Acid in food and drinks dissolves the surface of teeth, causing damage due to erosion. This results in sensitivity and unsightly loss of the tooth surface

 

acid eroded teeth

These deciduous ("baby") teeth have been dissolved by acid in the diet. This child is 10 years old. Fortunately the two most badly affected teeth will be replaced by new teeth soon. But the permanent tooth behind (with creamy coloured sealant on it) has been in the mouth four years and is already damaged. It's supposed to last the rest of the child's life!

We measure acidity using the pH scale. This rates acidity on a scale from pH1 (extremely acid - like stomach acid) to pH14 (extremely alkali - like caustic soda). Neutral (neither acid nor alkali) is rated as pH7.

The pH scale is interesting because it is not what it seems.  It's a logarithmic scale, which means each step of 1 is actually multiplying by 10. So, if we go from say, pH6 to pH4 we go two steps - ten times ten. This means that pH4 is a 100 times more acid than pH6.

If you'd like to be nerdy - pH1 means that one in every ten hydrogen atoms is an ion (the bit that makes it acidic). pH 2 means one in every 10 x 10, that is one in every hundred, pH 3 means one in 10 x 10 x 10, that is one in every thousand and so on …. each step down means ten times more acid.

Tooth enamel dissolves at an acidity below pH5.5. Dentine, which makes up the inside of the crown plus the root dissolves at pH6. So, if we start with the mouth being neutral and then change it to a pH of 3.5 by drinking an acid drink, the tooth surface can be dissolved because the tooth is bathed in something that's a hundred times more acidic than needed to dissolve it!

 

 acid eroded teeth

 

These teeth are interesting because they belong to a 20 year old. Notice the brown patches on the front teeth? An acidic diet, combined with an abrasive "whitening" toothpaste has stripped the enamel from the tooth near gum level. The result is a rough hollow in the tooth that collects stain. The only sensible solution here is to clean away the stain and then fill the area in with white filling material. But the white filling material will eventually pick up stain itself. If the habit doesn't change, I've seen cases where the filling material has stood proud of the tooth by as much as a millimetre because the tooth around it has dissolved away!

The acidity of many drinks is quite horrifying. It's also a little more complex, because some acids are more difficult to neutralise than others, something called titratable acidity. Basically, some acids need more alkali to be added to get back to pH7 than others. It's too complex to translate into real life, so let's stick with the basic pH value. If it's below pH5.5, it'll dissolve enamel. Below pH6 it'll dissolve dentine.

Click on this link to download a table of pH of drinks.

Have a look at this table - it's a sample of the drinks brought in by some of our patients. We test them using a pH meter - a two minute job. If you're one of our patients and you'd like something testing, bring it in! It can also act as a resource for everyone else because nobody else seems to be doing this out here in real life! Remember the cut off for safety is at 5.5 for enamel and 6 for dentine.

And what happens if the tooth surface is eaten away? The teeth become very senstitive  - go to advice about sensitivity here

 

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© Hesslewood Lodge Dental Practice, 23rd January 2015