C-Shaped Configuration in Right Third Molars
The odds of a right third molar being C-shaped are extremely low, with an overall prevalence of approximately 3.4% in maxillary third molars and 2.2% in mandibular third molars based on anatomical studies 1, 2.
Prevalence by Location
Maxillary (Upper) Third Molars:
- The overall prevalence of C-shaped canals in maxillary third molars is 3.4% in a Central India population study using CBCT imaging 2
- This represents a rare anatomical variant, with only one documented case report of a maxillary third molar with C-shaped anatomy in the literature prior to 2009 3
- The rarity is emphasized by the fact that this was described as "the first known description of a maxillary third molar with C-shaped anatomy" 3
Mandibular (Lower) Third Molars:
- C-shaped canals occur in approximately 2.2% of mandibular third molars with two roots 1
- The overall incidence in mandibular molars (including second molars where C-shaped canals are most common) is approximately 7% in the general population 4
- However, this prevalence is significantly higher in Chinese populations, reaching up to 31.5% 4
Clinical Implications
Diagnostic Challenges:
- C-shaped canals are challenging if not impossible to predict radiographically on conventional 2D imaging 4
- The C-shaped configuration may appear completely normal at the pulp chamber level but manifest in the middle or apical one-third of the root 4
- CBCT imaging is the essential technique for accurately assessing complex root canal anatomy when suspected 5
Anatomical Characteristics:
- C-shaped canals are characterized by a C-shaped groove connecting one or more root canals 4
- This groove can occur anywhere along the root canal system 4
- Canal orifices are typically located 1-3 mm below the cementoenamel junction (CEJ) in 98% of C-shaped molars 4
- The C-shape configuration varies greatly throughout the length of the canal 4
Population Variability
The prevalence shows significant ethnic variation, with Asian populations (particularly Chinese) demonstrating substantially higher rates compared to other populations 4. This ethnic predisposition should be considered when assessing the likelihood of C-shaped anatomy in third molars.