Conclusions Retreatment of the endodontic therapy with ultrasound is an effective and practical method.Nevertheless, its use in curved and severely obstructed root canals is limited.

• 结论证实了超声技术应用于牙髓治疗失败牙的实用性,但在处理弯曲根管方面由于成形作用差,故尚有一定局限性。