CBCT missed root canals remain one of the most common reasons for persistent periapical pathology after endodontic treatment. When a treating clinician suspects an untreated canal is the cause of ongoing symptoms, three-dimensional imaging provides the clearest path to diagnosis. At 3Beam Imaging Centre, our Morita CBCT system and consultant radiologist reporting help endodontists and referring GDPs identify accessory and missed canals before retreatment begins.
Quick Answer: Why Do CBCT Missed Root Canals Matter Clinically?
A 2025 systematic review and meta-analysis published in the Journal of Endodontics found that root-filled teeth with undetected canals had a post-treatment apical periodontitis rate of 85.1%, compared with 56.3% in teeth without missed canals. In addition, the study reported a sevenfold increase in the likelihood of persistent apical disease when a canal was left untreated (Algarni et al., 2025). Therefore, identifying every canal before or during treatment is essential for long-term endodontic success.
How Often Are Root Canals Missed on Conventional Imaging?
Periapical radiographs remain the standard first-line imaging modality in endodontics. However, two-dimensional images compress complex anatomy into a single plane. Superimposition of roots and canals frequently obscures accessory anatomy as a result.
The second mesiobuccal canal (MB2) of the maxillary first molar is the most commonly missed canal in clinical practice. Studies using CBCT consistently report MB2 prevalence rates of 70% to 96% in maxillary first molars. Clinical detection rates with periapical radiographs remain significantly lower. Consequently, a substantial proportion of maxillary molars receive incomplete treatment on the first attempt. CBCT missed root canals in the mesiobuccal root alone account for a large share of retreatment referrals.
Similarly, mandibular premolars and incisors frequently harbour accessory canals that two-dimensional imaging fails to reveal. A 2025 cross-sectional study found that teeth with extra roots demonstrated a 73.3% rate of missed canals. By contrast, teeth without additional roots showed a rate of only 20.0% (Wankhade et al., 2025).
When Should Clinicians Request CBCT for Missed Root Canals?
The joint position statement from the AAE and AAOMR recommends CBCT when conventional imaging provides insufficient diagnostic information. CBCT is indicated in the following clinical scenarios.
Before retreatment: A previously treated tooth with persistent symptoms and periapical radiolucency warrants three-dimensional assessment. CBCT identifies untreated canals, ledges, separated instruments, and perforation sites. It does so with far greater reliability than periapical radiographs. Scanning for CBCT missed root canals before retreatment prevents a second incomplete treatment.
Complex primary treatment: Teeth with unusual morphology benefit from pre-operative CBCT assessment. Examples include C-shaped canal systems in mandibular second molars and accessory canals in upper premolars. The FGDP Selection Criteria for Dental Radiography supports limited field-of-view CBCT when clinical findings and conventional radiographs leave diagnostic uncertainty.
Post-operative assessment: When healing does not progress as expected after 12 months, CBCT helps distinguish a missed canal from other causes. These include vertical root fracture and extra-radicular infection.
What CBCT Reveals That Periapical Radiographs Cannot
Three-dimensional imaging provides axial, coronal, and sagittal cross-sections through each root. This multiplanar view eliminates superimposition. It makes CBCT far more reliable than conventional radiography for canal detection.
MB2 canals in maxillary molars: The MB2 canal typically lies palatal and mesial to the main mesiobuccal canal. On a periapical radiograph, the superimposed palatal root frequently hides it. In contrast, axial CBCT slices clearly show both canals as separate radiolucencies within the mesial root.
Accessory canals in mandibular teeth: Mandibular premolars occasionally present with bifurcating canals that diverge in the apical third. Mandibular incisors may also harbour a lingual canal running parallel to the main canal. CBCT detects these variations at sub-millimetre resolution.
Isthmuses and lateral canals: Narrow connections between canals (isthmuses) harbour bacteria that contribute to persistent disease. CBCT cannot resolve canals smaller than the voxel size (typically 75 to 200 micrometres). However, it reliably identifies isthmuses and larger lateral canals. These structures would remain invisible on two-dimensional radiographs.
For a broader overview of CBCT interpretation in endodontic cases, see our guide to interpreting CBCT scans in endodontics.
CBCT Missed Root Canals: The MB2 Detection Challenge
The MB2 canal deserves particular attention because of its high prevalence and direct impact on treatment outcomes. In a CBCT assessment, the clinician examines sequential axial slices from the pulp chamber floor to the apex. The MB2 canal appears as a distinct radiolucent area. It is typically located between the mesiobuccal and palatal canal orifices.
Notably, the MB2 canal is not always a separate canal throughout its length. It may join the main mesiobuccal canal at various levels (Vertucci Type II). Alternatively, it may remain independent to the apex (Type IV). CBCT helps the clinician determine canal configuration before access preparation. This information directly informs the treatment approach.
When the MB2 is confirmed on CBCT, the endodontist can modify the access cavity design. Ultrasonic troughing then locates the orifice. This pre-operative planning, guided by CBCT missed root canals identification, significantly reduces the risk of leaving a canal untreated.
Radiation Dose and Justification Under IR(ME)R 2017
Every CBCT scan must be justified under the Ionising Radiation (Medical Exposure) Regulations 2017. For endodontic applications, a limited field-of-view scan delivers an effective dose of approximately 10 to 30 microsieverts. By comparison, a single periapical radiograph delivers approximately 1 to 8 microsieverts. The additional dose from a small-volume CBCT is therefore modest. It is justified when the diagnostic benefit outweighs the radiation risk.
At 3Beam, we use Morita Accuitomo and Veraview scanners. These allow precise field-of-view selection, ensuring the scan covers only the region of interest. This approach keeps radiation exposure as low as reasonably practicable (ALARP).
How 3Beam Supports Endodontic Referrers
When a referring clinician suspects CBCT missed root canals, 3Beam provides a streamlined referral-to-report pathway. The process works as follows:
Referral: The clinician submits a referral via our online referral form or by calling 0207 637 8227. The referral should specify the tooth, clinical symptoms, and the diagnostic question. For example: “query missed MB2 canal in upper right six”.
Scanning: Same-day and next-day appointments are available at 86 Harley Street, London W1G 7HP. The scan takes approximately 15 seconds.
Reporting: Where requested by the referrer, every CBCT includes a formal report from Dr Mandy Williams, our UK Dental Radiologist. The report identifies all root canals and notes any missed or untreated canals. It also describes relevant anatomical relationships. Reports are typically available within 24 hours.
For cases involving endodontic retreatment, the report also assesses existing root fillings, separated instruments, and periapical pathology extent. Additionally, for teeth with calcified canals, CBCT mapping guides the clinician toward any hidden anatomy.
Frequently Asked Questions
Q: Can CBCT detect all missed root canals?
A: CBCT reliably detects canals larger than the voxel size (typically 75 to 200 micrometres). It identifies the vast majority of clinically significant CBCT missed root canals, including MB2 canals, bifurcating premolar canals, and accessory mandibular canals. However, very fine lateral canals and apical ramifications may fall below the resolution threshold.
Q: What field of view is best for endodontic CBCT?
A: A small field of view (4 cm x 4 cm or 5 cm x 5 cm) centred on the tooth of interest provides the highest resolution at the lowest radiation dose. For more guidance, see our field-of-view selection guide.
Q: Should I request CBCT before every root canal treatment?
A: No. CBCT is not a routine screening tool. It is indicated when clinical findings and conventional radiographs leave unresolved diagnostic questions, when retreatment is planned, or when complex anatomy is suspected. Each scan must be individually justified under IR(ME)R 2017.
Q: How quickly can I get a CBCT report for an endodontic case?
A: At 3Beam, same-day scanning appointments are usually available. Radiologist reports are typically delivered within 24 hours of the scan. Urgent cases can be prioritised on request.
Q: Does CBCT replace the need for an operating microscope in endodontics?
A: No. CBCT and the operating microscope serve complementary roles. CBCT provides pre-operative mapping of canal anatomy, while the microscope provides direct visualisation during treatment. Together, they significantly reduce the risk of leaving a canal untreated.
The Bottom Line on CBCT Missed Root Canals
Missed root canals are a leading cause of endodontic treatment failure. CBCT imaging dramatically improves detection rates for accessory and untreated canals, particularly the MB2 canal in maxillary molars. For endodontists and referring GDPs, pre-operative or pre-retreatment CBCT assessment provides the anatomical clarity needed to plan complete and predictable treatment.
The evidence is clear: teeth with undetected canals carry substantially higher rates of persistent apical disease. Three-dimensional imaging eliminates the guesswork inherent in two-dimensional radiography. It directly supports better clinical outcomes by ensuring no treatable canal is overlooked. For any case where conventional imaging leaves doubt, a small-volume CBCT scan offers the definitive anatomical answer.
Refer a Patient to 3Beam
3Beam Imaging Centre is a CQC-registered private diagnostic imaging centre at 86 Harley Street, London W1G 7HP. Same-day and next-day appointments with consultant radiologist reporting included. Call: 0207 637 8227 | Email: info@3beam.co.uk | Book a scan or download a referral form.