This tooth has three roots. The palatal root is the longest, with an average length of 22 mm; the mesiobuccal and distobuccal roots are slightly shorter, at 21 mm average length. The percentage of mesiobuccal roots having two canals reported in the literature has increased steadily as research techniques have developed. In vitro studies have usually reported a higher incidence than in vivo studies. Stropko, reporting an extensive in vivo study,
found second canals in 73% of cases before the use of an operating microscope, but 93% following its use. The canals of the mesiobuccal root are often very fine and difficult to negotiate; consequently, more errors in instrumentation occur in this tooth than in almost any other. Anastomosis between these two canals may take the form of narrow canals or wide fins, both almost impossible to instrument.
The curvature of the roots can be difficult to visualize from radiographs, and the second mesiobuccal canal is nearly always superimposed on the primary mesiobuccal canal. The palatal root has a tendency to curve towards the buccal and the apparent length on a radiograph will be shorter than its actual length. The access cavity represents the shape of the pulp chamber, enlarged slightly, and flared up on to the mesiobuccal aspect of the occlusal surface to accommodate the angle of instrument approach when working at the back of the mouth.
found second canals in 73% of cases before the use of an operating microscope, but 93% following its use. The canals of the mesiobuccal root are often very fine and difficult to negotiate; consequently, more errors in instrumentation occur in this tooth than in almost any other. Anastomosis between these two canals may take the form of narrow canals or wide fins, both almost impossible to instrument.
The curvature of the roots can be difficult to visualize from radiographs, and the second mesiobuccal canal is nearly always superimposed on the primary mesiobuccal canal. The palatal root has a tendency to curve towards the buccal and the apparent length on a radiograph will be shorter than its actual length. The access cavity represents the shape of the pulp chamber, enlarged slightly, and flared up on to the mesiobuccal aspect of the occlusal surface to accommodate the angle of instrument approach when working at the back of the mouth.