I've read articles about how fluoride toothpaste is essential to maintaining a healthy mouth, and how it is beneficial to the enamel. However, I could not find articles/papers regarding the effect of fluoride on the layer beneath the enamel, also known as the dentin.

Let's assume a guy who has his enamel completely eroded away (tooth decay), and is only left with his dentin. (Side Question: How likely is this?)

If he starts brushing his teeth with fluoride toothpaste, will the toothpaste help in slowing down his tooth decay, and/or have other positive and negative side effects?

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1 Answer 1


This is usually seen in clinical settings: a child is left with an untreated enamel caries. Then the lesion progress and the lesion is cavitated. The dentin then start to react, ocludding the dentinal tubules. When the saliva (+ minerals) reach the dentin, the caries process start to slow down and the dentin change from dark brown to almost black. At the same time, the change in color represents a change in the surface composition, changing from a soft surface to a hard one.

This occurs with the minerals of the saliva. If you add fluoride, you will enhance this process. Hence, the fluoride of the toothpaste will slow down the caries process in the dentin.

About you side question: often. Keep in mind that any radicular surface clinically visible means exposed dentin. Google "radicular caries" images.

If you want to read the details, ten Cate has several (now classics) papers:

  • ten Cate JM. Remineralization of caries lesions extending into dentin. J Dent Res. 2001 May;80(5):1407-11.
  • Deng DM, van Loveren C, ten Cate JM. Caries-preventive agents induce remineralization of dentin in a biofilm model. Caries Res. 2005 May-Jun;39(3):216-23.

Bonus 1: nobody knows why the carious dentin is brown...

Bonus 2: a black spot in a teeth means a dentinal stopped carious lesion.

  • I would just correct one aspect : the roots are covered by cementum. If you remove the cementum from the root (by brushing too hard or having a cavity) or enamel from the tooth (for similar reasons, as well as grinding, eating acidic food), you will expose the underplaying dentin.
    – enap_mwf
    Feb 18, 2018 at 1:53
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    Indeed the root is covered by cement as long as the cement is protected by periodontal tissues. Periodontal disease is the cause of exposure and removal of the cementum. Google for any image of root under microscope, as google.cl/…:
    – sue
    Feb 18, 2018 at 2:28

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