For those of us with children, grinning Pixar animals, showing their anthropomorphic pearly whites, are a familiar site. But animals don’t have the same teeth as people. In fact, dentition can be one of the defining factors in determining species!
Take rodents, for example
Rodent teeth are unlike any other mammal teeth– they have massive incisors. At first, mammal teeth all started the same; the earliest of our mammal ancestors set themselves apart from reptiles by having four kinds: three pairs of incisors (primates, including humans, have lost the third pair), a set of canine teeth, a set of premolars, and finally the grinding molars.
However, everybody’s needs are a little different, and over the eons, we all started to specialize our dental structure so it was adapted to meet our dietary desires— heavy on the meat, heavy on the salad, or omnivorous.
Specialized for gnawing
Rodents’ first choice in food may be whatever is handy, but their teeth are especially adapted for extreme gnawing, and this is the reason for their astonishing success as a group of mammals– of all mammal species, roughly 40% are rodents!
As mentioned, rodent teeth are often characterized by their impressive incisors. Remember the 3 pairs of incisors that ancient mammals adapted? Rodents have that down to one pair– and it’s a doozy.
To start out with, rodents’ incisors don’t have roots like most other species’ teeth. For humans and other mammals, once our teeth have grown, their job is pretty much done– so the tooth structure narrows at the base to leave a small channel for the nerves and relatively few blood vessels necessary to supply a mature tooth. However, in rodents, this never happens. The “bottom” of their tooth remains wide and richly vascularized. This enables the tooth to keep growing.
Serious enamel for a cutting edge
Another thing that sets rodent teeth apart is that the front side of their incisors is thickly enameled, while the back side (facing the inside of the animal’s mouth) has no enamel to speak of and is instead covered by a softer layer of dentine. At the joining of “soft” back side and hard frontal enamel, the rodent’s gnawing creates a razor sharp cutting edge just like a chisel, perfect for making sawdust of trees to build dams, chewing through cardboard boxes holding food in your cupboards, and burrowing into logs or tree trunks. In short, their formidable incisors are what provide rodents their living.
But there’s more
Human teeth are evenly spaced across our mouths; not so with rodents. Between their big front incisors and their back molars is a large gap, called a diastema, which allows rodents to suck in their cheeks while hacking away at wood or other hard gnawing material, so the sawdust doesn’t go flying down their throat! Additionally, while rodents do indulge in non-vegetarian food (most commonly in the form of insects) they completely lack the pointy canines that are so prominent in carnivorous species. Finally, while humans and many other mammals have “milk teeth,” an early set of teeth during childhood that are replaced by permanent teeth, rodents are born with the teeth they will have– presumably, this gives them a jump start on all the gnawing that they’ll be doing throughout their lifetime.
Whew! That’s a lot to chew on!
If you’re thinking, “all I really care about rodent teeth is how eager they are to bite into the cheese I set on my mouse-trap,” well, think about it this way: understanding the dental anatomy of other species can be extremely helpful for scientists to learn more about human dental health and how we can treat disease. At McKinney Smiles, we’re always interested in what researchers are doing to improve the oral health of our patients, and we’re also committed to answering any questions you may have.
We hope you found this informative and we look forward to seeing you at your next appointment!