To observe the effect of bone lid technique on the extraction of the third molar deeply impacted in the bone, and to evaluate its clinical and imaging results.

A total of 52 patients who underwent extraction of deeply bone impacted mandibular third molar were recruited in Department of Oral & Maxillofacial Surgery, Hospital of Stomatology, Sun Yat-sen University, from April to December 2022, which included 26 patients in the bone lid group and 26 patients in the control group. In the bone lid group, a bone lid was prepared by piezo surgery before extracting the tooth, which was restored after the tooth extraction. In the control group, the tooth was extracted after bone remove with piezo surgery. Postoperative follow-up was conducted to observe the recovery of the patients and the therapeutic effect.

All patients showed a good recovery after surgery, without serious complications including nerve injury and osteonecrosis. There was no significant difference in postoperative pain between the bone lid group and the control group (P>0.05). The swelling reaction in the bone lid group was less than that of the control group on the 3rd day after surgery (Z_{3 d} = 2.088, P_{3 d} = 0.037). While there was no significant difference on the 7th day (Z_{7 d} = 1.866, P_{7 d} = 0.062). The bone lid integration and alveolar bone recovery were good, and the distal alveolar bone height of the adjacent teeth was also well preserved.

The bone lid technique can effectively reduce the bone tissue defect and postoperative complications, which is beneficial to the recovery of bone tissue, and can be used as a reliable choice for the extraction of the deeply impacted third molar.