Comparative evaluation of mechanical performance of plates manufactured by traditional method and plates manufactured by laser sinter method in oral and maxillofacial surgery

Open reduction and internal fixation are trauma treatment methods in oral and maxillofacial surgery. Reconstruction plates are one of the fixation devices used in open reduction. These plates are manufactured from stainless steel or titanium alloys. Ti6Al4V ELI is a commonly used alloy type among titanium alloys. The aim of our study is to evaluate the mechanical properties of reconstruction plates manufactured from Ti6Al4V ELI plates by CNC method and from Ti6Al4V ELI powder alloy by laser sintering (selective laser melting) method. For this purpose, 30 reconstruction plates of 54mm length and 3mm thickness were manufactured in both groups. Static 3-point bending test, fatigue test, torsion test, Vickers hardness test, SEM-EDS, XRD, ICP-OES and finite element analyzes were performed. Finite element analysis was performed as validation of the static 3-point bending test. The Mann-Whitney U test was applied to the maximum bending force, yield force and yield displacement amount obtained in the static 3-point bending test and the maximum torque values in the torsion test. Independent sample t-test was applied to the hardness analysis results. As a result of the fatigue test, laser sinter group plates reached 40N, while CNC group plates reached 1,000,000 cycles at 60N. In the ICP-OES analysis, Ti ratios were 92.57% in the CNC group and 91.32% in the laser sinter group. As a result of the finite element analysis, the maximum amount of stress that the plate can withstand was found to be 862.5Mpa. The CNC group was found to be statistically significantly higher than the laser sinter group in terms of maximum bending force, yield force and maximum torque values. The laser sinter group achieved higher values in yield displacement amounts, however, this difference was not statistically significant. In the Vickers hardness test results, the laser sinter group plates were found to be statistically significantly superior to the CNC group plates. Mechanical properties can be improved by changing the design, shape, length and thickness of the plate while manufacturing customized plates with the laser sintering method. In addition, plates with mechanically superior properties can be obtained by changing the parameters of manufacture (laser wavelength, focal diameter, layer thickness, etc.) and parameters of the heat treatment (heat treatment temperature, duration, etc.). Our study will guide us at this point.