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1. Abstract Second branchial cleft cysts are the most common type of branchial abnormalities and usually found high in the neck. Oropharyngeal presence of a branchial cleft cyst is very rare.We report a rare case of, oropharyngeal, second branchial, multilocular, cleft cyst in a nine-year-old child (8.0 x 5.0 cm in maximum diameter). The cyst was removed completely via extra / intra-oral approach and did not have tract-like structure. The anatomic location together with the histopathology results, which showed a squamous epithelium-lined cystic wall with lymphoid aggregation, were characteristic findings of a Branchial Cleft Cyst (BCC). Patient was discharged without any complication and a regular follow up, of 6 months, showed no evidence of re currency. Having reviewed the literature, it seems to be that this is the first case to be reported of a multilocular branchial cleft cyst, excised of this size, from the oropharyngeal area in a child. BCC shares a clinical presentation with other pathological entities of the neck, making diagnosis difficult at times. Health professionals should be aware of this entity because it can be easily confused with an odontogenic infection and submandibular or parotid gland pathology, especially if it develops high up in the neck.

UNLABELLED The progress in computer technology and the increased use of finite element analysis in the medical field by nonengineers and medical researchers lead us to believe that there is a need to develop a systematic approach to validate a finite element model (FEM), of a human orbit, that simulates part of the maxillofacial skeleton and to investigate the effects and the clinical significance of changing the geometry, boundary conditions, that is, muscle forces, and orthotropic material properties on the predictive outcome of an FEM of a human orbit. METHODS Forty-seven variables affecting the material properties, boundary conditions, and the geometry of an FEM of a human orbit including the globe were systematically changed, creating a number of FEMs of the orbit. The effects of the variations were quantified as differences in the principal strain magnitudes modeled by the original FEM (criterion standard), before the sensitivity analyses, and those generated by the changed FEMs. RESULTS The material properties that had the biggest impact on the predicted principal strains were the shear moduli (up to 21%) and the absence of fatty tissue (up to 75%). The boundary condition properties that had the biggest impact on the predicted principal strains were the superior rectus muscle and canthal ligaments (up to 18% and 23%, respectively). Alterations to the geometry of the orbit, such as an increase in its volume, had the greatest effect on principal strain magnitudes (up to 52%). CONCLUSIONS Changes in geometry, boundary conditions, and orthotropic material properties can induce significant changes in strain patterns. These values must therefore be chosen with care when using finite element modeling techniques. This study also highlights the importance of restoring the orbital fat and volume when reconstructing the orbital floor following a blunt injury. The possibility that the unrestored increase in the orbital volume and the resulting stresses may be a source of globe injuries, causing diplopia, cannot be excluded.

Purpose: To develop a finite element model (FEM) to study the effect of the vascular wall compliance on blood flow at the graft/recipient vessel junction. Materials and Methods: Finite element models of the end-to-end and end-to-side anastomoses were constructed. Simulations were performed with a computer using the finite element software NISA. The FEMs were then used to study the effects of changing the elasticity of the vascular wall on its predictions. Results: Deformations were relatively large; the maximum displacement for the compliant model, end-to-end anastomosis, was 55 and 88 mm for the 90-degree end-to-side anastomosis. The maximum displacement for the rigid model, end-to-end anastomosis, was 155 and 188 mm for the 90-degree end-to-side anastomosis. When the angle of inset was set at 45 degrees, there was no remarkable difference in deformation between the compliant and rigid models. Conclusions: The principal stresses were remarkably less at the graft/vessel junction in models of compliant grafts and compliant vessels than for rigid wall models. The 45-degree end-to-side anastomosis seems to be the best technique when planning microvascular anastomosis for elderly patients and/or patients with systemic disease, which reduces vascular wall elasticity.

In this report, we describe a 1-stage zygomaticomandibular composite flap for improved access to the retromaxillary space and the base of the skull. The zygoma and the mandible were not detached from the facial musculature or from its overlying tissues, maintaining an optimum bone-soft tissue relationship. The advantage of this approach was the enhanced exposure of the deep lesion, which provided a shorter and wider view to the maxilla, the retromaxillary space, and the base of the skull. Restoration of the skeletal symmetry and the three-dimensional contour of the maxilla was greatly enhanced by using preadapted plates and a stereolithographic model. To the best of our knowledge, no references were found in the literature regarding the use of the same technique for treating defects of similar nature to those described in this article. The deep circumflex iliac artery flap was used to reconstruct the midfacial defect and the base of the skull. The use of the flap provided optimum results because the defect was closed with the muscle that became epithelialized with minimal bulk.

The purpose of this study was to evaluate biomechanical loading of the temporomandibular joint when using a biodegradable laminate implant to replace the articular disc and to test the hypothesis that the use of the implant reduces stress distribution in the condyle, implant, and glenoid fossa. A finite element model of a female human mandible, including the temporomandibular joint, which had two standard endosseous implants inserted bilaterally in the premolar region, was constructed from computed tomography scan images using a commercially available finite element software. The disc, condyle, and glenoid fossa were arbitrarily divided into five regions: the anterior, posterior, medial, lateral, and central. The disc was then replaced with a poly-L/DL-lactide biodegradable laminate. The finite element model was then used to predict principal and Von Mises stresses. The use of poly-L/DL-lactide implant resulted in remarkable reduction in Von Mises stresses (approximately threefold) in the anterior, central, and medial regions of the mandibular condyle in comparison with slight to moderate stress reductions in the corresponding regions of the implant and glenoid fossa. The mandibular condyle also demonstrated the largest total displacement in all directions followed by the implant and glenoid fossa. The use of an alloplastic implant such as the bioresorbable, poly-L/DL-lactide laminate to replace the articular disc reduces loading of the mandibular condyle rather than the implant and glenoid fossa. These findings lead to support the hypothesis that the mandibular condyle more likely functions as a shock absorber than the disc. The use of bioresorbable laminate implants might prove an efficient technique to replace the articular disc and promote normal function of the temporomandibular joint.

Purpose of the study To develop a finite element model (FEM) to study the effect of the stress and strain, in microvascular anastomoses that result from the geometrical mismatch of anastomosed vessels. Material and methods FEMs of end-to-end and end-to-side anastomoses were constructed. Simulations were made using finite element software (NISA). We investigated the angle of inset in the end-to-side anastomosis and the discrepancy in the size of the opening in the vessel between the host and recipient vessels. The FEMs were used to predict principal and shear stress and strain at the position of each node. Results Two types of vascular deformation were predicted during different simulations: longitudinal distortion, and rotational distortion. Stress values ranged from 151.1 to 282.4 MPa for the maximum principal stress, from −122.9 to −432.2 MPa for the minimum principal stress, and from 122.1 to 333.1 MPa for the maximum shear stress. The highest values were recorded when there was a 50% mismatch in the diameter of the vessels at the site of the end-to-end anastomosis. Conclusion The effect of the vessel's size discrepancy on the blood flow and deformation was remarkable in the end-to-end anastomosis. End-to-side anastomosis was superior to end-to-end anastomosis. FEM is a powerful tool to study vascular deformation, as it predicts deformation and biomechanical processes at sites where physical measurements are likely to remain impossible in living humans.

Purpose The purpose of this study was to identify reasons for fracture of titanium mandibular reconstruction plates, when used to bridge lateral mandibular defects after ablative tumor surgery. Materials and Methods Sixteen titanium reconstruction plates from sheep mandibles were examined to identify reasons for the plate fractures. The broken plates and the seemingly unbroken plates were examined separately. The plates were removed from the mandibular bone and inspected by dye penetrant examination, metallography, optical microscope, scanning electron microscope, and energy dispersive X-ray spectrometer. Furthermore, axial load fatigue tests were performed in two different environments, air and physiologic salt solution, 0.9% NaCl, to compare titanium behavior in air and the human body. Results The site of crack initiation was the inner curvature of the reconstruction plate, and the cracks initiated as a result of stress concentration in the shoulder fillet of the plate. The cracks grew in a cyclic manner under masticatory loading of the mandible and the plate. The plate fracture occurred by means of fatigue. The corrosive environment did not affect the failure of the titanium plate, and the fracture was not caused by hydrogen embrittlement. The results revealed that the fatigue properties of the plates may have been impaired by the residual stresses generated in plate bending. Conclusions Adjustive bending of the plates, in the surgical operation, may thus be an important cause of fracture of the reconstruction plates, because of generated residual stresses, which affect the mean stress in fatigue loading. To make the plates function without failure the plates should match closely with the three-dimensional shape of the mandible, to avoid any bending in the operative phase. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007

The aim of this study was to investigate the condition of the temporomandibular joint (TMJ) in patients with different rheumatic diseases, and report correlations between the clinical, radiographic and magnetic resonance imaging (MRI) findings. The 67 patients were divided into four groups: 16 with rheumatoid arthritis (RA), 15 with mixed connective tissue disease (MCTD), 18 with ankylosing spondylitis (AS) and 18 with spondyloarthropathy (SPA). They were clinically examined, and panoramic tomography, lateral panoramic radiography and MRI of the TMJ were performed. MRI showed reduced articular cartilage in 25% (4/16) of RA, 0% (0/15) of MCTD, 17% (3/18) of AS and 17% (3/18) of SPA patients. Condylar changes included erosion, osteophytes and abnormal shape. Disc alterations included perforation, abnormal anterior position and decreased movement. These abnormalities were most frequent in RA patients, and least frequent in MCTD and SPA patients. Crepitation and reduced maximum opening of the mouth correlated with abnormalities of the disc and articular cartilage as shown by MRI. Severe condylar erosion in panoramic tomograms significantly correlated with MRI findings of condylar erosion (P0.01), diminished thickness of condylar cartilage, abnormal condylar shape, and abnormal shape of the temporal surface of the TMJ (Por =0.001). The presence of crepitation, limited mandibular movement and/or pain on movement of the jaw often indicated structural damage to the TMJ. Panoramic radiographs provide an alternative method to MRI but, to obtain a more detailed anatomic picture, MRI is recommended for patients with acute unexplained pain or as part of preoperative work up. A panoramic recording is not indicated when MRI is planned.

Purpose The purpose of this study was to compare our clinical findings on the use of autogenous bone grafts and bioresorbable poly-L/DL-Lactide [P(L/DL)LA 70/30] implants to repair inferior orbital wall defects. Patients and Methods Thirty-nine patients who suffered orbital blow-out fractures with ≥2 cm2 bony defect in the inferior orbital wall took part in the study. Each inferior orbital wall was reconstructed using either an autogenous bone graft or a triangle form plate of P(L/DL)LA 70/30. Computed tomography scans were taken before the operation and at 2 and 36 weeks postoperatively. To describe the distribution of complications and facilitate statistical analysis, we categorized our findings into diplopia, enophthalmos, numbness, gaze restrictions, size of bony defect after treatment, bone growth, and implant resorption. A comparative study was carried out using χ2 test and the Fisher exact test. We considered P < .05 to be statistically significant. Results The clinical outcome was excellent in 19 of the 24 (79%) cases treated with autogenous bone grafts and in 13 of the 15 (87%) cases treated with P(L/DL)LA 70/30. No statistically significant differences were found between the 2 groups in overall type or number of complications. The most frequent type of complication found in both groups was enophthalmos, with 5 cases (bone graft, 3; P(L/DL)LA plates, 2). Diplopia was the second most frequent type of complication; however, both complications caused no need for the removal of the implants in either group. Conclusion Autogenous bone grafts and P(L/DL)LA 70/30 implant plates do not present statistically significant differences in the parameters studied. Taking into account the availability and the advantages of P(L/DL)LA 70/30 implants when compared with autogenous bone grafts, our results allow us to conclude that there is no compromise regarding successful bridging of orbital floor defects using biodegradable P(L/DL)LA 70/30 osteosyntheses.

Central intraosseous adenoid cystic carcinoma (ACC) of the mandible, formerly known as cylindroma, is a rare neoplasm with only 16 cases reported in the literature. We describe the diagnosis, etiology, and treatment of a central ACC located in the mandibular premolar region. We also review the literature. This case illustrates 2 key facts regarding the diagnosis and etiology of ACC. First, central salivary gland tumors should be considered in the differential diagnosis of cystic lytic lesions in the mandible. Second, even though the origin of this type of tumor is still unknown, the presence of ectopic tissue anterior to the submandibular gland in the submandibular area indicates that this tumor might be made up of ectopic embryogenic inclusions.

Purpose The purpose of this study was to develop a 3-dimensional finite element model (FEM) of the human orbit, housing the globe, to predict orbital deformation in subjects following a blunt injury. Materials and Methods A FEM of the human orbit including the eye, fatty tissues, and extraocular muscles was constructed. Simulations were performed with a computer using the finite element software NISA (EMRC, Troy, MI). The orbit was subjected to a blunt injury of a 0.5 kg missile with 30 m/s velocity. The FEM was then used to predict principal and shear stresses/strains at each node position. Results Two types of orbital deformation were predicted during different impact simulations: a) horizontal distortion and b) rotational distortion. Stress values ranged from 112.12 to 262.3 MPa for the maximum principal stress, from −226.8 to −552.1 MPa for the minimum principal stress, and from 111.3 to 343.3 MPa for the maximum shear stress. Conclusion This is the first finite element study that demonstrates different and concurrent patterns of orbital deformation in subjects following a blunt injury. FEM is a powerful and invaluable tool to study the multifaceted phenomenon of orbital deformation.

The purpose of this study was to develop a three-dimensional finite-element model (FEM) of the human orbit, containing the globe, to predict orbital deformation in subjects following a blunt injury. This study investigated the hypothesis that such deformation could be modelled using finite-element techniques. One patient who had CT-scan examination to the maxillofacial skeleton including the orbits, as part of her treatment, was selected for this study. A FEM of one of the orbits containing the globe was constructed, based on CT-scan images. Simulations were performed with a computer using the finite-element software NISA (EMRC, Troy, USA). The orbit was subjected to a blunt injury of a 0.5 kg missile with 30 m s −1 velocity. The FEM was then used to predict principal and shear stresses or strains at each node position. Two types of orbital deformation were predicted during different impact simulations: (i) horizontal distortion and (ii) rotational distortion. Stress values ranged from 213.4 to 363.3 MPa for the maximum principal stress, from −327.8 to −653.1 MPa for the minimum principal stress, and from 212.3 to 444.3 MPa for the maximum shear stress. This is the first finite-element study, which demonstrates different and concurrent patterns of orbital deformation in a subject following a blunt injury. Finite element modelling is a powerful and invaluable tool to study the multifaceted phenomenon of orbital deformation.

The purpose of this paper was to share our clinical experience on the use of pre-adapted / fabricated plates using stereolithography for accurate repair of maxillofacial defects. We present five cases where pre-adapted / fabricated plates were either used to reconstruct defects following tumour resection or for secondary reconstructions of maxillofacial trauma. Our opinion concerning Stereolithography Models (SMs) is that they probably do not offer the surgeon relevant diagnostics information, but they are very useful in the surgical planning of any maxillofacial operation. SMs allow direct simulation of osteotomies, grafts and the measurement of bone movements. Prefabricated/ adapted plates combined with SMs reduce intra-operative time and morbidity, increase accuracy of the surgical reconstruction and minimize complications and surgeons’ stress. However, these technologies are expensive. Therefore, considering their cost, we see indications in secondary corrections of the maxillofacial trauma and tumour reconstruction.

The purpose of the study was to compare the preemptive analgesic effect of celecoxib, a cyclooxygenase 2 inhibitor, with a traditional nonsteroidal anti-inflammatory drug, ibuprofen, in patients after minor oral surgery procedures.This randomized, double-blind, placebo-controlled, prospective clinical trial was conducted over an 8-month period. Participants were randomly allocated to receive a standard oral dose of 200 mg celecoxib, 400 mg ibuprofen, or a placebo containing lactose, preemptively 1 h before surgery. Using a patient diary, patients recorded pain intensity, pain relief, and global evaluations throughout the 24-hour period after dosing. The overall analgesic effect, onset of action, peak effect, and duration of effect were evaluated, with the primary end point being total pain relief over 8 hours. The safety profile was assessed on the basis of physical findings and spontaneous reports of adverse experiences.The results showed that compared with ibuprofen, celecoxib had superior analgesic effects on all measures of analgesic efficacy, including overall analgesic effect (total pain relief over 8 hours: 18.1 vs 12.2, P0.001), time to onset of effect (30 vs 60 minutes, P = 0.003), peak pain relief (score, 2.7 vs 2.4, P0.05), and duration of effect (24 vs 7.0 hours, P0.001). The safety profile was similar across all treatment groups.This is the first reported study that demonstrates the superior analgesic effect of celecoxib, for the release of acute postoperative pain following surgery, when compared with the traditional nonsteroidal anti-inflammatory drug, ibuprofen. There was no safety compromise when celecoxib was used in lower doses to provide analgesia for patients who need minor surgery.

PURPOSE The purpose of this study was to develop a finite element model (FEM) of a human orbit, of 1 patient, who had an orbital blow-out fracture, to study the effect of using a "stiffness-graded" (SG) biodegradable implant on the biomechanics of bone-fracture repair. METHODS An FEM of the orbit and the globe, of 1 patient who had an orbital blow-out fracture and was treated with biodegradable poly-L/DL-lactide [P(L/DL)LA 70/30], was generated based on computed tomography scan images. Simulations were performed with a computer using a commercially available finite element software. The FEM was then used to study the effect of using an SG biodegradable implant on the stress distribution in the fractured bone. This was compared with the stress distribution at the fracture interface and at the bone-implant interface, when using P(L/DL)LA implant with a uniform stiffness. RESULTS The use of SG implants caused less stress shielding to the fractured bone. At 50% of the bone healing stage, stress at the fracture interface was compressive in nature, that is, 0.2 MPa for the uniform implant, whereas SG implants resulted in tensile stress of 0.2 MPa. The result was that SG implants allowed the 50% healed bone to participate in loadings. Stiffness-graded implants are more flexible and hence permit more bending of the fractured bone. This results in higher compressive stresses, induced at the fractured faces, to accelerate bone healing. However, away from the fracture interface, the reduced stiffness and elastic modulus of the implant cause the neutral axis of the composite structure to be lowered into the bone, resulting in the higher tensile stress in the bone layer underneath the implant. CONCLUSIONS The use of SG implants induced significant changes in the stress patterns at the fracture interface and at the bone-implant interface. Stiffness-graded biodegradable implants offered less stress shielding to the bone, providing higher compressive stress at the fractured surface, to induce accelerated bone healing, as well as higher tensile stress in the intact portion of the bone. It seems that this is the first reported study, in the literature, on the use of SG biodegradable implants to repair and promote bone healing at the fracture site of the inferior orbital wall bone defect.

PURPOSE OF THE STUDY The purpose of this study was to develop a finite element model (FEM) of a human orbit, who experienced a pure orbital blowout fracture, to study the effect of the geometrical mismatch-induced stresses on the orbital floor/graft interface and how to improve the graft design when restoring the orbital floor. MATERIALS AND METHODS A FEM of the orbit and the globe of 1 patient who experienced pure orbital blowout fracture and treated with autogenous bone graft was generated based on computed tomographic scans. Simulations were performed with a computer using a commercially available finite element software NISA (EMRC, Troy, MI). The FEM was then used to study the effects of changing the geometry, position, material properties, and method of fixation of the autogenous bone graft on its predictions. RESULTS The factors that had the biggest impact on the predicted principal strain magnitudes were absence of cancellous bone (up to 60%) and bony support of the graft (up to 50%). Applying rigid fixation reduced stresses by 30% posteriorly and by almost 100% anteriorly. Alterations to the geometry of the bone graft, such as an increase in its thickness, increased principal strain magnitudes (up to 42%). CONCLUSIONS Applying rigid fixation reduced principal stresses significantly. The role of rigid fixation becomes more prominent when there is no bony support posteriorly and/or medially. This study also highlights the importance of preserving cancellous bone, when harvesting and preparing the autogenous bone graft to reconstruct the orbital floor. The possibility that absence of cancellous bone and the resulting stresses may be a source of graft resorption and/or failure cannot be excluded.

The purpose was to study the biomechanics of bone fracture repair, of the orbital floor, using osteosynthetic bioresorbable implant and how to improve the implant design.A finite element model of the orbit and the globe of 1 patient who experienced orbital blowout fracture and treated with bioresorbable poly-L/DL-lactide (P[L/DL]LA 70:30) implant (PolyMax; Synthes, Oberdorf, Switzerland) was generated based on computed tomographic scans. Simulations were performed with a computer using a commercially available finite element software. The effects of changing the geometry, bony support, and method of fixation of the implant on the finite element model predictions were investigated.The factor that had the biggest impact on the predicted principal strain magnitudes was absence of bony support of the implant (up to 65%). Applying elastic fixation reduced stresses (up to 40%) posteriorly. The principal stresses inside the bone and the implant were evenly distributed when elastic fixation was applied to the implant. Applying rigid fixation increased stresses (up to 50% and 80% anteriorly and posteriorly, respectively). The resulting stress values indicated a likely rapid failure of the osteosynthetic implant when rigid fixation was applied.Applying rigid fixation induced a significant increase in stress patterns. Principal stresses were reduced remarkably when elastic fixation was applied to the implant. The role of fixation becomes more prominent when there is no bony support posteriorly and/or medially. It is recommended to avoid rigid fixation and to apply elastic fixation when using bioresorbable P(L/DL)LA 70:30 implants to reconstruct inferior orbital wall bony defects.

The purpose of this study was to report our clinical experience, in a pilot study, of the use of the selective cyclooxygenase-2 (COX-2) inhibitor celecoxib, pre-emptively, to control pain in patients after surgical extraction of a mandibular molar tooth.This randomised, double-blind, placebo-controlled, prospective clinical trial was conducted over an eight-month period. Participants were randomly allocated to receive a standard oral dose of 200 mg celecoxib, 400 mg ibuprofen, or a placebo containing lactose, pre-emptively, one hour before surgery. Each patient was prescribed amoxycillin 500 mg three times per day postoperatively for seven days. The participants were given standardised participant information sheets, and written informed consent was subsequently obtained from the participants prior to the commencement of the study.The results showed that 13% of the patients who had ibuprofen had severe pain two to three days postoperatively. This was diagnosed as alveolar osteitis, which is in line with the universally accepted outcome for the surgical extraction of mandibular molar teeth. Statistical analysis (Chi-square test) confirmed that the ibuprufen group had a significantly higher alveolar osteitis incidence than the celecoxib group (por = 0.05) and the placebo group (por = 0.05).This is the first reported study to demonstrate that the use of celecoxib resulted in a significant decrease in the occurrence of alveolar osteitis.

The purpose of the study was to develop a finite element model of the human mandible and to compare the functional deformation predicted by the model with that detected clinically.Three patterns of mandibular deformation (medial convergence, corporal rotation and dorso-ventral shear) were studied clinically in 12 subjects using custom-fabricated displacement transducers mounted on endosseous implants in the premolar region. The mandibular arches of 12 patients with dental implants were modeled using finite element techniques based on computerized tomographic (CT) scan images of the jaw.The finite element model was found to closely replicate the patterns of observed mandibular deformation. Differences between the predicted and measured deformation values were expressed as a percentage of the measured value and ranged between 0.0% and 22.2%. Medial convergence ranged between 14.4 and 58.4 pm. Dorso-ventral shear and corporal rotation ranged between 0.4 and 2.7 degrees.Using the finite element model described in this study, which represents the living human mandible, and clinical testing, there was close agreement between the predicted and measured deformation values. This study provided a high level of confidence in the finite element model and its ability to provide better insight into understanding the complex phenomena of functional mandibular deformation.

PURPOSE OF THE STUDY: The purpose of the study was to evaluate the effect of adding platelet rich plasma (PRP) to a particulate autogenous bone graft in the healing of bony defects following ablative surgery to resect malignancies of the mandible. MATERIAL AND METHODS: Ten patients, who underwent curative surgical therapy for a malignant tumour and who needed reconstruction of the body of the mandible were selected for this study. The patients were randomly divided into two groups of five patients. In the first group, the defect was reconstructed using an autogenous free bone graft taken from the anterior iliac crest. The five patients in the second group underwent the same treatment, except that the bone graft was mixed with platelet rich plasma (PRP). Panoramic radiographs were taken immediately, at 1 month, 3 months and at 9 months intervals, after reconstruction. Radiographic evaluation took place in a standardized way by two independent examiners. RESULTS: The clinical outcome of the surgical reconstruction was satisfactory. The initial bone healing in all patients was uneventful. The postoperative successive radiographs showed adequate consolidation of the bone in all cases. Bone healing, as manifested by the obliteration of the bone gaps at the osteotomy sites, was particularly present in the PRP group at 3 months period. This was found to be statistically significant (Chi-square test, P

The purpose of this study was to propose a systematic approach to validate a finite element model (FEM) of the human mandible and to investigate the effects of changing the geometry and orthotropic material properties on the FEM predictions. Thirty-eight variables affecting the material properties, boundary conditions, and the geometry of a FEM of a human mandible, including two dental implants, were systematically changed, creating a number of FEMs of the mandible. The effects of the variations were quantified as differences in the principal strain magnitudes modeled by the original FEM (gold standard), prior to the sensitivity analyses, and those generated by the changed FEMs. The material properties that had the biggest impact on the predicted cortical principal strain were the shear moduli (up to 31% in difference from the unchanged state), and the absence of cancellous bone (up to 34%). Alterations to the geometry of the mandibular cross section, such as an increase in corpus dimensions, had the greatest effect on principal strain magnitudes (up to 16%). Changes in the cortical thickness in relation to the width of the corpus section modified strain more than alterations to the corpus depth (14% and 5%, respectively). The relatively small difference (up to 13.5%) between the predicted and measured interimplant distances indicates the accuracy of the FEM. Changes in geometry and orthotropic material properties could induce significant changes in strain patterns. These values must therefore be chosen with care when using finite element techniques for predicting stresses, strains, and displacements.

The purpose of this study was to mathematically validate and clinically verify a finite element model (FEM) of the human mandible and to compare the functional deformation predicted by the model with that detected clinically. Mandibular surface strain, using 11 single strain gauges, and medial convergence (MC), using a custom-fabricated linear variable differential transformer (LVDT), were recorded in a dried human jaw. The mandible was treated with two endosseous implants, placed bilaterally in the premolar area, and mounted in a rig that simulated natural function of the jaw. Measurements were made in real time using a multichannel analogue/digital converter and a personal computer for data storage and analysis. A FEM of the mandible was constructed, using commercially available finite element software, based on CT scan images of the jaw. MC was predicted as the linear change in the orientation of the two implants in the horizontal plane. Predicted and measured values of MC ranged between 60 and 109 μm. The differences between the measured and predicted strain magnitudes were expressed as absolute percentages of the measured values and ranged between 3 and 18%. The limits of agreement between the predicted and measured strain values, as suggested by Bland and Altman (Lancet 1986; 1:307–310), were small enough for the predictions from the FEM to be considered clinically acceptable. The good agreement between the predicted and measured strain values indicates the accuracy of the present FEM. Finite element analysis is a powerful technique that provides a better insight into understanding the complex phenomena of mandibular functional deformation. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2007

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Purpose The purpose of this study was to share our clinical experience on the use of bioresorbable poly- l / dl -lactide implants (P[L/DL]LA) 70/30 (PolyMax; Synthes, Oberdorf, Switzerland) to repair, large (≥2 cm 2 ), inferior orbital wall defects and to evaluate whether P(L/DL)LA 70/30 implants adequately support the orbital soft tissue contents. Patients and Methods Thirteen patients who suffered orbital blowout fractures, with ≥2 cm 2 bony defects in the inferior orbital wall, took part in the study. The inferior orbital wall was explored via subconjunctival approach. After repositioning of orbital content, each inferior orbital wall was reconstructed using a round plate of P(L/DL)LA 70/30. Computed tomography and magnetic resonance imaging coronal sections were undertaken before the operation and 2 and 36 weeks postoperatively. Results The magnetic resonance imaging studies showed no abnormal tissue foreign body reactions in the orbital region. The material showed adequate strength to stabilize bone segments during the critical period of bone healing. The bone healing seems to take place along the bone fragments. The clinical outcome was excellent in 11 of the 13 cases (85%). At the end of the study, only one patient had mild enophthalmos. Conclusions Bioresorbable P(L/DL)LA 70/30 implants are safe and reliable for the repair of large defects (≥2 cm 2 ) in the inferior orbital wall. It seems that this is the first reported biodegradable material, in the literature, to promote bone healing along the bone fragments of the inferior orbital wall.

To develop a finite element model (FEM) to study the effect of the stress and strain, in microvascular anastomoses that result from the geometrical mismatch of anastomosed vessels.FEMs of end-to-end and end-to-side anastomoses were constructed. Simulations were made using finite element software (NISA). We investigated the angle of inset in the end-to-side anastomosis and the discrepancy in the size of the opening in the vessel between the host and recipient vessels. The FEMs were used to predict principal and shear stress and strain at the position of each node.Two types of vascular deformation were predicted during different simulations: longitudinal distortion, and rotational distortion. Stress values ranged from 151.1 to 282.4MPa for the maximum principal stress, from -122.9 to -432.2MPa for the minimum principal stress, and from 122.1 to 333.1MPa for the maximum shear stress. The highest values were recorded when there was a 50% mismatch in the diameter of the vessels at the site of the end-to-end anastomosis.The effect of the vessel's size discrepancy on the blood flow and deformation was remarkable in the end-to-end anastomosis. End-to-side anastomosis was superior to end-to-end anastomosis. FEM is a powerful tool to study vascular deformation, as it predicts deformation and biomechanical processes at sites where physical measurements are likely to remain impossible in living humans.

Purpose The purpose of this study was to measure corporal approximation, dorsoventral shear, and corporal rotation in edentulous subjects treated with dental implants, during normal mandibular movements. Materials and Methods Three patterns of jaw deformation (corporal approximation [CA], corporal rotation [CR], and dorsoventral [DV] shear) were measured using custom-fabricated displacement transducers in 12 edentulous subjects who had been treated with dental implants. Measurements were made in real time using a multichannel analogue/digital converter and a personal computer for data storage and analysis. Corporal approximation was measured as the linear change in the orientation of the 2 implants in the horizontal plane. Corporal rotation was recorded as a relative rotation of the right and left mandibular bodies projected into the frontal plane, and dorsoventral shear as the relative rotation of the 2 implants projected onto the median sagittal plane. Results All 3 patterns of mandibular deformation occurred concurrently and immediately on commencement of jaw movement. Different jaw movements produced different patterns of mandibular deformation. The highest values of jaw deformation were recorded during protrusion. CA ranged between 11.0 μm and 57.8 μm. Corporal rotation and DV shear ranged between 0.4° and 2.8°. Conclusion This clinical study shows and measures 3 different and concurrent patterns of jaw deformation, during normal mandibular movements, using custom fabricated displacement transducers. The transducers may have a potential for routine clinical applications.

To the Editor: We wish to report our clinical experience with the use of cyclooxygenase-2 (COX-2) inhibitors to control pain in patients treated with free vascular flaps after undergoing ablative s...