a. Oral Bacteria
The oral cavity hosts an environment full of life. The types of microbes found in the oral cavity include: streptococci, staphylococci, corynebacteria, methylotroph, neisseria, lactobacilli, candida, solobacterium moorei and many others. Bad breath is usually caused by the bacteria that live in a person's mouth. Bacteria live consuming foods and excreting wastes. The wastes of some oral bacteria are sulfur compounds and it is mostly these odoriferous wastes which usually is the reason of somebody's halitosis.
b. Gum Disease
Periodontal disease is caused by plaque, the colorless film of bacteria that continually forms on teeth. The bacteria create toxins that irritate the gums and gradually destroy the tissue surrounding and supporting the teeth. Blood coming from the gum fuels the bacteria with protein causing halitosis.
Gingivitis is an inflammation of the gingiva. The gingiva turns red and loses its natural shape. Bleeding occurs easily, especially toothbrushing. In some cases, however, it may lead to loss of tissue between the teeth.
Periodentitis is a more serious form of gingivitis, also called pyorrhea. Plaque and tartar are thin films of food particles and saliva that form on the surfaces of teeth. They provide a breeding ground bacteria that cause tooth decay. The teeth may become loose and may fall out.
e. Trench Mouth
A trench mouth is a painful form of gingivitis gum inflammation. Trench mouth happens when there is an excess of normal mouth bacteria resulting in infection of the gums, which turn into painful ulcers.
The bacteria that cause dental caries can metabolize sugar, produce a corrosive lactic acid and produce a sticky dental plaque. The acid in the plaque dissolves the mineral structure of the teeth. Eventually the enamel will get a hole. The smell comes from a pulp of a tooth that has become necrosed by tooth decay.
Abscess is an accumulation of infected material (pus) enclosed in the tissues of the jaw bone. An offensive odor may be present.
h. Dry Mouth
Dry mouth, also called xerostemia, happens when salivary glands don't work properly and the flow of saliva decreases. Saliva is necessary to cleanse the mouth and remove particles that may cause odor.
The surface of the dentures has bacteria, yeast, fungi, food particles and shedding cells collected from the roof of the mouth and the lower jaw, break down into the volatile organic compounds, which are very similar to the halitosis compounds that people with natural teeth have.
When people's mouths do not produce as much saliva the mouth becomes dry. Lack of saliva in the mouth means there is a lack of oxygen. That condition makes it easier for sulfur-producing bacteria to thrive.
k. Hairy Tongue
Hairy tongue is a common condition caused by defective descamation of the many small nodules (papillae) that give the dorsum of the tongue a furry appearance. It may cause halitosis and a burning sensation.