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CBCT Study Links C-Shaped Canals to Extra Root in Adjacent Molars

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Posted: July 3, 2026

CBCT Study Links C-Shaped Canals to Extra Root in Adjacent Molars

Edited by Dentaltown staff

C-shaped root canals in mandibular second molars were associated with the presence of radix entomolaris, an extra root, in the adjacent first molars, according to a CBCT study published June 30 in Clinical Oral Investigations.

Researchers reviewed cone-beam computed tomography scans from 1,637 patients, evaluating 3,274 second molars and 3,274 first molars in a Western Chinese population. C-shaped canal configurations were classified using an established five-category system, and extra roots were identified according to American Association of Endodontists criteria.

C-shaped canals appeared in 46% of second molars, while radix entomolaris was found in 31.6% of first molars. Both features showed strong side-to-side symmetry, present bilaterally in about 87% of C-shaped cases and 91% of radix entomolaris cases.

The presence of a C-shaped canal was linked to greater odds of an extra root in the neighboring first molar, a statistically significant association (odds ratio 1.27). Both variations were significantly more common in women, while age showed no relationship to their co-occurrence.

The authors concluded that recognizing the connection between the two anatomical features can support radiographic evaluation and endodontic treatment planning, and they recommended careful imaging, preferably with CBCT, to detect complex canal anatomy before treatment.

The study was conducted by H.H. Al-Awdi and colleagues at the West China Hospital of Stomatology, Sichuan University, and published in Clinical Oral Investigations.

Sources:
Clinical Oral Investigations, “Relationship between C-shaped root canal configuration in mandibular second molars and radix entomolaris in mandibular first molars,” by H.H. Al-Awdi et al., June 30, 2026 (DOI 10.1007/s00784-026-06991-9): link.springer.com/article/10.1007/s00784-026-06991-9
PubMed, PMID 42377571: pubmed.ncbi.nlm.nih.gov/42377571


CBCT Study Links C-Shaped Canals to Extra Root in Adjacent Molars

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