I did a little google search and found far more that I ever wanted to know about bad breath! However, there is little progress about you knowing about it if he doesn't feel like cooperating. Good luck, Aspies are known for dental neglect.
http://www.doctorspiller.com/halitosis.htm
There are essentially four sources of bad breath:
The mouth: This includes the teeth, the gums, and the top surface (dorsum) of the tongue, especially the very back of the tongue. Since this type of bad breath is the most common, its diagnosis and treatment will be covered extensively.
The term for odors from the mouth is Fetor Oris (not halitosis)___Fetor means "a strong offensive smell" and is a generic term. Oris means "from the mouth". Fetor oris is a strong 0ffensive smell originating specifically from the mouth.
Fetor Oris is the most common type of bad breath and accounts for about 80% of all cases. If you are young and generally healthy, the chances are good that your problem falls into this category.
The structures in the mouth that can harbor bad breath are:
The teeth
The Gums
The tongue (especially the back of the tongue)
The upper respiratory tract: This includes the nasal cavities, sinuses, throat, tonsils and the larynx (voice box).
The term for bad breath from the upper respiratory tract is ozostomia
Ozostomia is the second most common type of bad breath, and is most commonly associated with post nasal drip, but can be associated with infections of the various organs in the upper respiratory tracts as well, including sinusitis, sore throat and laryngitis.
The lungs: Bad breath originating from the lungs is either a temporary phenomenon caused by consuming certain foods or drugs, or it is a chronic problem caused by disease processes.
Stomatodysodia is the term for bad breath caused by outright disease processes in the lungs, such as various infections, emphysema, bronchitis or lung cancer.
Halitosis is the term for bad breath that results from physiologic processes elsewhere in the body and carried to the lungs by the bloodstream, or to the mouth by chronic vomiting.
The stomach: Technically, this type of bad breath is a subcategory of halitosis, but one that does not originate from the lungs. Bad breath originating from the stomach is caused by disease processes which produce chronic vomiting.
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