## 7 Discussion  
This work illustrated the significance of effective and accurate reconstruction techniques for accomplishing enhanced aesthetic and functional needs of a mandible. This is because the mandible and maxilla plays an important role in mastication, articulation, and cosmetic functions. They are both amenable to composite bone reconstruction. The WHO (World Health Organization) classifies mandibular lesions as benign and malignant, and the updated classification scheme is accessible in the ninth volume of the fourth-edition WHO series [40; 41]. Benign tumors represent a broad spectrum of lesions and can be classified as odontogenic, e.g., ameloblastoma, odotoma, and myxoma, and non-odontogenic, e.g., fibro-osseous lesions and giant cell tumors [42]. Benign tumors can grow larger, but do not spread to surrounding tissues, whereas malignant tumors invade, destroy, and spread. The most common malignant tumors include squamous cell carcinomas, osteosarcoma, and giant cell tumors [42]. Tumors represents a major challenge in clinical practice as they lead to facial deformation and functional impairment. The factors influencing the choice of initial tumor treatment are primarily the size (T stage), location (anterior vs. posterior), bone proximity (mandible or maxilla), and histology, including the grade, type, and depth of invasion [43]. Certainly, adequate assessment of the tumor invasion is crucial in diagnosis and optimal surgical treatment planning. It must be highlighted that, although the mirror image reconstruction technique is an effective tool for implant design, it is not without its drawbacks. A new approach known as cavity-filled reconstruction was, therefore, implemented to address its limitations. The two custom-design reconstruction techniques were compared and evaluated based on their virtual (STL file) and physical (3D-printed) prototypes. The accuracy assessment confirmed that the cavity-filled reconstruction technique provided higher accuracy. In the cavity-filled method, the RMS error was decreased by almost 13-16% compared to the mirror reconstruction technique. The mean RMS values recorded for mirroring and cavity-filled techniques in the physical prototype analysis were 1.2683 and 1.1019 mm, respectively. Similarly, when the STL files from the mirror and the cavity-filled reconstituted virtual equivalents were reviewed, the RMS error value was reduced from 1.8018 (mirror) to 1.5048 mm (cavity-filled). The study also established average values of 0.5194/\(-\)0.5392 mm (AD) for the cavity-filled approach as compared to the mirroring that resulted in the higher values of 0.7441/-0.8682 mm. Similar trends for AD were observed when STL data were investigated. The AD for the cavity-filled approach was \(-\)0.9675/0.6652 mm, and it was quite lower compared to the \(-\)2.9767/0.7746 mm in mirror reconstruction. It was, therefore, noted, based on the results of the 3D and 2D analysis, that the cavity-filled methodology exactly matched the bone contours. It is noteworthy that, in the cavity-filled approach, the bilateral condyle and chin were exactly in the same position unlike in the mirroring technique. Various techniques are used in the reconstruction of mandibular and maxillary defects, and the most important is mirror reconstruction. Several researchers and surgeons illustrated how the mirror technique can be used successfully in mandibular reconstruction [20; 44]. It is also widely used in the reconstruction of custom cranial implants, which replace defective parts of the skull [27; 45]. Human skulls are extremely complex and irregular in shape [46]. They are never symmetrically ideal and, thus, the construction of an anatomical frame based on their reference is extremely ambiguous [47]. Throughout clinical practice, the symmetrical plane of the skull is approximated to the mid-sagittal plane and manually calculated using known landmarks [48]. The recognition of the anatomical midpoint used in the mirroring tool is not as simple as one might presume.