Characterization of mouthguard materials: thermal properties of commercialized products.
OBJECTIVE
Several mechanisms have been purported to describe how mouthguards protect the orofacial complex against injury. As the properties needed for these mechanisms to be effective are temperature and frequency dependent, the specific aim of this study was to provide a comprehensive thermal characterization of commercial mouthguard materials.


METHODS
Five commercially representative thermoplastic mouthguard materials (Essix Resin, Erkoflex, Proform-regular, Proform-laminate, and Polyshok) were tested. Differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) techniques were implemented to measure thermal transitions and mechanical properties. Measurements were conducted three times per sample. One-way ANOVA and one-sample t-tests were used to test for differences between commercial products on selected mean thermal property values.


RESULTS
The DSC measurements indicated no differences between commercial materials for mean glass transition (p=0.053), onset melt (p=0.973), or peak melt (p=0.436) temperatures. Likewise, DMA measurements revealed no differences between commercial materials for the mean glass transition (p=0.093), storage modulus (p=0.257), or loss modulus (p=0.172) properties, respectively. The one-sample t-tests revealed that glass transition temperatures were different from intra-oral temperature (p<0.005) for all materials.


CONCLUSIONS
Commercialized mouthguard materials are sensitive to repetitive heating and cooling cycles, prolonged thermal treatment, and have glass transitions well below their end-use intra-oral temperature. As such, these materials are functioning as elastomers and not optimal mechanical damping materials. Dental clinicians, healthcare practitioners, or end-users should be aware that these materials are at best problematic with respect to this protective mechanism.
School of Human Performance, University of Southern Mississippi, Hattiesburg, MS, USA. Trent.Gould@usm.edu
Trenton E
TE
Gould
Scott G
SG
Piland
Junghwan
J
Shin
Olivia
O
McNair
Charles E
CE
Hoyle
Sergei
S
Nazarenko
D002152:Calorimetry, Differential Scanning; D003080:Cold Temperature; D003460:Crystallization; D003764:Dental Materials / Q000737:chemistry*; D055119:Elastic Modulus; D020724:Elastomers / Q000737:chemistry; D004867:Equipment Design; D006358:Hot Temperature; D006801:Humans; D055595:Mechanical Phenomena; D009064:Mouth Protectors; D011145:Polyvinyls / Q000737:chemistry; D012117:Resins, Synthetic / Q000737:chemistry*; D012212:Rheology; D013314:Stress, Mechanical; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors; D044366:Transition Temperature; D014783:Viscosity
D003764:Dental Materials; D020724:Elastomers; D011145:Polyvinyls; D012117:Resins, Synthetic; C016438:ethylenevinylacetate copolymer