Tooth Decay Explained

What is tooth decay? 

Inside the human mouth there is a large and varied population of bacteria. Many of these bacteria are harmless or even beneficial, but some species feed on the sugars and starches in the foods we eat and produce acid as a waste product. That acid attacks tooth enamel – the hard, protective outer layer of the tooth – and, over time, can cause tooth decay.

How decay develops
When sugars and carbohydrates remain on tooth surfaces, acid-producing bacteria metabolise them and lower the pH in the mouth. Repeated acid attacks cause demineralisation: minerals such as calcium and phosphate are leached from the enamel. Normally, saliva helps to neutralise acids and bring minerals back (remineralisation), especially when fluoride is present, but when acid attacks happen more often than the mouth can recover, enamel weakens and tiny pits form. These pits can develop into cavities (dental caries).

If decay progresses through the enamel, it reaches dentine – the softer, more porous layer beneath the enamel. Dentine contains microscopic tubules that communicate with the tooth’s nerve (pulp), so once bacteria reach dentine, sensitivity and pain are more likely. If left unchecked, decay can reach the pulp, causing severe pain, infection and sometimes the need for root canal treatment or extraction.

Where decay commonly appears

• Back teeth (molars and premolars): these have grooves and pits on their chewing surfaces where food tends to lodge, and they can be harder to clean. That is why they are frequent sites of decay.
• Between teeth: interdental spaces trap food and plaque; if flossing or interdental cleaning is neglected, cavities often form between adjacent teeth.
• Around fillings and restorations: margins of older restorations can break down or allow leakage, creating areas where bacteria can colonise.

Risk factors that increase your chances of tooth decay

• Frequent consumption of sugary or acidic foods and drinks – especially sipping sweetened beverages throughout the day.
• Poor oral hygiene – irregular brushing, no flossing, or ineffective technique.
• Low saliva flow (dry mouth) – saliva buffers acid and supports remineralisation; medications, medical conditions and ageing can reduce saliva.
• Inadequate fluoride exposure – fluoride strengthens enamel and supports remineralisation.
• Certain medical conditions – for example, acid reflux, eating disorders, and conditions that reduce immunity can influence oral health.
• Deep pits and fissures in teeth – anatomical features that trap food.
• Socioeconomic and behavioural factors – limited access to dental care, infrequent dental visits, and lack of preventive care increase risk.

Signs and symptoms to watch for

• Tooth sensitivity to hot, cold or sweet stimuli.
• Pain when chewing or biting down.
• Visible pits or brown/black spots on the tooth surface.
• Bad breath or an unpleasant taste that does not go away.
• Swelling, redness, or pus around a tooth (signs of infection).

Prevention – practical steps you can take now

• Brush twice daily with a fluoride toothpaste for two minutes each time. Fluoride helps rebuild enamel and prevents progression of early decay.
• Clean between teeth once a day using floss, interdental brushes, or water flossers to remove trapped food and plaque.
• Reduce frequency of sugary and acidic snacks and drinks. Eat sugary foods only at mealtimes where possible, not continuously throughout the day.
• Rinse with water after consuming acidic or sugary foods if you cannot brush immediately; wait 30 minutes to brush to avoid brushing softened enamel.
• Use sugar‑free gum with xylitol after meals to stimulate saliva flow and reduce bacterial acid production.
• See your dentist regularly for check-ups and professional cleanings – fluoride treatments or sealants can often stop early lesions
• Consider dental sealants for children and adults with deep pits and fissures on molars – these protect chewing surfaces from decay.
• Stay hydrated and discuss medications or conditions that cause dry mouth with your dentist or physician.

When professional treatment is needed

Small cavities: these are typically treated with a filling after removing decayed tissue and restoring the tooth with a suitable material (composite resin or amalgam in some cases).

Extensive decay into dentine: may require a larger filling or an onlay/inlay to restore strength and function.

Long-term consequences of untreated decay
Untreated decay can lead to persistent pain, spread of infection to surrounding tissues (abscess), systemic health risks in vulnerable people, tooth loss, and the need for more complex and expensive dental work. It can also affect nutrition, speech, confidence, and overall quality of life.

Special populations and considerations

• Children: Primary teeth are important for speech, chewing and guiding permanent teeth. Early childhood caries can progress rapidly. Parents should establish good oral hygiene early and limit sugary drinks in bottles or sippy cups.
• Older adults: Root caries (decay at root surfaces) becomes more common as gums recede. Medication-related dry mouth is also a key factor.
• If you have braces or other orthodontic appliances, take extra care to clean around brackets and wires – use fluoride and interdental cleaning daily.

Modern preventive and minimally invasive approaches
Contemporary dentistry emphasises prevention and minimally invasive care:

• Fluoride varnishes and high‑fluoride toothpaste can arrest early enamel lesions.
• Resin infiltration and sealants can halt progression of early decay in pits and fissures.
• Remineralisation protocols (fluoride, calcium phosphate treatments) can sometimes reverse very early decay without drilling.
• Patient education, risk assessment and tailored recall intervals help manage individuals according to their risk profile.

When to see your dentist
If you notice persistent sensitivity, pain, visible holes, or a change in colour on a tooth – see your dentist promptly. Early intervention limits the extent of treatment and preserves more natural tooth structure.

In summary
Tooth decay is a preventable disease caused by the interaction of bacteria, dietary sugars, and susceptible tooth surfaces over time. Good oral hygiene, reduced sugar intake, fluoride use, and regular dental visits are the most effective strategies to prevent decay. When tooth decay is detected early, it can often be treated conservatively. If left untreated, it can progress to cause pain, infection and tooth loss.

For more information on modern dental treatments and to arrange a check‑up, please visit Camden High Street Dental Practice.