Bitter mouth, bad breath and yellow phlegm in the morning are usually caused by poor oral hygiene, such as a history of smoking and incorrect brushing posture, or may also be caused by frequent consumption of spicy and irritating foods. Regular dental cleaning is generally recommended to ensure oral hygiene, and mouthwash can be used appropriately. Routinely, a cleaning is needed every six months to about a year. If the periodontal conditions are poor, it is recommended to clean every six months, and it is necessary to do subgingival scraping to avoid the phenomenon of receding gums and alveolar bone recession. And it is recommended to properly use the compound chlorhexidine gargle, or choose to recover the new liquid and so on. It is good for oral hygiene and can inhibit the infection of bacteria in the mouth. It is recommended to prohibit smoking, avoid eating spicy and stimulating food for a long time, and treat caries in the mouth in time.