Metronidazole tablets alone, for halitosis, have limited therapeutic effect. There are many clinical causes of bad breath, and indeed most of them are due to periodontal problems. 1 part of the inflammation of the periodontium is anaerobic bacteria, and among the anaerobic bacteria are gas-producing podococci, which often isolate foul-smelling gases and thus form bad breath. From this point of view, the application of metronidazole is symptomatic, but in actual clinical work, metronidazole only plays a bacterial inhibition role. To remove bad breath, the main thing is to remove the plaque and calculus from the periodontium. The best way to do this is to apply physical scaling, or what we normally call supragingival scaling, which is a process of shattering and removing the harder and stronger calculus through an ultrasonic scaler. The application of scaling can remove the periodontal calculus and plaque, thus fundamentally removing the conditions for bacterial attachment, which is the more basic method of treating bad breath, and can be supplemented by the application of metronidazole tablets, which is relatively effective.