Evaluation of root canal anatomy of mandibular first premolar by stereomicroscope.

Introduction: It is impossible to prepare and obturate  the root canal correctly without basic information about the root canal anatomy.
The purpose of this study was to evaluate the root canals of mandibular first premolar by the staining the canals and cross sectioning the roots by stereomicroscope.
Materials & Methods: In this study 100 extracted intact first premolar were selected and the root were sectioned at CEJ point  by metal disc. After removing the pulpal tissue, the teeth were cleaned completely from pulpal stumps and necrotizing tissue using the 30.% H2O2  for 48 hours. After washing and drying the teeth, all surfaces of roots except one millimeter around the apical foramen were covered with nail polish. Then they were centrifuzed with Eosin 5% for 20minutes after that the teeth were washed and the nail polish was cleaned by acetone.  Finally the teeth were sectioned  horizontally to 1-1.5mm sections by hand piece and metal disc.
The sections of apical to coronal were studied by stereomicroscope and the number of canals, the type of canals, the shape of canals in apical, middle root and coronal area, adjoining site of the canals and separation site of the canals and apical foramen position was evaluated.
Results: 57% of  teeth had one canal, 37% had 2 canals, 5% of teeth had 3 canals and 1% had 4 canals. 57% of teeth were type 1, 6% type II,  29% type IV and 8% of teeth were classified as miscellaneous group.
Adjoining site of canals in type II were 88%,  apical and 16.7% of  teeth were in middle part. Separation site of   the canals in type IV were 65.5%  apical and 34.5% in middle part. The cross sections of canals in coronal root were 6.8%,  ellipsoid  27%, striped 3% round and  2% figure 8.
The cross sections of canals in middle root were round in 74%,  ellipsoid in 21%,  striped in 4% and C. shaped in 1%.  Cross sections  of canals in apical part were round in 99% and striped in 1%.
Conclusion: According to the above findings,  it maybe concluded that considering the variety of canal configurations, mandibular first premolar could be easy or difficult to treat witch is in accordance with other studies.