You might have thought that it was bones, but it is actually tooth enamel that is the most solid substance of the body. It is so because of its high content (96 %) in minerals. The remaining 4 % is water and proteins. The primary mineral of enamel is called hydroxyapatite.
The second hardest substance in the body is not bone, but dentin, which is a tooth’s layer that is found under the enamel. Dentin also contains mineral hydroxyapatite (70%), and the rest is organic material (20%) and water (10%). Because dentin is softer, it is more easily decayed than enamel. Usually a cavity starts as a small hole in the enamel, but spreads more quickly and widely once bacteria reach the dentin.
Because enamel covers all teeth in the mouth, it is made to be very hard so it can chew and break soft and hard foods. But even though it’s the hardest substance of the body, enamel is brittle which means it can break more easily when under high pressure. Dentin is less brittle than enamel, and that property gives a tooth more flexibility.
- Chun KJ, Choi HH, Lee JY, Comparison of mechanical property and role between enamel and dentin in the human teeth, J Dent Biomech. 2014; 5;
- 10 things you didn’t know about teeth, Studio Dentaire;
- Bone and tooth minerals, Science Learning Hub;
- Tooth enamel, Wikipedia;