Dentin hypersensitivity can be treated by desensitizing the teeth or by filling the teeth. Dentin hypersensitivity is caused by chewing hard foods. The outermost layer of tooth enamel is worn away, exposing the inner dentin, which has many dentin tubules leading to the pulp tissue, which is also called the dental nerve and can sense hot, cold and sweet stimuli from outside. When the enamel is worn away, there will be hot and cold sensitivity, and in severe cases, there may be painful symptoms. Dentin hypersensitivity can be treated by desensitizing the teeth, using fluoride such as dorafluoride or sodium fluoride, applied to the affected area, or muscimol for desensitization, the main purpose of which is to close the dentin tubules and isolate the external stimulus to the dental nerve. Dentin hypersensitivity can also be caused by poor brushing habits, for example, horizontal brushing can lead to wedge-shaped defects in the teeth, where the bristles are mechanically abraded in the neck of the teeth over a long period of time, resulting in small horizontal grooves, also called wedge-shaped defects. The defect reaches the dentin layer causing painful hot and cold irritation. This condition requires filling of the tooth, which can be done with resin to restore the shape and at the same time isolate it from external hot and cold stimuli. Therefore, dentin hypersensitivity can be treated with fluoride to seal the dentin tubules, or with resin to fill the tooth and isolate it from external stimuli.