John Hale, of Dunedin, asks :-

When I clean my teeth, I find I always shut my eyes to do it, without knowing why. Is it to keep flying toothpaste droplets from getting in my eyes, or because I can rely on the feel of the brush doing its good work round my teeth and gums? or some intriguing reflex action? What do scientists do when they clean their teeth?

Dorothy Boyd, a Paediatric Dentist at the University of Otago, responded.

This is not something I have ever considered before, so I set about finding out more about it, and asking people I work with, and students that I teach at dental and medical school.

About a third of the people that I asked said they closed their eyes while brushing their teeth. Only one person had ever had toothpaste go into their eyes, and that was when they took an electric toothbrush out of their mouth while it was switched on, and the toothpaste and saliva on it splattered into her face!

So, the reasons people gave to explain why they close their eyes when brushing were to focus on what they were doing, because it feels funny like they are about to sneeze, and out of habit. Most people thought it was just a habit. New Zealand guidelines for toothbrushing recommend cleaning the teeth twice a day, for about 2 minutes, with a fluoride toothpaste on a soft toothbrush.

The fluoride content of the toothpaste should be no less than 1000 parts per million fluoride, which is written on the side of the tube as 0.76% monofluorophosphate, or 0.22% sodium fluoride. All surfaces of the teeth need to be brushed - the occlusal (biting) surfaces, the outside and the inside surfaces. Between the teeth can be reached with dental floss. So, it doesn’t seem to matter if your eyes are open or closed!