A comparison of the shapes of hydroxyapatite implants before and after implantation

Based on helical volume scan computed tomography (HVCT) data, it has been demonstrated previously that real-size models can be prepared with the binder-jet method with extremely high precision of various parts ranging from the outer structure of the cranio-maxillofacial bone to such fine parts as the cranial base and the orbital walls. The application of this method to clinical cases with large cranial bone defects has also been studied. The results showed the usefulness of the binder-jet method, employing starch for fixing, with which a model can be prepared faster and with less deformity caused by the weight of the material itself. Therefore, the binder-jet method is expected to attain greater clinical significance in this field. In this study the comparison between the shapes of implants before and after implantation revealed that the most important aspect of the design of hydroxyapatite (HAP) implants was determining the shapes of edges, especially its angles. That is, an implant needs very little trimming before being implanted to the patient's defective site if the shape of the edges of the implant can be designed and prepared to fix the incised bone surfaces properly. In addition, to obtain optimum results it was also shown that it is necessary to design optimal shapes of implants, taking into account thickness, porosity, and curvature, before processing the shapes of edges. It was found necessary to establish a technology and a method for producing HAP implants that perfectly fit cranial bone defects. For this purpose, it would be useful to make a template of the implants using the mirror-reversion and binder-jet methods.