Dr. Daniel Vinograd has established a long and prosperous career as the dentist San Diego prefers, because of his holistic, pain-free and biocompatible approach to dentistry. What you may not know is that he has a longstanding relationship with his alma mater, the University of Southern California.
Today, he’s a professor of dentistry for the university where he received his DDS degree.
USC is a private university founded in 1880 and based in Los Angeles. It’s the oldest private research institution of higher learning in California, trains a large number of international students and fully embraces its close proximity to Hollywood. It’s also consistently rated as one of the top colleges in the nation.
Here’s a bit of trivia that makes dentists like Dr. Vinograd proud: USC’s well-regarded fight song “Fight On” was composed by dental student Milo Sweet in 1922 — although Glen Grant has to be given partial credit for the lyrics.
Even if you’ve never been on the USC campus, you’ve probably seen it. That’s because its location means it features prominently on film and on television. You may have seen it in Forrest Gump, Ghostbusters, The Social Network or The Graduate. You may have also seen it on The Fresh Prince of Bel-Air, House MD, The Office or Monk, to name only a few of the many TV series that have filmed on the campus. Even Wheel of Fortune and Jeopardy have shot there.
The University of Southern California’s close relationship with Hollywood and pop culture doesn’t mean it takes its professional programs less seriously. If you think about it, good teeth are an important part of any Hollywood career, and quite a number of the entertainment industry’s top names depend on USC dental school graduates for their award-winning smiles.
Will you be the next to turn to the San Diego dentist citizens of all types entrust with their precious teeth? Getting started is as easy as setting up an appointment.
Not really concerned what brand of toothpaste you buy? Not interested in making your own toothpaste when you can buy one at the store that works pretty well?
Perhaps the best reason of all for making toothpaste at home, or carefully choosing what brand you use, is avoiding SLS. But what is SLS and why is it so bad? Keep reading and you’ll understand.
Getting To Know SLS
Sodium Lauryl Sulfate or SLS is found a lot of personal care products. But it doesn’t really belong there. In fact, putting it there doesn’t make much sense at all.
While it serves as a surfactant — a substance that breaks surface tension so a product can penetrate — it can cause skin irritation, the worsening of skin problems and other issues. Even worse, some people have an allergy to it, causing even more severe adverse reactions. And still worse yet, it can cause canker sores — those round white sores in your mouth that sting for days — and can cause dry mouth.
If you have a problem with skin issues, canker sores or dry mouth, you need to eliminate SLS from your toothpaste and from your other skin, mouth and healthcare products. Doing so could eliminate your problems or at least make them not as bad. In fact, research has proven a decrease in canker sores when using an SLS-free toothpaste.
If You Love Food…
Perhaps worst yet if you’re a foodie, SLS in toothpaste has been shown in one study to cause a temporary alteration in your ability to taste. Have you ever noticed that food tastes strange if you eat immediately after brushing your teeth? SLS could be the reason.
The reason this issue isn’t talked about more is that most people intentionally avoid eating after brushing their teeth to keep their teeth clean, so they may not necessarily notice this side effect.
Simply put, avoid SLS at all cost to avoid its side effects for a healthier and better life.
For a great homemade toothpaste recipe without SLS, visit: http://homemadetoothpaste.net
“Along with non-toxic dentistry, and helping fearful patients, the awareness and prevention of Gum Disease is a priority in our practice. We invite you to sign up for a free cleaning during our awareness week.” – Dr. Daniel Vinograd, DDS
To schedule your free cleaning in our San Diego office, call (619) 550-4904
Biological dental protocols for non-toxic dentistry:
One other thing that starts to become rather prominent here is this distal lingual cusp. This entire mass starts to become smaller in overall dimension. And this groove that comes out, the distal lingual groove, as it crosses our cusp ridge here and starts to come down to the lingual surface, it doesn’t usually cross this height of contour on the lingual surface and we don’t usually get this deep groove crossing the height of contour. We don’t very often have any groove down the root here at all. Just comes down part way on the lingual surface and stops. It’s lost its characteristic prominence. Our buccal groove does carry on onto our buccal surface and carries down on the surface away but again isn’t quite as sharp and as deep and as prominent as it what would be on the first. I should make one comment in looking at these buccal surfaces here. Usually our buccal cusps, our both first and second, are approximately equal in size. Very similar in size being equal. Equal in their width as well as their height. And this buccal groove frequently will come right down the middle of the buccal surface. On the lingual we find that this is not true. Our mesial lingual cusp is usually about 2/3 width of our lingual surface, 2/3 the mass dimension and our distal buccal cusp is smaller.
Come to our second this occurs even more so. We may have three quarters of our lingual surface mesial lingual cusp. Maybe only one quarter our distal lingual cusp. And actually when we go to our thirds we’ll find out that frequently we have our entire lingual surface, maybe just this mesial lingual cusp or we may not have any or maybe very, very small distal lingual cusp area here. But one thing we also should note and that is when this groove does come down on the lingual surface by the time it crosses the height of contour on the first it’s usually pretty close to the mid portion of the tooth. It comes out at an oblique angle and by the time it reaches a height of contour it’s almost in the middle of the tooth. In our seconds this is not reaching the height of contour and we are not flattening [inaudible] our lingual root here. Lingual root is usually very round in this area as is our outline of our tooth because this groove just isn’t crossing. Our anatomy occlusally is basically the same as far as the terminology. We have all four of the same cusp, we have same surfaces, same line angles, same point angles, same marginal ridges with again mesial marginal ridge being closer to the occlusal, further the from the cervical, either way you want to put it. And our distal marginal ridge dipping closer to the cervical. One thing that is fairly characteristic about this oblique ridge in this tooth is that it’s not nearly as prominent in the second as we find that we’re losing a lot of our general overall prominency.
Often times this central groove will cross right through this oblique ridge. And this becomes important when we are restoring the tooth. We kind of like to know whether we want to follow that groove out or whether we want to stop on this sharp incline of our oblique ridge and very frequently this will cross right over the ridge into the distal pit, make a groove right through it. Our root structure on our second is usually contained within the crown and I didn’t really point this out too prominently in the first…let me show you difference here in existence….but within the first our root structure is said to be trifurcated very close to the crown and we have a short root trunk. In the second our trifurcation is not as close to the crown and we have a longer root trunk. In the first this lingual root in particularly usually extends well beyond limits of the crown. It’s much broader than what the crown is. In our second we usually we usually will see this lingual roots is contained beneath the crown, it doesn’t extend significantly out beyond the width of the crown. On the buccal surface of the first we find that the roots are trifurcated close to the cervical and that the roots are well spread. On the second these roots are generally not spread very wide. Sometimes they will be a little bit but certainly not as wide as they are in the first. Sometimes they’ll actually fuse and here we can see a fusion occurring in them. Actually a little bit of bone that was left in that fusion. This becomes a problem anatomically where our roots separate towards the middle portion of the root and then fuse again at the apex. Then when you try to remove these teeth you got a little piece of bone that grows right through this area and locks right in on it but they’re not nearly as widely spread. The root structure in general is shorter. But again our crown structure is shorter. If we compare these with our bicuspids we’ll find that a mandibular…pardon me…the maxillary first molar has a shorter crown. We just got done saying that the mesial distal dimension, buccal lingual dimensions are all greater but the crown height from the cervical line to the tip of the cusp is about a millimeter shorter than our bicuspids. And when we go to our second molars again our crown becomes shorter for half a millimeter or so. As we go to our thirds it becomes even shorter yet. But our root structure does start to vary rather significantly and this becomes rather important in relation to surgery, in relation to our building restorative restoration on these teeth because we like a nice, heavy, strong root structure to hold these restorations and bridges and partials and other structures into the mouth. Also becomes very important as far as periodontal problems. If we get infection down in this trifurcation area this is very difficult to control. We have to go a lot further down the root surfaces to get this in second premolar or second molar where as in first molar we got just a very short distance before a gingival recession and pocket formation [inaudible] before we get into this trifurcation. So frequently it’ll cause us quite a little difficulty.
One thing I should point out here as I see these rings of calculus. This is kind of a ring of hardened calculus on here and this is a ring of calculus on this tooth here…little soft tissue. We showed you some bone and what have you. One of the things that’ll occur on these teeth are little white lines like this and this isn’t a surface deposit of any nature. And if you were to take your explorers and go over these teeth you’d find that some of these little areas you can’t feel. They just feel completely smooth. What we have here is what is called a decalcification line. At one time when this child evidently was 6 probably 8, 10 years old, before the second maxillary molar came in, he lost his toothbrush for 6 months or something and we got a plaque formation and a generalized beginning decalcification of this tooth, right at the gingival line. This is evidently where the gingival line was at that time. And this has started to decalcify which is the first beginning stage of our decay. But evidently he found his tooth brush, gingiva tissues receded and it stopped at that point and never did become a problem not having gone any further. Our outlined form, at least from the occlusal, on our third molars is no longer referred to as being rhomboid. Because of the prominent lack of this distal lingual cusp and a very large mesial lingual cusp we pick up more of a heart shape. So frequently we hear the maxillary third molars referred to as heart shaped teeth. If you look at the inner occlusal on these…we’ve got couple of them sat here… we find that they are rather distinctly irregular. We don’t find prominent pits, prominent grooves, we get just a lot of accessory fissures what we call supplementary accessory fissures and grooves developed in all types of irregular directions. We have some of our characteristics still prominently present including our three basic cusps on this. On the lingual having mainly our just mesial lingual. We’ve got very little distal lingual cusp on this. Our marginal ridges are still present though. we got… and our central fossa is still rather prominently present. s to if we have any oblique ridge or mesial distal ridges…we certainly have very little of any distal lingual groove or no lingual groove down the lingual surfaces of tooth at all. We looked to the root structure on these teeth. We frequently find that they are often times becoming fused and that they can be separate or they can be fused. If they are fused you’ll find that there’s usually grooves in between where the roots should be.
This sometimes frustrates student because they have difficulty identifying maxillary mandibular unless the can count 1 or, pardon of me, 2 or 3 roots. When they’re all fused into one this creates a problem. We have basically the same type of a situation with a very broad, flat, mesial surface as we have this broad, flat, mesial root and on our distal we have this much shorter, smaller or rounded distal buccal root which is usually distinctly different than other roots on it. We’re not going to spend a lot of time as I indicated studying these third molars because of the large variation that does exist. Because really the lack of importance in the mouth and many times they’re not present in the mouth at all but you should be able to identify first and second rather characteristically and if we haven’t got a first or a second then we generally toss it into third category. If we look at the pulpal anatomy on these maxillary molars you can see that in order to get into the pulp chamber of these molars we need to place our opening into the central and mesial fossa. Here you can actually see the lingual root canal exiting out of the pulp chamber. This opening is actually mesial to oblique ridge. Actually I should mention that this oblique ridge sometimes is referred to as a transverse ridge. Technically it is an oblique ridge and on our examinations and the State Board examinations, national boards it will be ab oblique ridge but in common daily terminology occasionally it’ll be referred to as a transverse ridge. So if somebody talks about a transverse ridge in a maxillary first molar you’ll know that they are really discussing the oblique ridge. It’s kind of a interchangeable term. You can see the type of opening that is needed in this tooth. You can see some of the pulp canals starting under the basal chamber.
Let’s look at the cross section here. We have a mesial distal section of the tooth which shows our two pulp horns in this section. Actually this tooth has four cusps now so it’ll have four pulp horns. We got our mesial buccal pulp horn and our distal buccal pulp horn. Our pulp chamber, very well defined in these teeth and then our two canals. We have our…oh, let’s see…we got to get our orientation right here. I think I called this one the mesial buccal…it will be over here…is our mesial buccal pulp horn. This is our distal buccal pulp horn. Distal buccal is a little bit smaller. We’ve indicated that our two buccal cusps are usually of equal size. Actually the mesial cusp is usually a little bit larger and not a lot and certainly it doesn’t have the variation in size that our lingual cusps have on our maxillary first molar. So this is our mesial side. We have our mesial buccal pulp horn pulp chamber and our mesial buccal root. Usually this mesial buccal root will have a little bit of a gentle curvature towards the distal line whereas our distal root is frequently straighter. And both these roots are protruding towards the distal a little bit. These canals are basically rather narrow from the mesial to the distal. If we look at a buccal lingual section on this tooth we find that we can just see one of our buccal canals. And this is our mesial buccal one here.
This is the largest root, the flat one, quite wide from the mesial to the distal. As we indicated sometimes this will have a concavity. Occasionally in a small percentage of these this will actually be two separate canals but most of the time it’s just one canal which is a little bit broader from the buccal to lingual sine our root is broader. We have to remember our external morphology on it. Our lingual root which is usually the longest root although we’ve got the tip on this one broke off here, is round and our canal frequently is round in this tooth. And it’s usually the largest canal on the tooth. It’s also the largest root usually on the tooth. Our maxillary second molars are usually very similar in our mesial distal section. We’re sectioning through our two buccal roots here again. We got our two pulp horns which are prominent, mesial buccal and distal buccal. And we’ve got our chamber and our canals which again are very narrow from the mesial to the distal. In this instance we got a little piece of bone that actually came out and stayed with this tooth. As the apex of our teeth became closer together it kind of pinched off a little piece of bone right in here. We look to our buccal lingual section on our second and we should have identified our pulp horns or mesial buccal pulp horns since we’re going through the mesial buccal root here, mesial buccal cusp… this will just be our mesial lingual pulp horn. This is the largest cusp on the lingual. We have a mesial lingual pulp horn we’re actually sectioning through here. But again we’ve got our round, rather long, fairly good sized lingual canal, lingual root canal. Then on the mesial we got our mesial buccal root canal. And again there’s a possibility that this could be two separate canals on this tooth although we usually just have one. They usually will constrict just before they come out the apex of the tooth at the apical foramen on these.
Distal marginal ridge is frequently just a little bit closer to the cervical. We have sometimes a groove that will come up to this mesial marginal ridge and occasionally will cross it just a slight amount and this again would a mesial marginal groove. Kraus text book talks about this groove. We haven’t found very many teeth in which this shows prominently enough to really point out. It’s not a really strong groove. Our real strong one is our central pit in our central groove that comes up to the mesial. Now we can look at these cusps and we find that we have ridges coming from the cusps, not only our triangular ridge that comes down into the central sulcus area. Again central sulcus would be a valley depression between our cusps and our central sulcus area pretty much includes our occlusal table. Remember our occlusal table is the portion in which our food divides and goes to the outside of the tooth or to the inside of the tooth into the central portion of it. So our triangular ridges will come down into our sulcus, central sulcus, area here. Now with our distal buccal cusp here our triangular ridge is what almost connects up to our ridge, triangular ridge from this mesial lingual cusp. We got several ridges, triangular ridges, coming down into the central area of the teeth. We also have ridges coming from these cusps which are cusp ridges but you have to be a little bit more specific in the terminology of these cusp bridges. Fact is we have two, for instance, two mesial buccal cusp ridges.
We got a mesial buccal cusp ridge on the mesial buccal cusp. And we got a, I should say, buccal cusp ridge…we got a cusp…mesial buccal would be…mesial buccal cusp ridge on the mesial cusp and a mesial buccal cusp ridge on this distal buccal cusp. So we may have to identify these further and say mesial buccal cusp ridge of the mesial buccal cusp or the mesial buccal cusp ridge of the distal buccal cusp. Let’s look at the root structure on these teeth. Actually as a group they are probably the most easily identifiable teeth in the mouth in so much as they have three distinct roots and they are the only teeth, maxillary molars, that have three distinct roots. And the root structure is quite characteristic between first, second and third molars but it doesn’t outweigh the prominence or characteristics of the occlusal anatomy.
The occlusal and crown anatomy is much more reliable than the root anatomy. Root anatomy varies. But on these 3 roots we’ve got specific terms for all 3 roots as we did for our multiple rooted premolars and even our multiple rooted mandibular cuspids. In the molars the roots are termed simply by the location. Now if we look at the occlusal to get our orientation mesially and distally here I would hope, we would find that one root comes out right under this lingual groove. And this is right in the center of the lingual surface and this is called a lingual root. Very same term and same type of location as we had in our maxillary premolars when we had the [inaudible] a lingual root. But on the buccal surface we usually have two roots. And these are termed by the area they are located at. We have a mesial buccal root and a distal buccal root. Now where these 3 roots join we have area which we are now calling a trifurcation meaning three roots joining. We called it a bifurcation when we had 2. Now we’re calling it trifurcation or sometimes abbreviated furcation, meaning division of roots but this is a trifurcation. The actual shape of these roots I think is important for many reasons. Not only from endodontic standpoints but also from surgical standpoints, periodontal stand… many reasons. Our lingual root is usually the longest root on this tooth. It’s a single root supporting the lingual half so it’s little larger and longer than our buccal roots. And has a [inaudible] tendency to be round in its overall structure. It’s the large, round type root. Our mesial buccal root is rather a broad, flat root. This is more similar to our roots on our mandibular incisors. It’s kind of a ribbon shaped broad flat root. And actually occasionally you will have a concavity down the center of it. It’s so broad and flat on this mesial surface and very frequently it will have a concavity on the distal surface of these mesial buccal root, right down on the inside in here. And this becomes rather significant when you’re trying to remove this tooth because this really locks into some bone there and becomes quite a problem.
Our distal buccal root is the smallest root and it’s kind of in between. It’s not really round and it’s not really flat and has a tendency to be a little bit on the broad side towards the occlusal but it has a tendency to round off as it gets down towards the apex. I really should say cervical. It doesn’t really come close to the occlusal. Usually referred to the cervical portion of the root here. Make sure I get my terminology straight here too. We have one section of this root here that we should’ve pointed this out on our premolars. Before the roots trifurcate here or bifurcate which is called the root trunk. That’s actually a new term for you. The root trunk is that portion of the root before we get a division. We have a root trunk. Actually if we go back and look at our occlusal outline on this tooth, this is often referred to as being rhomboid in shape. Mesial distal surface are somewhat parallel but not necessarily at right angles to the buccal and lingual surface. And we’ll make a drawing of this or if you make a drawing of it I should say we can make this rhomboid basically in its shape. That’s what they referring to. One other prominent characteristic I think we should point out to this and that is that even though we have four rather distinct line angles, our buccal line angles are more prominent or I guess you can say sharper. A little bit sharper than our lingual line angles which have a tendency to round more. We have one line angle which rounds very sharply as it gets toward the cervical. And this is your distal buccal line angle. Right as it gets to the cervical it becomes very rounded. In fact as the whole tooth has a tendency to tuck in in this area and this again becomes quite a problem in restorative and periodontal [inaudible] and should be noted. We had this present on the distal cervical area of our mandibular laterals and cuspids. We’ve pointed this out. For this rounding occurs very sharply and prominently on the cervical third of the distal buccal line angle area here. Sometimes this tooth is referred to as having a fifth cusp. When we have a fifth cusp present it kind of joins is and grows with the largest cusp on this tooth which we indicated to you as what? Mesial lingual being the largest cusp. Sometimes we’ll get an additional cusp which will occur in this area right here and I have a few of them. Sometimes it’s not present at all as in this tooth. And it can be present in varying degrees here. Again we find none here. It’s being our mesial lingual here. We find a small crevice right in here which indicates a very tiny cusp development.
Here this is getting just a little bit larger. Here our cusp has gotten so large that we’re actually creating a pit between the mesial lingual cusp and this fifth cusp. In this one you can see we have a very large fifth cusp and again a deep pit. I find that this pit frequently has a tendency to become carious and actually requires a separate restoration right in this pit that occurs between the mesial lingual and this fifth cusp. This is usually called just a fifth cusp or it could be called a cusp of Carabelli. It seems to be a jingling term that has gotten quite a lot of popularity. Cusp of Carabelli or just plain fifth cusp. Not always present and it’s rather highly variable in its amount and degree in size but generally always occurring when it does appear on this mesial aspect of this mesial lingual cusp. One thing we could point out to you also is our contact areas. Sometimes on these molars they start to become rather prominent and often times they will stain quite dark. And this becomes a problem occasionally when you lose the deciduous teeth that are in front of these and parents look into mouth and find a dark contact area and they rush Johnny in because he’s got a cavity. And you get to checking it and you find that it’s hard and stained and it’s just simply a contact area that has become stained. Here again we got a contact area on this tooth right in here that has stained up a bit. Notice how this calculus is collecting here. Notice where that is. It has a big tendency to collect there. That’s where we get that tremendous rounding of that distal buccal line angle right in the cervical. Very prominent area for calculus to collect because tooth just takes a sharp dip in that area. If we go to our 2nd and 3rds we’ll do more of a comparison study here, maybe pick up a few additional terms on it. We have differences in size and within the same mouth this becomes most important. This difference in size is about a millimeter in mesial distal width within the same mouth and our 2nd molar. And within the third molar, well, this can vary. Again about a millimeter smaller than the second [inaudible] in the mesial distal width. But this third molar becomes so variable and is so highly irregular and sometimes not even present. We are not going to spend too much time in studying this.
We’ll give you a little bit of information identification of it but we’re certainly not going to spend the time on it that it justifies in relation to the amount of a variations it has because it’s got a thousand and one variations. Our second molars are usually fairly characteristic in their occlusal anatomy. They are fairly sound in their anatomy. We have about the same width from the mesial to the distal, pardon me, from the buccal to the lingual as we do in our first molar within the same mouth that is. But we’re a little shorter on the mesial distal dimension as I indicated about a millimeter. We still have the basic rhomboid shape in it although our line angles, and particularly on the buccal here, are becoming rounded. Remember this was a characteristic between the first and second premolars. Our second premolars started to get quite a little rounding in the line angles while our 2nd molar does the same thing in comparison to first. It just starts to round out in our general anatomy. In our anatomy occlusally again it’s not quite as sharp and distinct and prominent as was our first molar. That’s the same basic characteristic between the second and first premolars.
Watch the video: http://www.learnerstv.com/video/Free-video-Lecture-4747-Dental.htm
In this presentation we will discuss the anatomy of the maxillary molars. Our objectives in this presentation will be to discuss the location and position of these teeth, to concern ourselves in relation to the occlusion, to study the morphology and the terminology on these teeth and to study identifying characteristics of the maxillary molars. We’ve got 3 maxillary molars which we will be concerned with. They are simply called first, second and third. I should say we have 3 in each quadrant: 3 on the right and 3 on the left. On the right there would be tooth number 1, 2 and 3 and on the left it would be 14, 15 and 16. Our first maxillary molar is the one that comes in about age 6, very frequently confused with deciduous, baby or primary teeth. Next one, second maxillary molar, comes in about age 12. Our third maxillary molar, frequently referred to as our wisdom tooth, varies in its eruption coming in anywhere from 17, 18 up to late twenties. It’s the one that has such a reputation as being a troublemaker and frequently, I shouldn’t say frequently, about 20 percent of the time it’s not found at. It seems to be disappearing in its presence. If we look at the cutaway scull on this we can get an idea of the root structure on it. Notice that we are seeing two buccal roots on each of these molars. And we’ll also notice that the angulation is a little bit forward on all of these teeth. They are coming a little bit forward on their angulation. We should start to take more specific notice in relation to the occlusion of these teeth and how they are actually occluding with mandibular. We may have mention that our bicuspids actually are what we call interdigitating.
We’ve got a cusp-fossa relationship but more specifically we can turn this cusp-embrasure relationship because the cusp of the bicuspids is actually coming up and touching on the marginal ridge areas in our premolar areas here. We’ll define embrasure more specifically for you but this is an area associated with the marginal ridges. We still have a significant amount of difference in the width of our arches here, our maxillary arch being much wider than our mandibular arch. And the difference in this width is measure term cold which is called overjet. Overjet is the distance the maxillary teeth overlap the mandibular teeth in a horizontal direction. It is also called horizontal overlap. And we can take a look at our gauge here. We can actually put on a gauge and measure this amount by using the back side of our boley gauge and measure the specific amount that we would have in overjet and measure right down to a tenth of a millimeter or so. We’ve noticed that with these maxillary molars as they are interdigitating we are getting the combination of cusp to embrasure or to our marginal ridge and we’re also getting cusps associated with the central portion of our teeth or the actual fossas. So we get a cusp embrasure and a cusp fossa relationship on these molars. We’ll break down a little further as we go. If we look at the other side here we’ll also notice one other relationship I think we should take note of and that is that we have a maxillary sinus [inaudible] and this is [inaudible] width about apex of our maxillary molars. If we were to take our skull part here a we’d note that these roots have a tendency to be directly in a relation to these [inaudible], these maxillary sinus. [inaudible] often can effect these teeth. Actually the lingual root of this maxillary first molar is penetrating into the floor of the sinus and sometimes the roots of second or third molars may also penetrate into the maxillary sinus. This can lead to confusing clinical symptoms. If we go to our individual teeth we’ll start to identify some [inaudible] marks here.
Actually we’re picking up a lot of new terminology with these teeth here now but the terminology is not really complex because it is associated with the mesial distal buccal and lingual. Those are our four basic surfaces so we probably should identify those first. If we look at the tooth in outlined form here, this is the easiest way to really identify the buccal and the lingual because our buccal surface has a height of contour that is closer to the cervical. This height of contour can also be called the buccal cervical ridge or the cervical ridge. It is a bulbous prominence down in here and frequently will be just called the cervical rage, meaning the height of contour. And then from this area up towards occlusal we have a tendency to flatten a bit through the middle third and actually into the occlusal third until we get up to our buccal cusp. On our lingual surface our height of contour is [inaudible] through the mid portion and our lingual surface is more evenly convexed. So this is the easiest way to identify our buccal and lingual. In identifying our mesial and distal I guess the best way would really be to look at your occlusal surface because you have one cusp which is prominently larger than the other. And this is the mesial lingual cusp. And this is always to the mesial surface. Actually we have 4 cusps on this tooth and they’re identified strictly by the surfaces. We got our mesial lingual being the largest in bulk, also being the largest in height or the farthest from the cervical. We have our mesial buccal, our distal buccal and our smallest cusp usually which is the distal lingual cusp. So we are basically talking about 4 cusp tooth when we are talking about our maxillary first molar. Our second and thirds have characteristics very similar to these and as a result we’ll spend much of our terminology identification on this and then just point out the differences in second and third molars. We have basically the same line angles at the junctions of the surfaces.
We’ve got basically the same point angles on this. If we look at the buccal surface of this tooth we can see our mesial and distal outline. Our most important characteristic in this view is the height of contour. Our height of contour is similar to our maxillary premolars. On the mesial it is usually found in the occlusal 1/3. On the distal the surface is usually rounding more and the height of contour is usually found in the middle 1/3. Our overall width on this tooth is about 1 millimeter wider from the mesial…no, it’s a 1 millimeter wider from the buccal lingual dimension than it is from the mesial distal. So the tooth is usually similar to the maxillary premolars, wider buccal lingually than it is from the mesial to the distal. But the tooth overall is about 2 millimeters wider both on the buccal lingual dimension as well as in the mesial distal dimension than our premolars were. We’ve got some other rather strong characteristics on this tooth that we should identify for you and start to put some terms in. Again terms are very similar to the surfaces and the cusps what have you but the most prominent features on this tooth is our central pit. One of the biggest problems in this tooth because this central pit is usually very deep and often times has a tendency to become carious. Now we have a fossa around this pit area. Sometimes these fossas will be called triangular fossas because of the…actually apexing into this single pit. And we’re getting groove from the central groove and the other grooves that seem to apex right in this. We generally [inaudible] triangular terminology. We’re just calling it a central fossa or mesial fossa or distal fossa or whatever it is and leave the triangular out. It doesn’t seem to add a great deal to the term other than just carrying some additional jargon with it. We have a mesial pit which is usually not nearly as distinct or located quite as prominent that it would be towards the mesial aspect of the tooth. We have a distal pit which is usually fairly prominent in the distal portion of the tooth. We have a central groove that connects up to the mesial pit but it doesn’t connect to the distal pit very well because we have a rather strong ridge that crosses the tooth. Let me see if I can point out this ridge to you here.
This ridge runs from the mesial lingual cusp distally a bit and then crosses the tooth to our distal buccal cusp. And this ridge is termed the oblique ridge. It runs crossways of the tooth not straight crossways but goes to the distal and runs across the tooth. Remember on our mandibular first premolars we had a transverse ridge. That was characteristic of the first mandibular premolar only. This oblique ridge is characteristic of our maxillary molars and very prominently in our maxillary first. It’s sometimes also in existence in our seconds and occasionally in our third molars but very prominent in this first. This will be a very important characteristic particularly when we get into restorative dentistry and reconstructing these for crown and bridge and [inaudible] and the variety of other purposes so that’s one area I warn you we have to know and know very well, it’s this oblique ridge across through here. There are two very prominent grooves on this tooth which we should point out and identify for you. One comes out in the central pit and comes to the buccal and it’s simply called the buccal groove. And it actually crosses the marginal…or I should say cusp ridge and it divides the cusp ridge. We’ll go over these cusp ridges in a minute. And extends down on to the buccal surface about half the way down on to the buccal surface but it doesn’t cross this cervical ridge or height of contour. Actually it comes right down the center almost of our buccal surface here. The other very prominent characteristic ridge, or groove I should say, is this distal buccal… distal lingual groove, excuse me. Which comes out of the distal pit and traverses at an oblique angle and comes to the lingual surface. And actually it does cross the height of contour of the tooth down on the center of the lingual surface. And in the outlined form you can see a little dipping that exists in this height of contour down here. Fact is it not only crosses the height of contour but it frequently in the maxillary first will go down and groove right into this root surface. That’s a very strong groove, particularly in the maxillary first molar. We have the same marginal ridge basically on our molars. Got our mesial marginal ridge and our distal marginal ridge.
They’ve looked at that for the last 40 or 50 years. Here’s that case basically in the mouth. You look at the one side, you look at the other. They’ve got this one pictured…cause this is the other side of the mouth. And what they’re using here is the proximal [inaudible]. There’s the try-in and if you go ahead and get teeth processed [inaudible]. Another lateral that has a longer span. Same thing. You got a long span here. You can look at this and you can block across to the other side of the arch. The idea is when you’re looking at into a case where you might think about using [inaudible] Definitely what you want to do is talk to your faculty, take a look at the case and decide whether rotational path is the way… Now swinglock removable partial. Basically this is what the framework would look like. This fits around labial of the teeth with these little eyebars that come out vertically. These little eyebars will engage into labial surface of the lower teeth. I don’t use these all that much anymore. Pretty much now with high speed instrumentation you can reshape the contour of the teeth fairly easily [inaudible] restoration without crowding teeth you can also build up undercuts where you need them. The other thing you want to know is that these frameworks will cost at least $200-$250 more than your conventional framework. So from [inaudible] and those folks it’s not uncommon for the framework to cost alone between $650 and $800. If the framework cost alone, you haven’t added teeth on, you haven’t processed anything plastic on it, if your framework cost alone is pushing six to eight hundred dollars you want to make sure you are being remunerated enough for the partial that you are not losing money on it. Several years ago one of our grad students did for a nice patient Mr Traylor and so we got the whole thing done anatomically. It was a very complex framework that overlaid the occlusal surface and everything else. We did the case and we were charging Mr Traylor basically the graduate fee for the partial denture which is around $1250 and that framework cost us $1800.
That’s a great business plan, isn’t it? If you’re losing money on each one of these you’ll make it up on the volume. Here’s accentuation also or some of these as I say [inaudible] the number of teeth missing or number of defects you’re trying to fill up is very extensive, it may be that the extra grip with the swinglock may be worthwhile. Now this is basically just a set of duplicate cast that goes through the sequence of how long these frameworks would be made, the standard blocking out they are going to go ahead and duplicate it. Here’s our study model and we go ahead and say how we’re going to watch the framework up. Here’s the wax up of the framework. Frameworks are waxed up as there are these stainless steel spindles that are incorporated into the wax up and the reason this stick up into the air as far as it does is just so that it can fit into a dental surveyor, like a surveying tool, but what’s going to happen is after casting all of this stuff that sticks out into the air will get cut off. So all this is for is extra things to use it in the tool that seats these down so that the bottom part of these spindles will be incorporated into framework but the top 80% of these things will be just cut off [inaudible] and made smooth finishing of the partial denture framework. Here’s another view of the framework. Here’s your labial plate, here’s your maxillary labial view, here’s your two spindles. One side is going to be the gate side. That’s going to be the hinge. The only difference on these things is which side is the gate and which side is the hinge. After way up stage if you look at the cast metal this vertical part right here is the bottom part of the spindle right here. This part of the spindle right here is what you see here. The top part of where the spindle was here has been cut off and polished so this has been cut off and polished it’s what stands up in the air. Now on one side when they do the wax up of this they carry the waxing all the way around that vertical spindle. On the other side there’s going to be the snap in gate.
The wax up on that side is only going to surround about little more than 180 degrees. It’s not going to surround all the way around that spindle. So one side is waxed up all the way around it and that becomes the gate side. On the other side the waxing over here wraps around part of this spindle but doesn’t go around the 180 degrees. Then when it’s cast there is just enough surface contamination on these they will allow these things to open up and swing. Here is your hinge side so you can see when the waxing was done here unlike on the hinge side on the other side this waxing didn’t warp all the way around this spindle. Again this spindle used to go up into the air or up in the surveyor but the top part of it was cut off. So the only difference is instead of being waxed all the way around the spindle, it was only waxed partly around the spindle [inaudible] The other things is because these are totally interchangeable which side do you want to wax all the way around and which side you want to wax partly around, you should make these things open either way. Just depends how they’re waxing up [inaudible] If you’re thinking of doing one of these you want to ask if the patient is right or left handed. Which side will be easier for him to get a hold of this gate and snap them open, if they had a preferred side. Here’s the situation clinically in which you look at the teeth from the anterior. We go ahead and basically have our partial denture here. Here’s examples of them. Here’s a swinglock .Again, we don’t need to do these so much anymore because nowadays there’s a high speed instrumentation [inaudible] materials that can alter the contour of these teeth to make them more favorable fairly easily. So if you see these used at all they will tend to be used in maxillofacial situations for the most part. These are ugly. Doesn’t this bite into patient’s lip? And isn’t that the food trap? We find with most patients that these have been done on [inaudible] Isn’t that the food trap?
Yes. But because partial can be taken out and cleaned and that’s your hope that the patient will continue to clean these things. Surprisingly a lots of patients when they smile these eyebars are located fairly close to the pregingival margin, they are not esthetically unsightly. So typically… here’s a nice lady, there is her upper denture but you don’t see lower swinglock partial at all. If you’ve got the same thing but with modifications face, the modification faces can be fitted on the partial and the gates just spin around the modifications face. Again with the materials we have available to us today I can’t justify anymore spending many hundreds more dollars for a framework like that when I can recontour the teeth to get a conventional partial pretty much the way I want it. These situations might be a little more challenging when you’ve got all the teeth on the one side. Again this shows a situation where you’re trying to clasp those teeth a little more firmly. You got these teeth clasped pretty firmly and this is our replacement teeth. Again the thing that is not available during your practicing lifetime. But I’ve been thinking about rather than taking a real expensive framework would be in a situation like this…over in this area is considering putting one or two dental implants over there strategically located. And then you can have partial denture in this area here it’s just under the partial denture in this area you’d have couple of [inaudible] attachments that were just snapped on. Again when these frameworks were involved we did not have that as one other option. Here’s another one that clasps teeth in two different ways. Again these are very expensive frameworks. They worked out okay but like I said I want to show you the swinglock partials as much as anything. If you heard of them you sort of know what some indications might be. Mostly maxillofacial. And nowadays when we have dental implants available to us and the possibility of recontouring teeth much more easily either by [inaudible].
Length of the span. This just sort of looks at that one situation saying if we’re doing it front to back, if we’re doing like the upper fixture that is class 4 partial that things are going to seat here first and then rock down distally. The shorter the span is the more you got to block out. And further away you are so that radius, the radius of arch that you’re going on, as that gets longer you got less block out because the things are becoming more [inaudible] that’s upper or lower. If the rotational axis is fairly straight across the arch side to side, when looked at from the front it’s also fairly [inaudible]. What happens when this partial denture is going to rock in place is going to rock pretty straight down in place. Cause you see here depict is the situation in which posterior plane of occlusion was uneven from side to side. Let’s say for whatever reason this tooth sits farther in the air than this tooth. So instead of going like this, this plane goes downhill like that. Can you see that if the plane was tilted like this [inaudible] coming down. People follow that? So the height up and down of the posterior teeth [inaudible]. Cause if they are the same height things are made level level. They are at the same height. You see the posterior path you rock it down and your arch is seated very straight down. If the two teeth at the back that you’re using as your primary rest are significantly not at leveling height so that height runs this way. Can you see that when it arcs forward it’s going to arc that way and that can cause you problems on how you block out or how well it seats on the anterior teeth. It’s basically the position of your rotational axis both in terms of is it straight across and also is it leveled. Cause again imagine that you are on two different teeth here and it was pronouncedly angular that way. So that would effect how the rotation happens. If it just sucked nobody would do it. The thing with this is labs really have to [inaudible] and the labs have to be up to speed to work really well.
Pretty much. The only thing in the question was are these so complex to put in that people have the hard time doing it? Not really. They go in as easy or easier than the conventional partial. Conventional class 3 in this situation right here you’ve got four sets of clasps all [inaudible] your teeth. So as far as how tight these things are going in you can see what’s seating it and taking it out. [inaudible] against the retentive features of four different clasps [inaudible] If it’s a rotational path then literally people toss them in after about 2 days they get really used to sort of feeling how it goes in. Cause it’s not that it’s a lot harder to put in. It just doesn’t go absolutely straight down. They got to consciously let the back part seat in first. But what really does wind up is that they’re really finicky to design and for the lab to do them so that they work well their finicky but if you find the lab that work that way they really work out well. In many of these cases [inaudible] mesially and lingually tilted molar, it’s really easy to do these kind of partials instead of trying to find some way to figure out how you’re going to get your framework to fit around those tilted molars. They are a little more challenging to design and your lab has to be on their game to make these things come out well but when they do they aren’t any harder at all for the patient to physically place or take out. Actually they are little bit easier. And the shape of the arch. The more V shaped the arch is you block out different areas. If the arch is pretty much square and straight front to back you don’t have to block out that much on the lingual of the teeth. If the arch is real V shaped [inaudible] you got little more block out to do on the distal lingual. Again, all of this stuff is in your book. If you’re looking at your undercut then what you want to see is that this class 4 partial that you were going to do is just like the one that’s on the cover of the Krol book. [inaudible] I’ve got some undercut on the mesial proximal on these cuspids. The other thing you want to look at when the surveyor is at level is to see how much undercut do I have at that back tooth. Will anybody care to tell me if I have a problem with that undercut right there what’s my problem? I’ve got some undercut but what’s wrong with the nature of the problem? You can see that my height of contour is absolutely at my occlusal buccal corner and I’d like the height of contour a little bit further down on the buccal of the tooth. [inaudible] The occlusal buccal corner of this tooth a little bit so we still had undercut down here at the cervical but undercut was softer and it was more gentle curved. Cause again if your height of contour is absolutely at that occlusal buccal corner there is no gentle curve for the clasp to flex over and seat. And then you go ahead and tilt the cast so that you are looking for your secondary path of insertion you tilt the cats posteriorly till you see the surveyor shows that [inaudible]. If I say that’s my secondary path of insertion and that’s primary path of insertion there’s whole new amount of undercut I have available to use is the difference between the two surveys. In this particular case we used as illustration, I can pretty much work out the survey that will let me use entire proximal of that as my undercut on my rotational path. Its’ the difference between the undercut between the two paths of insertion. Go ahead and put a set of marks on your cast of the level survey and you put a secondary set of marks on the tilted posterior survey. Two sets of surveying marks on these casts. One [inaudible] level level. And the other has tilting [inaudible] and pretty much eliminated the undercut on which ever proximal surface you are using for your rotational path. The rest seat preparations on these mesially tilted molars or lingually tilted molars. [inaudible] the reason we do elongated rest is because we are not having any reciprocal or [inaudible] or clasp on the buccal. When the framework engages this elongated rest over time the tooth will tilt and rotate. If I had just one tiny circle, this tiny dot for a mesial rest, over time the posterior tooth would [inaudible] around that rest but if it’s a long rest, if it’s a channel, the tooth can’t rotate or tilt at all. So in those situations where molars are [inaudible] So again if you look at these things if the teeth are tilted labially if you were to imagine taking a [inaudible] that would come straight down the lingual of that tooth, to have your framework clear on the surface of the tooth, it has a hard time resting against soft tissue. SO then your elongated rest will just use the occlusal and mesial proximal surface and you don’t care if there is no undercut on the buccal and you don’t care if the tooth is tilted labially. Here’s one of these sets of dividers that you can set up to different separations and if you can make two arms parallel to one another then you can look and set one arm [inaudible] and when you rotated down you’d see a block out. In these cases the area inside the dotted line or the area between the dotted line and the tooth, would be the areas that would need to be blocked out for the framework to be able to seat when it is rotating in. We’re going to show just some different examples of patients. Here’s basically the back to front.
So we go ahead at either one of these you just seat the framework from the back to the front, there’s your framework with set teeth on [inaudible] this seats first and rotates down the place with the clasp. We go ahead and get the teeth set up on it. So right away you see it’s all processed. We just got this elongated strap rest on the posterior molar. We got a clasp up front of these seats. [inaudible] forward, clasp goes down. So as long as this is seated the back arch can’t pull out. Front to back. You go ahead and look at these many [inaudible] We go ahead and get things set up. Here’s a framework. So this framework engages the mesial proximal of those teeth next to dentulous area. And then it locks posteriorly and seats over the posterior teeth. Here’s your replacement teeth and what you’ve got is no clasp. So you’ve got a situation where you are not showing any clasp. Here’s AP category one meaning that [inaudible] completely here and then just rock the clasp down in place. Here’s the same thing with longer spans. Then go ahead and front part of the framework seat is done. You see the distal down. No clasps. [inaudible] We got a clasp back here where it doesn’t show. Lateral. It’s the same thing that they show you in that book. Here’s one [inaudible] Basically you’re missing some teeth here so we are planning on laterally rotating from here across to here and so we will be clasping on these teeth. Here’s our edentulous span. We get our framework made. Again the framework engages the proximal [inaudible] so what do you? You first survey is what everything lateral and what you’re looking at there [inaudible] You are looking for where is your undercut on this tooth [inaudible].
How much undercut? [inaudible] More is better so that if we got much in excess of ten thousands we may not need more than ten thousand, fifteen at the most. But let’s say in the ten. If you can see some daylight when everything is levelled we see a nice undercut here and we can see daylight on either of these proximals. And when we do or secondary tilt, we tilt the laterally and I’m tilting it laterally to see if daylight disappeared and these things become perfectly parallel the that’s our secondary path of insertion. So the total amount of undercut available to you on those proximal surfaces is the difference between levelled and tilted.
I do because they’ve done many studies both for fixed partial dentures and for removable partial dentures. Depending on how tooth is tilted. [inaudible] and the tooth is tilted this much or it’s tilted more severely this much if you go ahead and [inaudible] if you are touching at all at the marginal ridge, even if there’s one undercut that you can use [inaudible] as long as it engages at that marginal ridge coming around the corner a little bit this tooth cannot fit mesially because it’s got a block there. And when they’ve done photo elastic studies on it vertical pressure right down here on these mesially tilted teeth [inaudible] fixed partial denture or removable partial that touches right there photo elastic studies tell you that the forces are directed along the long axis of the tooth. Cause it can’t lean over any more mesially if something’s in the way even if it’s just the first millimeter and a half to two millimeters up by the marginal ridge. So if it can’t fall mesially no matter how much you push down on, the forces are directed along the long axis of the tooth.
So the whole framework will go down levelled and everything engages at the same time. If there’s a curve on your path of insertion, or the rotational path, the back end seats first and then the front end rocks in. If people see if you are going to do your brock after this, one of the things you need to think through out with your brock out is on the distal side of this front tooth you can see that this is going to go off and on so if you have a pair of dividers then you put one on to the [inaudible] here and you put the other on to the [inaudible] so it just barely touched the [inaudible] the distal marginal ridge of that tooth that the arch that divided out this [inaudible] you have to brock that out. Because if your framework doesn’t fit any tighter to the distal corner of this tooth down to the cervical can you [inaudible] you try to rock it into place it wouldn’t seat at the time. That part of the proximal plate goes right here. If it wasn’t blocked out curves that line, if it fit tighter to the distal length too it wouldn’t rock into place when you seat it. So those are the things you want to look at when you want to brock it out for rotation [inaudible]. Okay, in the linear placement again all rest seats seat simultaneously. So if it’s not a curvilinear here, if it’s not a rotational path it’s just a straight up and down path of insertion for the most part, all the occlusional [inaudible] simultaneously. And you can see in this area we have brock [inaudible] where that undercut exists on the mesial of that tooth or when the undercut exists on the distal of that tooth, they [inaudible] blocked out parallel with the path of insertion. So when everything [inaudible] it just all slides down and what’s holding this partial denture framework on that tooth is an occlusal rest [inaudible]. So if you said okay in the same situation if there is a little bit of an undercut on the mesial proximal of that tooth but if I go and do a curvilinear path of insertion so that my brock out on the mesial of that tooth is entirely [inaudible] and I planned completely on having my proximal plate fit that more intimately. There’s still brock out here to allow that arching type motion to come down and clear the distal of that tooth. So if there’s not as much brock out here, there is no buccal clasp on ,there is no lingual reciprocal one. But when the partial denture is fully seated, this distal part can’t come up in the air because this proximal plate is wedged or captured in that undercut on mesial. So it’s an intentional use of that undercut without blocking it out. That’s the whole idea of rotational kind of partial. What types do you got? You got front to back, you got back to front, and in some situations you can do them sideways. So if I do basically front to back, that is very similar to the one that is right on the cover on your Krol manual. Again, if you look at that upper set of pictures it shows the case where you got a patient that’s got [inaudible] teeth being replaced when that partial denture goes into place front is going to seat first and then the back is going to rock in. So that’s going to be front to back. Okay?
We’ve got back to front and that’s the same one shown on the cover that you seat the back first and then you rock it to the front. So you got back to front or front to back and sometimes you can have a lateral. So that’s in teeth missing right here, so you’re missing basically your lateral incisor and cuspid. Instead of doing fixed partial denture they just thought could we fit a partial denture framework in there and then basically let this part seat down first and then arch or rock the partial denture down to get the clasp to the [inaudible] over here. So for as long as this part of the partial denture stays seated there is a couple of undercuts that have been gaged over our [inaudible] by rocking into them. So as long as this side stays fully seated, these things can’t lift up in the air because these are rocked in into a undercut. Categories. We got categories. Category one is more like the picture that we showed you at the very top of the lecture of the lower class 3 partial where the posterior rests would seat completely. The posterior rest seats would seat completely and then you rock the partial in place with those rest seats acting as a [inaudible] basically. Category 2 or dual path instead of [inaudible] rotation path… it is more similar to the picture on front cover of your book that’s the upper case. So the way that one works, if you got one of these clasps [inaudible] and you’re trying to make use of the undercuts on the mesials of the cuspids, or the mesials of the first bicuspids, you seta the partial denture in anterior angulation so that the end of the plane sits down first and then you rock it in. So the rest seats themselves don’t hit right away .You don’t sink the rest seats and then wrap it around the rest seats. In the back to front the rest seats are fully seated and then you rock it into place with the rest seats [inaudible]. That was that molar class 3. The upper class 4 the rest seats are not fully seated when you angle them from that front direction. You get the edge of the [inaudible] all seated and then as you brock it to place during the rocking to place the front rest seat sits and then just a little later the posterior rest seat sits.
But in the type 2 or the category 2, these rest seats are totally seated on the rotational part. You see [inaudible] dual path of insertion. So it would be seated at an angle and the rocked in. Here’s a category like one we talked about. It’s basically these rest seats sit completely. This would be the class 3 arch [inaudible] on the other side of the arch. SO this rest seat sits completely, you rock it down in place so when this is seated this wedges into the undercut. Okay, we look at basically category 2. Sometimes in these situations if you were to imagine this to have anterior teeth set out in the front, and that gain is the picture on the front to your manual. What would happen in these situations is as it was being seated in the front part seat first the end of the plane would sort of [inaudible] here but the rest seats themselves would not fully be seated. So we angle that on this forward angulation this way. Seat the flange in, start rocking it down and as it’s rocking down in place later on then the front rest seats come to rest and then last of all the back rest seats come to rest. So it’s first the flanges going in, then we start arching it, and then the rest seats of the front are seated a little bit later and the back rest seats seat last of all. But in the category 2 which is front to back or back to front, we don’t completely sink the rest seats and they are not [inaudible]. What we want to look at when we’re doing cast analysis. It’s basically sort of like any partial that we would be doing. You got to look at your plane of occlusion. And when you’re looking at the plane of occlusion, we sort of talked about that stuff, but as you got to set a cast…what does that really mean? If you are assessing the plane of occlusion can you see that if really goes up and down a lot that’s not a good thing? Or some teeth have gone missing. Let’s say posterior molar teeth are extremely up in the air and some [inaudible] upper teeth are going down. So your plane of occlusion [inaudible].
That’s’ not such a good thing. But if your plane of occlusion has posterior molars extremely tilted along way. So it seems like when you sort of look at your lower plane of occlusion it seems fairly reasonable at the front but as you get toward the back of the mouth it like really curves up in the air a lot so your overall plane of occlusion [inaudible] ski jump going up there. Not such a good thing. Maxillary plane of occlusion. Some posterior teeth on the [inaudible] have extremely [inaudible]. So your maxillary plane of occlusion goes level across here and then dives way downhill. Not such a good thing. So look at your plane of occlusion. How long is the edentulous span? Again many times what people look at is if the edentulous span is fairly short. One of the things you think about is [inaudible] fixed partial. There are some situations in which edentulous span gets longer. Think of the stress you’re potentially going to put on your buccal teeth. If you do a fixed partial denture there’s a lot. So those may fail over time. You might not just trash the teeth. Can people think of other possible problems with the really long span bridges that has nothing to do with losing the teeth or putting too much stress on them? How many people have delivered a crown and not that much later the porcelain fractured off? Anybody got one of them? [inaudible] The patient’s back and one of their complaints is a bunch of the ceramics fractured off my bridge that you’ve just done last year. Well, that kind of stuff happens as you build longer span bridges. How come? Cause the substructure may flex a little bit. And if the substructure flexes a little bit over a long span and the overriding ceramic doesn’t then it’s going to develop stress fractures and fall off. So the length of span is sort of an issue. As spans get fairly long they are almost easier to deal with an rotational path. Why? Cause spans get pretty long. If I were to imagine a molar and let’s say I had a short span not that I would do this with a rotational path. But I got a short span to bicuspid and I’m planning on making a rotational path and [inaudible] this first and then arching the partial denture down place. Let’s say I got a similar case. Molar’s the same way. Let’s say I miss first molar, I’m missing a bicuspid. [inaudible] The longer the span gets this way, at this thing arcs forward, I’ll need less block out on the distal of this tooth with a longer span that I’d need with a shorter span. [inaudible] As the radius gets longer any section of arch down here becomes more nearly a straight line. [inaudible] a very short radius your curvature here is pretty tight. So it takes a lot of block out right here. But when arch is a lot longer, arch is not nearly so tight you don’t need to block out so much. So can people see how longer edentulous span requires less block out when you’re doing a rotational path? And very short spans [inaudible] if you’re thinking about rotational path concept. The shape of the dental arch and how much undercut are we working with. So again what we’re looking. The plane of occlusion affects the depth of the undercut. So if we look here. Again, these are all in your books. Where do we locate the undercut on these?