Root Canal Anatomy

Krasner and Rankow -  The cementoenamel junction (CEJ) is a consistent landmark for the location and shape of the pulp chamber.

Bjorndal et al. - Root shape predicts the number, location, and morphology of canals within the root.

Vertucci's Canal Classification

• Type I represents a single canal.
• Type II indicates two canals that join at the apex.
• Type III begins as a single canal that splits into two canals and joins at the apex.
• Type IV is a root containing two canals.
• Type V is a single canal that bifurcates at the apex.
• Type VI begins as two canals, joins in the midroot area, and bifurcates at the apex.
• Type VII begins as a single canal, bifurcates in the midroot area, joins in the apical third, and again bifurcates.
• Type VIII indicates three separate canals.

Burch and Hulen - 92.4% of the major foramina of all classes of teeth open short of the anatomical apex.  Furthermore, the average distance between the foramen and the anatomical root apex is 0.59 mm.

Kuttler et al. - Demonstrated that the apical foramen is often not coincident with the root apex. He found that the average distance between the center of  the foramen and the apical center was 495 μm.

El Ayouti et al. - Found that the distance between the apical foramen and the apex was, on average, 0.9 mm when evaluated by cone beam computed tomography (CBCT).

Stein and Corcoran - Found that the average distance between the major and minor foramina was 0.724 mm, and the width of the CDJ remained constant with age at 0.189 mm.

El Ayouti et al. - Measured the mean distance between the apical constriction and apical foramen on CBCT scans at 0.2 mm.

Meder-Cowherd et al. - Unable to locate a defined apical constriction in 65% of the palatal roots of maxillary first molars evaluated by CBCT scans. This demonstrated that not all roots necessarily exhibit the traditionally defined apical constriction.

Gutmann - Theorized that these structures form via localized breaks in HERS around blood vessel communications.

De Deus et al.

• Lateral canal as one extending from the main canal to the periodontal ligament (PDL) in the body of the root
• Secondary canal as one extending from the main canal to the PDL in the apical region
• Accessory canal as one derived from the secondary canal branching toward the PDL in the apical region.

Research confirms the most common location for lateral anatomy is in the apical third (De Deus, Vertucci).

• 45%
• Rubach and Mitchell

• 27.4% (17% in apical third)
• De Deus

• 28%
• Gutmann

• 46%
• Vertucci and Williams

The DI forms via infolding of enamel and dentin into the root canal space.

Narayana et al proposed several potential etiologic factors including trauma, infection, growth retardation of specific cells, disruption in the regulation of the enamel organ, and genetic predisposition.

Hovland and Block - Reported an incidence of between 0.4% and 10% in the general population.

Rotstein et al - Found that 42% of DI cases occurred in lateral incisors.

Hulsmann - Found bilateral presentation 43% of the time.

Oehlers

• Type I represents a minor extension into the root canal space.
• Type II extends into the root and may perforate the pulp tissue.
• Type III penetrates to the apex and may have its own apical foramen.

DE forms from an out-pouching of enamel and dentin onto the occlusal or lingual surfaces of the dentition. The remaining portion of the clinical crown of teeth affected by DE is often normal in appearance.

Levitan and Himel - The variant can be found on any tooth but is most commonly observed on premolars and often presents bilaterally. If found on anterior teeth, it is frequently seen on the lingual surface and has been described as a talon cusp.

C-shaped canals have been described in mandibular and maxillary molars and mandibular premolars.

They present with large, interconnected tissue spaces and are often difficult to diagnose by two-dimensional radiographs alone.

Although the majority of these teeth exhibit fused roots, C-shaped canals have also been noted in nonfused roots (Lu et al).

Cooke and Cox - They have been observed in as many as 8% of mandibular second molars when examined clinically.

Lu et al. - Located the anomaly in 18% of mandibular premolars in a Chinese population.

Possible pulp chamber appearance in C-shaped mandibular molars:

• Continuous C-shaped orifice
• C-shaped medial orifice with a separate distal canal
• Continuous MB-D orifice and separate ML orifice
• Non-C-shaped pulpal floor

Caution must be exercised in the endodontic treatment of teeth with a C-shaped canal because of the presence of thin canal walls.