Some fruits themselves can be acidic enough to cause dental erosion. Lemons and other citrus are obvious examples, but white grapes and Red Delicious apples are also fairly acidic (pH 4.03 and 4.37 respectively). Less acidic fruits include bananas and melons. While fruit can be sweet, most of the sugar is fructose. The bacteria in our mouths find fructose harder to deal with than ordinary sugar (sucrose), so fruits are generally less harmful to teeth than processed foods with similar sugar content.
How tooth decay and erosion occur
Scientific studies consistently point to sugars as the most important dietary factor in causing tooth decay. Less well known is the fact that acidic foods and drinks, even sugar-free ones, can also damage teeth. Acid can directly damage the enamel surface of teeth – a process known as dental erosion. A recent survey found 68% of Australian children aged between six and 15 had at least one tooth that showed signs of erosion.
Teeth are made up of thousands of tiny crystals of calcium phosphate that are in a constant state of flux as calcium and phosphate ions move back and forth between the tooth enamel and saliva. Under acidic conditions (pH less than about 5.5), there is a net loss of calcium and phosphate ions from the tooth (a process known as demineralisation).
Tooth decay (dental caries) is caused by bacteria in plaque, which forms as a layer on the surfaces of teeth. These bacteria use sugar for energy, and produce acids as a by-product that can damage the crystals of the teeth. The more often you have sugary foods or drinks, the more acid the bacteria make and the more damage that occurs.
If you only eat three meals a day, with no sugary snacks or drinks in between, the bacteria have only three opportunities to produce acid, so there is minimal damage to your teeth. However, sugary drinks and snacks extend the time the bacteria are producing acid, increasing your risk of tooth decay. As damage accumulates, the tooth can become weak and break down, leading to a hole or cavity that may require a dental filling. If this process continues it can cause complete breakdown of the tooth, the only treatment option for which is extraction.
Dental erosion is caused by acids that come directly from foods or drinks (or from stomach acids regurgitating into the mouth). This acid attack is stronger than that produced by the bacteria in the tooth decay process, and leads to the complete dissolution of the outer crystals of the tooth. Every time an acidic food or drink passes your teeth and drops the pH in the mouth below 5.5, there’s a chance the outer crystals are dissolving and reducing the amount of tooth you have left.
Fortunately, your teeth are constantly bathed in saliva, which contains protective components such as calcium and phosphate ions that can help repair some of the damaged crystals. Saliva can also wash sugar and acid into the stomach and neutralise some of the acids. However, if sugary or acidic foods are consumed too often and too regularly, the damage they cause cannot be balanced by the repair properties of saliva and damage to the teeth will accumulate. Additionally, saliva also has difficulty neutralising the damaging acids of foods or drinks that are very acidic or have high acid reserves.
7 ways to prevent tooth decay and erosion
If you have a sensible diet, a good flow of saliva, a regular teeth and gums cleaning routine and your teeth get appropriate exposure to fluoride, you’re less likely to suffer decay or erosion. So to prevent damage to your teeth: