Successful root canal therapy requires a thorough knowledge of root and root canal morphology, as well as the ability to adequately clean, shape and fill all canals. Additional root canals may be detected by clinical investigation of the floor of the pulp chamber following cavity access preparation and by radiographic examination of the tooth.

Approximately 64% to 88% of maxillary first premolars have 2 canals, while 9% to 36% have just 1 canal. Three-rooted maxillary first premolars are uncommon, with an incidence of 0.5% to 1%. Mandibular second premolars have been shown to have 1 root canal at the apex in 97.5% and 2 canals in 2.5% of cases; only a 0.4% incidence of 3 root canals has been reported (Zillich and Dowson Oral Surg Oral Med Oral Pathol 1973). The dental operating microscope allows clear visualization of the site and enhanced detection of these enigmatic variations.

Rare variations in maxillary first premolar and mandibular second premolar root canal configuration and their management were presented in case studies reported by Rajesh et al from M.R. Ambedkar Dental College and Hospital, India. The first case study involved a 50-year old man with a noncontributory medical history who sought treatment for an infected maxillary right first premolar tooth. The preoperative periapical radiograph did not suggest the presence of extra roots or canals. After excavation of caries, entry into the pulp chamber was made, where 2 distinct canal orifices were found (buccal and lingual). During canal negotiation, a ledge-like obstruction was detected at the cervical third of the buccal canal.

The working length radiograph taken at an eccentric angle revealed that the mesiodistal width of the mid-root area was equal to that of the crown, and a double periodontal ligament space was found in the radiograph, which was suggestive of the presence of another root distally. At this point, access was evaluated using the dental operating microscope and extended so that the second canal in the buccal root could be negotiated (Figure 1).

In another case study, a 37-year-old man sought treatment for irreversible pulpitis associated with his mandibular left second premolar.

The preoperative radiograph revealed

  • a sudden disappearance of the main canal at the middle one~third of the root, indicative of splitting of root canals at that level
  • a radiolucent line running vertically from the midroot level to the apex, suggestive of an additional root

Access was made under rubber dam isolation, and only 1 buccal canal was easily negotiated. Using the dental operating microscope, 2 additional canals were located and treated.


Figure 1. (A) Access preparation of maxillary first premolar Two canal orifices are visible in the buccal root (Image courtesy of Or Frederic Barnett.) (B) Micro-computed tomographic reconstruction of mandibular premolar demonstrating complex root canal anatomy. (Image courtesy of Or Ronald Zapata.)


Teeth with extra roots or canals can pose a clinical challenge. Perhaps the greatest challenge in these cases is to identify the atypical anatomy early, which could prevent treatment coma plications, and plan for appropriate modifications in treatment.

Rajesh P, Thakur S, Kirthiga M, et al. The radiculous’ premolars: case reports of a maxillary and mandibular premolar with three
canals. J Nat Sci Biol Med 2015;6:442-445.