Abstract:

Objective

To identify the morphology characteristic of root canal orofices in the mesial canal of mandibular first molars using operating microscope， and to.

Methods

The mesial canals in 71 mandibular first molars were counted and detected by operating microscope. The root canals were shaped by using Protaper rotary instruments and ultrasonic instruments， cleaned by needle irrigation and ultrasonic irrigation with sodium hypochlorite， and obturated with warm gutta-percha by vertical condensation technique. The efficiency of preparation and obturation was analyzed with radiographs before and after operation.

Results

2 molars were found to have single root canal orifice （2.82%）， 65 molars were found to have two roots canal orifice （91.55%）， 4 molars were found to have three roots orifice （5.63%）. 38 cases have isthmus between mesiobuccal and mesiolingual root canals （53.52%），27 cases have no isthmus （38.03%）. There was no any complication in all cases. The treatment success rate after one year of treatment is 92.9%.

Conclusions

The morphology of mandibular first molar is complex， and the operating microscope is considered to be helpful in identification of the root canal morphology of mandibular first molars. The rotary nickel-titanium instrumentation， ultrasonic irrigation with sodium hypochlorite， and vertical condensation technique can obtain good treatment effect.

Key words: Mandibular first molar, Mesial canal, Operating microscope