced researchers think the words should mean.

What Does the Glossary Mean for Dental Education and Research?

Research stands to gain the most. Anatomy studies use very different tools, from CBCT in patients to high-resolution micro-CT on extracted teeth. If one study counts thread-like links as isthmuses and another doesn't, their numbers can't be compared. Shared definitions make systematic reviews more reliable.

For teaching, it means students can learn one set of terms from the start. The authors hope the terms will appear in curricula, textbooks, and continuing education.

Whether that happens isn't guaranteed. The American Association of Endodontists already has its own glossary, and the paper notes it has treated isthmus and anastomosis as interchangeable. Real change will depend on journals, professional bodies, and educators picking up the new definitions. Until then, it's a well-built recommendation, not a binding standard.

Bottom Line

The new glossary gives endodontics clear, agreed definitions for 15 anatomy terms that have been confusing for years. A few familiar words are on the way out, and isthmus and anastomosis now mean different things. It won't change how root canals are done, but it should make referrals, records, teaching, and research easier to follow. How much difference it makes will depend on how widely it's adopted.