EVA closed-cell foam and its effect on transmitted forces - Australian ...

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<strong>EVA</strong> <strong>closed</strong>-<strong>cell</strong> <strong>foam</strong> <strong>and</strong> <strong>its</strong> <strong>effect</strong> on transmitted forces in mouthguard material B. Westerman* 1 , P.M. Stringfellow 2 , J.A. Eccleston 3 & D.J. Harbrow 4 1 Private practitioner, 2 Professional engineer, 3 Department of Mathematics, The University of Queensl<strong>and</strong>, 4 Department of Dentistry, The University of Queensl<strong>and</strong> without air-<strong>cell</strong>s. In contrast, <strong>closed</strong>-<strong>cell</strong> <strong>foam</strong> <strong>EVA</strong> polymer showed a 4.96 percent reduction in transmitted forces compared with <strong>EVA</strong> without the gas inclusions. The reduction in transmitted forces under the same conditions (magnitude of test impact force, thickness of test samples <strong>and</strong> similar air-conditioned environment) <strong>and</strong> with similar <strong>EVA</strong> polymers showed that the improvements in the <strong>foam</strong> <strong>EVA</strong> polymer were only one sixth of those shown with the more controlled air-inclusions with regular volume <strong>and</strong> wall thickness. Conclusions The addition of <strong>foam</strong>ing agent to the <strong>EVA</strong> ( Shore A Hardness 83) commonly used in mouthguard materials produced <strong>closed</strong>-<strong>cell</strong> <strong>foam</strong>s which showed small increases in energy absorption, when impacted, compared with the same material without <strong>foam</strong>. Reductions of close to 5 percent in transmitted forces in these <strong>foam</strong> materials contrasted with the larger air-inclusions with fixed air-<strong>cell</strong> volume <strong>and</strong> wall thickness which demonstrated a 32 percent reduction in transmitted forces. Closed-<strong>cell</strong> <strong>foam</strong> <strong>EVA</strong> plastics with up to 10 percent by weight <strong>foam</strong>ing agent <strong>and</strong> with indiscriminate gas-inclusions do not provide statistically significant improvements in energy absorption <strong>and</strong> reductions in transmitted forces when compared with non-<strong>foam</strong>ed <strong>EVA</strong> polymers. Acknowledgments This study was supported by a grant from the Australian Dental Research Foundation Inc. The authors also thank Frank <strong>and</strong> John Oskam for their assistance in preparing the <strong>foam</strong> materials. References Wood AW. Head protection- cranial, facial <strong>and</strong> dental in contact sports. Oral Health 62:23-33, 1972 Wei SH. Prevention of injuries to anterior teeth. Int Dent J 24:30-49, 1974 Garon MW, Merckle A, Wright JT. Mouth protectors <strong>and</strong> oral trauma: a study of adolescent football players. J Am Dent Assoc 12:663-6, 1986 Print Index Table of Contents Quit
<strong>EVA</strong> <strong>closed</strong>-<strong>cell</strong> <strong>foam</strong> <strong>and</strong> <strong>its</strong> <strong>effect</strong> on transmitted forces in mouthguard material B. Westerman* 1 , P.M. Stringfellow 2 , J.A. Eccleston 3 & D.J. Harbrow 4 1 Private practitioner, 2 Professional engineer, 3 Department of Mathematics, The University of Queensl<strong>and</strong>, 4 Department of Dentistry, The University of Queensl<strong>and</strong> Hickey JC, Morris AL, Caelson LD, Seward TE. The relation of mouth protectors to cranial pressure <strong>and</strong> deformation. J Am Dent Assoc 74:735- 40, 1967 De Wijn JR, Vrijhoef MMA, Versteegh PA, Strassen HP, Linn EW. A mechanical investigation to the functioning of mouthguards. Biomedics:Principles <strong>and</strong> applications. The Hague:Martinus Nijhoff Publishers, 1982. Park JB, Shaull KL, Overton B, Donly KJ. Improving mouthguards. J Prosthet Dent 72:373-380, 1994 Going RE, Loehman RE, Ming Sam Chan. Mouthguard materials: their physical <strong>and</strong> mechanical properties. J Am Dent Assoc 88:132-8, 1974 Westerman B, Stringfellow PM, Eccleston JA. Forces transmitted through <strong>EVA</strong> mouthguard matterials of different types <strong>and</strong> thickness. Aust Dent J 40:389-391, 1995 Westerman B, Stringfellow PM, Eccleston JA. An improved mouthguard material. Aust Dent J 42:189-191, 1997 Francis KT, Brasher J. Physical <strong>effect</strong>s of wearing mouthguards. Br J Sports Med 25(4):227-31, 1991 Westerman B, Sringfellow PM, Eccleston JA. The beneficial <strong>effect</strong>s of air-inclusions on mouthguard performance. Submitted for publication 2001. Print Index Table of Contents Quit
Page 1 and 2: EVA closed
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Page 7 and 8: EVA closed
Page 9: Table 1. Mean maximum transmitted f

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