A lot of us think that we should visit the dentist every six months – even if it’s not what we do in practice. Whether those biannual check-ups are really necessary is, however, a matter of debate. In fact, it’s not even clear where the six-month figure initially came from. Some believe it dates back to the 18th Century, long before the advent of randomised controlled trials that could test its benefits.

People with a lot of problems with their teeth do, of course, need to visit the dentist often. But what about everyone else? Permanent teeth are more vulnerable to decay soon after they’ve come through, so when children have just grown their first permanent teeth at the ages of six to eight they need those regular check-ups. In the teens, teeth are less vulnerable, until wisdom teeth come through in your twenties. So the risk varies at different times of life.

In 2000, three-quarters of dentists surveyed in New York were recommending six monthly check-ups, despite the absence of studies examining whether the frequency of visits made a difference to patients at low-risk of tooth decay or gum disease. Today, many organisations such as the American Academy of Pediatric Dentistry still recommend six monthly check-ups.

But for several decades some have been arguing that the choice of six months as the ideal space between visits is rather arbitrary. Back in 1977 Aubrey Sheiham, a professor of dental public health at University College London, published a paper in The Lancet bemoaning the lack of evidence for six monthly check-ups. Almost 40 years on, he’s still making the same point.

In 2003 a systematic review examined the research that had then been done. The results were mixed. Some studies found no difference between the number of decayed teeth, fillings or missing teeth in those who attended the dentist frequently and those who didn’t, while other studies found fewer fillings in those who went a lot. When it came to gums most research found no difference in the amount of bleeding, plaque or gingivitis in permanent teeth. One study found that going to the dentist more than once a year made no difference to the size of tumours at diagnosis with oral cancer, while another found that if people waited more than a year between visits, tumours could be more advanced when they were found.

Last year the Cochrane Collaboration performed a similar systematic review of the research, and they were disappointed with what they found. The quality and quantity of the research was simply too poor to back up or refute the idea of six-monthly check-ups. They found just one controlled study where patients were randomised to attend the dentist either annually or every two years. Those who went annually did better, but it’s possible that the dental staff knew whether patients were in the annual or two-yearly group, which could have influenced the treatment they received and biased the results.

There’s something else we have to bear in mind. Even when a study finds, for example, that children who go to the dentist frequently have fewer fillings, there may be other factors at work. Those same children may have other advantages; they may belong to a higher socio-economic group, eat more healthily and have better quality dental equipment.

There is a secondary purpose to dental visits. Even if the dentist doesn’t spot any problems, they are likely to remind you to keep on caring for your teeth and cleaning them properly – although there’s no consensus about the best way of doing that either.

How often should you visit the dentist, then? Bodies like Nice, which provides guidance for the National Health Service in England and Wales, say that the frequency of dental visits all depends on the individual. They recommend that children go at least once a year because their teeth can decay faster, while adults without problems can wait as long as two years. They even go as far as to say that longer than two years is OK for people who have shown commitment to caring for their teeth and gums. Similar advice is given elsewhere. An expert group reviewing the evidence in Finland back in 2001 recommended that under-18s who are at low risk could visit between every 18 months and two years.

Where does this leave the rest of us the next time we receive a card through the door reminding us our next dental visit is due? We’d all like an excuse to go less often, and the good news is that if you don’t have any problems you can probably wait a little longer than six months between visits. But exactly how long you can wait before your appointment with the dentist’s chair will depend on the assessment you and your dentist make of your individual risk.

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