If a tooth encounters a hot temperature stimulus that causes pain, it is possible that dentin sensitivity has occurred. The normal dentition is composed of three layers: enamel, dentin and pulp, with enamel in the outermost layer, which is responsible for isolating external stimuli, and dentin in the middle, which is particularly sensitive to temperature stimuli. If a tooth is diseased and causes a tooth defect, the dentin will be exposed to the temperature stimulus directly, which will cause pain. In case of tooth caries, if the caries reaches the dentin or even the pulp cavity, when the tooth enters hot water, it will cause pain. Also, if there is periodontitis, which leads to the resorption of the alveolar bone, the dentin in the cervical part of the tooth will be exposed, which will also cause pain.