Impact absorption and force dissipation of protective mouth guards with or without titanium reinforcement.

BACKGROUND: Mouth guards are used to reduce the risk of experiencing dental injuries. Various individual and commercial designs are available. METHODS: The authors prepared 20 artificial maxillae from a polyether-resin to simulate teeth, jaw bone and gingiva. They customized two designs of mouth guards by using stone models from impressions of the artificial maxillae; one (n = 10) was constructed of four layers of ethylene vinyl acetate (EVA) (total thickness = 4.0 millimeters) (group EVA), and the other (n = 10) was constructed of EVA with an intermediate layer of 1.0-mm-thick sheet titanium from the left maxillary canine to the right maxillary canine (total thickness = 4.0 mm) (group EVA-Ti). They used a drop-weight impact testing machine (DTM 1000-S, Omnipotent Instruments, Seremban, Negeri Sembilan Darui Khusus, West Malaysia) for a frontal impact with 1.7 kilograms of mass dropped at 0.34 meter per second. The force of the drop was verified by means of a laser Doppler vibrometer (laser model OFV-323 and controller model OFV-3020, Polytec, Irvine, Calif.) to calculate the absorbed energy. They used a high-speed camera (FastCam APX-RS, Photron, San Diego) to obtain images of energy dissipation over the length of the mouth guard. RESULTS: The mean effective total impact energy that reached the maxillae-mouth guard models was 5.66 (standard deviation [SD], 0.035) joules. The mean absorbed energy in group EVA was 4.39 (0.023) J (77.8 percent of total impact energy). The mean (SD) absorbed energy in group EVA-Ti was 4.28 (0.013) J (75.9 percent of total impact energy). The mean (SD) total dissipated energy was 1.26 (0.21) J in group EVA and 1.36 (0.11) J in group EVA-Ti. The mean (SD) transmitted energy for the mouth guards was 1.08 (0.19) J in group EVA and 0.99 (0.05) J in group EVA-Ti. There was no statistically significant difference between the groups in terms of any energy transmission or absorption. CONCLUSION: The results of this study suggest that an additional intermediate titanium layer in the anterior area of a mouth guard may not have a beneficial effect on impact absorption and dissipation. PRACTICAL IMPLICATIONS: The use of mouth guards is a general requirement for physical sports activities, and it should be strongly encouraged for people playing contact sports in particular. However, the authors' results indicate that the total thickness of a mouth guard is more important than is the use of an additional intermediate layer (in this case, titanium).