SLM micro-roughness and fatigue in mandibular titanium implants

A titanium mesh facial implant manufactured by selective laser melting (SLM) has catastrophically failed after two years in service. The forensic analysis of the case focuses on determining whether the inherent micro-roughness of the sintering process acted as a stress concentrator, initiating mechanical fatigue cracks. This study combines computed tomography, finite element simulation, and surface analysis to replicate cyclic loading conditions and locate the origin of the fracture.

Forensic workflow: from volumetric scanning to load simulation 🔬

The analysis process begins with micro-CT scanning of the fractured implant in VGSTUDIO MAX. This software reconstructs the actual lattice geometry, including the surface irregularities from sintering. From this point cloud, a finite element mesh is generated and exported to Ansys Mechanical. In the simulation environment, cyclic loads representative of mastication and muscle contraction are applied. The parametric study of surface roughness allows modeling micro-notches as stress concentrators. Results show that the areas of highest Von Mises stress coincide exactly with the crack initiation point observed in the physical specimen.

Reflection on post-processing in SLM implants ⚙️

This case demonstrates that SLM surface roughness is not just an aesthetic issue, but a critical factor for the fatigue life of the implant. The absence of chemical or mechanical post-processing (such as electropolishing or sandblasting) left the micro-notches from sintering intact. For future designs, simulation must include a stress concentration factor derived from the actual roughness measured by tomography. The lesson is clear: in implants subjected to cyclic loads, the surface microstructure defines the boundary between clinical success and catastrophic fracture.

Is it possible to establish a direct correlation between SLM-induced surface roughness parameters and fatigue life reduction in mandibular titanium implants, or do other factors such as process residual stresses have a greater influence?

(PS: Material fatigue is like yours after 10 hours of simulation.)