Pilot study of 3D image correlation photogrammetry to assess strain and deformation of mouthguard materials

The purpose of this investigation was to conduct a pilot study to evaluate the use of 3D image correlation photogrammetry (3DIC) in comparing strain characteristics of three commercially available mouthguard materials in the actual form of a mouthguard.

3DIC was used to measure strain and deformation on the surface of a mouthguard and a resin model. A computed tomographic scan of a maxilla of a patient was used to fabricate a resin test model. Three mouthguard materials were tested: conventional ethylene vinyl acetate; Proform TM, a thermoplastic material; and Polyshok TM, an EVA product containing polyurethane. Three mouthguards of each of the three materials were fabricated and fitted to the acrylic model for testing. A speckle pattern was applied to the external surfaces of each of the mouthguards. Static mechanical tests using a servohydraulic load frame at 10, 25, and 50 pounds of force were applied to the mouthguards while on the resin model. Strains were measured in both the horizontal (x) and vertical (y) axes using (3DIC). Measured strains were analysed by 4-way anova.

For all three materials tested, the difference in strain between two measured directions (X and Y) was found to be statistically significant for all regions evaluated. The analysis indicated that each direction, region, and load was involved in a statistically significant effect (P < 0.001). Statistical differences in the strain were noted with the highest strain region being closest to the applied load for all three materials. Differences in strains in two directions were found to be significant for the materials studied (P < 0.001).

3DIC is useful in evaluation of mouthguard materials in the actual form of a mouthguard. Materials, along with larger sample sizes, may improve confidence levels of the results. Further testing is indicated before clinical claims can be made.