[The methodological study of improving the detected rate of mandibular central incisor with two canals]

To investigate the detected rate and modality of multiple canals in mandibular central incisor by 5 different methods and to compare the results and differences among the methods, in order to provide give theoretical evidence of choosing right method and treatment in clinic.

176 mandibular central incisors were examined by 5 different methods,including radiograph at a horizontal angle of 0, macrography 15#K- file, dental operative microscope, spiral CT scanning, and dental cross section. All statistical analysis was performed using SAS6.12 software package. Data of detected rate of these 5 methods were compared using McNemar exact probability test.

The result of dental cross section was the key standard, the rate in 176 mandibular central incisor was 9.66% with two canals, of which 4.55% were type II, 5.11% were type v. The detected rate of two-canal teeth was 0.00% by radiograph at a horizontal angle of 0, 2.84% by macroscopy15# K- file, 4.76% by dental operative microscope, and 9.09% by spiral CT scanning,respectively. The results from 5 methods were compared with each other by McNemar test to find out the difference. Validity of these 5 methods according to γ was dental cross section > spiral CT scanning > dental operative microscope > macroscopy 15#K- file > radiograph at a horizontal angle of 0.

Some mandibular central incisors have two canals, the clinicians should pay more attention to avoid missing canals. When radiograph at a horizontal angle of 0 and macroscopy 15#K- file can't effectively find two canals, we suggest using the other methods such as radiograph with an excursion angle, dental operative microscope and spiral CT scanning to make clear diagnosis.