Introduction:
Mouthguards constitute an important element in the prevention of the effects of head and mouth injuries. The type of appliance to be used remains the responsibility of the athlete, and the choice and frequency of the device depends on personal preferences and previous experience. The long-term use of protective splints, in conditions of increased physical and mental load, can influence the whole stomatognathic system.

Aim of the study:
To evaluate the impact of mouthguards on the masticatory muscles.

Material and methods:
In the course of the study, thirty athletes tested a total of 120 mouthguards. Each one was provided with two customized mouthguards – made of Impak material (Vernon - Benshoff Comp., USA) and Corflex Orthodontic (Pressing Dental, Italy) and two standard mouthguards - Porida (Combat Gear, Pakistan, India), and Shock Doctor Gel Max Strapless (Shock Doctor, Inc., USA). Surface electromyography examination of the masticatory muscles was carried out using a wireless system. The trials, including control and tested protectors, were performed in random order. The results of the electromyographic examination were subjected to statistical analysis with repeated measurements, where the variable was muscle tension, the independent variable, the mouthguard, and the covariant the gender.

Results:
The type of protective splint and the gender did not affect the measured variable. The application of a mouthguard had no impact on the masticatory muscles tension.

Conclusions:
1. Mouthguard users should be informed that its application does not increase the masticatory muscles tension. 2. Mouthguards can be used during both training and sports competitions.