Biomechanical feasibility of non-locking system in patient-specific mandibular reconstruction using fibular free flaps.

Mandibular reconstruction with free fibular flaps is frequently used to restore segmental defects. The osteosythesis, including locking and non-locking plate/screw systems, is essential to the mandibular reconstruction. Compared with the non-locking system that requires good adaption between plate and bone, the locking system appears to present a better performance by locking the plate to fixation screws. However, it also brings about limitations on screw options, a higher risk of screw failure, and difficulties in screw placement. Furthermore, its superiority is undermined by the advancing of patient-specific implant design and additive manufacturing. A customized plate can be designed and fabricated to accurately match the mandibular contour for patient-specific mandibular reconstruction. Consequently, the non-locking system seems more practicable with such personalized plates, and its biomechanical feasibility ought to be estimated. Finite element analyses of mandibular reconstruction assemblies were conducted for four most common segmental mandibular reconstructions regarding locking and non-locking systems under incisal biting and right molars clenching, during which the influencing factor of muscles' capacity was introduced to simulate the practical loadings after mandibular resection and reconstruction surgeries. Much higher, somewhat lower, and similar maximum von Mises stresses are separately manifested by the patient-specific mandibular reconstruction plate (PSMRP), fixation screws, and reconstructed mandible with the non-locking system than those with the locking system. Equivalent maximum displacements are identified between PSMRPs, fixation screws, and reconstructed mandibles with the non-locking and locking system in all four reconstruction types during two masticatory tasks. Parallel maximum and minimum principal strain distributions are shared by the reconstructed mandibles with the non-locking and locking system in four mandibular reconstructions during both occlusions. Conclusively, it is feasible to use the non-locking system in case of patient-specific mandibular reconstruction with fibular free flaps based on the adequate safety, comparable stability, and analogous mechanobiology it presents compared with the locking system in a more manufacturable and economical way.

Biomechanical validation of structural optimized patient-specific mandibular reconstruction plate orienting additive manufacturing.

BACKGROUND AND OBJECTIVE: Owing to the unexpected in vivo fracture failure of the original design, structural optimized patient-specific mandibular reconstruction plates (PSMRPs) were created to boost the biomechanical performance of bridging segmental bony defect in the mandibular reconstruction after tumor resection. This work aimed to validate the biomechanical benefit of the structural optimized PSMRPs relative to the original design and compare the biomechanical performance between PSMRP1 with generic contour customization and PSMRP2 with a tangent arc upper margin in mandibular angle region. METHODS: Finite Element Analysis (FEA) was used to evaluate the biomechanical behavior of mandibular reconstruction assemblies (MRAs) concerning these two structural optimized PSMRPs by simulating momentary left group clenching and incisal clenching tasks. Bonded contact was set between mandibular bone and fixation screws and between PSMRP and fixation screws in the MRA, while the frictionless connection was allocated between mandibular bone and PSMRP. The loads were applied on four principal muscles, including masseter, temporalis, lateral and medial pterygoid, whose magnitudes along the three orthogonal directions. The mandibular condyles were retrained in all three directions, and either the left molars or incisors area were restrained from moving vertically. RESULTS: The peak von Mises stresses of structural optimized PSMRPs (264 MPa, 296 MPa) were way lower than that of the initial PSMRP design (393 MPa), with 33 and 25% reduction during left group clenching. The peak magnitude of von Mises stress, minimum principal stress, and maximum principal strain of PSMRP1 (264 MPa, 254 MPa; -297 MPa, -285 MPa; 0.0020, 0.0020) was lower than that of PSMRP2 (296 MPa, 286 MPa; -319 MPa, -306 MPa; 0.0022, 0.0020), while the peak maximum principal stress of PSMRP1 (275 MPa, 257 MPa) was higher than that of PSMRP2 (254 MPa, 235 MPa) during both left group clenching and incisal clenching tasks. CONCLUSIONS: The structural optimized PSMRPs reveal their biomechanical advantage compared with the original design. The PSMRP1 presents better biomechanical performance to the patient-specific mandibular reconstruction than PSMRP2 as a result of its superior safety, preferable flexibility, and comparable stability. The PSMRP2 provides biomechanical benefit in reducing the maximum tension than PSMRP1, indicated by lower peak maximum principal stress, through tangent arc upper margin in mandibular angle region.

Preclinical study of additive manufactured plates with shortened lengths for complete mandible reconstruction: Design, biomechanics simulation, and fixation stability assessment.

BACKGROUND: A combination of short titanium plates fabricated using additive manufacturing (AM) provides multiple advantages for complete mandible reconstruction, such as the minimisation of inherent implant deformation formed during AM and the resulting clinical impact, as well as greater flexibility for surgical operation. However, the biomechanical feasibility of this strategy is still unclear, and therefore needs to be explored. METHOD: Three different combinations of short mandible reconstruction plates (MRPs) were customised considering implant deformation during the AM process. The resulting biomechanical performance was analysed by finite element analysis (FEA) and compared to a conventional single long MRP. RESULTS: The combination of a long plate and a short plate (Design 3 [LL61 mm/RL166 mm]) shows superior biomechanical properties to the conventional single long plate (Design 1 [TL246 mm]) and reveals the most reliable fixation stability among the three designs with short plates. Compared to conventional Design 1, Design 3 provides higher plate safety (maximum tensile stress on plates reduced by 6.3%), lower system fixation instability (relative total displacement reduced by 41.4%), and good bone segment stability (bone segment dislocation below 42.1 µm) under masticatory activities. CONCLUSIONS: Preclinical evidence supports the biomechanical feasibility of using short MRPs for complete mandible reconstruction. Furthermore, the results could also provide valuable information when treating other large-sized bone defects using short customised implants, expanding the potential of AM for use in implant applications.

Biomechanical comparison of locking and non-locking patient-specific mandibular reconstruction plate using finite element analysis.

Patient-specific mandibular reconstruction plate (PSMRP), as one of the patient-specific implants (PSIs), offers a host of benefits to mandibular reconstruction. Due to the limitation of fabricating screw hole threads in the PSMRP, 3D printed PSMRP is applied to the non-locking system directly in the mandibular reconstruction with bone graft regardless of the locking system. Since the conventional manual-bending reconstruction plate (CMBRP) provides better fixation in the locking system, it needs to be validated whether the locking PSMRP performs better than the non-locking PSMRP in the patient-specific mandibular reconstruction. Thereupon, the purpose of this study was to compare the biomechanical behavior between the locking and non-locking PSMRP. Finite element analysis (FEA) was used to conduct the biomechanical comparison between the locking PSMRP and non-locking PSMRP by simulating the momentary incisal clenching through static structural analysis. Mandible was reconstructed through the virtual surgical planning, and subsequently a 3D model of mandibular reconstruction assembly, including reconstructed mandible, PSMRP, and fixation screws, was generated and meshed for the following FEA simulations. In the form of equivalent von Mises stress, equivalent elastic strain, and total deformation, the locking PSMRP demonstrated its higher strengths of preferable safety, desirable flexibility, and anticipated stability compared with the non-locking PSMRP, indicated by much lower maximum stress, lower maximum strain and equivalent displacement. Locking PSMRP/screw system provides a better fixation effect to the patient-specific mandibular reconstruction than the non-locking one as a result of its productive fixation nature. FEA plays a paramount role in pre-validating the design of PSMRP through the biomechanical behavior evaluation in static structural analysis.

Construction and application of carbohydrate microarrays to detect foodborne bacteria.

The rapid detection of pathogenic bacteria is vital for the prevention of outbreaks of infectious diseases, including infections by the common foodborne bacteria E.coli and Salmonella Carbohydrate microarrays have been developed as a powerful method to investigate carbohydrate-protein interaction with only very small amounts of glycans, which show great potential for detect the carbohydrate mediated interaction with pathogens. Here, different mannose-coated microarrays were constructed and tested with E.coli (K-12 and BL-21) and Salmonella enterica strains (ATCC9184 and ATCC31685) exhibiting different mannose binding affinities. The optimized carbohydrate microarray was then applied to test the binding of 12 Salmonella enterica and 9 E.coli isolates from local patients for the first time and showed strong binding with certain serovars or subtypes. The results showed that microarray probed with the single mannose structure is not enough for the detection of bacteria with various serovars or subtypes, which contain a high degree of allelic variation in adhesin. We suggest that a complex carbohydrate microarray containing different glycan conformation may be needed for detection of different bacteria isolates.

Overview on the antiviral activities and mechanisms of marine polysaccharides from seaweeds.

Marine polysaccharides are attracting increasing attention in medical and pharmaceutical development because of their important biological properties. The seaweed polysaccharides have now become a rich resource of potential antiviral drugs due to their antiviral activities against various viruses. The structural diversity and complexity of marine polysaccharides and their derivatives contribute to their antiviral activities in different phases of many different viral infection processes. This review mainly introduces the different types of seaweed polysaccharides and their derivatives with potent antiviral activities. Moreover, the antiviral mechanisms and medical applications of certain marine polysaccharides from seaweeds are also demonstrated.