Tooth 27 Retreatment for a Missed Fourth Canal

Dr Urszula Leończak

Microscope-Assisted Endodontic Specialist

💡 Stories from the clinic: Recurrent pulsating and burning sensations following root canal treatment of tooth 27 were associated with a missed additional canal. CBCT diagnostics and microscope-assisted treatment made it possible to locate the fourth canal and eliminate the source of the symptoms.

Radiograph of tooth 27 showing the suspected location of a missed fourth root canal

👤 Challenge

A 35-year-old patient presented with recurrent discomfort that was difficult to localize on the left side of the maxilla.
He described the symptoms as pulsating and burning sensations without the typical spontaneous tooth pain associated with acute pulp inflammation.
Tooth 27 had undergone root canal treatment approximately one year earlier, but the unusual symptoms persisted.

🔍 Diagnostics

A digital radiograph of tooth 27 showed filling material in three root canals.
When considered together with the patient’s persistent symptoms, the radiographic appearance raised suspicion that an additional canal had been missed during the previous treatment.
Due to the atypical nature of the symptoms, the differential diagnosis also included possible sinus-related, muscular, and neurological causes.

🧠 CBCT Diagnostics

A CBCT examination was performed to provide a detailed assessment of the root canal anatomy of tooth 27.
The scan demonstrated:

the presence of an additional, previously untreated fourth root canal
incomplete previous root canal treatment of tooth 27
a close anatomical relationship between the roots of the tooth and the maxillary sinus
the need for microscope-assisted endodontic retreatment

The axial CBCT section made it possible to determine the precise location of the missed canal and safely plan access during retreatment.

Axial CBCT section of tooth 27 showing a missed fourth root canal

📋 Diagnosis

Previously root canal-treated tooth 27
Incomplete root canal treatment with a missed additional canal
Symptomatic apical periodontitis
Atypical symptoms associated with a persistent endodontic infection

💡 Treatment Plan

Endodontic retreatment of tooth 27 under operating microscope magnification
Removal of materials remaining from the previous root canal treatment
Location and preparation of the missed fourth canal
Thorough disinfection of the entire root canal system
Complete obturation of the canals and restoration of the tooth with composite material

⚙️ Step-by-Step Treatment

1. The procedure was performed under local anesthesia with rubber dam isolation.
2. Materials remaining from the previous root canal treatment were removed.
3. Rotary nickel-titanium instruments were used to prepare the canals.
4. Working lengths were determined using an electronic apex locator.
5. The CBCT findings and visualization under a Zeiss operating microscope were used to locate the very narrow missed fourth canal.
6. Ultrasonic tips were used to gain conservative access to the additional canal while preserving healthy tooth structure.
7. All four canals were mechanically prepared and underwent intensive chemical disinfection with ultrasonic activation.
8. The canals were completely obturated in accordance with the established treatment protocol.
9. The tooth was restored with composite material to restore its seal and function.

The entire treatment was completed during a single visit lasting approximately 90 minutes under magnification using a Zeiss operating microscope.

Intraoperative radiograph of tooth 27 showing endodontic instruments in four root canals

📍 Before & After

Before

Recurrent pulsating and burning sensations on the left side of the maxilla
Previous root canal treatment involving only three canals
Missed additional root canal

After

Fourth canal located and prepared
Entire root canal system disinfected
Complete resolution of the reported symptoms

Before

After

CBCT diagnostics and treatment under operating microscope magnification made it possible to locate the missed fourth canal of tooth 27 and complete successful endodontic retreatment.

“A missed canal can remain a source of infection and atypical symptoms for a long time. CBCT and operating microscope magnification allow us to identify the cause and treat it precisely.”

📌 Conclusions

Persistent symptoms following root canal treatment may be caused by a missed canal, particularly in teeth with complex anatomy.
The combination of CBCT diagnostics, operating microscope magnification, and advanced disinfection protocols allows accurate assessment of the root canal system and predictable endodontic retreatment.
In this case, locating the fourth canal led to complete resolution of the symptoms by the early follow-up visit.

Abhijit Chatterjee

I have been a patient of Warsaw Dental Center for the past two years. During this time I have had Invisalign treatment done by Dr Karolina, root canal done by Dr Urszula and implants done by Dr Bartosz. Every experience was positive. Doctors and staff speak English fluently or natively. They helped arrange and accommodate me on my multiple short visits from USA. So far I have recommended this clinic to multiple friends in USA and they have all been satisfied. I am updating this review after a year, my experience remains first class. Recommended with both thumbs up.

📝 From the Dentist’s Desk