The development in the field of dentistry has developed quite rapidly, it is motivated from the weakness obtained from existing light sources. Light design and filter systems are developed to provide maximum absorption targets. For light curing most dentists use light citting LED type (light emitting diode) because for LED light sources have advantages such as, effective life time of 1000 hours, which can produce polymerization depth level and greater flexural strength than halogen. The purpose of this study is to facilitate the work of the dentist when performing the composite resin hardening with a short time. The experiment was conducted by testing the dental material of OA2 nano hybrid composite resin type. Then measured the duration of the irradiation and the hardness of the composite resin. The tool used to test the hardness of composite resin is Universal Testing Mechine (UTM). From the result of measurement of hardness of composite resin material which has been done by light curing irradiation can be concluded that effective irradiation at 20 second time setting got chew strength 315 Mpa-358 Mpa. Because in more than 20 seconds the hardness of the composite resin gets harder resulting in the material being easily cracked or broken. For the strength of human chewing can hold until 314Mpa.