Halitosis is a relatively common social phenomenon that exists at all ages. Many scholars have proposed their own classification of halitosis, and one of the most accepted classifications is the classification of halitosis into three major categories: true halitosis, pseudohalitosis, and halitophobia. The causes and treatment needs of different types of halitosis are significantly different, and the selection of treatment options for halitosis status based on the determination of halitosis category is what this article is about. Halitosis, or bad breath, is a strong oral or respiratory odor that not only directly affects people’s social interactions, but also has the potential to cause psychological disorders. The International Society for Breath Research (ISBOR), held in Tokyo in July 2001, attracted 350 experts to participate. The fact that Americans spent more than a billion dollars on chewing gum, mouthwash and mouth fresheners in 2000 alone shows that bad breath is being taken more and more seriously in today’s society. It is commonly believed that bad breath is caused by the production of volatile sulfides and other odoriferous substances (e.g., indoles, diamines) by oral microorganisms through the decay and digestion of stagnant material in the mouth. The main odor components that cause bad breath are VSCs, of which hydrogen sulfide (H2S) and methyl mercaptan (CH3SH) are the two most important ones. The vast majority of bad breath is caused by local factors in the oral cavity, with periodontal pockets, tongue and saliva being the main sites of halitosis formation. Because the determination of halitosis is subjective and brings many unstable factors to clinical examination and diagnosis, the existence of halitosis needs to be determined by rigorous testing methods, and there are two types of methods used: sensory analysis and chemical analysis. Sensory analysis method that is, the human body’s sensory organs nasal discrimination, to 0 ~ 5 integer points recorded, the subject is required to fast 2 hours before the test, water, smoking, brushing teeth, chewing gum or use of other mouth cleansers, specific methods include verbal odor, licking wrist test, plastic spoon test, condensation bath, etc. Chemical analysis method is to quantify and analyze the odor components in the breath with instruments to more objectively determine the presence or absence and degree of halitosis, and currently more chemical analysis methods are used: gas chromatography detection method and sulfide detector analysis method. Many scholars have expressed their views on the classification of halitosis, and the one currently accepted by many scholars is the Miyazaki’s classification approved by ISBOR. Different types of halitosis do not require the same degree of treatment, and it is logical that the corresponding treatment plan differs, so Treatment Need (TN) was born. In the following, we will discuss the classification and treatment needs of halitosis. 1. Classification Many scholars have studied the classification of halitosis and have proposed various classifications. Some of these classifications are from the etiological point of view, some are from the analysis of the site of production, and some are for clinical guidance purposes to propose a more detailed classification. 1.2.1, physiological halitosis causes physiological halitosis are: ①, reduced saliva flow during sleep; ②, the metabolism of specific foods and beverages to produce volatile fatty acids or other odorous substances excreted by the lungs, such as alcohol, garlic, onions; ③, smoking; ④, female menstrual period. 1. 2. 2, pathological halitosis Causes of pathological halitosis are: ①, oral diseases: poor oral hygiene, plaque, dental caries, gingivitis, stomatitis, periodontitis, polychromatic tongue, oral cancer, etc.; ②, upper respiratory tract diseases: nasal obstruction, open mouth breathing, chronic sinusitis, foreign bodies, atrophic rhinitis, tuberculosis, syphilis, nasal sclerosis, nasopharyngeal abscess, laryngeal cancer, laryngeal sclerosis, etc.; ③, lower respiratory tract diseases. Lung abscess, lung cancer, bronchitis, necrotizing pneumonia, abscess chest, etc.; ④, upper gastrointestinal tract abnormalities: salivary gland disorders (anticholinergics, dehydrating agents, head and neck area radiation therapy, Schegren’s syndrome), peri-tonsil abscess, retropharyngeal abscess, occult tonsillar disease, tonsil cancer or pharyngeal cancer, congenital bronchoesophageal fistula; ⑤, digestive tract disorders: gastric cancer, esophageal hiatal hernia, pyloric stenosis, Crohn’s disease; ⑥. neurological disorders: olfactory disorders, gustatory disorders can make patients consciously feel bad breath, while the deficiency of the trace element zinc is believed to cause abnormal taste and smell; ⑦, systemic diseases: leukemia, granulocyte deficiency, azotemia, ketoacidosis; ⑧, drugs: such as lithium salts, penicillamine, ashwagandha, thiourea will change the sense of taste and smell causing subjective halitosis, some sulfur-containing drugs such as dimethyl sulfide will be metabolized in the body and with respiratory Some sulfur-containing drugs, such as dimethyl sulfide, are metabolized in the body and excreted with the breath; ⑨, functional diseases: psychosis, depression. 1.3, Miyazaki classification The classification proposed by Miyazaki et al. in 1999 has been accepted and cited by many scholars, and was recognized by more people at the ISBOR in Tokyo in 2001. Their classification divides halitosis into true halitosis, pseudohalitosis and halitophobia. 1.3.1 True halitosis is determined to have a distinct odor that can be detected by others is true halitosis. Which is divided into physiological halitosis, pathological halitosis due to different reasons. Details are as follows: the source of physiological halitosis is mostly located in the oral cavity, produced by the local decay process, does not have a disease or pathological factors that can be clearly proven to cause bad breath. Most scholars believe that the odoriferous substances in the oral cavity are VSCS produced by microbial decay of sulfur-containing proteins, peptides, exfoliated epithelium, blood cells, etc. Saliva and tongue moss are the sources of bad breath substances, and the tongue moss on the back of the tongue is considered to be the most important source of bad breath, with most of the odor arising from the back surface of the tongue, which has a large number of odor-causing anaerobic bacteria. Also, studies have shown that PH and acid-base metabolism of oral bacteria play an important role in halitosis, thus confirming that saliva plays a central role in halitosis formation. Reduced saliva flow during sleep promotes the decay process of anaerobic bacteria in the oral cavity and causes the so-called “morning sickness”. Temporary halitosis due to food: There are many specific foods that cause transient halitosis due to irritating odor or odor remaining in the mouth after consumption, such as garlic, onion, durian, etc., which can be reduced or even disappeared with mouth rinsing, brushing and other appropriate cleaning measures. It has also been reported that garlic, onions and other foods can cause temporary bad breath even if they are not chewed. Many people believe that bad breath from food comes from the stomach, but that is not true because the odor from the stomach does not escape from the mouth on its own unless burping or vomiting. The causes of physiological bad breath are also smoking and temporary bad breath due to changes in hormone levels during women’s menstruation. Pathological halitosis: As opposed to physiological halitosis, halitosis is caused by the presence of certain specific diseases or pathological states. According to the different sources of the following categories: (1), orogenic halitosis: the vast majority of halitosis is orogenic halitosis, accounting for about 85％ of halitosis. Orogenic halitosis is generally caused by the following aspects: Because oral microorganisms produce volatile sulfide (VSCS) and other odoriferous substances by corrupting and digesting the stagnant material in the oral cavity to produce halitosis, the local state of the oral cavity remains the main causative factor of halitosis. Periodontal pockets, saliva, and tongue are the main sites of bad breath formation, and bad breath symptoms can be produced when the state and environment of these three are changed by diseases or pathologies such as poor oral hygiene, periodontal disease, hirsute tongue, and dry mouth. Bad breath can also be caused by necrosis of tissues and mucous membranes in the oral cavity, such as oral ulcers, gangrene, necrotizing ulcerative gingivitis, deep caries, oral cancer, etc. Long-term improper use of dentures also cause bad breath symptoms because of denture stomatitis or food residue residue. (2), non-oral halitosis: including nasal, perinasal and / or nasopharyngeal sources, lung, upper gastrointestinal tract sources and other parts of the body diseases caused by the blood carrying odoriferous substances excreted in the lungs and bad breath. 1.3.2, pseudohumor Pseudohumor is delusional halitosis, patients feel bad breath without being noticed by others, and there is no evidence of halitosis after examination. Usually by psychological counseling, halitosis knowledge health education and appropriate reassurance explanation and eliminate the patient’s self-conscious halitosis symptoms. Rosenberg, in collaboration with other scholars, found that people suffering from halitophobia are extremely sensitive when interacting with others and have obsessive-compulsive tendencies. 1.4, in the study of halitosis, the classification of halitosis into orogenic and non-orogenic. 1.4.1, orogenic halitosis 1.4.2, non-oral halitosis The contents include: upper respiratory tract sources; lower respiratory tract sources; transmitted through the blood: ①, systemic diseases: liver necrosis, diabetic ketoacidosis; ②, metabolic disorders: persistently high methionine will raise the level of methionine in the blood, the high level of methionine base transfer effect is caused by the concentration of dimethyl sulfide in the blood, urine, breath (iii), drug effects: some sulfur-containing drugs such as dimethyl sulfide will be metabolized in the body and excreted with respiration; (iv) food. All of the above classifications have their own characteristics, and the classification proposed after comprehensive consideration has more clinical treatment and research significance, not only from the etiology but also from the psychological division of the type of halitosis, which is conducive to analyzing the actual condition of different patients and guiding treatment with it. How to develop the appropriate treatment plan for different types of patients is what we will discuss below. 2, Treatment Needs (TN) Until a few years ago, the term treatment needs was not proposed, and the general advice of doctors for patients with halitosis was to brush their teeth carefully several times a day, apply mouthwash and chewing gum, and eat more vegetables and fruits, etc. However, patients with halitosis, even if they suffer from true halitosis, are more or less overly concerned about the degree of their halitosis in psychological terms, and in some ways induce doctors to make inappropriate diagnosis and treatment. The establishment of TN is to guide clinicians to determine whether a patient has halitosis and what kind of halitosis condition he or she is in by certain testing methods, and then treat the patient appropriately, which is undoubtedly a more effective way to treat halitosis. The current TN standard is the treatment need standard corresponding to the classification of halitosis, which is divided into TN-1 to TN-5.