The Christmas excesses are behind us, but now it's pay back time. Many of us will be dieting to shed those unwanted kilos. But beware, there may be an unexpected consequence: bad breath. Peta Newbold reports.

It's socially unacceptable and impossible to keep to ourselves. It affects around 50 to 60 per cent of the population, yet no one likes to talk about it. It's bad breath, or to use the polite medical term, 'halitosis'.

There's a common misconception that people who suffer from halitosis are sick.

"Illness can contribute to the problem, but in some otherwise healthy people it's a physiological phenomenon", says Dr Myles Lear of the Fresh Breath Clinic in Sydney.

"Everyone has their own base level of odour and it can be compounded by a number of factors including stress, dieting, and medication."

What is bad breath?

There are 50 billion germs in our mouth and if the bacterial balance is upset our breath will smell. It is caused by gases, which consist of a group of compounds known as volatile organic sulphur compounds (VSC). Some have graphic names like Cadaverine and Putrescine, which leave little to the imagination!

The main groups are:

• Hydrogen Sulphide (smells like rotten eggs). It's present in the highest concentrations and around 1.3 times higher than:
• Methanethiol (smells like rotting cabbage).
• Dimethylsulphide (apparently smells a little sweet).

How to tell if you have bad breath.

"We can't smell our own breath," says Dr Lear. "People who work in a fish and chips shop stop smelling fish and chips and that's because they become desensitised. We too become desensitised to the smell of our own breath."

It is said to be 'something only your best friend can tell you about' but the reality is that even those close to you can be reluctant to tell you your breath is offensive. It's more likely you'll notice people backing away when you're speaking to them.

Alternatively you can:

• Ask your best friend and hope for an honest answer.
• Do something called the 'wrist lick test' where you lick your wrist and sniff it. However Dr Lear warns it is unlikely to be a good indicator and the odour can be worse than the smell of your breath!
• See a dentist who has a halimeter. It is a sulphur pollution detector
• that measures VSC and gives the results in parts per billion.

Curing bad breath.

It depends on what is causing it and it's likely to be more than one factor. A common misconception is that disturbances of the digestive system are to blame, but gum disease and tooth decay are the most common reasons people have anti-social breath.

How your dentist can help.

Stagnant food, dead plaque and dead gum cells cause gum disease and tooth decay. The result is 'smelly' VSC.

To combat these gases your dentist will:

• Advise on effective brushing, flossing and tongue scraping.
• Tongue scraping can be particularly effective because it removes the bacteria from the back of the tongue caused by 'post nasal drip'.
• Replace failing crowns and fillings, fill cavities or remove decayed and rotting teeth that are beyond repair.
• Advise on an effective mouthwash. Most mouthwashes tend to mask the problem by replacing one odour with another. Although they do contain antibacterial agents they may kill only certain kinds of bacteria so the effective is temporary. According to Dr Lear, mouthwashes that do work contain Chloride Dioxide.

Diseases that can lead to bad breath.

Sinusitis and tonsillitis produce mucus, which is attacked by the bacteria at the back of the throat or nose to produce VSC. Other diseases like diabetes and hepatitis can sometimes be a contributing factor.

Having ruled out dental problems and disease, bad breath can often boil down to one important factor; dry mouth. On average, we generate about half a millilitre of saliva every minute, except when we're asleep. This works out to roughly 800 to 1500 ml a day. Saliva is good for us. It is a strong antibacterial substance and without frequent flushing bacteria will multiply and decompose.

Factors that reduce saliva flow are:

• Dieting. Eating and chewing food stimulates saliva and scrapes bacteria from the teeth, gums and tongue and so it is better to eat small amounts more often, than 'starve' for long periods.
• Medications. According to Dr Lear, all medications will eventually reduce saliva flow but the main culprits are blood pressure medications, antidepressants, anti anxiety, anti psychotic agents and diuretics.
• Old age. Saliva flow reduces with age but the reason some old people smell is because the problem can be compounded by the fact that they tend to take more medications.
• Disease. 'Dry mouth' can also be caused by one auto-immune disease in particular, 'Sjoegren's syndrome'.

Drinking water frequently is good for general health and helps keep breath fresh. Saliva flow can also be stimulated by flavoured sugar free chewing gums.

Morning breath.

It is defined as 'malodorous breath upon waking after a night's sleep' and whether we're willing to admit it or not, it's something we all experience. When we go to sleep, the production of saliva plummets, and every night the bacteria multiply. Unlike halitosis, 'morning breath' tends to disappear within an hour of getting up. The easiest cure is to eat breakfast and brush your teeth and your tongue.

References:

The Fresh Breath clinic at http://www.myles-lear.com

Karl Kruszelnicki's 'Great Moments in Science': http://www.abc.net.au/science/k2/moments/s426489.htm

'The Health Report': http://www.abc.net.au/rn/talks/8.30/helthrpt/stories/s222.htm

Your Dentist: http://www.dentist.com.au