The human body is an incredibly complex and amazing machine. It has the ability to heal and repair itself from many types of injuries and ailments. However, there is one part of the body that does not have the ability to regenerate or repair itself – the teeth.
Why Teeth Cannot Repair Themselves
Teeth are unique structures in the body and are the only exposed parts of the skeleton. They are made up of multiple tissues including enamel, dentin, pulp, and cementum. The enamel is the hard, outermost white layer that contains no living cells. Under the enamel is dentin, a bonelike tissue that also does not contain living cells. The pulp contains nerves and blood vessels, providing nutrients to the tooth. Cementum covers the root of the tooth helping attach it to the jawbone.
Unlike other tissues in the body like skin and bone that can regenerate and repair themselves, once the enamel layer of a tooth is damaged or worn away, it cannot grow back. Enamel does not contain living cells that can reproduce to make new enamel. Any damage to the enamel from cavities, trauma, acidic foods, grinding, etc. is permanent. The underlying dentin may react by producing more dentin to protect the pulp if the enamel layer is compromised, but it cannot reproduce enamel.
Tooth Repair Mechanisms
Teeth do have some limited natural repair mechanisms. Saliva contains minerals like calcium and phosphate that can slowly diffuse into small areas of demineralization in enamel and help “remineralize” these spots. But the process is very slow and cannot completely regenerate large amounts of lost enamel or dentin. When decay gets deep enough to damage the pulp, the pulp may respond by activating odontoblasts to produce reparative or tertiary dentin. But this process cannot regenerate true dentin. Once the pulp dies due to infection, no repair can take place.
Dentin Repair
When the dentin layer is damaged by tooth decay or trauma, the tooth can respond by generating more dentin for a natural repair process. Odontoblasts in the pulp area can produce reparative or tertiary dentin when stimulated. This new dentin is laid down along the inner surface of existing dentin. However, the reparative dentin has an atypical structure, does not have the same properties as original dentin, and cannot replace dentin that is lost.
Pulp Repair
The dental pulp contains connective tissue, blood vessels, and nerves. If the pulp becomes inflamed or infected with tooth decay, the body will try to repair and heal it. Mild inflammation causes formation of reactive dentin. The pulp may regenerate new odontoblasts and nerve tissue over time. However, if the inflammation is too severe, the pulp can die. Once the pulp dies, no further repair is possible.
Why Tooth Repair is Important
Since teeth cannot repair themselves, it is extremely important to prevent damage and decay in the first place through good oral hygiene and preventive dental care. Lost tooth structure needs to be repaired by dental professionals with fillings, crowns, or other restorations. If cavities are left untreated, they will continue to grow, causing pain, infection, and eventual tooth loss.
Preventing Tooth Decay
Some ways to prevent tooth decay and damage include:
- Brushing twice daily with fluoride toothpaste
- Flossing once daily
- Using antimicrobial mouthwashes
- Applying fluoride gels or sealants to vulnerable surfaces
- Eating a healthy diet low in sugary foods/drinks
- Getting regular dental cleanings and exams
Treating Early Decay
Detecting tooth decay in the earliest stages allows for stoppage and remineralization before major damage occurs. Some early interventions include:
- Applying high concentration fluoride varnish
- Minimally invasive bondings
- Using calcium phosphate remineralization products
Dental Stem Cell Research for Tooth Repair
Exciting research is being done to explore the possibilities of using dental stem cells to regenerate tooth structure. Adult dental pulp contains mesenchymal stem cells that have the potential to regenerate dentin. Periodontal ligament stem cells might also regenerate cementum, periodontal ligament fibers, and alveolar bone. Researchers have had success generating tooth-like structures in animals by seeding stem cells onto biodegradable scaffolds. More research is needed, but dental stem cells may provide a way to truly regenerate teeth someday.
Pulp Stem Cells
Stem cells isolated from dental pulp tissue retain the ability to differentiate into odontoblasts that can form new dentin. When pulps are exposed, direct pulp capping with bioactive materials like MTA can allow regeneration of dentin bridge over the exposure site utilizing the pulp stem cells.
Periodontal Ligament Stem Cells
Stem cells present in the periodontal ligament can differentiate into cementoblasts that form cementum, fibroblasts that make collagen fibers, and osteoblasts that form alveolar bone. This gives them great potential for whole periodontal regeneration.
Challenges for Implementation
While dental stem cell research is very promising, there are still many challenges to overcome before stem cell therapies become routine dental treatments. Developing the intricate scaffolding needed to generate whole functional teeth is difficult. Getting the stem cells to differentiate into the correct cell lineages in proper alignment is also a challenge. Vascularization to nourish the new structures and nerve regeneration are other hurdles.
Why Salamanders Can Regrow Teeth
While humans cannot regrow teeth, some animals like sharks and salamanders can actually replace teeth continually throughout life. Salamanders are especially interesting because they can completely regenerate many body parts including the jawbone, together with a brand new set of teeth. How do they do this?
Continuous Dental Laminae
Salamanders retain specialized dental epithelial stem cells in dental laminae which are remnants of tooth development present in the jaw epithelium. These allow new teeth to form from the epithelium.
Regenerative Ability
Salamanders have extremely powerful regenerative capabilities through pathways like Wnt/beta-catenin signaling. Genes involved in tooth development like Shh and Bmp are upregulated during the process.
Differences From Humans
Humans lose the dental lamina after tooth development is complete. We also do not have the regenerative powers of salamanders. Identifying the genetic and molecular differences may help apply salamander tooth regeneration abilities to human teeth.
Artificial Tooth Implants
Since adult teeth cannot heal or regenerate, replacement teeth are needed when teeth are lost. Removable dentures can replace some missing teeth, but come with difficulties like discomfort and bone loss in the jaw. Dental implants anchored directly into the jawbone are a much better permanent solution.
Types of Implants
Several types of implants may be used depending on the situation:
- Endosteal implants – Screw or cylinder shaped implants that go directly into the jawbone. Most common type used.
- Subperiosteal implants – Metal frame implanted under the gums and on top of the jawbone.
- Plate form implants – Rectangular frame implants anchored between the bone and tissue.
The Implant Procedure
Getting implants requires multiple steps over weeks or months:
- Incision made in gums and implant anchored to jawbone
- Osseointegration period of 3-6 months for the bone to fuse tightly to the implant
- Small connector abutment attached to the implant post
- Impressions taken for the crown
- Custom-made artificial crown attached on top of the abutment
Benefits of Implants
Dental implants have many benefits over dentures and bridges:
- Do not rely on neighboring teeth for support
- Stable and comfortable fit
- Preserve jawbone by preventing resorption
- Long lasting – Estimated to last 10-15 years or longer
Conclusion
Unlike other tissues that can self-repair, tooth enamel and dentin cannot regenerate once lost due to the absence of living cells. This makes prevention of tooth decay through good oral hygiene critical. Promising dental stem cell research may someday make biological tooth repair possible. For now, prosthetic implants are the best solution for whole tooth replacement when needed.