Author(s): NASROLAHZADEH, N., POPESCO, T., CHOUKROUN, R., WYSS, C., PIOLETTI, D., PLACE, N., BROOME, M., Institution: EPFL, Country: SWITZERLAND, Abstract-ID: 1014

INTRODUCTION:
The primary function of a mouthguard (MG) is to absorb part of the energy transmitted to the jaw during a direct impact. Dental protection mainly depends on the design of the frontal region [1]. Currently, the gold standard is a multi-layered custom MG produced by a thermoforming technique with a reinforced frontal structure. Alternatively, the occlusal region of a MG can be designed to allow strong, comfortable, and secure jaw clenching when needed. We aim to show that a specifically designed MG for clenching, enhances head stability through biting-induced neck muscle activation by providing a stronger linkage between the head and the body. This enhanced head–body connection would lead to reduced head acceleration/deceleration following an impact, which is a main cause of mild traumatic brain injury [2].
METHODS:
Four customized mouthguards (MGs), having around 4mm thickness and covering the teeth up to the second molars, were prepared for 5 volunteers either by conventional thermoforming or by vat-based 3D-printing. In this pilot study, which adhered to the ethical recommendations outlined in the CER_VD guidelines (1.0.- 04.06.2020), muscle activation levels for masseter, sternocleidomastoid (SCM) and trapezius were measured using bipolar surface electromyography (EMG) with/without a MG, in a randomized test scenario. Three maximal clenching trials of 4 seconds each with 45 seconds recovery time were recorded for every MG. All EMG signals were processed identically, and root mean square values during two seconds of clenching were calculated and compared after normalization to reference clenching data without a MG. The tested MGs included a conventionally fabricated custom MG (Erkodent® Playsafe HeavyPro), two single-layer 3D-printed MGs made from KeyOrtho IBT resin (KeyPrint®, Shore-90A) and a custom-made softer resin (G2n, Shore-70A), as well as a 3D-printed modular MG (G2p&n). The latter comprised soft occlusal regions made from G2n resin, interlocked with an U-rail component manufactured from a custom-made resin (G2p, Shore-85A).
RESULTS:
The mean normalized SCM activation level was approximately 75% higher for the 3D-printed single-layer and modular MGs having a softer occlusal region compared to the reference clenching condition without a MG. For the harder MGs, the mean normalized SCM activation level was approximately 30% higher than the reference condition. A statistically significant difference (p < 0.1) in SCM activation was observed for the modular and single-layer 3D-printed MGs with softer occlusal materials compared to the conventional thermoformed customized MG.
CONCLUSION:
Our data suggest that a soft occlusal modular MG can increase head stability through biting-induced neck muscle activation, thereby reducing the risk of indirect impact-induced brain injury. This innovative design has the potential to reduce concussion risk during impacts, offering a promising new direction in sports safety.

[1] DOI:10.1186/s40798-024-00728-2.
[2] DOI:10.1115/1.4037399.