In search of necessary mouthguard thickness. Part 1: From the viewpoint of shock absorption ability

Purpose: To date, the minimum thickness required for a mouthguard has been assumed to be around 2 mm to 4 mm. However, this figure is based mostly on experience and is yet to be standardized. The purpose of this study is to determine the minimum thickness required to obtain sufficient energy absorption.Methods: The thicknesses of the tested ethylene vinyl acetate) samples were 1, 2, 3, 4, 5, and 6 mm. The pendulum-type testing equipment used in the present study was also used in a series of earlier studies. Three types of sensors (strain gauge, accelerator, and load cell) and two different impact objects (a steel ball and baseball) were used.Results: The results showed that all the abovementioned mouthguard thicknesses reduced shocks for all the three types of sensors and both types of impact objects; little difference was observed between sensors and clear results were obtained for the steel ball. An improvement in the energy absorption was observed with an initial increase in the thickness. However, a further increase in the thickness from 4 mm to 5 mm and 6 mm tended to yield a smaller improvement in energy absorption.Conclusion: Within the limitations of this study, from the viewp int of energy absorption ability, the minimum thickness required for a mouthguard is 4 mm, which is generally too large from the viewpoint of player comfort. This finding indicates the necessity of improving the impact absorption ability of mouthguards by considering new designs and developing new materials.