原著
超音波を利用した根管スミヤー層の除去における周波数の影響
2022 年 43 巻 1 号 p. 22-27
詳細
2022 年 43 巻 1 号 p. 22-27
Abstract : The smear layer must be removed from the root canal wall, because it affects the residual source of infection and the root canal sealing ability. This study investigated the efficiency of removing the smear layer by using different ultrasonic frequencies with EDTA solution.
Thirty extracted human permanent teeth with a single straight root canal were used as experimental teeth. All the crowns had been removed 15 mm from the apex. Experimental root canals were enlarged to #40 with NiTi rotary files. The root canals were filled with saline solution during the procedure, and then thoroughly irrigated with 6% NaClO.
The experimental teeth were randomly divided into three groups to compare the removal effects of the smear layer formed by the root canal enlargement. Group 1 : the root canals were irrigated with 17% EDTA solution (4.0 mL/min) using a syringe ; Group 2 : the root canals were filled with EDTA and ultrasonic vibration at 30,000 Hz was applied ; Group 3 : the root canals were filled with EDTA and ultrasonic vibration at 40,000 Hz was applied. In each group, five teeth were irrigated for 15 seconds and 30 seconds each. After the procedure, EDTA was thoroughly flushed with NaClO. The experimental roots were mesio-distally divided into two pieces for SEM observation of the root canal walls. The root canal walls were divided into three portions, the coronal side, the middle portion, and the apical portion, and the residual condition of the smear layer was scored and evaluated according to Torabinejad et al.’s classification method from the SEM images.
Thirty seconds of irrigation was better than 15 seconds in Group 1. In Groups 2 and 3, there was almost no difference in the removal effects of the smear layer depending on the application time. In all groups, better removal of the smear layer was observed on the crown and middle portions compared to the apical portion.
From the results of this study it was concluded that the combined use of EDTA and an ultrasonic device is more effective in removing the smear layer. The removal effect was not affected by the frequency of the ultrasonic device.
