A study using electric toothbrushes by the University of Newcastle upon Tyne, UK, found that when researchers increased the length of people's brushing regime and the pressure they applied to their teeth, the removal of harmful bacteria was only improved up to a point.
Beyond that point, say experts from Newcastle University's School of Dental Sciences and the Centre for Health Services Research, who carried out the study, the risk of causing oral health problems, such as the abrasion of tooth enamel or gums, gets bigger.
Yet the experts also say that while people are able to time how long they brush their teeth for, it is extremely difficult for them to accurately gauge how much pressure they should apply without seeking professional advice.
Similar results would be expected if the study was carried out using ordinary toothbrushes, say researchers.
The research, published in the Journal of Clinical Periodontology, found that two minutes and 150 grams (about the weight of an orange) was the optimum time and pressure for the average person's brushing regime.
Twelve volunteers took part in the four-week study, which examined 16 combinations of brushing times (30, 60, 120 and 180 seconds) and pressure (75, 150, 225 and 300 grams). The volunteers were trained how to use an oscillating electric toothbrush, which was wired up to a computer that took time and pressure measurements.
Brushing your teeth helps remove and prevent plaque, the bacteria-ridden, glue-like substance which can form on teeth and gums when bits of food are left in the mouth. It causes dental problems such as gingivitis and periodontal disease.
Researchers recorded the levels of plaque before and after brushing and found that plaque removal steadily improved as brushing times and pressure were increased. However, their results showed that when people brushed for longer than two minutes, at a pressure higher than 150 grams, they were not removing any additional plaque.
Peter Heasman, Professor of Periodontology with Newcastle University's School of Dental Sciences, and research team leader, said:
"Although we found that you have to brush your teeth reasonably long and hard to get rid of the harmful plaque which causes dental diseases, our research shows that once you go beyond a certain point you aren't being any more effective. You could actually be harming your gums and possibly your teeth.
"Despite this, anecdotal evidence within the dental profession suggests that the majority of the population still believe that the longer and the harder you brush, the better for your teeth it is.
"The way in which you brush your teeth is just as important, and this goes hand in glove with the time you spend brushing and the pressure you apply to them.
Prof. Heasman added: "Some electric toothbrushes contain a timer and they also provide instructions which tell you how to use them. However, it is virtually impossible for the average user to gauge how much pressure they are applying during their brushing regime.
"For example, the force you apply to your toothbrush could be quite light but the pressure will be much greater because you are applying that force to a very small area.
"If you are unsure how to go about brushing your teeth, the best thing to do is to make an appointment with your dentist or dental hygienist who will be able to train you in the correct techniques and will show you approximately how much pressure you should be applying."
Five toothbrushing tips
- Take advice from your dentist or dental hygienist on the size, shape and consistency of your toothbrush.
- Take advice on your cleaning technique, which should ensure that all teeth surfaces are cleaned effectively.
- Avoid scrubbing teeth
- Floss, or use interdental toothbrushes (available from all major pharmacies) to reach the areas that normal toothbrushes can't.
- Brush effectively and thoroughly at least once a day.
Journal
Journal of Periodontology