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.