Methods: A computer model, based on the Finite Element Method (Femlab®) was used to investigate the reductive capacity and the conductivity of mouthguards consisting of different combinations of soft and hard layers. The characteristics of soft Erkoflex® (poly(vinyl-acetate-ethylene) co-polymer (EVA)) and hard Erkodur-S® (styrol-butadien-co-polymer) material were introduced into the computer model. The thickness of the soft layer of the mouthguard varied between 1 and 4 mm. The hard layer of the mouthguard was either 0.8, 1.6 or 2.4 mm thick. The different layers of mouthguard material were placed on top of a layer simulating the tooth enamel surface. Stress distributions were calculated at the interface of the mouthguard and the tooth enamel surface.
Results: Calculations of the stress distributions showed that a mouthguard, consisting of a combination of Erkoflex® and Erkodur-S®, offered a better protection than a mouthguard of a comparable thickness but consisting of Erkoflex® only. The protection by the mouthguard became more effective by placing the Erkodur-S® layer towards the external surface of the mouthguard. Further improvement of the protection was obtained by increasing the thickness of the hard layer.
Conclusion: According to the computer simulations it would be possible to construct protective mouthguards with a reduced thickness and thereby an improved wearability. However, a thorough thinking out of the configuration of the soft and the hard layers within the mouthguard is crucial to achieve this goal. Improvement of the mouthguards' wearability is important in rousing up athletes to wear a mouthguard more often and thereby avoiding severe trauma.