The aim of current cross over clinical trial is to evaluate the effect of topical 5-FU as adjunct therapy in reducing risk of the recurrence of OKCs

The main inclusion criteria in this study will be 48 patients with biopsy proved odontogenic keratocyst with no relevant systemic diseases which might affect healing process. patients will be treated with 5-FU cream (Efudex; Valeant Inc, Laval, Quebec, Canada) after enucleation and peripheral ostectomy of the odontogenic keratocyst.

• A detailed preoperative assessment for all patients will be carried out including history taking, clinical and radiographical examination.
• All surgical procedures will be carried out under general anesthesia with nasal endotracheal intubation.
• Through an intraoral incision, the full thickness mucoperiosteal flap will be raised. The entire cyst lining radically enucleated in conjunction with any overlying mucosa, followed by extensive cavity thorough curettage with meticulous evaluation of any residual daughter cyst lining with reduction of the lingual and buccal undercut bony walls to remove residual macroscopic cystic epithelium.
• After enucleation and peripheral ostectomy of the OKC lesion, a sterile radiopaque quarter-inch ribbon gauze is coated with 5-FU cream and packed into the surgical wound. The wound is closed in the usual manner using 3/0 vicryl leaving a small distal end (approximately1 cm) of gauze exposed to allow for gauze removal at 24 hours postoperatively.

All patients will be regularly followed up for 12 months postoperatively clinically and radiographically

Inclusion Criteria:

• patients with biopsy proved odontogenic keratocyst

Exclusion Criteria:

• relevant systemic diseases which might affect healing process.