and welcome back and we are going to go over mandibular central incizers first. Teeth numbers 24 and 25. Specific overall features they erupt between ages 6 and seven and the roots are completed at age 9. They are again cussed. They usually erupt before the maxillary central incizers. Mandibular central incizers are the smallest and simplest teeth of the permanent dentition. And this tooth and the maxillary third mer are the only teeth that have one antagonist. And we talked about characteristics of teeth before. What makes a tooth distinct? And this is a really important characteristic of the mandibular central incizers. When we talk about an antagonist, when we bite together and we're in occlusion, the mandibular central incizers only touch one other tooth from the maxillary arch. They only touch the maxillary centrals. So the mandibular central incizers only touch one other tooth in the opposite arch. They only touch the maxillary centrals. A very important characteristic for these teeth. The centrals have a simple root which is widest from the facial to the lingual aspect compared to nial distal. The root has pronounced proximal root concavities. They vary in both length and depth and a shallow depression extends longitudinally along the mid portion of the root. And I'm going to highlight those deep depressions there. The root in shape is narrow oval as an ovoid or egg-shaped on cervical cross-section. The root length is about 12.5 mm. The pulp cavity of the mandibular central is quite simple. It has a single pulp canal and three pulp horns. The crown is symmetrical from the facial view and it's said to resemble a fan shape. Both the encizal angles, the misiocizal and the disto incizal angle are sharp or only slightly rounded. The miso incizo angle again is a little bit sharper than the distal. So if you have an intact central incizer, one that has not been worn down, you should be able to figure out do I have tooth number 24 or 25 based on that messio incizal angle. So go ahead and take your mandibular central incizers out. Take a look. Can you determine, do I have 24 or 25 based on the sharpness of that messio incizal angle. Now take your central and flip it over. Let's take a look at that lingual aspect. The crown is narrower on the lingual than the facial, which is the reverse of the facial view. Overall, the lingual surface is less pronounced. It has a small centered singulum. Generally, not a whole lot going on with that lingual aspect of the centrals. There is a single lingual fossa, really, really shallow, barely noticeable. The mesial marginal ridge and distal marginal ridge are barely noticeable as well. So, again, not a whole lot going on from that lingual aspect. Looking at the proximal view now the measial or distal it has deep proximal root concavities and it's similar when we look at the CEJ the measial aspect that CJ will have a more pronounced curvature compared to the distal. So if you're looking at one of your central incizers, can you determine am I looking at the right central or the left central? The incizal edge is lingual to the long axis. So if we look at these images here, let's look at number seven. Where that incizal edge is, you can see it's tipped more towards the lingual compared to the facial. So take a look at your flat wax 24 and 25. You could take them out, shake them up in your hand. Can you determine, just looking at that messial, do you have number 24 or do you have number 25? Next, hold up your central. So, you're looking at the incizal view. Uh, it is nearly symmetrical with the crown outline. From this view, the singulum is nearly centered messial to distal. And this is an important distinction when we look at the lateral incizers next. So it's the singulum is centered on the central incizers. All right. Moving on to the mandibular lateral incizers. Teeth numbers 23 and 26. They erupt between ages seven and eight with root completion at age 10. These teeth usually erupt after the mandibular central incizers. It is slightly larger overall than the central. It does have more variation in form. So, it's it's easier to figure out do I have the central compared to the lateral because there is more distinct anatomy with your laterals. The crown is slightly larger than a central, but it resembles a central in most other ways. Let's look at the facial. The facial lingual views. The crown appears tilted or twisted distally in comparison with the long axis of the tooth and it gives the impression that the tooth has been bent at the CJ. So it's been twisted like someone grabbed the crown and just twisted it a little bit. An important distinction with this lateral has a single root usually straight slightly longer and wider than that of a central incizer. The root has pronounced proximal root concavities especially on the distal surface. And I mentioned before generally speaking the roots the tips at the apex generally point to the distal. It is not an always. So these laterals may go a little bit towards the meial or just be straight. Just something else to consider when you're trying to figure out do I have the right or the left of any given tooth. The pulp cavity for this tooth is simple. Has one pulp canal and three pulp horns. It is elliptical in cross-section. And there is our it's showing our the arrows are central as well as our lateral and it is 14 mm in length. from the facial. The crown is not as symmetrical as that of the central and just mention that it appears like it has been twisted distally from the facial view. So take a look at your mandibular laterals and compare them to the central. Can you see how the crown appears twisted on the lateral? Look at the singulum. It appears that the singulum is twisted a little bit compared to the central incizer where that singulum is centered compared to the lateral. So staying on the facial view, the mesio incizal angle compared to the distal is sharper and that's the same with all of the insizers. So if you had your lateral incizers in your hand from the facial, can you determine the messial angle from the distal compared uh comparing the sharpness of one to the other? Do you have tooth number 23 or tooth number 26? Then compare that to the central. Can you figure out looking from the facial, do I have a central or do I have a lateral? And flip your tooth over. Let's look at the lingual for a minute. The crown lacks bilateral symmetry and appears tilted or twisted distally on the root. From the lingual view, the outline is the reverse of the facial. So, as if looking at the lingual aspect there, someone grabbed that crown and twisted it to the distal. The lingual has more prominent features compared to the central. The central doesn't have a whole lot going on. a little bit more with that lateral and that's another way to help you figure out do I have the central or do I have the lateral has a small single singulum it lies just distal to the long axis of the root. So looking at your flat wax model again, look at the lingual. Look at that singulum. The singulum shifts towards the distal. Knowing that do you have tooth number 23 or 26? And again compare those singulums to the central incizers. Mandibular central incizers. The singulum is centered. The laterals it's going to be shifted to the distal. Let's look next at the proximal view on your laterals. Again, looking at that messial aspect, the same with all of the other incizers, the CEJ curvature is more pronounced. It's greater on the mesial compared to the distal. So, if you have your laterals, can you see the difference between the messial and the distal aspects based on that CJ curvature? The incizal edge curves towards the lingual and its distal part. And we can look at let's see what tube would be a good one to look at. Number eight, one label. Number eight, that incizal edge is tipped more towards the lingual compared to the facial. All right, take your lateral and let's look at the incizal view. It's a more rounded appearance noted both facially and lingually compared to the central incizer. The entire incizal ridge is not straight messodistally as it is on a central incizer. So if we look at these teeth here, the incizal ridge or incizal edge curves towards the lingual and its distal part. The singulum, a really important characteristic of the mandibular lateral is that singulum. The singulum is shifted towards the distal and it kind of matches that incizal edge or incizal ridge. The ridge shifts to the distal towards the legal aspect. Looking at the teeth here, I've highlighted the ones that are a little bit more prominent. If you look at tooths labeled number one, the singulum shifts towards the distal. Number two, the singulum shifts towards the distal and the same with 6 8 9 labeled there. So knowing that, could you figure out is tooth labeled number one? Is that tooth number 23 or is that tooth number 26? Knowing the singulum shifts to the distal tooth labeled number one, that would be tooth number 26 in the mouth. The tooth labeled number two, that would be tooth number 23 in the mouth. The singulum shifts towards the distal. So you should be able to figure out, am I looking at the right or the left based on where that singulum is shifting? So take a look and see if you can figure out do you have 23 or 26. And then again, compare that to your centrals, the difference in that lingual anatomy. And we'll wrap up the lecture with a couple review questions. The incizal ridge on this tooth exhibits a distingual twist. On which tooth type? Take a look. See what you think. Mandibular lateral incizer. It's as if we took the crown and we just twisted the whole crown to that distal little bit. Very distinct anatomy with the lateral. All right. The root is very narrow messodistally with meial and distal root depressions. What do you think? Both the mandibular centrals and mandibular lateral incizers are very narrow misodistally with deep messial and distal root depressions. And let's take a look at the image here. Lots of teeth. These are all maxillary lateral incizers. But can you tell which ones are the right lateral incizers? Which ones are number seven? Take a a little bit and look through them and see what you can come up with. All right, let's see what you have. The ones labeled 1 2 3 6 7 8 9 are all tooth number seven. We can compare those distal incizal angles here that I'm circling are much more rounded compared to the mesial. We know the messial angle is much more sharp, much more pronounced compared to the distal. And then we can also consider the apaces here. They're shifted to the distal. So these would all be tooth number seven. All right, give yourselves a hand. We uh have completed the lecture for the maxillary mandibular incizers. Thanks for listening. Have a great day.