Dental decay

Clinical definition of dental decay

Dental decay is characterised by the loss of mineral ions from the tooth caused by the presence of bacteria in plaque and their acidic by-products.

Early mineral loss (known as demineralisation) is only visible microscopically, but further loss becomes evident in enamel as a chalky appearance on the tooth – a white spot lesion.

The basic carious process can also be called an acid attack. Bacterial plaque builds up on the tooth surface. When sugars enter the mouth they are absorbed by this layer. Inside the bacterial cells the sugars are broken down (or metabolised) and acid is produced.

The acids accumulate in the plaque layer and start to demineralise the tooth. Find out more about demineralisation and remineralisation.

Why we need to address dental decay

Dental decay, also known as tooth decay or dental caries, is a widespread condition in the Western world and a particular problem in Scotland.

The NDIP's (National Dental Inspection Programme) research in 2008 highlighted that 42 per cent of Scottish children have signs of dental decay by the time they reach Primary 1 (P1) and this figure is even higher in areas of deprivation.

It has become apparent that dental caries is essentially a disease associated with social deprivation. In Scotland, lower levels of caries are now being seen in more affluent areas.

NDIP 2010 showed that those in quintiles three, four and five reached the 2010 National Target for P1 of 60 per cent with no obvious decay experience. While quintiles one and two, the most deprived areas, fell short, with only 46.5 per cent of P1 children in quintile one having no obvious decay experience.

NDIP 2011 reported that: "there is a continuing trend of improvement in the oral health of Primary 7 (P7) children in Scotland over time, with 69.4 per cent having no obvious decay experience in 2010/11. For the first time, all NHS Boards across Scotland have achieved the target of 60 per cent of P7 children with no obvious decay experience. Socioeconomic inequalities in the oral health of P7 children persist, with those from all but the most deprived backgrounds having reached the 2010 National Target of 60 per cent with no obvious decay experience".

NDIP 2012: The oral health of P1 children in Scotland continues to show improvement in terms of both an increase in the proportion with no obvious decay experience and a decrease in mean d3mft. All SIMD quintiles and SIMD deciles saw an improvement in oral health compared to the results of 2010 and the extent of disease continues to fall in those most affected by decay. However, clear health inequalities remain.

NDIP 2013: For the first time, P7 children in all SIMD deprivation quintiles have reached the 2010 National Target of 60 per cent with no obvious decay experience. P7 children from all socio-economic backgrounds saw an improvement in oral health compared to the results of 2011, and the extent of disease continues to fall in those most affected by decay. Clear health inequalities remain, but the largest improvement in oral health is seen in areas in the most deprived SIMD quintile.


Dental decay is a process that is preventable by following these basic oral health messages:

  • brush teeth twice at least twice daily, in the morning and last thing at night using toothpaste containing at least 1000 parts per million (ppm) fluoride
  • supervised toothbrushing until the age of 7
  • foods and drinks containing sugar should be kept to a minimum and are best given at mealtimes
  • register with a dentist and visit regularly
  • spit out toothpaste, don’t rinse after brushing (to give the fluoride time to work).

In the early stages, there are effective treatments for preventing the decay from causing pain and requiring a filling or eventual tooth loss. However, sometimes dental extraction is the only treatment option.

Failure to prevent dental decay in a pre-school child, through modifying poor dental related behaviour of both child and parent, will generally condemn the majority of affected children to a lifetime cycle of dental treatment (SIGN 83: ‘Prevention and Management of Dental Decay in the Pre-School Child’) (external link).

Demineralisation and remineralisation

Demineralisation (loss of minerals) can be followed by remineralisation (gain in minerals) where the tooth takes up mineral ions, and in some early stages this can be enough to reverse the early carious process.

However, as this is a dynamic process (with remineralisation being followed again by demineralisation) it is only when the demineralisation occurs much more often than the remineralisation that the teeth are at risk of cavitation (breaking down to form a cavity).