The aim of this study is to compare multi-detector CT and CBCT as pre-surgical diagnostic imaging before surgical retrieval of iatrogenic displaced mandibular third molar teeth/roots.

Sixteen patients will included in this study that they had previously a challenging and unsuccessful extraction of an impacted mandibular third molar by a general dentist under local anesthesia.

Groups allocation:

For detailed radiographic examination, when a displaced tooth/root fragment is suspected the patients will randomly divided into two equal groups, each of eight patients:

Group (1): Multi-detector computed tomography (MDCT ) are performed using CT scanner (SOMATOM Emotion6, Siemens, Germany). The protocol is 200 mAs, 120 kVp, 512 × 512 matrix, 1.172 pitch, 64 × 0.625 mm section collimation, 2 mm slice thickness, 0.6 mm section reconstruction Group (II): CBCT** scans are performed with an exposure performed at 15 mA, 85 KV and at a field of view 7.5 cm x 14.5 cm x 14.5 cm.

Image reconstruction All images will be reconstructed at 0.6 mm and the reconstructed axial images are transferred to a workstation, and multi-planar reconstructions are generated using the included standard dental software package. The panoramic and paraxial images were obtained perpendicular to the transverse images. Then multi-planar reformation (MPR), maximum intensity projection (MIP) and shaded surface display (SSD) are done in different planes.

Image interpretation (analysis):

Axial and reformatted images are evaluated to detected the position of displaced third molar tooth or root in relation to the mandible and the mylohyoid muscle.

Preoperative instruction It will intended for all patients to have their displaced tooth or root fragments retrieved using an intra-oral approach while being under general anesthesia following standard blood tests and pre-anesthetic examinations.

Surgical procedure All surgeries are performed in a standardized fashion, using the same surgical and pharmacological protocols. All surgeons had at least 5 years of experience in third molar teeth extraction. Before surgery, the patient performed a mouth rinse of chlorhexidine 0.12% for one minute. Dexamethasone 8 mg is given orally to the patient one hour before surgery to promote the best possible postoperative results.

Under general anesthesia, a lingual envelope incision is performed to access and remove the displaced third molar tooth or root, and a mucoperiosteal flap was released from the retromolar trigone to the medial surface of the mandibular first premolar. By carefully retracting the lingual soft tissue, an envelope flap was raised on the lingual side from the second premolar to the anterior boundary of the ramus. This protected the lingual nerve from injury. With great caution, the lingual flap is reflected up to the submandibular area so that the tooth or root fragment will be identified. An extra-oral finger is used as support. (Jo Through blunt dissection, the loose tooth or root is located, grabbed using a pair of artery forceps, and extracted. The flaps are sutured using 3-0 Vicryl sutures after the wound was irrigated with normal saline.

Post-operative evaluation At the conclusion of the intervention, the same operators meticulously filled out a data collection form for each patient. These documents are momentarily kept in a secure location inside the operational unit. A progressive numerical code is given to each patient as a means of identification. Gender, birthdate, the anatomical location of the misplaced tooth or root, and the duration of the operation (calculated from the incision to socket cleaning) are all collected.

On the seventh post-operative day, the sutures are removed, and the patients are evaluated for the following: Pain , swelling ,Trismus and Sensory disturbances

Inclusion Criteria:

- Patients had a challenging and unsuccessful extraction of an impacted mandibular third molar by a general dentist under local anesthesia.

Exclusion Criteria:

• Patients presented with pathologic lesions (dental cyst or tumor) around the tooth to be retrieved