Fabrication of sports mouthguards using a semi-digital workflow with 4D-printing technology.

Purpose This technical procedure report explains the fabrication protocol for a newly developed 4D-printed sports mouthguard (MG) based on 4D-printing technology.Methods An intraoral scanner was used to scan a maxillary arch model. A two-layer sports MG was designed based on the scanned model using computer-aided design software and output in a standard tessellation language file format. Two types of filament materials were used for the MG material: a thermoplastic shape memory polyurethane elastomer with a unique glass transition temperature for the external layer and a thermoplastic elastomer for the internal layer. Both MGs were printed using a fused deposition modeling 3D printer and assembled using adhesives after trimming the support material. To confirm the shape-memory performance of the fabricated 4D-printed MG, a deviation analysis was performed by superimposing the internal surface data of the fabricated MG and the MG whose shape was recovered. The distance between the data obtained by deviation analysis was calculated, and the root mean square error value (mm) was determined.Conclusions The 4D-printing technology simplifies the complex processes required with conventional methods. It also overcomes the issues of conventional and 3D-printed MGs, such as the reduced fitting accuracy caused by deformation, because this technology employs shape memory materials.