Two-Phase Material Shape Optimization of an Additively Manufactured Integrated Metal and Ceramic Resin Implant-Supported Dental Crown

The screw-retained implant-supported crown is a durable, aesthetic restoration, but debonding between the crown and abutment remains a challenge to survivability. The purpose of this work was to devise an abutment shape that can be embedded into the crown while the crown is being additively manufactured. The result was a mechanically retained, no-adhesive abutment and crown unit that is mounted to the implant fixture. To generate the best internal shape for the new restoration design concept, a shape optimization method was developed using nTop software with the objective of pursuing low structural compliance (maximizing stiffness), withstanding mastication loads, and complying with the unique manufacturing constraints of the proposed design. The optimization results showed a 39% and 51% reduction in structural compliance for molar and incisor restorations. Validation finite element analysis (FEA) on the molar restoration was accomplished for comparison of the initial, optimized, and traditional Ti-Base screw-retained designs. Under vertical and angled loads, the optimized design reduced maximum Von Mises stress by 38% compared with the traditional design, and under upwards load, the optimized design reduced maximum principal shear strain along the abutment-crown joint boundary by 67%. A successful prototype was created using a stereolithography (SLA) printer for fit and form testing. The design concept in this study showed promise as an alternate method to join the two components, while removing the debonding failure mode and maintaining aesthetics and strength. This may offer a more suitable screw-retained restoration option for patients with constraints such as small interocclusal space.