Abstract: A dental device for treating dental infection includes a dental cast comprising at least one groove to receive teeth and/or gums of a dental arch of the patient; and at least one light diffusing fiber arranged on the dental cast around the at least one groove. The dental device is used in a photodynamic therapeutic system, in which a light source instrument emits light onto a photosensitizer applied in mouth of the patient. The dental device is optically coupled to the light source instrument. The light for treating dental infection of the patient is transmitted by the at least one light diffusing fiber of the dental device and activates the photosensitizer to produce free radicals or oxidants to destroy the bacteria and microbes causing dental disease.