Teeth do many different jobs. Humans use their teeth to break down food by chewing, bite, speak and even to smile. Other mammals also use their teeth to grind, stab, tear, chew, and a few species dig with them. Elephants sometimes use their tusks, which are giant teeth, to lift things. Most reptiles and fish also have teeth, and even a few bird species have something similar to teeth. The shape of a tooth can help you to figure out what species it belongs to, what job the tooth does, and what type of food the animal eats. Since teeth are the hardest substance in the body and make great fossils, scientists can guess what a dinosaur ate by the size and shape of its teeth.
Humans primarily use their teeth for biting and chewing. The baby teeth, or primary teeth start appearing at around six months, and usually start with the bottom front incisors. There are twenty primary teeth and they usually all erupt by age two. The first of 32 permanent teeth begin to erupt around age six when the primary teeth start to fall out, and the last to appear are the wisdom teeth in the late teens or early twenties. To learn more about the structure of human teeth see here.
Mammals have four types of teeth: incisors, canines, premolars and molars. Each type has a slightly different function. While humans and many mammals have all four of these types of teeth, some species of mammals only have two or three.
Today we are going to focus on interesting facts about incisors in humans and animals. Incisors are the front teeth in the mouth which are seen in a beautiful smile. Humans have eight, four on the top and four on the bottom. We have these in the primary set of teeth, and they are replaced with permanent teeth. Incisors have thin, straight edges, which are perfect for cutting off small pieces of food. Just ask a child who has lost these teeth, but their permanent teeth haven’t grown in yet, and they will tell you how important these teeth are for biting and cutting food!
Incisors look flat but are actually slightly curved toward the back of the mouth and each have one root. The bottom front incisors are the smallest teeth in our mouths. They are also important because they help us pronounce words and support our lips.
When teeth are aligned correctly, the top (maxillary) incisor will slightly overlap the lower (mandibular) incisor beneath it. A common problem with incisors is when they do not line up correctly because of a misaligned jaw or crooked teeth, which causes an underbite, overbite or crossbite, and makes it hard for the teeth to do their job and bite efficiently.
What about incisors in animals? Their size and number depend on what the animal uses them for. Dogs, cats, pigs and horses have twelve. Rodents like mice have four, but their incisors never stop growing! This makes sense because they chew on tough things like wood, and their tiny teeth would wear down quickly if they did not keep growing. Deer and cattle have six, but their incisors are all on the bottom. Opossums have 18, rabbits have six and armadillos don’t have any.
Herbivores, which are plant-eaters, usually have sharp incisors for tearing plants, although cattle and deer only have them on the lower jaw. This may sound painful, but they have a bony pad on the upper jaw to protect against the rough edges of the plants they eat.
Elephants, which are herbivores, have two incisors, but they look very different from our small flat version! Their tusks are incisors and are used for defense, lifting things, and gathering food. Tusks protect their trunk and can strip bark from trees. Elephants even use their tusks, along with their feet and trunks, to dig water holes in a dry riverbed. The tusks never stop growing, but they can break and will stop growing if the root is damaged. In the same way that we are right or left-handed, an elephant will primarily use their right or left tusk!
Fish also have incisors which are usually used for cutting. Parrotfish have fused incisors which form a beak. Their beak is stronger than individual teeth, which is super important because they use it to bite off pieces of coral!
Carnivores, which primarily eat meat, also have incisors, but theirs are often much smaller than the rest of their teeth. Many carnivores, such as lions, use them to grip and tear meat, or scrape it off the bone. A carnivore can use incisors for jobs that need greater control, like carrying something, peeling skin off a fish, removing burrs from fur and even catching fleas. Cats use them to carry their kittens by the scruff of the neck, and pet dogs and cats like to carry toys in these useful front teeth.
Omnivores, which can eat plants and meat, have less specialized teeth than herbivores or carnivores. Each species of omnivore has teeth useful for their type of diet. Humans and animals which use their teeth for chewing, have some sharp teeth which can rip and tear, and other, flatter teeth for grinding. Most omnivorous reptiles have teeth which are a similar size and shape. This is because their teeth are used more for capturing food than chewing and processing it.
Teeth are amazing because of all the different sizes, shapes and uses that they have. Just looking at teeth can tell you the species of an animal and its particular diet. Incisors are only one type of teeth, but they can look vastly different and have many different jobs!
If you enjoyed this post stay tuned! In the next few blogs we will talk about the other kinds of teeth and how they differ and are used by various types of animals.
At Jungle Roots Children’s Dentistry & Orthodontics, we strive to provide the highest comprehensive pediatric and orthodontic dental care in a unique, fun-filled environment staffed by a team of caring, energetic professionals. We believe the establishment of a “dental home” at an early age is the key to a lifetime of positive visits to the dentist.