## 4 Discussion
Indeed, simultaneous microvascular mandibular grafting techniques with satisfactory results have been described by other authors but, again, surgery did not involve the TMJ or enable its sufficient reconstruction when necessary [18; 21; 22]. Virtual surgical planning and custom biomaterials have already found clinically proven applications in the treatment of orbital trauma [11], cosmetic facial surgery [23], orthognathic surgery [24], free flap reconstruction of midface defects [25], and treatment of facial gunshot wounds and other injuries [26], providing improved efficiency and precision for complex surgical operations and assisting in the restoration of maxillofacial unit functionality, facial volume, symmetry, and harmony [26; 27]. However, no data have been reported to date regarding the reconstruction of the pediatric mandible, its implication in further growth, and the possibilities for dental and orofacial treatment. In this study, we describe the first protocol where VSP and alloplastic prosthesis of the TMJ with microvascular free flaps is combined with 3D planning of the resection areas and shape of the graft, and the precision operation was performed using individually designed surgical guides, which are more commonly used in the reconstructive facial surgery of adults [21; 25]. This approach minimizes the risk of unwanted trauma and over-resection, reduces the duration of the surgery, and ensures a perfect fit of the graft at the donor site. The alloplastic 3D custom TMJ prosthesis allows full reconstruction of the lost joint and ensured physiological functioning. Similarly to the previously published results, VSP provides improved reconstruction, precision bony segment contact, and anatomical correction of the bone deficiency [25]. No resorption of the bone grafts was observed in the follow-up. The microvascular graft, fixed to the TMJ prosthesis and mandible by a customized microplate, allows further mandible growth and prevents TMJ ankylosis. In the follow-up, growth of the operated side was observed in comparison to the contralateral healthy side. It must be noted that in pediatric patients, reconstruction plates must be removed within 3-4 months of the reconstruction surgery to allow the continued proper and undisturbed growth of the facial skeleton. The surgical procedure described within this study provides significant improvement in TMJ functionality, mouth opening range, food intake effectiveness and satisfactory aesthetic results. It is worth mentioning that in some cases the planning of the surgery and bone reconstruction should include hypercorrection of the grafted side in order to reduce or eliminate genital asymmetry at the follow up. Three-dimensional VSP has inherent issues that have to be taken into account during the planning stage. Pitfalls resulting from excessive tumor growth, nonfitting of the guides, or misconceived osteotomy lines may lead to incomplete adherence or complete abandonment of VSP-based treatment. Furthermore, it must be noted that communication with the manufacturing engineer is critical for the successful application of 3D-designed biomaterials [28]. Frequently, a multidisciplinary 3D-VSP meeting with a maxillofacial surgeon, orthodontist, oncologic surgeon, and clinical engineer or technician is arranged in order to develop a coherent and prospective surgery and treatment plan [29]. In some cases the design and size of either the surgical guide or the implant itself requires modified and extended operational access in order to properly fit the device. This represents the most disturbing intraoperative factor as 3D-printed biomaterials usually cannot be easily modified, bent, cut, or trimmed, unlike stock solid titanium implants. VSP requires a highly skilled and experienced surgeon and suitable preoperative planning to take full advantage of VSP's possibilities.