[Music] hey everyone today we're going to be continuing our Dental Anatomy learning modules and we're going to be talking about the premolar so we're going to talk a little bit about the forms functions how they're different from anterior teeth and then we're going to again flip the camera and I'm going to show you some anatomical things that sort of distinguish these unique teeth and learn about how they're important so first we're going to talk about their function the further back we move in the mouth the more that the teeth are going to be used for mastication and so these are right next to the Kines so the primers are kind of like play Pinch Hitter here they're going to do a whole bunch of things so first they're going to assist the molers in mastication or chewing our food right so they're going to grind they're going to chew but they're also going to assist the canines in shearing or biting or tearing of food so they're going to do a little bit of both next they're going to help maintain our vertical Dimension that's the dimension from here to here and it gives us our face shape and also supports um the corners of our mouth and cheeks so again um supporting the perod donum in the hole and this is true for most of the teeth because when we start to lose teeth we start to lose support so the prolar give us support and chewing power and they're just super great in terms of development they develop from four or five loes typically there's three on the facial and one or two on the lingual and what you'll see is that there can be a extra cusp on our second mandibular prolar so there are times where we do have a three cust prolar and because of those variations in this module you're going to hear me say but there's an exception and a lot of the times those exceptions are just for one type of a prolar instead of all the prolar and it's always important when we're talking about these things to remember that all of this information is averages the textbooks take averages and make generalizations based on those averages what's important to remember is that all teeth have variations of normal just like our tissues just like our body not one prolar is going to be the same we're just talking about General averages and what we typically see so unique to the anteriors or different from the anteriors our primers are going to have a couple different surfaces that we want to talk about so it has the traditional surfaces facial lingual mesial distal but instead of having that incisal edge it's going to have an accusal table and within that accusal table there's a couple different anatomical things that we'll be looking at we'll be looking at ridges and what ridges make up the accusal table uh we'll look at grooves and fossa and we'll sort of highlight why those things are important in total you have eight premolar you have two per quadrant uh the first maxillary first are tooths number five and 12 those erupt around 10 to 11 years old our maxillary second prolar are teeth number four and 13 those are wrapped anywhere from 10 to 12 years old old our mandibular first prolar are numbers 21 and 28 those are rubed from anywhere 10 to 11 just like the maxillary first and our maxillary seconds are tooth numbers 20 and 29 and those are wrapped anywhere between 11 and 12 years old again just a reminder those are just averages if your child does not fall within that that's okay it's a variation of normal so we're we're going to highlight a few similarities the similarities between premolar and anterior teeth include having the crowns taper cervically and they will tap taper cervically more than molers uh MERS also taper cervically but not as much and the further back in the mouth you get the less it's going to taper the cervical lines are also sharper on the misal we talked about that with Kines and inzer how that's one really good way to find out what's a mesial surface and what's a distal surface the misal cervical lines are always sharper on the misal and then the roots taper towards the lingual and the apical thirds are always bent towards the distal again another really good way to tell if you have a right or a left but now let's talk about some differences differences is now we are past the labial commissure which means that instead of a facial surface it's a laal surface excuse me I'm saying that wrong so now we're going to talk a little bit about the differences between anteriors and premolar so the first main difference is because now we are a posterior tooth and we're behind the labial commissure remember everything in front of the labio commissure sorry there's a fly uh is termed labial and everything behind the labial Chaser is termed Buckle so uh Buckle terminology can be for that but I do want to just say clinically and practically a lot of this terminology is facial so um just remember anything prolar or molar uh Buckle or facial number two is that we don't have an incisal edge anymore right we have an accusal table which means we have an accusal surface and the accusal surface is where all of the mastication comes from it's the chewing the grinding all of that mashing up of food happens in the accusal table and so no incisal surface only an accusal surface next is the location of the marginal ridges the marginal ridges for our anterior teeth were on the lingual plane or the vertical plane they come together and make a singul now it's like we've um if our if our marginal ridges are like this now what we've done is we've lifted them up and made them horizontal so the marginal ridges now are on the horizontal plane um the mandibular first is a little bit of an exception it has a really small lingual cusp so depending on the size of the lingual C cusp that's going to be how far down those marginal ridges go and that's a variation and you may see some that look a lot like canines because their lingual cusp is is so small another thing is that the anterior crowns are longer than prolar crowns prolar are really short they're kind of just like stocky and and short the height of Contours are slightly more occlusal um and again because that mandibular first Sometimes is similar to a canine that could be an exception and then the contacts are more cervical and they're bigger so they widen out the teeth are widening out and so they're touching the next tooth next to it lower that's what that means so uh contacts are more cervical okay so we now are going to transition to the overhead shot so that way we can look at some of these things on the actual teeth themselves so I'll be with you in a second okay I put my gloves on again just so there's uh some difference in color here and you can really hopefully see what I'm talking about um in instead of my you know skin that might not be very good contrast so hopefully this is a good contrast and you can see here some of the things that we're going to be talking about uh the first thing we're going to do is talk about class traits and I think like the enzers and K9s I'm just going to take the teeth out so that way they're easy to grab we're going to cover all the prolar and I'll keep them sort of lined up here so they're easy to find and we'll just start with number four um and talk about class traits so class traits if you remember is anything with the whole class and the the class is premolar so all premolar have these things in common the first thing is that they're five shaped pentagons and that means we have one 2 3 four five so the outline of the cusp cusps when you look at the facial VI view or straight on the outline of the crown shape is a pentagon the mesial contacts here are between the accusal and middle third which so they're higher so the next tooth next to it is going to touch it a lot higher than the distal so the distal contact is going to be lower it's going to touch the tooth next to it at a lower position distal prosto contacts um are at the middle third except the mandibular first which is more cervical remember that that uh lingual cusp may be just a little bit lower so that might be an exception for your patient next we're going to talk about cusp ridges the tip of the Buckle cusp so the tip of the Buckle cusp right here is going to be mesial to the root axis line that means the distal cusp Ridge is going to be longer and the misal cusp Ridge is going to be shorter the exception here is the maxillary first where there um let's just pull it out so that's our first this is our second where the um distal Ridge is shorter and the mesial ridge is longer so you can see the difference here when you look at both of them straight on for the lingual surfaces the crown is narrower on the lingual than on the Buckle so you can see that this is quite a bit more narrow than the Buckle is which means that's going to push the height of Contours out towards the Buckle so when these are standing together that's going to follow that U shape and the crowns are going to touch each other towards the Buckle the exception is a three cust mandibular second prolar which we have this is our three cusp and because of that third cusp there on the distal grab my pointer because of this third cusp on the distal this lingual is wider than the Buckle so marginal ridges the marginal ridges are going to be right here and right here those are the marginal ridges that we're referring to when we're talking about the accusal table the mesial marginal ridges are more ausy positioned than the distal so that means when I turn this tooth and I look at the mesial view this marginal Ridge or this Edge is more is higher is higher that's a better way to say it than this this is the distal marginal Ridge the distal view this is lower that means when you look at it from the distal view which is what you're looking at right now you'll be able to see a lot more Anatomy than you would from the misal see when we turn it to the misal we don't see a lot of the anatomy because that Ridge is higher and we can't see the accusal table from the misal view from the accusal view the crowns are wider facial lingually then they are misio distally so facial lingy then misio distally and you can see that they're a rectangle not a square so the long part of the rectangle is facial to lingual and the short part of the rectangle is mesial to distal the accusal table is outlined by The Ridges and The Ridges that have the accusal table are the distal marginal Ridge the distal Ridge of the Buckle cusp The misal Ridge of the Buckle cusp the misal marginal Ridge The mesial Ridge of the lingual cusp and the distal Ridge of the lingual cusp so those are all of the margins that make up the accusal table then we have triangular ridges triangular ridges are The Ridges that extend from the Buckle and lingual cusp and meet in the central Groove if we have a two cusp version the Triangular ridges will meet together and create a transverse Ridge but if you have that third cusp our little exceptions here if you have that third cusp you can see that the Triangular ridges make a y an upside down Y and so there is no transverse Ridge on a three cusped mandibular second prolar we also have grooves and fossa the central Groove which I guess I already sort of talked about runs right down the middle and then each Groove is going to end in a little fossa or a little space so towards the misal that space on the other side of the Triangular ridges is going to be the misal fausa and the distal fausa is right behind on the distal surface the proximal contacts like I said are going to be more buckle and so I'm going to put the teeth back in and just show you what I mean here where these two teeth touch is not going to be running along the central Groove you can see there there's quite a bit of space here and the contact of where this prolar is touching this prolar is located Buckle or towards the cheek to this line the midline and so the cusp tips are going to kind of make an outline and the contacts are going to be right inside that cusp line all right next we're going to talk about Arch traits and so that is going to be the difference between the maxillary and the mandibular premolar we're going to follow this order of looking at all the different views so in the facial view or the Buckle view we're going to look at the Buckle Ridge so here is my mandibular right second and here is my maxillary right second so when I look at these two from the facial view I'll notice that this Buckle Ridge is a lot more prominent sorry I'm just going to lay them in my fingers here if I can get them to go this Buckle Ridge is a lot more prominent than this Buckle Ridge right here also there's no distal Crown tilt on the maxillary relative to the root but on the mandibular we have a distal Crown tilt for the lingual View I'm going to turn these around for the lingual view there's less difference on the maxillary in the height of the lingual cusp so if you can see here when I look at my lingual cusp the Buckle cusp is just right behind compared to the mandibular the mandibular cus tips are a lot lower on the lingual meaning we can see the Buckle cusp tip from the lingual View for the proximal view we'll just rotate here so from the proximal view we have the clusel outline for the maxillary aligned pretty right over that root tip and with the linguals the crowns are actually going to tilt lingual and this is uh kind of the reason why that don't have a strong Buckle Ridge but it's also because that has to fit within the upper maxillary Arch and if you remember back when we talked about the incisal edge and of our anteriors so our mandibular and Cil edges were lingual and our maxillary and Cil edges were Buckle this is kind of the same thing but now with cusps and a broader Crown so mandibular the crowns tilt lingual maxillary they're lined up pretty much you know as they should be next we're going to talk about the accusal view for the maxillary accusal view Crown shape is oval or or rectangular and uh we we talked about that with the marginal ridges the crown is considerably wider facial lingually than it is misio distally compared to and you can really see it on the typodont teeth um so for the mandibular the crown shape is closer to a square the crown is less rectangular it's not as long next we're going to be talking about type traits and type traits are talking about the differences between the first premolar and the second premolar so I'm going to be looking at these individually um but also right next to each other so what I have here is a maxillary second primar this is tooth number four and then a maxillary first prolar this is tooth number five and we're just going to be looking at these sort of side by side and comparing the individual unique differences of them I'm going to try to get them in my nice purple gloves so you can really see the contrast so this is a buckle view we'll start there the first difference is the cusp angle if I can get them sorry guys so the cusp angle Here Comes nice and sharp down to a point compared to the um second that this cusp angle is more round the first tapers more cervically so there's more of an angle here and that's similar as we're moving back in the the mouth so you had your canine over here that really tapers this one tapers a little this one tapers less we forgot the Buckle Ridge we also have a more prominent Buckle Ridge this one's uh sticks out farther than this one this one is less prominent the mesial cusp Ridge is longer for the first so this um makes the cusp T tip distal to the vertical axis line compared to the second the distal C cusp bridge is longer which makes the cusp tip mesial so you have a distal cusp tip and a misal cusp tip the misal Buckle Ridge depression is more common on the first so that means this little groove right here mesial Buckle Ridge depression and then on the second we have a distal cus Bridge depression uh the the firsts are commonly bifurcated and so for the typod dant teeth they are this is a variation of normal not every first proler is going to be bifurcated but it does happen more often than the seconds the seconds are less likely to be bifurcated and they have the greatest root to Crown ratio on your maxillary teeth because their Crown is so small the root to Crown ratio um is pretty large let's go to the lingual View so I'm just going to turn these so for our maxillary first our lingual cusp is shorter and so two cusps are visible from the lingual you can see this cusp and you can see this cup tip that's because we talked about this cusp tip on the Buckle is really pointed really um out there this one's more blunt so that means these two cusp tips are going to be closer in size than the max lary first for the proximal view so here we'll look at the meal uh we have on the max first two roots or if they aren't bifurcated we usually have a really deep root depression and this one has both this typodont has both so you see a bifurcation and you see a RIT depression um you also see that the depression runs all the way up to the crown and so it affects the Crown shape as well on the maxillary seconds you do have a mesial rot depression but it typically stops at the cervical line so it doesn't affect the crown shape as much your mesial root depression is going to be deeper than the distal on the maxillary first so tooth number five the mesio root depression is greater than the distal compared to n the second number four the distal root depression is is deeper than the mesial r depression for the first we talked about it our Buckle cusp is longer we've talked about that but you can see that from the proximal view so when you turn them to the side you can see the differences in their sizes and your maxer first may have a mesial marginal Ridge Groove um your seconds could have it but it's more rare for your seconds so what that looks like is that Groove that follows the depression remember I said you might have a misio rot depression that Groove that follows that depression up can come right here and form a Groove that ties into that Central Groove so that's more common in a maxillary first not a maxillary second next is accusal views for our maxillary first the crown outline is asymmetrical with a mesial concavity okay and for our maxillary seconds we have a symmetrical Crown a more symmetrical I know it's not you know perfectly symmetrical but we are more symmetrical on the second and uh we have a mesial contour that's more convex the first taper lingually which contributes to them being asymmetrical and the maxar seconds have less tapering lingually the firsts are going to have a long longer Central Groove than the second stew the first again you can see from this view as well the misio marginal Ridge that we talked about tying into the central Groove and the seconds are less likely to have that and these typ ofon teeth do not have that for the first again we have that prominent Buckle Groove that or Ridge excuse me prominent Buckle Ridge that we can really see well from The accusal View and for the seconds that is not as prominent for the first our distal contact is more buckle and for the seconds our mesial contact is going to be more buckle and that is the differences between the maxillary types so the maxillary firsts versus the maxillary seconds so now I'm going to transition into the mandibular first or seconds and these also have a lot of differences as you can already probably tell when we talked about having a cust that's probably the biggest difference so we're going to start by turning them to the Buckle View and just for context what I'm looking at here is uh maxillary or excuse me a mandibular first this is on your right mandibular first and this specifically is tooth number 28 then right next door on your left we have a Mand second and this is tooth number 29 so from the Buckle view our Max or I'm going to just be in the habit of saying that now from the Buckle view our mandibular firsts compared to our seconds our firsts have longer crowns the crown itself tapers from the contact to the cervical more than the second stew so this Crown is shorter it's wider at the cervix the cusp tips just like the maxillary this tip is more sharp and pointed this tip is more blunt the misal cus Bridge notch on the first are more common so that's right here that cus bridge and on the second's the distal cus Bridge very similar to the maxillary for the first the misio contact is more cervical than the distal and uh for the seconds the distal contact is more cervical from the lingual view so we're just going to turn these right around for the mandibular first and this is sort of what we were talking about in the really bigger differences the maxillaries are closely more closely in shape the mandibular types are really different when it comes to the lingual cusps that's because one the mandibular first their lingual cusps are significantly smaller their borderline like a hybrid canine and because the lingual cusp is so small it's really a lot of the times it's nonfunctional meaning it's not going to really contribute to a lot of mastication but then we also have these seconds that are outliers and these seconds especially the cre three cusp versions those can also be a variation of normal so the lingual view really depends on the lingual cusps if you have two cusps obviously the lingual is going to be a lot wider because you're making space for the lingual cusp if you have a mandibular first that's really small the the lingual view is going to be a lot more narrow and it's going to taper down and that is going to be just a tiny little cusp almost looks like a singul so that means this marginal ridges are going to be more in a vertical plane than the seconds the second the marginal ridges are a lot more in that horizontal plane or parallel from the proximal view so let's just turn we're going to look at the mesial views so I've turned these hopefully you can see that now we're on The misal View our first our misio marginal Ridge is lower and parallel to the Buckle triangular Ridge compared to our seconds our misio marginal Ridge here is a lot higher and U more horizontal that's because that that tiny little lingual cusp on the first is bringing that marginal Ridge down this one is more like a real cusp so it stays up it stays horizontal this one has a lingual Kilt to the head or the crown of the tooth it really tilts lingually to sort of allow itself to fit within that Arch this one has less tilt the second mandibular second has less tilt for the first the lingual cusp is obviously shorter we talked about that but because of that you can see a lot more of the accusal table from this view compared to the second you can barely see any of this accusal table on your second because that marginal Ridge is so high and then the misal lingual groove on the first is seen from the mesial and then the two lingual cusps on most of the mandibular second primers can be seen from the dist so I'm just going to turn this guy and when you do that you can typically see a lot of the accusal table and you can see these two cus now we're going to turn to the accusal view so here we have the accusal view for our mandibular first right here the outline is like a diamond shaped and that's because the lingual cusp is so small so it looks like a diamond the second is more like a square and especially if you have the three cusps if you just have one cusp it might be more like a symmetrical Circle but with the two cusps it really does give it a square shape because of the third cusp it also gives the second a larger accusal table this really varies again the accusal view is going to vary a ton but based on that the first because it only has two cuts it could have two fossa and with a three cusp type you can have three fossa because you have one here one here and one here and so that's just going to vary if you have a second that only has two cusps it's going to align more with the anatomy of a first because you're not having that variation in where your triangular ridges are remember we talked about the Triangular ridges as going from the cusp tip down to the central grooove so if you have a three cus variation you're never going to have a transverse Ridge because that Ridge would never go all the way across it's going to be more like three triangular ridges in the shape of a y compare that to the first where you'll only have one in one so the transverse Ridge on a first is more evident because it follows those two triangular ridges for the manipular first our distal fossa is going to be larger than the mesial so this fossa over here is larger than this one and for the second it really just depends right we talked about we don't know if it has this variation um you know all three of them look fairly similar in size because there's not much surface area there for a fossa to be so that is the premolar in terms of class and type so as you're going through this pause the video um look at your PowerPoints look at your resources and really blow the video up if you need to really make sure that you can see some of these differences and if you have any questions please reach out to me and let me know and we can talk about it further thank you for listening and we will see you next time when we talk about the MERS [Music]