Does this not sound familiar: yesterday a good dinner at a Greek restaurant, onions and garlic included, today people keep their distance. While the deterrent effect of various foods casts itself off after hours or even days, some patients suffer constantly from socially stigmatising halitosis.
More than 25 percent of all Germans are affected by it in phases, and six percent are tormented by this problem permanently. Going on the basis of literature in English, halitosis naturalised itself as a term, regardless of the mechanisms ultimately behind it. Modern analysis methods reveal many a smelly molecule.
In the clutches of the chemist
In the respiratory air of halitosis patients chemists have, using gas chromatography with mass spectrometry (GC-MS), identified 700 volatile substances. Not all molecules are responsible for foul odour. Rather, hydrogen sulfide, methyl mercaptan, dimethylsulphide and other volatile sulphur compounds are guilty as charged. Also, amines, aromatics, alcohols and short-chain carboxylic acids contribute to the unwanted odour-potpourri. The relevant breakdown products occur up to a level of about 85 percent in the oral cavity. Only rarely are pathological processes in the ENT region (ten percent) or disorder of internal organs (five percent) concealed behind it.
Comfort zone for bacteria
Germs as Solobacterium moorei (Bulleidia moorei) are active in the oral cavity. They are not alone: More than 80 species derive from sulphur-containing amino acids, such as cysteine, hydrogen sulfide, or synthesise mercaptans. Food debris, saliva and blood serve as sources, wherein proteases from the saliva also come into play. They degrade proteins to amino acids, among them cysteine – an ideal substrate. Microbes are particularly comfortable in patients with reduced salivary flow. Aside from reduced fluid intake, various drugs, such as anticholinergics, antidepressants, antiallergenics or antihypertensives, can be hidden causes. Xerostomia on rare occasions indicates separate underlying diseases, such as Sjögren Syndrome, diabetes mellitus or malfunction of the thyroid. After radiation therapy, patients also complain of dry mouth.
In the oral cavity, germs like to colonise confined spaces, such as crumbling fillings, carious lesions or periodontal pockets. Periodontitis, gingivitis or localised infections lead to similar outcomes. Up to 80 percent of all bacteria of the oral cavity however accumulate on the tongue. In cases of visible tongue coating, there are about 25 times more microbes active on the site than is normal. While dental care today is already on the agenda in kindergarten, our organ of taste is often punishingly neglected. In the search for successful strategies, researchers compared the effectiveness of different cleaning methods: a dental cleaning with toothpaste and toothbrush, an additional tongue cleaning with commercially available tongue brush and toothpaste, as well as use of a special tongue gel. In addition to sensory evaluations, volatile sulphur compound levels were determined by measuring – both before and after each cleaning. In fact a combination of brushing teeth and cleaning of the tongue with gels delivered the best results. What’s also interesting is the group of active ingredients.
In order to reduce the number of undesirable microorganisms, antibacterials make sense. Chlorhexidine is the gold standard, with prolonged use however leads to discoloration and partly to an irritation in taste. Therefore some products contain cetylpyridinium, tin or amine fluoride, triclosan or highly diluted hydrogen peroxide as an alternative. And heavy metal salts such as zinc or tin form gaseous sulphur compounds by creating lightly soluble sulphides. Yet the mixture does the job: as a Cochrane Review already showed in 2008, chlorhexidine plus cetylpyridinium plus zinc lactate reduced halitosis significantly compared to a placebo. And tea tree oil has at least in smaller studies demonstrated a clearly pronounced antimicrobial effect, especially against Solobacterium moorei. Yet not every product lives up to its full-bodied slogans. Brazilian fellow researchers assessed the extent to which mouthwashs containing extracts from zedoary root (Curcuma zedoaria) or green tea (Camellia sinensis) neutralise gas forming suphurous compounds. An effect was not found. Generally, for dentists the question of how long antibacterial substances should be applied is also a subject of controversy. As maintenance therapy they suppress the desirable oral flora just as much.
The great evil
Only rarely are diseases of other organ systems the cause behind unpleasant odours, for instance rhinosinusitis or tonsillitis. After a successful recovery, in addition to primary symptoms there is improvement in halitosis. For laymen, in cases of bad breath diseases of the gastrointestinal tract come to mind – this is less likely than many had assumed for years. In a prospective study, Turkish fellow researchers examined 121 men and 237 women with dyspeptic difficulties. Patients in the halitosis group were significantly more often plagued by belching, flatulence and nausea. In diagnostic terms however there was no accumulation of common diseases such as oesophagitis, cardiac failure, hiatus, gastritis or duodenitis. Helicobacter pylori also has no clearly perceivable influence on the formation of malodorous sulphur compounds. In individual cases, however, connections between bad breath and oesophagal diverticula were demonstrated.
Metabolism out of control
Various metabolic processes – albeit rarely – can lead to bad breath. When the liver metabolises fatty acids to ketone bodies due to lack of carbohydrates, acetone is formed. The molecule is not further utilised, but released via the urine or the breath – a characteristic smell allows its presence to be detected. In diabetic patients, this ketoacidosis can lead to coma. And last but not least, patients with trimethylaminuria, in American-English known as “Fish-Odour Syndrome”, emit smelly trimethylamine.
Behind this there is a genetic, incurable enzyme defect. Liver and kidney diseases also sometimes result, due to changes in metabolism, in recurring halitosis – these are mere individual cases in internal medicine. In most cases, doctors and dentists can however help their patients in doing away with these unpleasant evils.