What Is Dentin
Dentin is the layer of the tooth that lies beneath the tooth enamel on the crown and beneath a hard layer called cementum on the root. It surrounds the dental pulp, the soft tissue at the center of the tooth, and forms the bulk of the tooth.
Dentin is one of the tooth's three hard tissues, alongside enamel and cementum. It is softer than enamel and slightly harder than bone. Unlike enamel, which contains no living cells, dentin is formed and maintained by cells called odontoblasts that line the pulp.
What Is Dentin Made Of
Dentin is mostly mineral, in the form of a crystalline material called hydroxyapatite, with the remainder made up of collagen, a structural protein, and water.
Running through its full thickness are microscopic channels called dentinal tubules, which contain extensions of the odontoblasts.
Types of Dentin
Primary Dentin
Primary dentin forms while the tooth is developing, until the root is complete, and makes up most of the tooth.
Secondary Dentin
Secondary dentin begins to form once the root is complete. It is deposited much more slowly than primary dentin and continues for the life of the tooth. As it builds up, the space occupied by the pulp gradually becomes smaller.
Tertiary Dentin
Tertiary dentin forms in response to a stimulus such as tooth wear, decay, or a dental procedure. It is produced only by the cells directly affected by the stimulus, and it can be less regular than the original dentin and may contain fewer tubules or none at all. It is also known as reactive or reparative dentin.
What Does Dentin Do
Dentin supports the enamel above it. Its elastic quality gives the tooth flexibility and helps prevent the brittle enamel from fracturing. Together, enamel and dentin form a mineralized shell that protects the pulp.
Dentin also carries sensation. Where it is not covered by enamel or cementum, its tubules allow heat, cold, and acidic or sticky foods to reach the nerves and cells inside the tooth. Finally, because light passes through the enamel and reflects off the yellowish dentin beneath, dentin contributes to the color of the crown.
What Can Expose or Damage Dentin
Dentin is normally covered by enamel on the crown and cementum on the root. It becomes exposed or damaged when that covering is lost or breached. Recognized causes include:
- Worn enamel, including from acid erosion, abrasion, or teeth grinding known as bruxism
- Gum recession, which exposes the tooth root
- Tooth decay, also known as cavities
- Cracked or fractured teeth
- Worn fillings
- Gum disease
Signs That Dentin May Be Exposed
The main sign of exposed dentin is sensitivity. You may notice:
- Discomfort or pain with hot or cold food and drinks
- Sensitivity to acidic or sticky foods
- Discomfort when brushing or flossing
These signs can also come from cavities, cracks, worn fillings, or gum disease, so an examination is needed to find the cause. The sensitive teeth entry covers this in more detail.
If you notice new sensitivity, book an appointment at Drs. Nicolas & Asp Centers so a dentist can find the cause.
Why Protecting Dentin Matters
Dentin is less dense than enamel, and once its covering is lost, its tubules give heat, cold, and acidic or sticky foods a route to the nerves and cells inside the tooth.
Decay that advances through dentin and is left untreated can inflame the pulp and eventually lead to infection and death of the pulp tissue. In advanced cases, it can form a dental abscess and lead to tooth loss. Treating decay before it reaches the pulp helps protect the pulp.
How Dentists Protect and Restore Dentin
Treatment depends on what is exposing or damaging the dentin, so your dentist will first identify the cause.
Desensitizing Treatments
Desensitizing toothpaste contains compounds that help block the transmission of sensation from the tooth surface to the nerve, and it usually takes several applications to reduce sensitivity. A dentist may also apply fluoride gel in the office as a fluoride treatment, which strengthens enamel and reduces the transmission of sensations.
Fillings, Inlays, Crowns, and Bonding
Where decay or a flaw has damaged dentin, the tooth can be restored with a filling, an inlay, a crown, or bonding.
When decay is deep, a dentist may in some cases remove only part of the decayed dentin to reduce the risk of exposing the pulp.
Gum Grafting
If gum tissue has been lost from the root, a surgical gum graft can protect the root and reduce sensitivity. Treatment options for gum recession are explained under gum recession treatment.
Root Canal Treatment
If sensitivity is severe and persistent and cannot be treated by other means, root canal treatment may be recommended.
Can Dentin Damage Be Prevented
Dentin is protected by the enamel and gum tissue that cover it, so caring for both helps keep dentin covered. Steps that help include:
- Following a consistent daily oral hygiene routine
- Limiting acidic foods and drinks, such as soda, sports drinks, and citrus
- Wearing a night guard if your dentist recommends one to protect your teeth from grinding during sleep
- Having cavities, worn fillings, cracks, and gum disease treated early
- Seeing your dentist regularly so that early changes are found
Frequently Asked Questions
Enamel is the hard outer layer that covers the crown of the tooth, while dentin lies beneath it and forms the bulk of the tooth. Enamel is harder and contains no living cells. Dentin is softer, elastic, and contains microscopic tubules.
Dentin can repair itself only in a limited way. The pulp can form additional dentin in response to wear, decay, or a dental procedure. This tertiary dentin can be less regular than the original dentin, so damaged dentin still needs to be assessed by a dentist.
Dentin contains microscopic tubules, and when enamel or cementum no longer covers them, heat, cold, and acidic or sticky foods can reach the nerves and cells inside the tooth, which can cause hypersensitivity. The cause determines the treatment, so an examination is the way to find out.
Yes. On dental X-rays, dentin appears darker than enamel and lighter than the pulp. Dentists use X-rays such as bitewing X-rays to view the internal structure of the tooth as part of an examination.
Yes. Our dentists identify what is exposing or damaging the dentin and recommend treatment, from fluoride treatment and bonding to fillings, crowns, and gum recession treatment. Where the pulp is affected, root canal treatment is available. To book an assessment, call 04 394 7777.
Start with a general dentist, who can examine the tooth, identify the cause, and treat it or refer you. Where gum recession is the cause, a Specialist Periodontist may be involved, and where the pulp is affected, a Specialist Endodontist manages root canal treatment.
Coverage depends on your insurance plan and the treatment required. At Drs. Nicolas & Asp Centers, we accept most major insurance cards for direct billing and handle all pre-approvals and paperwork on your behalf. Where direct settlement is not available, our team assists with reimbursement documentation. The full list of insurance providers we have direct billing agreements with is on our insurance page.
- American Dental Association. "Tooth." MouthHealthy, American Dental Association. mouthhealthy.org. Accessed 29 Sept. 2026.
- Nanci, Antonio. "Dentin-Pulp Complex." Ten Cate's Oral Histology: Development, Structure, and Function, 8th ed., Elsevier, 2012, chap. 8. shop.elsevier.com
- Goldberg, Michel, et al. "Dentin: Structure, Composition and Mineralization." Frontiers in Bioscience (Elite Edition), vol. 3, no. 2, 2011, pp. 711-735. doi.org
- American Dental Association. "Sensitive Teeth." MouthHealthy, American Dental Association. mouthhealthy.org. Accessed 29 Sept. 2026.
- American Dental Association. "Dietary Acids and Your Teeth." MouthHealthy, American Dental Association. mouthhealthy.org. Accessed 29 Sept. 2026.
- American Dental Association. "Teeth Grinding." MouthHealthy, American Dental Association. mouthhealthy.org. Accessed 29 Sept. 2026.
- Bjørndal, Lars, et al. "Management of Deep Caries and the Exposed Pulp." International Endodontic Journal, vol. 52, no. 7, 2019, pp. 949-973. doi.org
