A method of filling a dental root canal is disclosed herein. The method includes gaining access to the dental root canal and introducing a flowable photosensitizer into the dental root canal. After introducing the flowable photosensitizer into the dental root operation is performed for activating the flowable photosensitizer by exposing the walls of the dental root canal to light via an optical fiber within the dental root canal. Activating the flowable photosensitizer at least partially kills bacteria within the dental root canal and pulp chamber. After activating the flowable photosensitizer, the dental root canal is obturated.