How long a patient with periodontitis can be cured after taking metronidazole is determined by the specific condition and cannot be generalized. In the acute phase of periodontal disease, that is, the septic phase, oral or sedative metronidazole can have a therapeutic effect, usually about 7 days to heal. However, if the periodontitis is chronic, there is usually no obvious effect after taking metronidazole. It is recommended to go to the dentistry department of a regular hospital for standardized periodontal treatment, especially to do ultrasonic scaling and subgingival scaling and root planing, and then to keep the periodontal pockets clean by repeatedly rinsing them. However, if the inflammation is difficult to control or does not ease for more than 1 week, relevant examinations need to be conducted promptly and the treatment plan should be changed as prescribed by the doctor. It should be noted that patients suffering from periodontal disease should pay attention to oral hygiene, brush and rinse their teeth regularly, and eat less spicy and stimulating food to avoid aggravating the disease.