What are teeth?
Open your mind and mouth wide. Chris Smith was joined by dentist Nick Williams, from Devonshire House Dental Practice in Cambridge, to chow down the science of teeth plus we put intern, Eva Higginbotham, to the dental test. But first up, what exactly are teeth?
Nick - We adults have about 32 teeth in our mouths and they're made up of enamel, which is the hard outer layer, which is about 97 percent mineral -that's the white bit. Dentine in the middle layer which is about 70 percent mineral. And then you have the nerve and blood supply in the middle of the tooth called the pulp and that has extensions of the nerves - it extends into the dentine. And when you get sensitive teeth often that's because the dentine is exposed there.
Chris - When you say the dentine is 70 percent mineral, what do you mean by mineral and what's the other 30 percent then?
Nick - So it's mineral in terms of crystal called hydroxyapatite and there's much more of that in the enamel which makes it harder. It's a similar matrix to bone. And then the other bit is made up of collagen and in other extensions of the nerve and blood supply, so it’s quite a tubular structure.
Chris - And the hydroxyapatite's the stuff that makes the enamel tough and hard. And when we put fluoride in toothpaste that gives it additional strength doesn't it? How does it do that?
Nick - It does indeed. So if you have sugar in your diet the bacteria feed off the sugar and that actually can take mineral out of the teeth, making it more porous. That's the start of tooth decay and fluoride in toothpaste helps to remineralise the tooth so it can actually reverse the harmful effects of that decay.
Chris - How does it actually do that though, how does it get onto the enamel and do something?
Nick - If you remember your periodic table it's on the right hand side. It's quite a reactive element. Instead of hydroxyapatite you have hydroxyfluorapatite which is actually a bigger crystal and that's actually more resistant to that erosion in there.
Chris - Because it's added to drinking water isn't it, fluoride? And also toothpaste. And is the amount in drinking water sufficient to actually protect teeth?
Nick - That's a great question. It depends where you are in the country. It's a naturally occurring element, it's often quite a controversial subject water fluoridation. In fact the Center for Disease Control in America named it as one of the biggest breakthroughs in science and healthcare in the 20th century for protecting teeth because it's getting a frequent application of that fluoride onto the teeth just by drinking that water with the fluoride in it.
Chris - And that's clinically proven is it? I know that’s the language that the adverts love to use but like it's clinically proven that that fluoride does protect if it does strengthen teeth?
Nick - Yeah. Unequivocally, thousands of studies prove it and it's one part per million so it doesn't have to be very concentrated. And you’ll be pleased to know that in Cambridge the Cambridge water authority actually do add to the water to actually get that ideal concentration.
Chris - And apart from fluoride in toothpaste, what else is in toothpaste that helps us to clean teeth?
Nick - So I suppose in a nutshell just a foaming agent!
Chris - Is that to show it works?
Nick - That just helps helps the foaming and helping the fluoride actually get onto the teeth. And interestingly a top tip is after you finish brushing just spit out, don’t rinse off, because that fluoride will actually stay on the teeth.
Chris - Yes well a dental colleague of mine said you know lots of people go swish swish swish before they go to bed and it's the worst thing you can do. Because actually leaving some of that stuff sticking to your teeth - because there’s also a sort of sticky agent in the material that's in toothpaste isn't there that makes it more sticky - and they said, you know, plonk it on your teeth before you go to bed and leave it on because it will help to strengthen teeth overnight.
Nick - Definitely and if you’ve got sensitive teeth as well, you can apply sensitive toothpaste on the neck of the tooth and that will help to reduce that sensitivity.
Chris - Now in terms of actually cleaning physically using toothpaste, what's best in the battle of the brush? Is it electric or traditional manual toothbrush? What's the best way to clean teeth?
Nick - I would tend to recommend electric toothbrush over manual brushing. The aim of the game is still the same but results are generally better with the electric toothbrush. And actually we're going to run a little test here aren’t we?
Chris - Yes, well and we’ve found you a victim. Hello Eva, welcome
Eva - Hello!
Chris - Eva is our Naked Scientists intern at the moment. She’s actually a PhD student studying how the brain develops so we thought actually she put her mouth where her money is this week! So tell us what you've done in the name of science today?
Eva - So today I have not brushed my teeth or used mouthwash or any other agent like that. I brushed my teeth last night and then I haven't brushed this morning or any other point during the day.
Chris - So every dentist listening to this is now shuddering Nick. This is all in the name of science. So you've also eaten a disclosing tablet that will show us where the muck is.
Eva - Yes, I have yeah. I just chewed that up a few minutes ago.
Chris - And this binds to plaque, which is the stuff that coats your teeth and shows where the bacteria are. So Eva now has a blue mouth. Nick so what do you want her to do?
Nick - Excellent well - it's a really helpful sort of visual aid to help with brushing and it’s something we use a lot to help with patients. So what I'll do is if you can split your mouth into left and right, and if you brush your right hand side with your manual toothbrush then the left hand side with the electric toothbrush and then we'll see what the results are.