Formation of Tertiary Dentin
- Tertiary dentin forms as a reaction to stimulation, such as caries, wear, and fractures.
- It acts as a mechanism for tooth healing and protects the pulp chamber.
- Tertiary dentin is easily distinguishable on the tooth's surface and appears darker than primary dentin.
- It may not be visible on the tooth's surface but can be viewed on a Micro-CT scan.
- Gorillas have a high rate of tertiary dentin formation, while hominins have a lower rate.

Protective Function of Tertiary Dentin
- Tertiary dentin forms to protect the pulp chamber when there is severe wear on the tooth's surface.
- It helps prevent abscesses and infection by providing a barrier.
- Different species have varying rates of tertiary dentin formation.
- Gorillas show a high rate, with over 90% of worn teeth exhibiting tertiary dentin.
- Hominins have a much lower rate, with around 15% of exposed dentin showing tertiary dentin formation.

Research and Studies on Tertiary Dentin
- Clinical studies have investigated the properties of tertiary dentin formation.
- Studies have focused on both humans and animal models, mainly from an oral health perspective.
- Genetic changes in animal models can increase tertiary dentin production.
- Research suggests that certain species may have evolved to produce tertiary dentin in response to dietary changes.
- For example, gorillas may have developed high rates of tertiary dentin formation as protection against severe wear caused by their tough vegetation diet.

References
- Towle, Ian. 'Tertiary Dentine Frequencies in Extant Great Apes and Fossil Hominins.' Open Quaternary, vol. 5, no. 1, 2019, pp. 2.
- Hillson, Simon. Teeth. 2005. doi:10.1017/cbo9780511614477. ISBN 978-0-511-61447-7.
- Moggi-Cecchi, Jacopo et al. 'Root caries on a Paranthropus robustus third molar from Drimolen.' bioRxiv, 2019, pp. 573964.
- Zuo, Jing et al. 'Effect of Low-Intensity Pulsed Ultrasound on the Expression of Calcium Ion Transport-Related Proteins during Tertiary Dentin Formation.' Ultrasound in Medicine & Biology, vol. 44, no. 1, 2018, pp. 223-233.
- Neves, V.C.M. and Sharpe, P.T. 'Regulation of Reactionary Dentine Formation.' Journal of Dental Research, vol. 97, no. 4, 2017, pp. 416-422.

Additional Information
- Tertiary dentin is formed as a response to various dental stimuli.
- It plays a crucial role in preserving tooth health and preventing complications.
- The frequency of tertiary dentin formation varies among different primate species.
- Gorillas, with their high rate of tertiary dentin formation, demonstrate a strong protective mechanism.
- Understanding tertiary dentin formation can provide insights into dental evolution and oral health.

Tertiary dentin (Wikipedia)

Tertiary dentin (including reparative dentin or sclerotic dentin) forms as a reaction to stimulation, including caries, wear and fractures. Tertiary dentin is therefore a mechanism for a tooth to ‘heal’, with new material formation protecting the pulp chamber and ultimately therefore protects the tooth and individual against abscesses and infection. This form of dentine can be easily distinguished on the surface of a tooth, and is much darker in appearance compared to primary dentine. Tertiary dentine will often not be visible on the surface of a tooth, but because it is more dense it can be viewed on a Micro-CT scan of the tooth.

Wear on the surface of a tooth can lead to the exposure of the underlying dentine. When wear is severe tertiary dentine may form to help protect the pulp chamber. Frequency of tertiary dentin in different species of primate suggests teeth 'heal' at different rates in different species. Gorillas have a high rate of tertiary dentin formation, with over 90% of worn teeth showing tertiary dentine. Hominins have a much lower rate of tertiary dentin formation, with around 15% of teeth that have dentin exposed through wear showing tertiary dentin formation. Chimpanzees have rates in between gorillas and humans, with 47% of worn teeth showing ‘healing’.

Clinical studies have researched the properties of tertiary dentine formation, including anatomy in both humans and animal models, usually from an oral health perspective. Genetic changes in animal models can increase tertiary dentine production. This suggests certain species may have evolved to produce tertiary dentin in response to dietary changes. For example, gorillas may have evolved high rates of tertiary dentin as protection against severe wear, since they consume a lot of tough vegetation.