Analysis using the finite element method of a novel modular system of additively manufactured osteofixation plates for mandibular fractures - A preclinical study

Comparative evaluation of a patient-specific customised plate designs and screws for partial mandibular reconstruction

Mandibles with odontogenic tumors are often partially reconstructed with a metallic bone graft analogue with dental roots, crowns, along with a customized plate fixed with monocortical or bicortical screws, following resection of the tumor. In this study, two different designs of patient specific customized Ti reconstruction plates, solid and plate with holes, were considered. Fixation through both bicortical and monocortical screw types were investigated. FE models of the reconstructed mandibles were developed to analyse the influence of the plate-screw type combination on the load transfer across the mandibles under a mastication cycle. The effective homogenized orthotropic material properties of the lattice structures with 0.6 mm fibre diameter with 0.5 mm inter-fibre space were assigned to material properties for the bone graft analogue. The study shows that the combination of plate and screw types influences the state of stresses in the reconstructed mandible. Based on the results of this patient specific study, following resection of the tumor, either solid Ti plate with bicortical screws or Ti plate with holes along with monocortical screws may be used for partial mandibulectomy. It should also be noted that stresses in none of the plates or screws exceeded the yield limit for Ti under the mastication cycle indicating that the components are safe for mandibular reconstruction. However, the choice of this combination of reconstruction plates and screws is dependant on the condition and severity of the tumor in the diseased mandible.

3D Printing and Virtual Surgical Planning in Oral and Maxillofacial Surgery

Compared to traditional manufacturing methods, additive manufacturing and 3D printing stand out in their ability to rapidly fabricate complex structures and precise geometries. The growing need for products with different designs, purposes and materials led to the development of 3D printing, serving as a driving force for the 4th industrial revolution and digitization of manufacturing. 3D printing has had a global impact on healthcare, with patient-customized implants now replacing generic implantable medical devices. This revolution has had a particularly significant impact on oral and maxillofacial surgery, where surgeons rely on precision medicine in everyday practice. Trauma, orthognathic surgery and total joint replacement therapy represent several examples of treatments improved by 3D technologies. The widespread and rapid implementation of 3D technologies in clinical settings has led to the development of point-of-care treatment facilities with in-house infrastructure, enabling surgical teams to participate in the 3D design and manufacturing of devices. 3D technologies have had a tremendous impact on clinical outcomes and on the way clinicians approach treatment planning. The current review offers our perspective on the implementation of 3D-based technologies in the field of oral and maxillofacial surgery, while indicating major clinical applications. Moreover, the current report outlines the 3D printing point-of-care concept in the field of oral and maxillofacial surgery.

Personalized, 3D- printed fracture fixation plates versus commonly used orthopedic implant materials- biomaterials characteristics and bacterial biofilm formation

Additive manufacturing enabled the development of personalized, ideally fitting medical devices. The topography of the surface of the 3D-printed implant may not only facilitate its integration but also cause its rejection, as the surface may become a reservoir for different bacterial strains. In this study, the innovative, raw, 3D- printed fracture fixation plates, manufactured by using selective laser melting (SLM) from Ti-6Al-4V were compared with commercially available, surface-modified plates commonly used in orthopedic surgery. The topography surface of the plates was studied by atomic force microscopy. Susceptibility to the development of biofilm was tested for Staphylococcus epidermidis, Staphylococcus aureus and Streptococcus mutans by using crystal violet staining of biomass, confocal, and scanning electron microscopy (SEM). 3D- printed plates showed higher roughness (Sa=131.0 nm) than commercial plates (CP1 and CP2), Sa= 60.67 nm and Sa=55.48 nm, respectively. All strains of bacteria colonized 3D- printed raw plates more densely than commercial plates. The microscopic visualization showed biofilm mostly in irregular cavities of printed plates while on commercial plates it was mainly located along the edges. The research has indicated that there is need for further development of this technology to optimize its effectiveness and safety.

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.