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Porcine mandibular defect models are commonly used for the preclinical evaluation of reconstruction techniques. Existing studies vary in technique, complexity, and postoperative outcomes. The procedures are complex and often described without sufficient detail. We describe in detail a simple and reproducible method for creating a critical-size mandibular defect in a porcine model. Seven hemimandibular critical size defects were created in five male Yorkshire-Landrace pigs, three with unilateral defects and two with bilateral defects. A transverse incision was made over the mandibular body. Periosteum was incised and elevated to expose the mandibular body and a critical-size defect of 30 × 20 mm created using an oscillating saw. The implant was inserted and fixed with a titanium reconstruction plate and bicortical locking screws, and the wound closed in layers with resorbable sutures. Intraoral contamination was avoided. Dentition was retained and the mental nerve and its branches preserved. The marginal mandibular nerve was not encountered during dissection. All pigs retained normal masticatory function, and there were no cases of infection, wound breakdown, haematoma, salivary leak, or implant-related complications. The procedure can be performed bilaterally on both hemimandibles without affecting load-bearing function. All pigs survived until the end point of three months. Postoperative computed tomographic scans and histology showed new bone formation, and a three-point bend test showed the restoration of biomechanical strength. Straight-segment mandibulectomy is a simple and reproducible method for the creation of critical-size mandibular defects in a porcine model, simulating a load-bearing situation. [ABSTRACT FROM AUTHOR]

The reconstruction of mandibular defects using particulate grafts is a proven technique that restores the osseous anatomy effectively. Secondary osseous reconstruction can be accomplished with endoscopic assistance and reduced-access incisions if an intermediate spacer is placed during resection. Two patients required reconstruction after resection of mandibular ameloblastomas. We used a modified protocol that involved the implantation of a graft of particulate corticocancellous bone after removal of the spacer, and prepared the recipient site under endoscopic guidance with small extraoral incisions. The grafts healed uneventfully and matured into ossicles suitable for the placement of osseointegrated implants. [ABSTRACT FROM AUTHOR]

Our aim was to evaluate the effect of a digital template in the preservation of the inferior alveolar neurovascular bundle during osteotomy for benign lesions of the mandible in 6 patients who were treated with mandibular osteotomies during 2013. Computed tomographic (CT) data were imported into ProPlan CMF 1.4 software. The borders of the lesion and the inferior alveolar canal were marked, and a digital template designed to mark the borders, outline the canal, and guide the osteotomy. A mirror image of the unaffected mandible was used to make a stereolithographic model by a rapid prototyping technique to prefabricate the reconstruction plate for the bone graft. The accuracy of the designs and the templates was evaluated during operation and postoperatively by CT. The sensation of the skin was tested using a Neurometer® CPT (current perception threshold) sensory detector (Neurotron Inc, Baltimore USA) to evaluate the function of the preserved inferior alveolar neurovascular bundle during follow up. With the digital template it was possible to guide removal of the bony lesion while accurately protecting the neurovascular bundle. Follow up for a mean of 8 months (range 5 -12) showed good facial symmetry, a stable occlusion, and recovery of sensation in the lower lip on the affected side. We conclude that a digital template can successfully help the resection of benign lesions of the mandible while preserving the function of the inferior alveolar neurovascular bundle. [ABSTRACT FROM AUTHOR]

We did biomechanical loading tests to compare the quantity and quality of interfragmentary movement in fractured human cadaver mandibles that had been reconstructed with iliac crest using 3 different osteosynthesis systems. Eighteen mandibles from human cadavers with a 4.5cm paramedian L-type defect were reconstructed with bone from the iliac crest using 3 different osteosynthesis systems and continuously loaded on the “Mandibulator” test bench. Six mandibles each had the bones joined together using 2 monocortical non-locking plates, 2 monocortical locking plates, or a single bicortical locking plate/fracture gap. Macroscopic deformation, failure mechanisms, and movement of the fracture gap in all 3 dimensions were assessed and quantified over increasing loading by PONTOS® optical measurement systems. Final mechanisms of failure were excessive deformation of the plate, fracture of the mandibular fragments, and failure of the iliac crest graft. The plate became deformed mainly in the miniplate group. The iliac crest graft failed in all the specimens in which osteosynthesis was performed by a 6-hole TriLock® plate. Interfragmentary movement was minimised in the miniplate group. All three osteosynthesis systems provided sufficient stability for reconstruction when mechanically loaded up to 100N. The miniplate allowed less movement in the gap and gave better stability than the two TriLock® plate systems. The superiority of the miniplate was significant when compared with the 4-hole TriLock® plate. The transplant failed mainly in the 6-hole TriLock® group, which suggests that the iliac crest graft works better with the miniplate as a more malleable osteosynthesis system. [ABSTRACT FROM AUTHOR]

Abstract: In our previous studies, prototyped individual bone-grafting trays have been used to restore discontinuous mandibular defects. However, the attempts have shown that the trays have shielded the graft from stress, which caused considerable resorption of bone. To eliminate the shielding, we designed a flexible tray. Finite element analysis was used to compare the distribution of strain on the bone grafts that were placed in flexible and conventional trays. The analogue computation suggested that most of the strain on the graft in the flexible tray resulted in a beneficial mechanical environment, while in the conventional tray more than half of graft was in the lowest class of strain (disuse – <50μstrains). Animal experiments were conducted on hybrid dogs, and the prototype flexible tray was used to carry particles of autologous cancellous iliac bone to reconstruct a 40mm defect in the mandibular body. Sequential radionuclide bone imaging was used to monitor the bone metabolism. Animals were killed at 4, 12 and 24 weeks, and specimens processed for quantitative histological examination. The data from the flexible trays were compared with those from the conventional trays, as in our previous study. The results showed that bone metabolism was more active in the flexible tray than in the conventional tray during the early stages. There was increased bony adaptation in the flexible tray. These results indicate that the flexible tray can efficiently eliminate the shielding from stress, and allow more occlusive force to be conducted on to the bone graft, which results in better remodelling of the graft. [Copyright &y& Elsevier]

Abstract: Our aim was to use the deep circumflex iliac artery (DCIA) flap together with a costochondral graft as a safe and reliable bone flap for routine reconstruction of the mandibular body and the temporomandibular joint (TMJ). Five patients with benign tumours of the mandible had segmental mandibulectomy including the condyle, and this was reconstructed in one stage using the DCIA combined with a constochondral graft. The rib was inserted into the iliac crest as a whole transplant, and fixed to the proximal stump of the mandible with a prebent reconstruction plate according to a computer-aided design. The grafts healed uneventfully, and dental implants were inserted in 4 cases. During the 2-year follow-up these patients had good mandibular function, including mouth opening, force of bite, and occlusion. The radiographs showed good bony consolidation between the graft and the stump of the mandible and function of the TMJ. A DCIA flap combined with a costochondral graft is a safe and reliable way to provide not only a large bulk of bone to suit the mandible, but also good function of the TMJ in the absence of radiotherapy. [Copyright &y& Elsevier]

Fibular free flaps are routinely used to reconstruct segmental mandibular defects after resection. While ossification of the vascular pedicle is uncommon but well reported, to our knowledge, heterotopic ossification remote from the pedicle has not previously been described. We report a case in which this occurred. It serves as a reminder that bony, hard lumps in the neck can present years after reconstruction with a fibular flap. [ABSTRACT FROM AUTHOR]