[Music] this video is sponsored by bootcamp.com check it out for iron bde prep and use coupon code mental dental for 10 off hey everyone dr ryan here and welcome back to our dental anatomy series in this video we're going to focus on the maxillary central incisor so if we're talking about the universal notation that will refer to tooth number eight and tooth number nine so this is all about the permanent maxillary central incisor so from the facial aspect we can notice quite a few important things that i want to point out for you so first the tooth is wider at the proximal contacts and narrower at the neck and so it's described as having a trapezoid shape from the facial view next the inciso cervical dimension is greater than the mesio-distal dimension which i've abbreviated as ic is greater than md by the way this statement right here is true for all permanent anterior teeth this tooth specifically has the second tallest crown incisor cervically the tallest is the mandibular canine it's also the widest anterior tooth again we're talking amongst the permanent dentition in this series so this is the widest anterior permanent tooth and it's bigger wider and longer than the maxillary lateral incisors that are next to them and that's in all dimensions the incisal edge should be almost perpendicular to this long axis the long axis is an imaginary line that runs from the apex through the middle of the root to the middle of the crown there are three developmental lobes that form the facial portion of the tooth so there's a mesial facial lobe there's a middle facial lobe and there's a distal facial lobe and the fourth lobe makes up the cingulum area on the lingual surface of the tooth by the way all anterior teeth develop from four developmental lobes those three facial lobes that i drew here manifest in the crown as three little bulges on the facial surface with little ripples in between them called developmental depressions i'll erase those lobes there so you can appreciate those developmental depression areas that i'm talking about and then we have these mamalons or little bumps along the incisal edge they're not visible here because most of the time they wear away with normal wear by the age of 10 but those little bumps can manifest on the incisal edge coordinated with each of those three developmental lobes the mesial incisal corner is sharper and roughly a 90 degree angle whereas the distal incisal corner is more rounded the distal surface both the root and the crown is more curved and tends to be more convex as a whole and that will be true for most teeth in the mouth the root also tends to point in a distal direction not always but most of the time i unfortunately misspoke in the last video the pericamata are the cervical ridges and the imprecation lines are the grooves between those ridges and they're probably most noticeable on the maxillary central incisors and you'll see them on the cervical third of the tooth near the gum line by the way this cervical third area is the most convex part of the entire tooth everything else from the facial perspective is pretty flat both the crown and the root the mesial height of contour is in the incisal third of the crown and the distal height of contour is at the junction of the incisal and middle thirds this is also where the mesial and distal proximal contacts are which makes sense because they're the parts of the tooth that stick out the most and thus where adjacent teeth will touch each other here's another trend i want you to remember height of contours and proximal contacts will start more incisively at the midline and as you go distally or posteriorly around the arch these height of contours and proximal contacts will move cervically so the contact between the two central incisors is going to be in the incisal third and the contact between two molars way back here is going to be in their middle thirds an easy way to remember that is incisors will contact incisal and molars will contact in middle so i and i and m m the tooth is narrower on the lingual aspect both the crown and the root and that's because there's only one lingual developmental lobe as compared to the three facial lobes you can even see a bit of the mesial and distal aspects of the tooth because it's again more narrow from this view the cervical line or the cej is deeper on the lingual aspect than the facial aspect but on both aspects it's convex toward the apex and the cervical line being convex on both the facial and lingual surfaces is actually true for every tooth by the way you can appreciate the mesial marginal ridge and the distal marginal ridge from this view and also the cingulum the cingulum is formed from that lingual developmental lobe there's a lot of variations that can happen in this lingual surface sometimes it's very flat and sometimes it's very bulbous with big thick marginal ridges and sometimes there's even an abnormal groove that forms back here but we'll talk more about that in the next video on maxillary lateral incisors where those variations are more common alright from a side view here we're looking at the mesial aspect the maxillary central incisor is wedge or triangular shaped at the crown and that's tapering from the cej to the incisal edge for all anterior teeth the height of contour for both the facial and lingual surfaces will always be in the cervical third of the crown also note from this view that the cervical line is now concave toward the apex and that's going to be true for both the mesial and distal aspects and guess what that's generally true for all teeth it's just more pronounced in anterior teeth than posteriorly so to review the cervical line is always convex toward the apex from facial and lingual and concave toward the apex from mesial and distal this is just a cool thing to point out a lot of things conveniently fall along the long axis from the mesial and the distal aspects the number one here is that incisal edge and that's the exact line where the facial surface meets the incisal ridge so number one is that incisal edge number two is that proximal contact or height of contour number three is the height of the cej concavity and number four is the root apex from the distal aspect you'll notice a lot of the same things we just saw from the mesial aspect the cervical line is still concave toward the apex but it's just a little bit flatter than it was on the mesial aspect and that's yet another great trend to remember that the cervical line gets flatter the more distally and posteriorly that you go from the midline from the incisal aspect you'll notice that the mesio-distal dimension here is larger than the facial lingual dimension also the cingulum is slightly off to the distal it's slightly off centered and this corresponds to the shape of the arch having that cingulum slightly off-centered helps to fit all the teeth into that u-shaped arch now about the pulp the pulp chamber which is the part of the pulp in the crown of the tooth usually has three pulp horns areas that stick up that correspond to the three different facial developmental lobes one two and three outside of the molars this is the tooth most frequently with both a mesial and distal pull porn this tooth almost never branches with multiple roots and so for ease of learning we'll say that a hundred percent of maxillary central incisors have just one pulp canal that's the part of the pulp in the root of the tooth except for molars this is the tooth least likely to have a bifurcated root if we cut that root into cross section at the middle of the root horizontally we see a triangle formed between the facial mesial and distal surfaces remember how the whole tooth is kind of flat on the facial surface and then tapers toward the lingual aspect and that's why that cross section appears triangular the maxillary central incisor has the most natural axial inclination of all the teeth what we mean by axial inclination is that the incisor crown is facial to the root and why is that well the apex fits in the alveolar housing towards the lingual you can think of it this way the roots are a lot smaller than the crowns in diameter so the crowns have to lean out in order to fit into the arch so it's slightly inclined in the mouth in order for everything to fit and teeth are progressively less inclined as you go posteriorly and you can visualize that in both of these images alright so a summary of the maxillary central incisor the incisor cervical dimension is greater than the mesio-distal dimension which is greater than the facial lingual dimension it has the greatest axial inclination it has the second tallest crown it's trapezoidal from the facial view it's triangular from the side incisal and cross-section views and it most often has four lobes three pull porns and one pulp canal and to summarize the trends that we went over in this video starting from the midline and going posteriorly proximal contacts move more cervically cervical lines get flatter and axial inclination decreases that's it for this video thank you so much for watching please like this video if you enjoyed it and subscribe to this channel for much more on dentistry if you'd like to support me please check out my patreon page and thank you to all of my patrons for their support you can unlock access to my video slides to take notes on and practice questions for the board exams so go check that out the link is in the description thanks again for watching everyone i'll see you in the next video [Music] you