  Because of the relatively rigid coupling between the upper dentition and the
skull, instrumented mouthguards have been shown to be a viable way of measuring
head impact kinematics for assisting in understanding the underlying
biomechanics of concussions. This has led various companies and institutions to
further develop instrumented mouthguards. However, their use as a research tool
for understanding concussive impacts makes quantification of their accuracy
critical, especially given the conflicting results from various recent studies.
Here we present a study that uses a pneumatic impactor to deliver impacts
characteristic to football to a Hybrid III headform, in order to validate and
compare five of the most commonly used instrumented mouthguards. We found that
all tested mouthguards gave accurate measurements for the peak angular
acceleration (mean relative error, MRE < 13%), the peak angular velocity (MRE <
8%), brain injury criteria values (MRE < 13%) and brain deformation (described
as maximum principal strain and fiber strain, calculated by a convolutional
neural network based brain model, MRE < 9%). Finally, we found that the
accuracy of the measurement varies with the impact locations yet is not
sensitive to the impact velocity for the most part.
