Good morning everybody. This is chapter 16 the permanent anterior teeth and we will start off with just an overview of the permanent insizers and then we will break down the chapter into several smaller lectures. So starting off with the term cussadenous all that means is that all of the permanent anterior teeth the insizers as well as the canines are cussidaneous. So that means the permanent teeth follow the primary teeth. So, as you are starting to go through this lecture and learning your teeth, have your kilgore, your flat wax models out. And so, you can start taking these teeth out and looking at them and inspecting and looking at the anatomy as you go through these lectures. For our permanent incizers, we do have eight in total. We have four central incizers. We have four lateral incizers. And to review the quadrants, we do have four. One, two, three, four. And you do have to know what teeth are in each quadrant. And what is the purpose of the incizer? Generally, uh, they help to support the lips and our facial muscles. They help us with speech to articulate our speech and they also are there to help guide and cut food into the mouth. When we start looking at specific features for a tooth type, start making a note of the characteristics for that particular tooth. What stands apart uh the characteristics for that tooth compared to the other teeth. It will help you to identify these teeth when we are doing a handson tooth identification in the classroom. But for the insizers, they are special because they are the only teeth that have two incizal angles, a nial angle and a distal angle. Those are formed and joined by the incizal ridge which we will talk about soon. Comparing next the maxillary centrals to the maxillary lateral incizers. The centrals are just bigger overall. They have similar form but the lateral is smaller compared to the central incizer. Both are wide messial distal compared to facial lingual. The maxillary incizers have more lingual features. There's more distinct anatomy on the maxillary incizers compared to the mandibular incizers which we will cover later. So if we look at the image in B and we look at tooth number C, they tend to have some deeper anatomy, some deeper lingual pits and there happens to be an amalgam present on the lingual of that image C. And looking at the developmental loes, which is something that you learned about in embryology and hisystologology, the insizers have four developmental loes in total. Three are on the facial aspect. The fourth is lingual. So on the facial we have the mesial, middle and the distal loes and then in between each lobe we have then two developmental depressions. So on that lingual aspect your fourth lobe would be then your singulum. Looking next at mamalons. So here we have an image of very distinct mammalons in A. So the mamalons are the rounded extensions of those developmental loes that appear along the incizal edge or the incizal ridge. But as teeth naturally get used, we have wear and it's called attrition that will eventually wear away those mammalons if the teeth are in contact. If for some reason the teeth are not in contact as in the image on the left hand side that person has it's called an open bite. So when the patient closes the teeth are only touching on those back teeth the posterior teeth leaving the anterior teeth open. So there's no wear there. So that's why we still see those mammalons present on those insizers. I'll draw it in for you there. But if teeth are in occlusion as in the image on the right and this would be very severe wear again it's called attrition this is really severe but eventually those teeth will just wear down along that incizal edge and we had mentioned on the previous slide the difference between the ridge or the edge when teeth initially erupt it is called the incizal ridge. There is no wear there. We can still see the mammalons and we know the incizers their job is to cut food. So that incizal ridge is considered the masticatory surface. So through wear and tear over the years it will then wear down to become the incizal edge. Whether we call it the ridge or the edge in clinic there's really no preference. You can say either one. But if it comes to the board exam there may be a difference. So if there is where we have lost those mammalons then it is called the incizal edge. Moving on to tooth form. The crown outline of anteriors is triangular when viewed from the proximal surface. So proximal means either the mesial or the distal surface. So it creates an apex at the incizal ridge and the base would then be up at the along the cervical area of that tooth. A reminder so the uh insizers they're wider messiodistally compared to labial lingually and those mandibular incizers will act as a blade against the maxillary incizers. So here we have contact areas. So each of the two contact areas of anterior teeth are usually centered facial lingually on their proximal surfaces. So it's centered on the mesial surface and centered on the distal surface. Generally these are going to be in the incizal third of these teeth. So the contact areas and I I kind of drew in the best I could an incizer next to that one to kind of give you an idea of where that neighboring tooth would sit where that contact area is at. So when you are flossing your teeth, when that floss snaps through, that is the contact point where the floss snaps. But the contact area will be in the widest part of that tooth. As I drew in here, that little pink area, that is going to be the contact area. That's the widest part when you look at that tooth. Next is height of contour. Height of contour for both the crown's facial and lingual surfaces is in the cervical 1/3. So if we look at the proximal surface here and this is going to be the messial surface of this incizer. It is the widest part when you look at this tooth. The height of contour from this proximal is going to be in the cervical 1/3. So as a reminder we split these teeth into thirds. That would be the incizal 1/3. This would be the middle 1/3. This would be the cervical 1/3. So the widest part height of contour looking at the proximal surface the cementto enamel junction we just say CEJ for short much quicker much easier the CEJ on each proximal surface so the messial or the distal the CEJ curvature of all interior teeth is greater than that of the posterior teeth. The curvature is also greater on the mesial surface of any of the teeth in the mouth. The maxillary central incizers has the greatest CEJ curvature on the mesial of any tooth in the dentition. That is a characteristic that you should know that sets the maxillary incizers apart and we will review that again a little bit later. The singulum and marginal ridges. So all anteriors have a singulum on the cervical third of the lal surface and they do vary in size. A reminder, the singulum would be that fourth developmental lobe that shows up on the lingual aspect. The lingual surface is also bordered on the mesial and the distal by the marginal ridge. It's a raised border and we will go over the ridges in depth later. It's really important that we know and can recognize those marginal ridges. FASA or FSY. FASA would be a single uh wide shallow depression. When we talk about more than one then it becomes fsy. So it's on the lingual aspect just a shallow wide depression. And we will talk more about the pits that may or may not be present coming up shortly. The developmental pits and grooves. Developmental pits are located in the deepest part of each fossa. We may have developmental grooves. They may call it a primary groove. It's a sharp, deep, V-shaped linear depression that marks the junction between the developmental loes. And then we may have supplemental grooves. They may call it a secondary groove. It may be present on the lingual surface of anteriors, which is a shallower, more irregular linear depression than the developmental grooves. What significance do the grooves have or the pits or maybe both? Why are they significant? Why do we need to know about them? And where do we need to look for them? It happens to uh be related directly to dental plaque bofilm. So any kind of groove, any kind of pit is going to be an area or a niche where plaque bofilm is going to live and hang out and that can lead down the road to increase risk of carries. carries is the technical term for a cavity and then these grooves can also increase the risk for periodal disease in that site which we will go more in depth in later but of the pits and the grooves the lateral incizers the maxillary incizers tend to have more prominent pits and grooves. Looking next at roots of the incizers. Incizers have a single root and it has one pulp canal. The roots appear either triangular, oval or elliptical or maybe say an elongated oval on cervical crosssection. And what this does it results in the lingual aspect being narrower compared to the facial aspect. So clinically what that means for us is that instruments we have more room when we come from the lingual aspect because that lingual surface is narrower compared to the facial aspect. And we will certainly go more uh in depth and explain why that is in clinic. But know that it is significant for the insizers that we have more room coming lingual compared to the facial. On the previous slide, I mentioned the cervical cross-section of what those roots look like. Here we have uh a crosssection in the cervical area. Kind of shows you what the uh teeth look like in cross-section and why we have different shapes. So, a cross-section, think of we're taking a a log and we're cutting it in two sections. This is the equivalent of what we're seeing in this image on the left hand side of a cross-section. And so, we have different shapes. We had mentioned the roots can be oval and I circled in orange. That would be the lateral incizer number seven. It could be triangular. Number eight would be our right central incizer. And then on the mandible in yellow there we have the central incizer and lateral incizer 25 26 shown here. They are elliptical in cross-section. So we have three different shapes in cross-section of our insizers. A few clinical considerations when we're looking at insizers. One is going to be lip overhang. Patients may when they look in the mirror and they brush their teeth, they may only brush what they can see. So lips may naturally overhang as we see in the image here. So if this patient was in the in in the bathroom in front of the mirror and they're brushing their teeth, they may only brush their teeth and not get up high enough to areas that they can't see in the mirror. This is called lip overhang. When we are talking with parents or caregivers about their little ones about helping them to brush their teeth, we'll use a phrase called flip the lip. So it's taking that lip and flipping it up so we can see the entire tooth including the gingiva to make sure that we are not missing anything. Another thing that uh we will see is mouth breathing and you learned in hisystologology we have different types of tissues in the mouth. The mucosa the mucosa is supposed to be kept moist and when it's not if we are mouth breathing that mucosa that's supposed to be moist dries out and we can see significant inflammation in the anteriors and the facial aspect especially of sex 2 which would be the maxillary anteriors. So, a couple of things to consider looking at lip overhang and mouth breathing smile design and that's something you may hear when you do get out into private practice. When we are looking at a patient and someone is smiling like we have here, the central incizers, the maxillary centrals are supposed to dominate the smile. They are the largest tooth in the anterior and then as we progress going down the smile, each tooth gets progressively smaller. So this is called smile design. So we're supposed to have those larger central incizers. Another aspect of smile design is where the midline is at in relation to the filtrum. And the filtrum is that little depression that is just beneath the tip of our nose to the lip. And maybe you could recognize this person. This is an actor based just on the smile. So, let me bring this image up. And uh this would be Tom Cruz's smile before he had some orthodontic work done. In this case, the the filtrum should line up with the midline of the dentistician. And so here we could see that the midline for his smile previously was shifted to the left. And we will teach you this in clinic on how to find the midline and then you have to record is their midline deviation and does it go to the right does it deviate to the left and then you will have to measure how far is that deviation. So we'll show you this in clinic. Next is called lip competence or maybe called lip incompetence. So it is the resting posture when we are at rest. So as you are listening to this lecture resting posture means that your currently your lips should be closed touching but your teeth should be a couple of millimeters apart and your tongue should be resting flat on the roof of your mouth. There should be no tension in the muscles anywhere especially in the mentalis muscle. That's that muscle that is present on your chin. So you should be nice and relaxed. That's called resting posture. If for some reason we have uh issues with patients who can't comfort comfortably close their lips at rest, that could be an issue. As we see the image on the top, that's called lip incompetence. That patient cannot comfortably close their lips without having strain somewhere in the face. And we'll see it uh more commonly in that mentalis muscle, that chin region. We'll see some tension there. This is lip competence. On this slide, it is called dens and dente. And it's a term that will come up again when you are in oral pathology in your second year. But dense translates to tooth within a tooth. And you may have heard about this in hisytologology in the summer. So, it's when uh there's a disturbance when that tooth is forming, the enamel organ vaginates in and creating this what looks like a little tooth inside of that tooth. And I'm going to circle it there for you. But for now, you just need to know den denzente simply means tooth within a tooth. And the next slide is an image of Hutchinson insizer. And I know you talked about this uh in your summer courses. So it is a congenital condition. It is an infection from trapema paladum and that causes syphilis. And this is going to be a a classic board question. So absolutely have to know hydrogen incizer what it is and what causes it. And you will review this again in oral pathology in your second year. In this image, we have a talon cusp. And it is simply a sharp small extra cusp. That means like a claw, like an eagle's talon. It occasionally appears as a projection from the singulum of incizer teeth and can happen within both dentitions. We tend to see it more commonly on the lateral incizers. And the lateral maxar incizers have the most variability of any tooth except for our third mers or our wisdom teeth. And there is our talent cusp. We're going to jump down to the mandibular incizers for a few slides here. Just some general features. So on the slide here we have 24 and 25 would be our mandibular central incizers. They are the smallest teeth in the permanent dentition. Usually a mandibular lateral is slightly larger than a central which is exactly the opposite of the situation in the maxillary arch. So again in the maxillary arch here we have numbers 8 and 9 are going to be bigger than the lateral insizers 7 and 10. The opposite in the mandibulars 24 and 25. The centrals are smaller than the mandibular lateral insizers. The crown is wider facial lingually compared to messio distally. The mandibular incizers the root is longer than the crown for both incizers. The facial and lingual root surfaces are extremely narrow. They have really wide proximal root surfaces. So that measial and distal root surface is really wide compared to the facial and lingual aspects of the roots. those root on the proximal surfaces have really deep concavities. And so when we are looking on an X-ray, those concavities could be so deep that it may look like those insizers have two roots. They really don't. It's just because the messial distal root surfaces have really deep depressions or really deep concavities. Next looking at clinical considerations of those mandibular incizers. Um generally the anatomy and especially in the lingual is much less pronounced. Not a whole lot going on when we compare it to the maxillary incizers. We will have a greater accumulation of plaque bofilm. Calculus is the technical term uh for tartar. Then we could have some stain here as well. And we have all of these things. We collect more plaque bofilm and calculus in this area because of the salivary glands or ducts that empty into the floor of the mouth. More on that later. And then we have minerals in our saliva. Calcium would be one that transforms soft plaque bofilm into hard calculus and in the insides there's this region of the mouth. We also see misial drift and teeth uh may start out when we're younger in that saxant five area mandibular anteriors it may start out straight but over the years we get things like attrition and wear and changes the shape of those teeth a little bit and because of that teeth will start to drift towards the midline of the mouth. It's called bial drift. And we may start seeing a little bit of overlapping, a little bit of crowding as we mature, as we get older that you didn't notice when you were younger. So, we get more overlapping here. Potentially more overlapping, harder to get that plaque off of there. And then when that transforms into calculus later because of the crowding that we often see in the sextant 5 instrumentation can be a little bit more challenging. And then also those insizers may tip lingually. So you may see that incizal edge tipping back a little bit more towards the tongue which also makes it a little harder for us to do our work in that sex. And we talked about attrition previously that that physical wear along that incizal edge. All right, we are going to wrap up this lecture with a couple of review questions. So first up, maxillary incizers have how many facial developmental loes? And I hope you said three. So read carefully. Make sure it's asking is it asking what surface or is it asking in total? So there are three facial developmental loes. There's one lingual. There is a total of four on incizers but only three on the facial aspect. Which teeth may develop deep lingual pits and deep gingible grooves? And I hope you said teeth numbers seven and 10. That would be the maxillary lateral incizers. Maxillary laterals have the most variability in tooth form except for our third mers or our wisdom teeth. And we are done with the overview of the insizers. Thanks for listening and I'll see you in the next part.