An investigation on the percentage of two root canals in the distal lower first molars using staining – section method (In- vitro)

An investigation on the percentage of two root canals in the distal lower first molars using staining – section method (In- vitro) Dr. H. Razmi *- Dr. H. Hooshyar ** *- Associate Professor of Endodontics Dept.-Faculty of Dentistry – Tehran University of Medical Sciences. ** - Dentist. Background and Aim: The number of roots, the number and configuration of root canals in distal root of lower first molar teeth display a wide range of variations and having knowledge of the internal anatomy of the roots plays an important role in the success of each endodontic therapy. Materials and Methods: In this in vitro descriptive study, the internal anatomy of distal root of 310 lower first permanent molar teeth extracted from people living in different cities in Iran were studied to investigate the percentage of two root canals, the number of roots, the type and number of root canals based on Vertucci's classification using staining – section method. A syringe with gauge 27 needle was used to inject Fushin 1% into the distal root canals. Fushin color penetration was assisted by a vaccum suction applied apically. The distal roots were then sectioned horizontally. Results: The findings showed that 4.5% of the studied teeth had two distal roots and 100% of their root canal configurations were type I for each distolingual and distolingual roots. 37.7% of the studied teeth had two canals in their distal roots, 22.6% had two apical foramina and 32.9% had two canal orifices. The root canal configurations included: (Vertucci's classification): 57.5% type I, 15.2% type II, 4.8% type III, 12.6% type IV, 4.5% type V, 0.6% type VI, 0.3% type VII and 0% type VIII. Conclusion: 37.7% of the studied teeth had two distal root canals. The dentist must always looks for the second canal in the distal root of a lower first molar. If one is missed, it could lead to endodontic treatment failure. Access cavity with rectangular outline would permit better visualization and exploration of a possible second canal in the distal root. Key words: Root canal anatomy – Distal root – lower first molar