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.