Video: Teeth

Hey everyone! It's Nicole from Kenhub, and in this tutorial we're going to talk about the different types of teeth. As you can see in this image of the mandible, the human jaw contains several different types of teeth, each of which differ in their size, shape and function. And of course for dentists, the different types of teeth are important to know as they each have their own special role in chewing otherwise known as mastication. But it's also important for other health professionals such as doctors to know as well. And in this tutorial, we're just going to have a chat about the four different types of teeth before going over some clinical notes related to the teeth.

So before we begin looking at the different types of teeth, let's just have a brief chat about the anatomy and the development of teeth. So as you may be able to tell, a tooth is a small calcified structure located within the jaw of human beings. And as I mentioned earlier, the main function of the tooth is to break down food into smaller pieces in a process called mastication or mechanical digestion and, therefore, the tooth can be considered to be part of the upper digestive system. And human beings are diphyodont which means that they develop two sets or two generations of teeth.

The first set or the first generation of teeth is often referred to as the deciduous or primary dentition and are usually around twenty teeth in this set. The primary dentition is usually complete by the age of 3. Around about the age of 6, the primary dentition goes through a process called exfoliation whereby the deciduous teeth are lost to be replaced by a second set or second generation of teeth also called the permanent dentition. And the permanent dentition usually contains around thirty-two teeth usually reaching completion between the ages of 18 and 21. And the process of the permanent dentition becoming visible in the mouth is known as eruption.

The bones of the jaw provide a skeletal structure from which the teeth can originate and as we can see in this image, the teeth are imbedded in the jaws of which there are two. The upper jaw or the maxilla in green and as you can see in the image, the maxilla forms the roof of the mouth and the floor of the nasal cavity and the teeth are located along its alveolar ridge, and the upper teeth are often referred to as the maxillary teeth. Similarly, the lower jaw or the mandible forms the floor of the oral cavity as well as the structure of the face we would externally identify as the jaw. And as per the upper teeth, the lower teeth are located along the alveolar ridge of the mandible and are often called the mandibular teeth. And the alveolar ridges are part of the alveolar processes of the respective bones which are the parts of the jaws that contain the tooth sockets.

So before we go on to talk about the teeth, I just wanted to show you this brief overview of the different types of teeth found in the jaw and talk about how they fit together. And by the way, the different types of teeth we're going to talk about are the teeth in the permanent dentition. So as we mentioned, there are four types of teeth found in each jaw, the maxilla and the mandible and though we're going to just look at the maxilla in this particular slide, there are equivalent types located in the mandible.

And these four types moving from the anterior aspect of the jaw to the posterior aspect of the jaw are the incisors highlighted in green, the canines highlighted in red, the premolars highlighted in blue, and the molars highlighted in yellow. And as you can tell, the number pattern and the position of the teeth are identical on either side of the midline of the jaw which when divided into two is called a half-jaw or quadrant when taking the lower jaw into consideration. And so generally speaking it can be said that there are the same four types of teeth in each quadrant.

And just to show you how different they are in terms of their shape and size, we're just going to have a quick look at the teeth out of their sockets beginning with the incisors, the canines, the premolars, and the molars. And note that the superior part of the tooth and the part that inserts into the jaw is called the root of which there can be more than one per tooth whereas the inferior part – the part that is visible in the mouth – is called the crown.

So let's begin by talking about the incisors which we can see are our most anteriorly placed teeth in this image of the maxilla. And as in addition to the anterior placement, the incisors are shaped like chisels. It's clear that the main function of the incisors is to cut food. And from our definition of our quadrants on the previous slide, we can say that there are two incisors on each half of the jaw or quadrant with a total of four in each jaw. And this image is just to show you that of course there are also four incisors in the mandible bringing the total number of incisors in a human mouth to eight.

The incisors can be further divided into two sub-types – the central incisors and the lateral incisors. And again referring back to our quadrants, there is one central and one lateral incisor in each half-jaw or quadrant with a total of two central and two lateral incisor teeth each in the upper and lower jaw.

So coming back to our image of the incisors out of their roots, the incisors are of course our teeth over here on the left highlighted in green. The one on the left here being our central incisor and the one on the right being the lateral incisor. And as we can see, the incisor teeth usually only have one root. And just make note that these are all ventral views of the teeth that we're looking at, that is, we're looking at them as they're viewed from the front.

And coming back to our subtypes of our incisors, we're going to begin with a look at our central incisors which are given the name because they're on either side of the midline. And this image shows the central incisor teeth of the lower jaw also known as the mandibular central incisors. And this image shows the central incisor teeth of the upper jaw or the maxillary central incisors. And the maxillary central incisors are usually the first teeth that you see when someone smiles. And note in the lower image, the central incisor tooth that has been isolated from the oral cavity.

And as we mentioned before in addition to the central incisors, we also have the lateral incisor teeth and as you can see in this image of the mandible, these teeth are located laterally to the central incisors and of course the teeth in the image are referred to as the mandibular lateral incisors. And in our inferior image of the maxilla, we can see the maxillary lateral incisor teeth highlighted in green. And again in the lower image, we can see a lateral incisor tooth that has been isolated from the mouth.

So our second type of teeth found in the mouth are the canines. And as we can see in our image, these teeth are the ones that are located laterally to the lateral incisors and there are four canine teeth in total – two in the upper jaw and two in the lower jaw. And the main function of the canine teeth is to shear and hold food to allow it to be torn apart. And in our image of the isolated teeth, we can of course see our canine highlighted in green. And as we just discussed, the function of the canine is to rip and shred food so we can say that reflected in its morphology with the tip of the crown coming to a point or a cusp giving to the name cuspid which is what teeth with a single cusp are often called. And like the incisors, the canine tooth has a single root but as you can see these roots are longer than the root of the incisor tooth.

The next type of tooth I want to have a chat about is the premolar teeth. And as we can see in the image, the premolars are located lateral to the canines which with usually two in each quadrant which makes for around about eight premolars in total. The premolars are considered transitional teeth as they contain qualities from both the canines and the molars – the final type of tooth in the mouth. And as you can see, the premolars have two pointed edges or cusps and are therefore sometimes referred to as bicuspids. As they have features of both the canines and the molars – the shredding qualities of the canines for example as well as the chewing qualities of the molars – they are able to move food back from the front to the back of the mouth in the process of mastication.

And just to reiterate, the main function of the premolars is to tear and grind food as well as move food from the front of the mouth to the back. And as we just mentioned, the premolars have two cusps and these cusps of the premolars can usually be divided into anterior and posterior cusps. The anterior cusp as indicated by the black arrow is often referred to as the buccal cusp as it is closer to the cheek and the posterior cusp indicated by the green arrow is often referred to as the lingual cusp as it is closer to the tongue.

And of course we're back at our image of the premolars isolated from the mouth and as this is a ventral view, we can see the buccal cusp on both of the premolars. And as you can see, the premolars have one root but often maxillary premolars will have two. And as we've mentioned, there are two premolar teeth in each quadrant and the premolars can be divided into the first premolar teeth and the second premolar teeth. And we'll talk about both in the next couple of slides.

The first premolar teeth are the premolars which are located lateral to the canines. In the lower image, we can see a first premolar tooth isolated from the mouth. The second premolar teeth are located between the first premolar and molar teeth. In the lower image, we can see a second premolar tooth that has been isolated from the mouth.

And the fourth and final type of teeth we are going to look at are the molar teeth and as you can see, there are three molars in each quadrant so in total there are six in the upper jaw and six in the lower jaw or twelve molar teeth. And it's important to note that the size of the molars decreases as we move more distally. In this image of the mandible, we can see that the molar teeth have four cusps but occasionally, the molars have more. And the main function of the molars is to grind food during mastication. And of course here's our image of the molars isolated from the mouth and as you can see, each of the molars have more than one root and you can also see two of the cusps. And in this image, the cusps closest to us are the buccal cusps whereas the ones posteriorly located are the lingual cusps as the view of the teeth is ventral.

And like the premolars, the molars can be further divided into types of teeth of which the molars have three and these are the first molar teeth, the second molar teeth and the third molar teeth or the wisdom teeth. The first molar teeth of the lower jaw highlighted in green are located between the second premolar teeth and the second molar teeth. And in this slide, we can see an isolated first molar tooth with its four cusps as well as multiple roots.

The second molar teeth highlighted in green are located between the first molar teeth and the third molar teeth. And in this image, we have our ventral view of an isolated second molar tooth and we can see clearly the two buccal cusps as well as multiple roots and note that the second molar tooth is smaller than the first molar tooth to its left. And finally, we'll now have a look at the last of our molars – the third molar teeth. And the third molar teeth are commonly referred to as the wisdom teeth. Most people have one third molar in each quadrant so in total normally four wisdom teeth but it is possible to have less than or more than four. And these teeth are last to erupt in the mouth usually doing so between the ages of 17 and 25.

Occasionally when these teeth erupts they can grow at odd angles which usually requires them to be removed. And any additional molars besides the third molar teeth that erupt in the mouth are considered supernumeraries. And of course in our image of the isolated teeth, we can see a third molar or wisdom tooth isolated from the mouth. And as you can see, this tooth is smaller than the first and the second molar teeth on its left.

So now that we've finished talking about our types of teeth, let's quickly summarize them by looking at this image of the upper jaw which we saw at the beginning of the tutorial. And as we can see on either side of the midline, we have four incisors with two on each side and the closest incisor at the midline is the central incisor while the other incisor is the lateral incisor. Laterally or distally to the incisors, we have one canine tooth on each side of the jaw which is highlighted in red, so in total two canine teeth in each jaw. Distal to the canines, we have two premolar teeth on each side so four premolar teeth on each jaw and the premolar closest to the canine is called the first premolar whereas the more distal premolar is known as the second premolar. Finally, we have three molar teeth on each side of the jaw or six molar teeth in each jaw and these are named the first molar, the second molar and the third molar or wisdom tooth as we move more distally. And this makes up the 16 teeth in total on the upper jaw and the lower jaw has the same configuration of teeth giving us thirty-two permanent teeth in total.

And now to finish up this tutorial, we're just going to go over some clinical notes that are relevant to the teeth. So the first clinical note I wanted to discuss is the failure of teeth to develop in the oral cavity otherwise known as hypodontia. And usually if there are any missing teeth, it will be the third molar or the wisdom tooth followed by the maxillary lateral incisors and the maxillary or mandibular second premolars. On the other hand, the presence of more teeth than usual is referred to as hyperdontia. And the most common extra tooth that we find in the mouth is usually situated between the central incisors and is known as the mesiodens.

Another important thing to note about the teeth are the systems used to identify them. And dental professionals normally use dental notation systems to associate information about a specific tooth and of these there are three most commonly used – the ISO System, the Palmer Notation Method, and the Universal Numbering System. And I'm just going to briefly talk about each of them.

The ISO System is an internationally used notation system that was developed by the World Health Organization and it is a two-digit notation system with the first number referring to the quadrant the tooth is in and the second number referring to the number of the tooth away from the midline. In the permanent dentition, the upper right quadrant is referred to as 1, the upper left is 2, the lower right is 3, and the lower left quadrant as 4. Therefore, the central incisor on the upper right quadrant is referred to as 1-1 and the lateral incisor in the upper quadrant would be called 1-2. The deciduous dentition is named the same way but using the numbers 5 to 8 to refer to the quadrants.

The Palmer Notation Method was the first notation method to be developed of the three and is still used in the UK. It names permanent teeth from 1 to 8 as they move away from the midline with symbols being used to determine which quadrant the tooth is in. The deciduous dentition uses the capital letters A to E to name the teeth as they move away from the midline.

And the final notation method is the Universal Numbering System which is commonly used in the United States. This system uses the numbers 1 to 32 for permanent teeth from right to left on the upper jaw and then left to right on the lower jaw. Therefore, the maxillary right third molar is given the number 1 and the mandibular right third molar is given the number 32. The deciduous dentition is named in the same way but using the capital letters A to T.

Now that you just completed this video tutorial, then it’s time for you to continue your learning experience by testing and also applying your knowledge. There are three ways you can do so here at Kenhub. The first one is by clicking on our “start training” button, the second one is by browsing through our related articles library, and the third one is by checking out our atlas.

Now, good luck everyone, and I will see you next time.