Tooth Decay (Cavities)

How tooth decay happens

1. Plaque forms: a sticky film of bacteria (especially Streptococcus mutans) builds up on teeth.
2. Sugars and starches in food and drinks feed the bacteria, which produce acid.
3. Acid dissolves minerals from enamel for 20 to 30 minutes after each sugary exposure.
4. Saliva and fluoride help replace minerals between snacks.
5. When acid attacks outnumber repair, minerals are lost faster than replaced, and decay progresses.

Stages of tooth decay

Medical and dental professionals call this disease dental caries.

Signs and symptoms

• white, brown or black spots on teeth
• visible holes or pits
• sensitivity to sweet, hot or cold foods
• toothache, especially when biting
• bad breath or a bad taste
• food trapping between teeth
• a broken or chipped tooth
• swelling of the gums or face with a dental abscess

Early decay often causes no symptoms, which is why regular checkups and X-rays matter.

Risk factors

• frequent sugary snacks and drinks, including juice, soda, sports drinks and sweetened coffee
• sipping or snacking throughout the day
• poor brushing and flossing
• not enough fluoride
• dry mouth from medicines, radiation or Sjogren's syndrome, since saliva protects teeth
• acid reflux and eating disorders (also cause dental erosion)
• receding gums from periodontitis, exposing softer root surfaces
• babies put to bed with bottles of milk or juice (early childhood caries)
• limited access to dental care

Diagnosis

A dentist finds decay by examining the teeth, probing suspicious areas and taking dental X-rays (bitewings) to see between teeth and below fillings.

Treatment

• fluoride treatments: varnish, gels or prescription toothpaste can reverse early white-spot lesions
• fillings: remove decay and fill the hole with tooth-colored composite, amalgam or other materials
• crowns: for large cavities or weakened teeth
• root canal treatment: removes infected pulp, cleans and seals the root, often followed by a crown
• extraction: when a tooth cannot be saved; replaced with an implant, bridge or denture
• silver diamine fluoride: a liquid that stops decay, useful for children and people who cannot tolerate drilling (it stains decayed areas black)

Antibiotics do not treat decay itself. They are used only for spreading infection alongside dental treatment.

Pain relief while waiting for the dentist

• ibuprofen or acetaminophen (paracetamol), following the label dose
• avoid very hot, cold or sweet foods
• rinse with warm salt water
• do not place aspirin directly on the gum, which burns the tissue

Prevention

• brush twice a day for 2 minutes with fluoride toothpaste; spit, do not rinse, to leave fluoride on teeth
• clean between teeth daily with floss or interdental brushes
• limit sugary foods and drinks, and keep them to mealtimes rather than grazing
• drink fluoridated tap water
• dental sealants on children's back teeth
• chew sugar-free gum with xylitol after meals to boost saliva
• regular dental checkups, usually every 6 to 12 months
• for babies: wipe gums, start brushing with a smear of fluoride toothpaste when the first tooth appears, avoid bedtime bottles, and see a dentist by age 1

Frequently asked questions

What are the first signs of tooth decay?

The earliest sign is a white, chalky spot on the enamel, which usually causes no symptoms. As decay progresses, you may notice brown or black spots, small holes, sensitivity to sweets, hot or cold, and eventually toothache.

Can tooth decay be reversed?

Only in its earliest stage. White-spot lesions can be remineralized with fluoride toothpaste, fluoride varnish, less sugar and good hygiene. Once a cavity forms, it cannot heal on its own and needs a filling.

What are the stages of tooth decay?

Decay progresses from demineralization (white spots), to enamel decay, dentin decay, pulp infection, and finally abscess. Each stage needs more extensive treatment, from fluoride and fillings to root canal or extraction.

How can I stop tooth decay from getting worse?

Brush twice daily with fluoride toothpaste, clean between teeth, cut down on sugary snacks and drinks, drink fluoridated water and see a dentist. Existing cavities need professional treatment to stop them progressing.

Is tooth decay contagious?

The bacteria that cause decay can pass from parent to child through saliva, for example by sharing spoons. Good oral hygiene in caregivers and not sharing utensils with babies reduce this.