Narrow and flat in the labial-lingual dimension, the mandibular incisors are the smallest human adult teeth. Visible radiographically from only one plane, they often appear more accessible than they really are. The narrow lingual crown offers a limited area for access. Smaller fissure burs and no. 2 round burs cause less mutilation of coronal dentition. The access cavity should be ovoid, with attention given to a lingual approach. Frequently the mandibular incisors have two canals. One study reported that 41.4% of mandibular incisors studied had two separate canals; of these, only 1.3% had two separate foramina. The clinician should search for the second canal immediately upon completing the access cavity. Endodontic failures in mandibular incisors usually arise from uncleaned canals, most commonly toward the lingual. Access may be extended incisally when indicated to permit maximum labiallingual freedom. Although labial perforations are common, they may be avoided if the clinician remembers that it is nearly impossible to perforate in a lingual direction because of the bur shank's contacting the incisal edge. The ribbon-shaped canal is common enough to be considered normal and demands special attention in cleaning and shaping. Ribbon-shaped canals in narrow hourglass cross-sectional anatomy invite lateral perforation by endodontic files and Gates-Glidden drills. Minimal flaring and dowel space preparation are indicated to ensure against ripping through proximal root walls. Apical curvatures and accessory canals are common in mandibular incisors (Burns RC, Buchanan LS. Tooth Morphology and Access Openings. Part One: The Art of Endodontics in Pathway of Pulp, 6th Ed. p. 152).
Keywords: micro-computed tomography, micro-ct, marco versiani, micro-computer tomography, high resolution x-ray tomography, dental anatomy, root canal anatomy