Sandwich osteotomy for vertical and transversal augmentation of the posterior mandible.

The aim of this study is to describe the treatment outcome after alveolar ridge augmentation in the atrophic posterior mandible by segmental sandwich osteotomy combined with an interpositional autograft prior to placement of endosseous implants. Thirteen consecutive patients (five males, mean age 48 years, and eight females, mean age 61 years) were included in this study. The postoperative course was uneventful in six patients. Sensory disturbances in the mental nerve were found in five patients, all of them with hypoaesthesia. None of these patients complained of permanent sensory disturbances. Vertical gain ranged from 2.0 to 7.8mm (mean value 4.61mm). Horizontal gain ranged from 2.0 to 6.3 (mean value 3.42mm). A total of 41 implants were placed in 22 surgical sites, 12 weeks after bone reconstruction. In conclusion, segmental mandibular sandwich osteotomy is recommended to meet the dimensional requirements of preimplant bone augmentation in atrophic posterior mandible.

Prefabrication of vascularized bioartificial bone grafts in vivo for segmental mandibular reconstruction: experimental pilot study in sheep and first clinical application.

The key elements for bioartificial bone formation in 3D matrices are large numbers of osteogenic cells and supplies of oxygen and nutrition. Vascularization becomes more important with the increasing size and complexity of seeded scaffolds required for clinical application in reconstructive craniomaxillofacial surgery. Prefabrication of vascularized bioartificial bone grafts in vivo might be an alternative to in vitro tissue engineering techniques. Two cylindrical beta-TCP-scaffolds (25 mm long) were intraoperatively filled with autogenous bone marrow from the iliac crest for cell loading and implanted into the latissimus dorsi muscle in 12 sheep. To determine the effect of axial perfusion, one scaffold in each sheep was surgically supplied with a central vascular bundle. Sheep were killed 3 months after surgery. Histomorphometric analysis showed autogenous bone marrow from the iliac crest was an effective source of osteogenic cells and growth factors, inducing considerable ectopic bone growth in all implanted scaffolds. Bone growth, ceramic resorption and angiogenesis increased significantly with axial perfusion. The results encourage the application of prefabricated bioartificial bone for segmental mandibular reconstruction in man. In clinical practice, vascularized bioartificial bone grafts could change the principles of bone transplantation with minimal donor site morbidity and no shape or volume limitations.

Comparison of computed tomography and microradiography for graft evaluation after reconstruction of critical size bone defects using beta-tricalcium phosphate.

INTRODUCTION: The aim of the study was to evaluate the accuracy of computed tomography (CT) for in vivo follow up after mandibular reconstruction. MATERIAL AND METHODS: Unilateral mandibular defects were surgically created in ten sheep and either reconstructed using blood soaked beta-tricalcium phosphate (beta-TCP) cylinders (group A, n=5) or blood soaked beta-TCP cylinders that were additionally loaded with autologous bone marrow (group B, n=5). The two graft designs resulted in different stages of graft ossification representative of different stages of healing. CT datasets were fused with microradiographs and measurements of ceramic area based on both methods were compared. RESULTS: Two animals (groups A (n=1) and B (n=1)) presented infection and graft dislocation that was visible on CT and were excluded from statistical evaluation. Group A grafts underwent moderate degradation (53.55%+/-9.7) and incomplete bony incorporation representing an intermediate state of healing while ceramic grafts within group B developed a high grade of osseointegration and degradation (94.2%+/-3.3) consistent with progressive healing. Statistical comparison of measurements based on both methods revealed a significant bias (p<0.05) and a non-significant variance for group A and a significant variance (p<0.05) and non-significant bias for group B. CONCLUSION: Our results indicate that conventional CT is not suitable to objectively evaluate ossification and degradation of a beta-TCP graft in vivo and further attempts to improve clinical visualization of beta-TCP need to be undertaken.

Comparison of different harvesting methods from the flat and long bones of rats.

Different harvesting methods have been developed for bony augmentation before implantation. The aim of the present study was to assess the viability of endochondral (femoral) and membranous (mandibular) bone cells harvested by different methods under standard conditions in an animal model, and to investigate the surface of the bone in the harvested area. Samples of mandibular and femoral bone were harvested using a drilling burr, a piezoelectrical device, or a Safescraper(®). Blocks of bone that had been harvested with cutting forceps were used as controls. The size of the samples was measured and they were examined by conventional microscopy and immunohistochemical analysis; osteoblast-like cells were also cultured. The surface of the harvested area was analysed with scanning and conventional microscopy. There was no significant difference between mandibular and femoral bone in the size of particles harvested, but bone chips were significantly smaller when a drilling device had been used in both harvesting areas. Viability of cells in these smaller particles was significantly less than among cells harvested with a piezoelectrical device or Safescraper(®). Scanning microscopy showed a smooth bony surface where a drilling burr or piezoelectrical device had been used, whereas small disruptions were observed after the Safescraper(®) had been used. Harvesting of particulate bone is feasible using a drilling burr, piezoelectrical device, or Safescraper(®) from mandibular and femoral bone. The piezoelectrical device and the Safescraper(®) gave comparable results concerning the viability of osteoblast-like cells, and so are preferred to a drilling burr.

Comparison of two beta-tricalcium phosphate composite grafts used for reconstruction of mandibular critical size bone defects.

OBJECTIVE: The aim was to compare osseointegration of blood perfused beta-tricalcium phosphate cylinders (beta-TCPB) with similar composites that were additionally loaded with cancellous bone and bone marrow (beta-TCPB/BM/CB) for mandibular reconstruction. METHODS: Twelve German Black-Headed sheep with an average weight of 72.5 +/- 10 kg underwent segmental resection of the right hemi-mandible. The animals that were assigned to group A (n = 6) were reconstructed using beta-TCPB while the sheep that were assigned to group B received beta-TCPB/BM/CB grafts. Tissue quality was histologically assessed and bone-, scaffold-, cartilage- and fibrous-tissue area were estimated using semiautomated histomorphometrical software. RESULTS: Composite grafts that were loaded with bone marrow and cancellous bone (beta-TCPB/BM/CB) exhibited significant (p<0.01) higher amounts of bone formation than beta-TCPB. The patients that were assigned to group B achieved defect union and a high grade of bone maturation. Residual ceramic remnants were rare and disconnected. Bone maturity within group A was inferior and none of the specimens showed defect union. The defect centre was still occupied by a ceramic core. CLINICAL SIGNIFICANCE: Bone and bone marrow augmented beta-tricalcium phosphate composites may qualify as a promising alternative to autograft bone for mandibular reconstruction in human and veterinary medicine.

Computer-assisted therapy in orbital and mid-facial reconstructions.

BACKGROUND: Management of orbital and mid-facial fractures requires a thorough ophthalmic evaluation and precise imaging. A principle goal of therapy is to anatomically reduce fracture segments and to restore a normal orbital volume as soon as possible. Diagnostic advances such as new surgical and imaging techniques have dramatically improved both the functional and aesthetic outcome of reconstructions. METHODS: Orbital reconstruction is performed using computer-assisted navigation. This technique makes preoperative simulation by mirroring the unaffected side onto the affected side. RESULTS: Results from computer-assisted navigation application to both primary and secondary orbital and mid-facial reconstruction are shown. CONCLUSION: Navigation technique it offers significant advantages in both primary and secondary reconstructions. Navigation facilitates reconstruction in unilateral defects through mirroring techniques, and in bilateral defects by importing virtual models from standard CT datasets improving the software tool to fulfil the need for maxillofacial surgery reconstruction.

Cone beam CT imaging of airgun injuries to the craniomaxillofacial region.

In airgun injuries, the removal of the projectile is often recommended. The material properties of airgun projectiles make it difficult to determine their precise anatomical location using conventional radiological techniques. Conventional X-rays give only a two-dimensional representation of projectiles and do not allow a foreign object to be located precisely. Multi-slice computed tomography (CT) has become a standard tool in diagnosis. Metal objects can cause artefacts in CT scans and make it difficult to identify adjacent anatomical structures. By contrast, cone-beam CT (CBCT) provides three-dimensional images largely free from metal artefacts. The authors present three cases of airgun injuries and discuss the diagnostic and treatment approaches used. CBCT has proved to be a useful diagnostic tool in planning the treatment of craniofacial airgun injuries. It is superior to CT in detecting hard-tissue structural damage in the immediate vicinity of high-density metal projectiles.

Dose inhomogeneities on surfaces of different dental implants during irradiation with high-energy photons.

OBJECTIVES: The aim of this study was to determine the radiation doses in mucosa and bone close to the surface of different dental implant materials. METHODS: Radiation dose was measured at the interface of bone or soft tissue and various implant materials for 6 MV photons generated by a medical linear accelerator using a phantom and ultrathin thermoluminescent dosemeters. RESULTS: Increasing thickness of implant materials resulted in a dose decrease in bone immediately behind the implants. Directly in front of titanium implants, dose increases of 18.2% and 30.4% were found in bone and soft tissue, respectively, independent of implant thickness and surface structure (polished/plasma coated). Even a titanium coating with 70 microm hydroxyapatite did not affect the scattering dose. In contrast, for aluminium oxide ceramics, a scatter-induced notable dose increase could not be assessed. CONCLUSIONS: During irradiation with high-energy photons, an implant-induced dose enhancement could be reduced in bone using the technique of multiple fields and in soft tissue using ceramic abutments.

Inferior alveolar nerve transposition--an in vitro comparison between piezosurgery and conventional bur use.

An in vitro comparison between a new ultrasound-based piezoelectric device and a conventional bur was performed for lateralization or transposition of the inferior alveolar nerve to evaluate the effects on soft and hard tissue. Transposition of the inferior alveolar nerve was performed in the cadaver mandibles of 10 sheep: the left nerve was uncovered with a saline-cooled diamond-coated spherical bur (2000 rpm), and the right nerve was uncovered with the piezoelectric device mounted with a spherical diamond tip. The surface, the zone of bone defect, and the nerve were examined by light microscopy and laser microscopy. Bone treated with the rotary bur showed significantly smoother surfaces and shallower defect zones (50 microm) in comparison with the piezoelectric device (150 microm). Lesions of the epineurium and an increased amount of bone particles were found in the lesions prepared with the piezoelectric device. In vitro preparation with the piezoelectric device was more invasive to the bone than was a conventional diamond bur. Touching the inferior alveolar nerve resulted in roughening of the epineurium without affecting deeper structures. The degree of injury was lower than when using the conventional rotary bur.