Abstract: Objective: To compare the clinical effects of ultrasonic bone knife and chisel in extraction the broken root of mandibular third molars. Methods: A total of 200 patients with root fractures of mandibular third molar were enrolled from 2017,1 to 2018,1. The patients were randomly divided into the traditional group (99 cases) and the experimental group (101 cases). Both groups were treated with minimally invasive extraction before root fracture. Conceptual technology, the traditional group of conventional bone-cutting method was used to remove the root after root-cutting. The experimental group used the super-bone knife to remove the root, and statistical analysis was performed on the operation time and complications of two groups. Results: The time of the traditional group was (13.11±2.14) min, and the experimental group was (19.57±3.11) min. The root withdrawal time of the experimental group was longer than that of the traditional group (P<0.05), and the roots were completely removed after operation. There was no vascular nerve injury in the experimental group, and there were 24 cases of nerve injury in the traditional group. In the traditional group, 8 cases had lingual bone plate fracture, and 3 cases were broken into the sublingual, submandibular, and parapharyngeal spaces. The postoperative complications in the experimental group were lower than those in the traditional group (P<0.05). Conclusion: Ultrasonic osteotome, when removing the root of the mandibular third molar, significantly reduces the intraoperative and postoperative complications. The piezoelectric bone knife has good clinical significance.

Key words: Piezoelectric bone knife, Mandibular third molars, Broken root, Effect evaluation