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Dental caries (cavities) is the world's most prevalent chronic disease — affecting 3.5 billion people. Yet it is almost entirely preventable. The bacteria, the acid, the weakened enamel: understanding each step of cavity formation gives you the knowledge to stop the process before it starts.
How Cavities Form
Cavities begin with a specific group of bacteria — primarily Streptococcus mutans — that colonise the dental plaque film on tooth surfaces. When you eat fermentable carbohydrates (sugars and refined starches), these bacteria metabolise them within seconds, producing lactic acid as a byproduct. This acid lowers the pH of the plaque below 5.5 — the critical threshold at which calcium and phosphate minerals dissolve out of enamel in a process called demineralisation.
Saliva naturally buffers this acid and redeposits minerals (remineralisation) during the 20–40 minutes after each acid attack. The problem arises when acid attacks are frequent and prolonged, tipping the balance permanently toward demineralisation. Early cavities (white spot lesions) are reversible; once the cavity physically breaks through enamel, mechanical restoration is required.
The Sugar Science
The key insight from decades of research: it is not how much sugar you eat, but how often. Each sugar exposure triggers an acid attack lasting 20–40 minutes. Three meals with sugar = 3 acid attacks. Three meals plus three sugary snacks = 6 acid attacks. The enamel never fully recovers between attacks.
The Role of Fluoride
Fluoride is the single most evidence-based tool for cavity prevention. When fluoride ions are present during remineralisation, they are incorporated into the reformed enamel crystal as fluorapatite — a mineral structure up to 10 times more acid-resistant than the original hydroxyapatite. Fluoride also directly inhibits the enzyme systems that allow S. mutans to produce acid.
- Use a fluoride toothpaste (1,000–1,450 ppm for adults; 1,000 ppm for children over 3). Do not rinse after brushing — spit and leave the residual fluoride in contact with teeth.
- A fluoride varnish applied professionally twice a year reduces cavity incidence by 43% in children and 46% in adults.
- If you live in an area with low water fluoride, a fluoride rinse at a different time from brushing provides additional daily protection.
Dental Sealants
The deep fissures (grooves) on the biting surfaces of molars are responsible for more than 80% of cavities in children and adolescents — toothbrush bristles are physically too large to clean them. Dental sealants are thin resin coatings applied to these grooves in a painless, no-injection procedure. They reduce molar cavity risk by up to 80% for 2–4 years per application. Ideal timing is shortly after the first permanent molars erupt (age 6–7) and the second molars (age 11–13).
Diet Habits That Matter
Your Anti-Cavity Routine
- Brush twice daily with fluoride toothpaste — after breakfast and last thing at night. Do not brush immediately after acidic foods; wait 30 minutes.
- Floss or use interdental brushes once daily — interproximal surfaces are the most common cavity sites in adults.
- Professional cleaning and check-up every 6 months — early cavities identified at this stage cost a fraction of the treatment of advanced decay.
- Ask about fluoride varnish at your next appointment — particularly valuable for high-risk patients (dry mouth, orthodontic braces, frequent sugar intake).