Tending toward an oval shape, the crown of the maxillary lateral incisor is as near to ideal for endodontic access as that of the central incisor. Fiber-optic illumination may, likewise, be helpful during access to this tooth. The initial entry, with the end-cutting fissure bur, is made just above the cingulum. The access cavity is ovoid. Often the fissure bur will engage the shallow pulp chamber while making the initial opening. When the chamber roof is removed, a no. 4 or 6 round bur is used to sweep out all remaining caries, discoloration, and pulp calcifications. It may be necessary to return to the fissure bur in refining the ovoid access cavity. Adequate flaring is then accomplished with round burs. Care must be exercised that explorers, endodontic cutting instruments, and packing instruments do not contact the access cavity walls. To ensure that the canals remain clean and hermetically scaled, all caries and leaking restorations must be removed and replaced with temporary sealing materials. The radicular cross-sectional pulp chamber varies from ovoid at the cervical to round at the apical foramen. The root is slightly conical and tends toward curvature, usually toward the distal, in its apical portion. The apical foramen is generally closer to the anatomic apex than in the maxillary central but may be found on the lateral aspect within 1 or 2 mm of the apex. On rare occasions, access is complicated by a dens-in-dente, an invagination of part of the lingual surface of the tooth into the crown. This creates a space within the tooth that is lined by enamel and communicates with the mouth. Dens in dente most often occurs in maxillary lateral incisors, but it can occur in other teeth. These teeth are predisposed to decay because of the anatomic malformation, and the pulp may die before the root apex is completely developed. This mostly coronal mass should be dealt with mechanically and either removed or bypassed. Goon and others reported the first case of complex involvement of the entire facial aspect of a tooth root. An alveolar crest to apex facial root defect led to early pulpal necrosis and periapical rarefaction (Burns RC, Buchanan LS. Tooth Morphology and Access Openings. Part One: The Art of Endodontics in Pathway of Pulp, 6th Ed. p. 138).
Keywords: micro-computed tomography, micro-ct, marco versiani, micro-computer tomography, high resolution x-ray tomography, dental anatomy, root canal anatomy