下颌切牙根管形态：Mandibular Incisors

舌侧中空而平滑的下颌切牙是成人牙齿中最小的。

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).