Twenty patients with benign mandibular lesion will be included in this study. the patient will be divided randomly (10 patients each group). Group I the lesion will be treated using bone lid technique. Group II the lesion will be treated using the standard technique. The patients will be received, clinically and radiologically examined, and managed at the Oral and Maxillofacial surgery Department, Faculty of Dentistry, Tanta University.

The patients will be evaluated clinically to evaluate healing and radiographically using cone beam CT (CBCT) scan to identify bone healing, the extension and the volume of lesion six months later

Purpose: This study aimed to compare the clinical and radiologic outcomes of the bone lid technique performed using a piezoelectric device versus the traditional technique in patients requiring excision of the mandibular bony lesions

Materials & Methods: Twenty patients with mandibular lesion will be included in this study. the patient will be divided randomly (10 patients each group). Group I the lesion will be treated using bone lid technique. Group II the lesion will be treated using the standard technique. The patients will be received, clinically and radiologically examined, and managed at the Oral and Maxillofacial surgery Department, Faculty of Dentistry, Tanta University.

Preoperative evaluation: The patients will be evaluated clinically and radiographically using Cone beam CT(CBCT) scan to identify the extension and the volume of lesion.

Surgical procedure: A full thickness flap will be elevated in both groups to achieve access to the bone above the lesion, in group I osteotomy of bone will be designed to extend beyond the actual extension of lesion in radiograph using piezoelectric device to secure a latter repositioning of the lid on a healthy stable bone. The osteotomy will be performed with an internal bevel angle to facilitate repositioning. The removed bone lid will be soaked in saline. After excision of the lesion, the bony lid will be repositioned to its original position and fixed to the bone with an absorbable suture.

In group II the bone will be removed buccally using surgical bur then the lesion is removed. Finally, the flap will be sutured in both groups.

Postoperative evaluation: The patients will be evaluated clinically regarding healing, presence of infection, inflammation, necrosis, or bone exposure each week for one month then monthly for six months.

Radiographically, (CBCT) scan six months later to evaluate Healing and integration of the repositioned bone lid, any signs of recurrence in the case of cysts, and filling of the bone defect bone healing and volume of the defect.

All selected cases of both groups b were went for CBCT scan using fixed exposure parameters (Kv, mA) and the same field of view prior surgery and 6 months post-surgical using the same axial slicing to evaluate the following

1. Cyst area in coronal view for posterior region and sagittal view for anterior region
2. Evaluating lesion location by making perpendicular line from alveolar crest on the occlusal plane and measuring the distance from alveolar crest to the lesion using (Coronal view posterior, sagittal anterior).

3- recurrence of lesion , integration of buccal cortex 4- bone density

Inclusion Criteria:

age ≥ 6 years

• presence of bony lesion (cysts, benign tumors, odontoma) located in mandibular region,
• the existence of a normal residual buccal cortical plate with the adequate thickness (≥1 mm) at least at the periphery of buccal cortical plate

Exclusion Criteria:

• • patients taking medications that affect bone metabolism,

  • patients underwent head and neck radiotherapy