Mouthguards Based on the Shear-Stiffening Effect: Excellent Shock Absorption Ability with Softness Perception

Mouthguards are used to prevent craniomaxillofacial injuries when collisions happen during contact and high-speed sports. However, poor compliance with mouthguard wear in athletes is attributed to discomfort because of its thickness and hardness. These drawbacks significantly restrict their protective performance for oral tissues and applications during contact sports; as a result, the incidence of craniomaxillofacial injuries increases. In this study, non-Newton material is introduced into mouthguard material and then a mouthguard with shear-stiffening behavior is fabricated, which is named the shear-stiffening mouthguard (SSM). Compared with commercial mouthguard materials (Erkoflex and Erkoloc-pro), SSMs show remarkable enhancement of shock absorption ability with an approximately 60% reduction in peak force relative to commercial materials and approximately 3-fold extensive buffer time. Moreover, Young's modulus of SSMs (average 0.48 MPa) is extremely lower compared to commercial materials (22.88 MPa for Erkoflex and 26.71 MPa for Erkoloc-pro). This manifests that SSMs have not only excellent shock absorption ability but also softness perception. Moreover, SSMs show biocompatibility in vitro. In conclusion, this work provides a platform to develop a new type of thin and soft mouthguard with a shear-stiffening effect and broadens the horizon in protecting oral tissues with shear-stiffening materials.