bad breath that is caused by a fragrant meal or a night of sleeping with one's mouth open may not necessarily be a regular thing. Single instances of oral odor might be called, in medical parlance, "acute" bad breath. However, some forms of halitosis recur day after day. Experts say that this kind of chronic bad breath can have many sources.
One of the most common causes of chronic oral odor is excess bacteria in the mouth, periodontist James Hanley recently told the Boston Globe. He estimated that 90 percent of persistent bad breath is caused when oral microbes are not regularly rinsed away.
Hanley, who practices at the Tufts School of Dental Medicine, said that if the mouth is not cleaned regularly, the interaction between food particles and bacteria can lead to a severe gum infection called periodontitis, which can cause tooth loss and severe halitosis.
The Ohio State University Medical Center has stated that a chronically dry mouth and tongue can also lead to oral odor. Without saliva to rinse away bacteria from the teeth and tongue, these microorganisms can multiply quickly and emit foul smelling gases as a byproduct of their digestion.
The Mayo Clinic adds that sinus infections and post-nasal drip can also contribute to chronic bad breath. To eliminate the smell associated with any of these conditions, individuals may consider brushing more often and swishing with a specialty breath freshening rinse.