*4.1. Limitation Statement*

Within the framework of the study, the models of materials and objects of the study had a number of limitations.

When modeling the EVA behavior model, it is possible to consider the viscosity of the material. Additional studies of the deformation material and further clarification of the constitutive relations are required. Friction coefficients of EVA-tooth material and EVA-A-silicone are constant at 0.3; the coefficient of friction was taken from the reference literature. Investigation of the friction of materials requires specialized equipment and an original test procedure. Considering the experimentally obtained frictional properties of materials will make it possible to obtain a better picture of deformation of the elements of the dentition.

Within the framework of the task, the multilayered teeth were not considered, which introduces an additional error into the model. The tooth is a composite structure. In further studies, it is planned to consider the multilayered tooth with different properties of the materials of the layers.

The 2D FEA problem was solved. The contact between the layers of the mouthguard was considered, but the level of the parameters of the EVA-A-silicon contact zone was a lower order of magnitude than in the occlusion area. No delamination of the interlayer was observed during the simulation. Frictional contact with a previously unknown contact area, and the nature of the distribution of contact state status zones was realized in the zone of teeth closing.

The study of the influence of the geometry of the mouthguards on the deformation of the elements of the dentition was carried out in the first approximation. Researchers have a number of challenges that follow:


Mouthguard thickness has a significant impact on the patient's comfort. Recent studies considered an influence of the mouthguard's thickness on its performance [22–24]. Westerman et al. [22] revealed that the rational thickness for an EVA mouthguard is 4 mm. When a mouthguard's thickness exceeds 4 mm, there are some negative effects on the patient's speech and breath. Bochnig et al. [23] studied various mouthguards with thicknesses ranging from 2 up to 11 mm. It was concluded that thickness increase by insertion of additional layers results in protective properties of the construction. Sarac et al. [24] obtained similar results.

We studied multilayer mouthguards with 7 mm thickness, including harder intermediate layers. The thickness of the mouthguard can have a number of limitations when athletes use them.
