INTRODUCTION: Dental cysts constitute a considerable share in the jaw bones disorders. The cystic lesions are the major factor causing jaw destruction. Bone grafts are used to reduce risk of jaw weakness and to shorten the period of healing after cyst enucleation. OBJECTIVES: To evaluate the influence of collagenated heterologous cortico-cancellous bone mix radiologically and clinically after enculeation of mandibular cysts. MATERIALS AND METHODS: A total of twenty-four patients suffering from cysts affecting the lower jaw bones and seeking for surgical treatment. Patients were assigned into 2 parallel groups with allocation ratio 1:1. Group A: Consisted of twelve patients, into whom Collagenated heterologous cortico-cancellous bone mix (Osteobiol® Gel 40 E, Italy) was applied as grafting material after enculeation of mandibular cyst. Group B: consisted of twelve patients with enculeated cyst without applying any grafting material acting as control. A cone beam computed tomography was performed for each patient to evaluate bone density immediately and after 6 months. RESULTS: Radiographic analysis using cone beam computerized tomography revealed that there was gradual increase in bone densities in the grafted defects. The mean value of bone density pre-operatively was 734.8 ± 105.1 HU which increased to 1634.4 ± 222.2 HU at the end of the follow up period. CONCLUSIONS: The use of collagenated cortico-cancellous bone graft greatly enhances bone deposition in bony defects