Halitosis is the odor emanating from the mouth or other air-filled cavities such as the nose, sinuses, and throat. About 10-65% of people suffer from bad breath. With the increasing frequency of social interaction, bad breath has received more and more attention. Halitosis can be caused by a variety of intraoral and extraoral factors. For the latter, systemic diseases such as ear, nose and throat diseases, respiratory, gastrointestinal, endocrine, hepatic and renal diseases can cause bad breath. The metabolites of vegetables such as onions and garlic or certain medications can also produce bad breath. In addition, some patients may suffer from imaginative bad breath. Most bad breath comes from the oral cavity, tartar and periodontal pockets are closely related to bad breath. For patients with good oral hygiene and periodontal health, halitosis mainly originates from the back of the tongue, and for patients with periodontal disease, the back of the tongue also plays an important role in halitosis. Studies have shown that there is a positive correlation between the degree of halitosis and the presence or absence of tongue coating, as well as the thickness and extent of tongue coating. In addition, dental, mucosal and neoplastic diseases in the oral cavity, and unclean dentures can also cause halitosis, but these factors account for a smaller proportion. From a microscopic point of view, halitosis is the result of the decomposition of sulfur-containing amino acids (methionine, cysteine, cystine, etc.) by microorganisms in the oral cavity. The main component of bad breath is volatile sulfur compounds, 90% of which are hydrogen sulfide and methyl mercaptan. Treatment of bad breath When there are dental, periodontal, mucosal diseases or tumors in the mouth, these diseases should be treated. Most patients with halitosis do not have obvious oral diseases, but the tongue, which retains a lot of microorganisms and food residues, and poor oral hygiene are the main causes of halitosis. Therefore, cleaning the back of the tongue and maintaining good oral hygiene become the focus of prevention and treatment of halitosis. 1, mechanical removal methods (1) scraping tongue In the absence of special etiology, the main cause of bad breath is the presence of excessive and thick tongue coating. Mechanical removal of tongue coating can reduce VSCs by 36%-50%. Therefore, gentle and effective cleaning of the back of the tongue should be an important step in oral hygiene measures for the treatment of halitosis and should be part of the daily oral hygiene regimen. The tools used for tongue cleaning should be small, inexpensive, wear-resistant and easy to use. The steps of tongue cleaning can be referred to as follows: ① Extend the tongue out of the mouth as far as possible. ② Observe the location of debris accumulation. ③ Put the tongue cleaning tool or tongue scraper as far back as possible, and apply some pressure to make the tongue lie flat, so that the tongue scraper and the tongue surface coincide with the ④ from back to front, slowly move the tongue scraper back and forth. ④ Move the tongue cleaner slowly from back to front. ⑤ Wash the residue on the tongue cleaner with running water. Repeat the above steps until the back of the tongue is clean. Repeat the above steps until the back of the tongue is clean. ⑦ Wash and dry the appliance for next use. (2) Scaling is also known as periodontal scaling. Periodontal disease is closely related to bad breath, and professional and systematic periodontal treatment can help reduce bad breath. A recent study has shown that a full mouth cleaning, root planing, and mouth rinsing with chlorhexidine can reduce the sensory perception score by 90%. (3) Cleaning the interdental space Compared with the effect of tongue coating on VSCs, the effect of interdental space is smaller, but the role of interdental space should not be ignored. Interdental cleaning tools such as toothpicks, interdental brushes, etc. are also effective in cleaning interdental spaces and reducing bad breath. 2, chemical removal methods (1) Chlorhexidine mouthwash gargle Chlorhexidine is a broad-spectrum bactericidal agent, with 0.2% chlorhexidine solution or chlorhexidine gluconate gargle, can reduce bad breath and the amount of bacteria in the mouth. (2) Metal Ion Gargle Gargle containing zinc acetate is effective in suppressing bad breath; in addition, chewing gum containing 2mg of zinc acetate has the same effect as 0.02% zinc chloride gargle. (3) Chlorhexidine + ciprofloxacin + zinc lactate Gargling with chlorhexidine + ciprofloxacin + zinc lactate solution can significantly reduce the amount of oral odor and bacteria. (4) Oil-water two-phase mouthwash This mouthwash contains 0.05% of cipiridium chloride and a mixture of olive oil and essential oils, with the addition of sweeteners and food coloring. This gargle works through the mechanism of oil droplets adhering to a large number of oral microorganisms, and the two-phase oil-water gargle can reduce the odor in the mouth by 80%. (5) Gargling with oxidizing agent Hydrogen peroxide is an oxidizing agent with disinfecting, antiseptic and deodorizing effects. It meets with hydrogen peroxide enzyme in the tissue, it can be rapidly decomposed to release oxygen and produce bubbles. Studies have shown that gargling with 3% hydrogen peroxide solution can significantly reduce bad breath. (6) Yujieol toothpaste Yujieol is a kind of fat-soluble antimicrobial drug, which is only recently applied in oral health care products such as toothpaste or mouthwash. It has both plaque inhibiting and anti-inflammatory effects. A toothpaste containing 0.3% Yujieol can effectively control bad breath within 7-12 hours after brushing. 3, remove systemic factors part of the cause of bad breath is due to other systemic diseases, such as diabetes, hepatitis, uremia, gastrointestinal diseases and blood diseases. If these patients want to cure bad breath, we need to address the cause, first of all, we should treat these systemic diseases. 4, change lifestyle smoking, alcoholism, and like to eat onions, garlic and other food patients to eliminate bad breath, you need to change your lifestyle, research shows that long-term smokers and drinkers, the mouth will emit a strong odor. Studies have shown that long-term smokers and drinkers emit a strong odor from their mouths. Therefore, if you want to be free of bad breath, you must quit smoking.