# Fabrication and Analysis of a Ti6 Al4V Implant for Cranial Restoration
## 3 Analysis Results  
The accuracy of the fabricated cranial implant was estimated by employing a 3D comparison analysis in Geomagics Control(r)[48]. It can be assumed as one of the comprehensive and dynamic techniques to graphically estimate the surface deviations between the actual object and the reference CAD model [49]. As shown in Figure 12a, the custom made cranial implant was mounted and fixed on the skull and digitized to acquire the test data. The scanning was performed by employing the laser scanner on the Faro Platinum arm (FARO, Florida, USA). The visual investigation on the actual part in conjunction with the visualization of the captured point data (Figure 12b) revealed satisfactory appearance, aesthetics and a near perfect outer profile on the defective side of the skull when the implant was mounted on the cranium prototype. Figure 11: EBM Fabricated parts: **(a)** Top view of titanium cranial implant with supports; **(b)** Bottom view showing support structures; **(c)** Top view of cranial implant after support removal; **(d)** bottom view after support removal; **(e)** Enlarged view illustrating no burr or protrusion and **(f)** Cranial implant fitting rehearsal on a polymer skull model. The 3D comparison analysis commenced with the definition of the test object and the reference CAD model. To digitize the test data, the outer surface of the remodeled skull (or the skull mounted with implant) was scanned and imported as an STL model in Geomagics Control(r). The outer surface was investigated, since the customized cranial implant was designed depending on the outer profile of the skull. The reference CAD model was obtained by taking out the defect and improvising (or mirroring) the healthy side on it. This CAD model obtained using the mirroring technique was used as a reference because it could satisfactorily represent the ideal anatomy [29; 30]. Subsequently, the 3D comparison analysis was performed to determine the accuracy of the remodeled skull. The test data (acquired point cloud) as shown in Figure 12b was then aligned with the reference CAD model using the best fit alignment procedure. The best fit alignment was significant to ensure that both the test and reference objects were positioned in the same coordinate system. The statistics used to quantify the accuracy of the implant on the skull were the average deviation in the positive and negative directions as well as the root mean square (RMS). The RMS value (i.e., the square root of the average of squared errors) provided the overall accuracy for the remodeled skull. The average deviation statistics were selected because they report the average variations, thereby approximating the difference between the remodeled skull with the customized implant and the original skull of the patient in the outward and inward directions. The outcome of the 3D deviation analysis has been represented graphically in Figure 13. When the remodeled or reconstructed skull was analyzed with the mirrored cranium, the average deviation was in the range of 0.9294 mm in the outside direction and \(-\)1.0587 mm in the inward of the skull. Based on average deviation and RMS (1.5347 mm) values, the author inferred that the reconstructed skull was acceptable and it provided satisfactory aesthetics and appearance. Figure 12: (a) Data acquisition using Faro Platinum arm; (b) Digitized point cloud data. To analyze the tensile strength, the EBM produced dog bone specimens (n = 5) as shown in Figure 13(a) were subjected to an axial tensile test. The tensile test was carried out using an Instron universal testing machine (5984 30 K, UTM-USA) as illustrated in Figure 13(b). The load and displacement data were regularly observed and noted. A constant displacement speed was maintained and its load and elongation were measured to test the tensile durability of the EBM built specimens. The strains were measured using strain gauge which was glued onto the specimens. The state-of-the-art built-in control platform Blue hill 3 was used to define, program, and perform the novel tests.