Factors behind caries
What you need to know
- Keyes drew it as 3 overlapping circles: host (the tooth), microorganisms and substrate (the diet). Later, Newbrun added time.
- Plaque bacteria, such as Streptococcus mutans, ferment sugars and produce acids.
- When the pH on the tooth drops below 5.5, the enamel starts to lose minerals.
- Frequently eating sugar or having acidic drinks increases the risk.
- Saliva protects. If there is little of it (due to medications, radiation therapy or diseases), the risk goes up.
- It is a balance: caries only progresses when mineral loss outpaces recovery.
Terms in plain words
SubstrateWhat bacteria feed on: the sugars in the diet.
CariogenicThat promotes caries.
Critical pHThe acidity level (≈5.5) at which the enamel starts to demineralize.
For the exam
Below what pH does enamel start to demineralize?
Show answerHide answer
Below about 5.5.
Sources
- Hennessy BJ. Caries. MSD Manual, Professional Version (2026 revision). View source
- Gugnani N, et al. International Caries Detection and Assessment System (ICDAS): A New Concept. Int J Clin Pediatr Dent. 2011. View source
More from Cariology & Operative Dentistry
Caries
Stages of caries
Caries progresses from the outside in: enamel → dentin → pulp. While it is only in the enamel, it can still be remineralized.
Black
Black's classification
G. V. Black classified caries and cavities by where they are on the tooth: Classes I to V, and Class VI was added later.
Fluoride
How fluoride protects
Fluoride helps with remineralization, makes enamel more resistant to acid and can reduce the acid made by bacteria.