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The current treatment of large bone defects has several disadvantages. An alternative for using grafts or bone cement for the filling of bone cavities is the use of a bone scaffold that provides a temporary load-bearing function. This paper describes a biomechanical design procedure for a personalized implant with a geometry that has a good fit inside the defect and an internal architecture that provides a scaffold with optimized mechanical properties. These properties are optimized for a load-bearing application, for avoiding stress shielding in the bone surrounding the implant and for activation of osteoblasts seeded inside the scaffold. The design is based on medical images both of the defect and of healthy bone tissue that is representative for the tissue being replaced by the scaffold. Evaluation of the scaffold's mechanical properties is done with high-resolution finite element analyzes of the scaffold and healthy bone. This allows matching of the scaffold and bone mechanical properties, thus giving the scaffold its biomimetic properties.

A valuable alternative to the existing biomedical implant coatings is a bioactive glass BAG coating that is produced by reactive plasma spraying.A mechanical performance requirement that is of the utmost importance is the adhesion strength of the coating. Considering the application as dental implant, a new adhesion test shear test, which was close to the service conditions, was designed. A Ti6Al4V rod ∅3 mm with a sprayed BAG coating of 50 μm was glued with an epoxy glue to a hollow cylindrical counterpart and was used as such in the tensile machine. This test was evaluated by finite element analysis FEA. Preliminary experiments showed that a conversion from shear to tensile adhesion strength is possible by using the Von Mises criterion σ 312τ, indicating that thin coatings of brittle materials can behave as a ductile material. The new coating technique was proved to produce a high quality coating with an adhesion strength of 40.1 ± 4.8 MPa in shear and 69.4 ± 8.4 MPa in tension. The FEA revealed that no one homogeneously distributed shear stress is present but several nonhomogeneously distributed stress components shear and tensile are present in the coating. This analysis indicated that real service conditions are much more complicated than standard adhesion tests. © 1999 John Wiley & Sons, Inc. J Biomed Mater Res, 44, 243–252, 1999.

Abstract: This study was designed to gain insight into the influence of the attachment system on the loading conditions of oral implants supporting a mandibular overdenture on two implants. Five patients were selected and were provided with two implants in the canine area of the mandible (Brånemark System). All patients received a new mandibular overdenture that could be mounted on an ovoid-shaped bar (Dolder, C&M): (a) with and (b) without bilateral extensions and (c) on ball-attachments (Nobel Biocare). Using three strain gauges attached to the outer surface of the 5.5-mm standard abutments, the axial forces and bending moments on both supporting implants could be quantified. Load registrations were made during application of 50 N on seven predetermined positions along the occlusal surface of the prosthesis and during maximal biting in maximal occlusion (clenching). The results revealed no differences in induced axial force for the various anchorage devices, unlike the differences in bending moment. Although there is a tendency for better axial load sharing with bars and better sharing of bending moments with ball attachments, these differences were not significant.