Those of us who are of a certain age can most definitely recall the infamous Ipana Toothpaste television commercial. In it, America was introduced to Bucky Beaver, who orbited Earth on his toothpaste rocket ship, preaching about ‘happy teeth’. But was Bucky Beaver adopted to provide a child-friendly approach to dental hygiene, or was there more to the toothy rodent than met the eye? We’re guessing the latter, as a recent study conducted at Northwestern University’s McCormick School of Engineering and Applied Science suggests that Bucky and his fellow beaver friends may hold the key to better understanding the highly complex enamel structure. Further, the findings of Derk Joester and his team could not only potentially help us detect premature tooth decay earlier, but could go so far as to ultimately improve—if not reinvent—current oral decay treatments.
A complicated structure to study, enamel is the protective outer layer of your tooth which is composed of intricately layered hydroxylapatite “nanowires”. These nanowires, discovered Joester and his team, are further encapsulated by a material which houses small amounts of amorphous iron and magnesium-rich minerals, which are fully responsible for controlling the tooth’s acid resistance, as well as its mechanical properties. The first to introduce the exact composition and structure of this amorphous phase of enamel, Joester and his team have taken “a really big step forward in understanding the composition and structure of enamel.” According to Joester, “The unstructured material, which makes up only a small fraction of enamel, likely plays a role in tooth decay.” He continues, “we found it is the minority ions—the ones that provide diversity—that really make a difference in protection.” In human enamel, it’s magnesium; in the pigmented enamel of beavers, it is iron.
The amorphous iron present in beavers’ enamel is also responsible for the reddish-brown color of beaver teeth. This protective pigmented layer, says Joester, is a significant improvement “over fluoride-treated [human] enamel’s acid resistance.” The study—which consisted of Joester and his colleagues first imaging the amorphous structure surrounding the nanowires, and then mapping the enamel’s structure one atom at a time—identified unstructured biominerals in the enamel’s composition, and learned the ways in which these biominerals contribute to the mechanical hardness of enamel, and the enamel’s resistance to acid dissolution.
Because “a beaver’s teeth are chemically different from our teeth, [but] not structurally different,” this discovery has the potential to improve on our enamel. “The strategy of what we call ‘grain boundary engineering’–focusing on the area surrounding the nanowires—lights the way in which we could improve our current treatments,” Joester states.