Additive Manufacturing (AM), also known as 3D printing is an emerging technology in oral & maxillofacial surgery with respect to reconstructive bone surgery. Such treatment protocols often require customized implants to fulfill the functional and aesthetic requirements. Currently, such customized implants are being manufactured using AM technology. This paper describes a mandible defect of oral & maxillofacial surgery. The fracture and defect of the mandible inferior border is one of the serious complications during alignment and fixing of the implant. Reconstruction of such defects is daunting tasks. The case report describes a method based on Computer Aided Design (CAD) and AM for individual design, fabrication and implantation of a mandible inferior border. A 40-year old male meet an accident with rash drive. The patient specific customized implant is designed with patient Computed Tomography (CT) data. The CT images in Digital Imaging and Communication in Medicine (DICOM) file format is used to develop a 3D CAD model of customized implant. The implant is designed to maintain the symmetry of mandible from right to left. The designed implant model is manufactured by Fused Deposition Modelling (FDM) techniques with a biocompatible material. The patient mandible prototype model was manufactured by AM process, which is helpful for pre-planning of surgical procedures. For these pre-planning surgical procedures, a perfect fit obtained during surgery. The patient ultimately regained reasonable mandible contour and appearance of the face.