Few studies performed a microstructural analysis of dental restorations to evaluate fatigue impact under various tensions, because of a lack of analytical equipment. In this study, the fatigue of restorative materials was evaluated using the force tester's fatigue method at 0.30, 0.3, 0.40, and 0.45 N. The fatigue effect analysis of tooth restorations was performed with each sample by randomly dividing the sequence into grades 0-4 and the evaluators were blinded to the test results. The evaluation methods involved visual and stereoscopic approaches, and used synchrotron radiation (SR). The evaluation facilitated the observation of microscopic cracks in the material using SR. The initiation of cracks was attributed to air bubbles, invisible to the naked eye or under the microscope. The fatigue effect analysis using SR enabled closer observations compared with other types of evaluation. We expect that this strategy will provide a basis for the study of physical and mechanical properties of dental materials.