Tooth decay might seem like a minor inconvenience, but left untreated it can cause real damage, from painful toothache to tooth loss and even wider health effects. Understanding what causes it is the first step to preventing it.
How tooth decay develops
Tooth decay is a disease that destroys tooth structure. It starts with bacteria in the mouth, which are always present. When you eat or drink anything containing carbohydrates (sugars and starches), those bacteria feed on them and produce acids as a by-product. These acids attack the tooth enamel, the hard outer layer of the tooth. Over time, repeated acid attacks weaken and demineralise the enamel, eventually creating a hole: a cavity.
Without treatment, decay can progress through the enamel into the dentine (the softer layer beneath the enamel), and eventually reach the pulp (the inner part of the tooth containing the nerve and blood vessels). At that point, root canal treatment or extraction may be the only options.
The main risk factors
Sugar and refined carbohydrates
Sugar is the primary fuel for decay-causing bacteria. Every time you eat something sugary or starchy, the bacteria in your mouth produce acid for about 20 minutes. This means it’s not just how much sugar you eat, but how often. Sipping a sugary drink over a long period is much worse for your teeth than drinking it in one go. Frequent snacking, even on things that seem fairly harmless like crackers or breadsticks, prolongs the time your teeth are exposed to acid.
Poor oral hygiene
Bacteria that cause decay live in dental plaque, the sticky film that forms on teeth throughout the day. Brushing twice a day removes plaque from the tooth surfaces, and flossing removes it from between the teeth, where a toothbrush can’t reach. When plaque isn’t removed regularly, it builds up and the bacteria in it have more time to produce acid and attack the enamel.
Dry mouth
Saliva plays an important protective role. It helps wash away food particles and bacteria, neutralises acids in the mouth, and contains minerals that help repair early-stage enamel damage. People who produce less saliva (a condition called xerostomia) are at a significantly higher risk of decay. Dry mouth can be a side effect of many medications, as well as conditions such as Sjögren’s syndrome or the effects of radiation therapy to the head and neck area.
Acidic diet
It’s not just sugar that causes enamel erosion. Acidic foods and drinks, including citrus fruits, fizzy drinks (even diet versions), and vinegar-based foods, directly attack enamel without needing bacteria as an intermediary. This type of damage is called erosion rather than decay, but the end result is weakened enamel that’s more vulnerable to cavities.
Fluoride deficiency
Fluoride strengthens enamel and makes it more resistant to acid attacks. It’s found in most toothpastes and in the water supply in many areas. People who don’t use fluoride toothpaste, or who live in areas without fluoridated water and don’t get fluoride another way, have a higher risk of decay.
Deep pits and fissures in back teeth
The chewing surfaces of the back teeth (molars and premolars) have natural grooves and fissures. Food and bacteria can get trapped in these, and they’re harder to clean thoroughly. This is why back teeth are so often the first to develop decay. Dental sealants, a thin plastic coating applied to these surfaces, can help protect them, particularly in children.
Gum recession
When gums recede (pull back from the teeth), the root surfaces become exposed. Root surfaces don’t have an enamel coating, making them much more vulnerable to decay. Gum recession can occur as a result of gum disease, over-brushing, or simply with age.
Can tooth decay be reversed?
In its earliest stages, before a cavity has actually formed, the enamel can remineralise with the help of fluoride and saliva. This is why dentists sometimes take a “watch and wait” approach to early lesions spotted on X-ray, alongside advice on diet and hygiene. Once a cavity has formed, though, it can’t heal itself and needs to be filled.
Prevention
The most effective way to prevent tooth decay is a combination of good home care and regular professional attention:
- Brush twice a day with fluoride toothpaste (at least 1000 ppm fluoride for children, 1350-1500 ppm for adults)
- Floss daily to clean between the teeth
- Reduce the frequency of sugary and acidic food and drinks
- Drink water, which helps wash away bacteria and acids
- Attend regular dental check-ups so any early signs of decay can be caught and treated promptly
Tooth decay is almost entirely preventable. With the right habits and regular dental visits, the vast majority of people can keep their teeth for life.
