Topology design and structural optimization of Co-Cr frameworks for implant-supported prostheses

Cobalt chromium (Co-Cr) frameworks for complete arch implant-supported fixed dental prostheses may be excessively heavy in patients with increased occlusal vertical dimension. This limitation necessitates consideration of lower density materials, which may substantially increase treatment costs.

The purpose of this study was to investigate the effects of topology optimization on the biomechanical behavior and weight reduction of Co-Cr frameworks used in complete arch implant-supported fixed dental prostheses.

Different occlusogingival heights (10 mm and 14 mm) of complete arch implant-supported fixed dental prosthesis frameworks were virtually modeled using a dental computer-aided design (CAD) software program. For each height, 4 lattice types (Schwarz, Gyroid, Diamond, and Neovius) and 2 different maximum lattice thicknesses (2 and 3 mm) were designed. Subsequently, topology optimization was applied to each framework configuration. A total of 16 framework designs were generated, while 2 solid, nonoptimized frameworks without lattice structures were used as controls. In all optimized designs, vertical occlusal loads of 200 N were applied to the canine, premolar, and molar (cantilever) regions. Finite element analysis (FEA) was conducted for all designs to assess von Mises stress (MPa), maximum displacement (μm), reaction force (N), and weight reduction (%). Statistical analyses were performed with 1-way ANOVA and the t test (α=.05).

Topology-optimized lattice frameworks achieved up to 51.2% weight reduction without exceeding the material's yield strength. The occlusogingival height of the framework significantly affected von Mises stress, displacement, and reaction force values (P<.05). The Gyroid lattice demonstrated optimal performance in terms of weight reduction (P<.001). All stress and displacement values remained within the physiological tolerance limits of the supporting structures.

Co-Cr frameworks can be significantly reduced in weight through topology optimization without compromising their mechanical integrity. The lattice geometry and the occlusogingival height of the framework are critical factors contributing to successful optimization.