In the animal kingdom, which animals put their teeth through the most rigorous use and require the strongest teeth? Beavers would probably get my vote. With the ability to cut down trees using only their front teeth, I’m certainly impressed by the dental power of beavers. According to a recent study put out by Northwestern University, there might be something more to this.
Humans and rodents, such as beavers, have similar tooth structure on the microscopic level. Our tooth enamel is composed of a hard inorganic substance called hydroxyapatite. The arrangement of hydroxyapatite molecules is what gives enamel its strength; it is not just a random grouping of molecules. In teeth, the hydroxyapatite molecules are stacked together to form hydroxyapatite “nanowires.” Bundle millions of these nanowires together and you have enamel rods. Bundle enamel rods together, and you have tooth enamel. The “bundling” molecules are also made of hydroxyapatite, but they are not highly organized like the hydroxyapatite wires. Essentially, the Northwestern team of scientists was able to visualize and inspect the complex structure of enamel at a level of detail previously not achieved. They found that the amorphous “bundling” hydroxyapatite to be rich in minerals such as magnesium and iron. These minerals are important in giving enamel its acid-resistance, color, and strength properties. In regular teeth, magnesium is the most important mineral in making teeth strong. In rodent incisors (such as a beaver’s front teeth) it’s iron. The high levels of iron account for the orange color of these special teeth and also give them their amazing strength and durability. This special iron-strengthened enamel is far stronger than any other enamel that scientists have studied, even fluoride-treated enamel.
So what does all this mean for us? The real breakthrough of the Northwestern team is improved imaging ability. They used atom-probe tomography and other sophisticated techniques to map out enamel structure on an atom by atom basis, an achievement that is absolutely amazing to me. This detailed imaging has led the way to something called “grain boundary engineering,” science that focuses on the composition of the amorphous “bundling” hydroxyapatite mentioned above. We have known for years that fluoride strengthens teeth by converting hydroxyapatite to fluorapatite, but the newly found imaging abilities will allow scientists to play with the composition of the material around the nanowires. This could lead to strengthened tooth enamel through better use of fluoride or other substances.
-Nicolas K. Young, DMD