Int. J. Oral Maxillofac. Surg. 2005; 34 (Supplement 1): $ 1 - $ 1 8 1
MANDIBULAR AMELOBLASTOMA - EXCISION AND RECONSTRUCTION
N. Papadogeorgakis, E. Parara, S. Kyriakou, C. Perisanides, K. Alexandridis. University of Athens, Oral and Maxillofacial surgery
Dept., Athens, Greece To present cases with extensive ameloblastomas of the mandible requiring immediate reconstruction Patients with mandibular ameloblastomas diagnosed histopathologically were treated in our department with wide local excision and immediate reconstruction with iliac crest bone graft and reconstruction plates. All patients recovered well. The facial nerve was not affected in any patient treated extra orally. One patient presented wound dehiscence, with saliva expression, which healed after a few days. Ameloblastomas are benign locally aggessive odontogenic tumours occuring more commonly in the mandible. Such lesions can often be very extensive and difficult to manage, concerning radical excision. Immediate reconstruction is of great importance in such cases as it minimises the risk of recurrence, provided adequate resection has preceded.
6FE-ANALYSIS - •OF MECHANICAL - • STRESS IN RECONSTRUCTION PLATES FOR BRIDGING LATERAL MANDIBULAR DEFECTS
E Maurer, W.D. Knoll, J. Schubert. Department of Oral and Plastic Maxillofacial Surgery, Martin-Luther University Halle-Wittenberg, Germany The aim of the present study was to evaluate the mechnical stress by means of the finite element method (FEM) in reconstruction plates and the screw-plate-bone-interfaces used in bridging a mandibular angle defect. Based on the geometrical data of a human mandible, an angle defect bridged by a titanium reconstruction plate was generated and exposed to chewing force of 135 N. The reconstruction plate was tightly fixed with 2.7mm bicortical screws. Starting with conventional plate designs plate design, screw configuration and screw diameter were varied. The mechanical stress was calculated according to von Mises stress hypothesis. A maximum stress of 1363 Nmm-2 in the distal portion of the reconstruction around the drilling holes is calculated. The value is almost twofold of the ultimate tensile stress of titanium (610 Nmm-2). Also the mechanical stress in compact bone reaches a maximum value of 175 Nmm-2 which exceeds the ultimate tensile stress of the bone (85 Nmm-2) by more than twofold. Enlarging the diameter of the screws to 4 mm a reduction of the mechanical stress in the reconstruction plate and in the compact bone to 525 Nmm-2 and 47 Nmm-2 respectively was found. Investigating a quadrangular screw configuration the values even drop to 95 Nmm-2, respectively 29 Nmm-2 (4 mm) and 102 Nmm-2, respectively 42 Nmm-2 (2.7mm). Using the FEM it is possibe to idenify the weak links of an alloplastic reconstruction of the mandible. Therefore the result may add a value information in further mechanical improvement of reconstruction plates
were given microvascular free fibular graffts with excellent acceptance and early recovery with minimal donor site morbidity, microvascular free grafts are farmost the best option for mandibular reconstruction though it requires fine expertise and armamentarium, cortico-cancellous grafts with bmp are giving the equaly satisfactory results in comparision to cortico-cancellous bone grafts as a block, the choice of correct procedure depends mainly on the expertise of the surgeon, the site of disease, the aetiology and the extent of the destruction.
M. Suhr, M. Vesper, I. Springer. HBEC, Germany Donor site morbidity, infection, insufficient amount, uncontrolled bone resorption and imperfect shape are potential disadvantages of free bone grafting for the restoration of mandibular continuity. The length of mandible which can be reconstructed using a free bone graft is limited to 9cm, long-span is defined as >6cm, with graft and implant failure rates proportional to length. Sufficient soft-tissue cover and mechanical stability are prerequisites for graft survival. Mechanical stability can be adequately achieved by the use of 2.7mm thick titanium reconstruction plates and bicortical screw osteosynthesis (Martin Maxiplates®, Tuttlingen, Germany), which should be removed 3 - 6 months later in order to allow the bone to heal along biomechanical principles. Implants may then be placed. Preoperative radiation to half the tumouricidal dose for oropharyngal squamous cell carcinoma is common in several centres in Switzerland, Austria and Germany. Bone-grafting at the time of tumour surgery is not advisable in this setting. Bone-grafting is possible after a 12 month recurrence-free interval (even if further postoperative radiation to the full tumour dose of 64-70Gy has been performed). For diseases not requiring radiation (e.g. ameloblastoma, osteosarcoma) the reconstruction plates are immediately supplemented by bone-grafting in the same operation. We set out to ascertain our results with free bone-grafting. We present our results in cases where vascularised grafts were declined (n = 6). This includes manual labourers who were unhappy with the possibility of weakened lower limbs or hip joints. The overall success rate of grafting was 83%. Implant placement into grafts had a success rate of 86%. Long-span defects can be reconstructed with free bone grafts, the graft failure rate of 17% and implant failure rate of 14% are significant and need to be communicated to the patient. Longspan mandibular reconstruction using bicortical, non-vascularised grafts is possible, though not as successful as vascularised bone-grafting. Implant insertion may result in fracture, as was the case in one of our patients. Radiation to the full tumour dose is not a contraindication to free grafting. Mobility after harvesting of bicortical grafts consists of crutches on the first day and the climbing of stairs after the first week. Long-term X-ray follow-up of the iliac crest reveals residual defects which are not clinically relevant.
~-~--] MANDIBULAR RECONSTRUCTION - VARIOUS MODALITIES
R.B. Dhirawani, J.N. Khanna. Dept of maxillofacial Surgery, Jabalpur
LONG SPAN MANDIBULAR RECONSTRUCTION USING FREE BONE-GRAFTS
RESTORE AND RECONSTRUCTION OF THE MANDIBULAR DEFECTS - 170 CASES REPORT
Z.G. Cai, J. Zhang, J.G. Zhang. Dept. of oral and maxillofacial surgery,
Peking University School of Stomatology, China
Hospital & Research Centre, Jabalpur, India The purpose of this paper is to discuss the advantages of primary reconstruction, preceding secondary reconstruction with bone grafts or microvascular graft and to duscuss the advantages of microvascular grafts over conventional methods resection in cases of ameloblastoma and malignancy, in mandibular body were done and primary reconstruction with titatinium reconstruction plates using condylar process (leibinger) was done. secondary reconstruction was done using iliac crest-cortico-cancellous grafts in a few cases, in other cases concellous bone mixed with platelet rich plasma (bmp) was used. in another group of cases micro-vascular free grafts (fibular graft) were used and results were compared radiologically. Out of 18 cases 2 cases did'nt come back for follow-up for more than 2 yrs. Of these 2, one case turned up with broken implant after 221 yrs. reconstruction plate was removed and mandibular reconstruction was done with microvascular free fibular graft. 6 cases treated with cortico-cancellous iliac crest graft which was taken up with more than 20% resorption of bone material after a period of one year. 7 cases were treated with cancellous grafts mixed with prp (bmp) and all of them healed well with good quality bone. 3 cases
To study the clinical indications of 4 kinds of methods for mandibular restore and reconstruction. One hundred and seventy cases with various mandibular defects were included in this study. Etiology and classification of the mandibular defects, the restore and reconstructive methods and the influence factors were retrospective analyzed. In all of 170 cases, the ratio of male and female was 2:1, the range of age was from 14 to 82 years old with median age 45 years. Benign and malignant lesions were respectively half of all of cases, and the most of mandibular defects were a half of mandible defect and simple mandibular body defect, but the ramus defects and the mandibular block defects were very rare. The age and pathological classification of the lesions were not the key point again for the mandibular restore and reconstruction. There were different characteristics and indications in the four kinds of methods: free vascular fibular flap was the best reconstructed method for the larger defects of mandible or with soft tissues defects; autologous non-vascularized free iliac was used in block bone graft or the length of mandibular defect is under 6cm resulted by benign lesions; reconstructive titanium palate was used in recurrence malignant lesions; distraction osteogenesis was propitious to block defects of mandible.