A porcine mandible was separated to prepare thin periodontium specimens consisting of a molar, periodontal ligament (PDL), and alveolar bone. Occlusion was simulated by applying a forced compressive displacement using a table-top material tester. We photographed images of the displacing periodontium specimen and simultaneously obtained the load–displacement curve during the test. The displacement and deformation distributions were examined using digital image correlation analysis. Then, we correlated the distribution with the load–displacement curve, which was characterized by biphasic behavior, as noted in many previous studies. We found that the displacement and deformation distributions of actual periodontium correlated with the load–displacement curve during dental occlusion. Regarding the biphasic characteristics of the load–displacement curve, we showed experimentally that the first phase indicated deformation of the PDL and the second indicated deformation of the alveolar bone and tooth.