Development of Bioabsorbable Interference Screws: How Biomaterials Composition and Clinical and Retrieval Studies Influence the Innovative Screw Design and Manufacturing Processes - Biologically Responsive Biomaterials for Tissue Engineering - page 131

Fig. 6.20 Physical model of
the innovative interference
screw made by FDM
processes

Fig. 6.21 Silicon mold

Thus, based on 3D CAD model of the screw and using a layer manufacturing
technique type FDM we obtained the physical prototype presented in Fig. 6.20 .
This prototype was used for making a silicone mold (Fig. 6.21 ). The mechanical
properties of the obtained molded screw, as well as its geometric accuracy, proved
unsatisfactory for the considered application because fine details could not be
obtained.
The method of manufacturing which ensured the necessary mechanical proper-
ties of the screw was injection molding. Composite biomaterial obtained as a cylin-
der is grinded in a mill to obtain granules to be used in the injection machine. This
last manufacturing process provides both precision and productivity.

6.5 Conclusions

Clinical studies of implant failures showed the importance of the screw thread and
wedge designs on its engagement in the bone plug, as well as the importance of the
type of bioresorbable material on the soft-tissue reactions and risk of cracks or
breakage.