Methods: 156 premolars were collected and divided into two groups.The experimental group was prepared with ultrasonic instrument;the control group was prepared with manual instrument.是什么意思_Methods: 156 premolars were collected and divided into two groups.The experimental group was prepared with ultrasonic instrument;the control group was prepared with manual instrument.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句