hello and welcome to the module odo470 this is a lecture that forms part of the division of the endodontics i'm dr b cannon and today we're going to be talking about a little bit about rotary endodontics today's the first lecture and the first lecture that forms part of the series is the molar access cavity so in your recommended textbook it's no longer a prescribed textbook that's endodontics principles that practice the sixth edition you can find more information regarding endo access cavities in chapter 13 the chapter is called isolation endodontic access and length determination previously in the course we've covered access cavity preparations on anteriors and primality in some detail and in the beginning of your fourth year up until about halfway through or towards the end of fourth year you will only be doing excess cavities and endodontics on anterior teeth and premolar teeth but the focus later on in the course especially in the final year is to do root canal treatments on molar teeth that is maxillary and mandibular molar so obviously we need to give you some more information regarding the excess cavities and the anatomy of these two types and that's exactly what we're going to do so today we're going to focus a little bit on the on the motors and we're going to look at both the upper motors that's the first motors and the second motors as well as the lower moments also the first and second motors there we're not going to give too much information on the maxillary or mandibular third molars because these teeth don't often get root canal treatments performed on them but the principles that you learn about the first and the second molars will you will be able to apply them to root canal treatments on the third molars as well so just to recap you'll remember that i gave you guys an article once from from dr scott weed in 2011 regarding the five steps that are essential in root canal treatment and of course excess cavity is the first step in the sort of essential steps along a root canal treatment so this is exactly where we're going to start so whilst it's the again the first part of the technical procedure of the root canal treatments prior to doing an excess cavity we would have always done a thorough examination of our patients including our special tests we would have done our coal tests we would have taken radiographs and we would have come to a diagnosis a pulpal or a periodical diagnosis and we would have formulated a treatment plan including the informed consents of the patients and all that would have already been completed and of course in a perfect world it would be ideal if we could also place our rubber dam isolation first in cases of difficult access it is acceptable to to complete the excess cavity uh prior to placing the rubber dam and that's often the way that we do it during the clinical training at the university of pretoria but ideally speaking and when you do become experienced in cutting excess cavities you should actually place your rubber dam first and then cut your excess cavity afterwards so let's just review the anatomy of the maxillary motors quickly again you can find more information in the root canal anatomy chapter of the textbook as well but if we look at the maxillary first molars and the maxillary second motors these teeth most often have three roots okay so there's a usually a mesiobaccal roots a disto bottle roots and a palatal root so this is the external form the external morphology the morphology of the roots that i'm talking about so there's three roots and found within these roots there's uh more often than not in the distobuckle roots and the palatal roots there's usually only one canal so there's a distorbachel canal and a palatal canal and then in our mesio-buccal roots we often have a more complex canal system so you know in the vast majority of these cases and some of the studies even on south african populations have demonstrated that in maxillary first motors so you're one six and you're two six we very often and i'm talking about ninety percent of the time nine out of ten cases there's usually more than one canal so whether they they are two completely independent canals so something like a vetsuchi type four where you've got uh two orifices two canals and two foramens or whether it's something like a type two it starts as two canals and fuses uh to form only one exit at the at the bottom or if it's a type three where it starts as one splits into two and exits as one again now that's the material the uh the taiko message is that we have additional anatomy we most often we most commonly have two canals in a maxillary first mailer and we have that situation about 90 of the time then in maxillary second motors uh the situation is the same so one canal usually in the distorbachel root one canal usually in the palatal root and then in the mesiobuccal root we can also have additional anatomy there so an mb1 and an mb2 however in second molars this doesn't occur quite as often as it first matters so the prevalence in in our second molars is usually closer to about 60 60 sometimes 70 at the time according to uh to the study you read and the population group that you that you're looking at but in the south african population those numbers should hold up pretty well so what we need to know the take-home message is this we almost always have additional anatomy in our mesio-battle roots and we have to we have to be on the lookout for that because if we don't treat us there's a much higher chance that the canal uh that the case will fail okay and if we move on to the mandibular molars uh if you look at the pictures here i think the most prevalent type for both the mandibular first and the mandibular second molars is the image that you see on the left hand side so most commonly we have two roots so there's a mesial root and a distal root and then within these roots we have obviously our canal system so in the mesial root system uh we most commonly find that there are two canals so we have a mesiobacal canal and a mesiolingual canal and then in the distal root system we most often just have one canal so most commonly two roots and three canals and i think that's true of both men to be the first motors as well as second motors when you start moving further back so if we look at uh our second molars uh and then our third molars as well we very often find in second and third mandibular motors that will have some type of root fusion and a significant proportion of them and in these cases it is possible for there to be less anatomy as well but the the opposite is also true you you also get middle mesial canals um especially in the two rooted teeth and you you also get middle distal canals as well so you can either have additional anatomy in these teeth or in some cases you can possibly if you find that the root is conical you might find that you actually have less anatomy as well but you will assess this on the radiographs of every case but i think the picture that you need to be concentrated on and and what has to be sort of the default setting in your mind is the picture on the left hand side and that's for both the first and second mandibulars okay so let's just briefly review the principles of the excess cavity again and they remain the same as what we thought for the anterior is in the pre-members so first and foremost is remove all caries if there's carries presents on the tooth you can actually remove those carries and very often you'll find that if you have deep carries uh in a mandible or an axillary mole if you remove all those carries you'll often find that that you will actually drop into the pulp chamber automatically and if that happens at that point you you literally just have to switch over to your windows edbur and uh and create that outline form and that will sometimes create the the access cavity for you obviously we can't teach that as the defaults um because you know in many cases there will be restorations or crowns on the tooth or perhaps not carries that's uh that's that big but step one is to remove all carries and it's important to remove the carries because we want to get rid of the the infection and the carries is what caused the the infection in the pulp space in the in the first place uh so we once you remove the carries that's it's it's the first thing is that we want to work in a sterile environment but the second thing is if you remove all your carries you're going to be able to assess the restorability of the tooth that you're working on as well and the same can be said for the unsupported enamel so remove the carries and the unsupported enamel and then you can decide for yourself can we restore this tooth and you need to ask yourself that as a question and if your answer is no you need to then start considering alternative treatment options like an extraction and a replacement there because it doesn't help we do a nice root canal treatments but we are unable to restore the tooth afterwards then the design of your excess cavity is then of course going to vary according to the tooth that you're treating we're going to run over the mandibulars and and meteorite molars in a couple of slides in greater detail and then the last principle of your access cavity is that once you've completed it you need to be able to have some kind of straight-line access into the orifices of all the canals so it's very important to assess the restorability of the teeth so what i want you to do is take a look at this picture have a look at the radiograph on the left hand side and the clinical image on the right hand side and ask yourself can we reliably place a filling or a crown in these situations and even if your answer is well yes i can do a filling yeah maybe for a while ask yourself how long will that last you know what is the long-term prognosis of these cases and i think we need to be very selective in the endodontic treatments that we do so endo is a it's a wonderful thing it's a wonderful discipline but there's almost also limitations to what we can achieve and what we can reliably restore with with endodontic treatments and if a tooth is past a position where we can predictably and reliably uh restore and do a root canal treatment we do need to start thinking about other options so in both these cases the radiograph on the left clinical image on the right it's not the same tooth but in both these cases i would say that there's just too much going against the the ability to restore this tooth for us to decide on going forward with the root canal treatment so you'll recall this picture from the third year pre-clinical lectures um we have a number of burs available to us when we consider doing an excess cavity so if we've gone through our tests we've evaluated our case 100 sure we can proceed with this endo then we can move on to our material so we'll start with a burst so we're looking at the birds and the birds are essentially the mainstay of what we'll do with an access cavity so you have your round diamond bur on the left hand side the endo access bur in the middle and then your dome shape fijibu or your diamond cylinder bur on the right hand side so whilst we we did use round diamond burst for excess cavities on anterior teeth you'll recall that we never use a round diamond bird to access a pre-molded tooth and the same thing is true for a molar teeth so we're never going to use a round diamond bird to access a molar whether that's an upper molar or a lower motor so the burs of choice for our melee access cavities or either the indo access burr you will find that there will be some available in the wards if you don't have access to an endo access bill if you can't find one you can alternatively use a diamond cylinder boom theoretically speaking you can use your your dome shape fisher boot but i find them to be a little bit too small so remember mola's quite a big tooth so i like to use a relatively large bur to create my initial access right so the first thing that you want to do is to identify the cusps and this is going to be particularly important when we get to the preclinical section as well um of this course because remember you're not going to have context of where this tooth was so you're actually going to have to have a look at the anatomy and determine that for yourself it's much easier in the mouth in the mouth you can just look at the tooth position in the arch and identify from there but imagine you've got a preclinical tooth in front of you so you must identify the mesial the battle the distal and then the palatal or lingual aspects as necessary because what we're actually looking for the starting point is the mesio buckle castle so knowledge of the position of the of the pulp chamber in relation to the surface anatomy of these teeth is absolutely essential to make our male access correctly so you you need to study your tooth clinically and pay attention to it clinically because you'll find that some teeth are rotated some teeth might have crowns on them and that crown might have changed the uh the surface anatomy some teeth are lingually tilted or badly tilted so you have to be very very careful to look at the uh the teeth clinically and evaluate it's its degree of rotation or angulation or what maybe previous restorative treatments have done to change it and then of course you must also evaluate your diagnostic radiograph prior to access and this will give you important information perhaps you have a calcified pulp chain that perhaps you have a very small pulp chamber maybe it's eccentrically positioned it can also give you information on rotations and angulations so it's very very important to assess the situation properly before you start and then the first thing you want to do is you want to in your mind plan the outline form uh you might need to extend this outline form in in order to give yourself a convenience form because you'll find that very often the canals or the pulp chamber isn't exactly where you thought it was going to be and you need to be willing to uh to alter your your access cavity preparation just a little bit carries removal as we've mentioned before and obviously clean the the periphery of nature that you don't have any additional uh restorative materials or you know an old piece of irm or glass animal that that might get in your way and that might be displaced into the pulp chamber or down into the canals as a general principle the pulp chamber of uh of your mothers so this is your upper malleus and your layer my list tends to be more towards the mesial of the tooth so your excess cavity isn't perfectly in the middle of the tooth it's not really a sensitive thing it's always a little bit more towards the mesial if you have a look at the pictures and the following slides you will find that yes it is relatively uh you know sort of centrally placed but it's always a little bit more towards the mesial and it's definitely never towards the uh the distal and uh as a sort of as a general principle again uh and this is not absolute i like to say that it that they form more or less a triangular shape now this isn't absolutely a triangular it can be a little bit trapezoid or a little bit more rhomboid or rectangular in shape but i i think if you think about it as a triangle it will help you to identify the the excess um shape that you want to make in both the upper and the lower teeth so in the maxillary motors the base of this triangle is towards the buckle so it's basically the the short side is towards the buccal and the apex of that triangle lies towards the palatal and that's different from your mandibular molars because in your mandibular malas the base will be towards the mesial and the apex of the triangle is going to lie towards the distal and i think that should be well demonstrated in the following slide so there we have it if you have a look at the image on the left hand side that's that's the mirror view of a 2-6 so if you were sitting behind a patient looking through your mirror that is the picture that you would see i've given you your orientation there mesial distal battle palatal and there you can quite clearly see that the base the short end of the triangle is sitting on the buccal side and the apex of the triangle points towards the palatal now that orientation is is uh quite different from a lower mailer so if you look at the picture on the right hand side that's a 3 6 and you're not looking in the mirror you're looking down directly at the 360 with uh with direct vision there again i've given you your orientations mesial distal battle and lingual and then you can quite clearly see that the base of the triangle is at the mesial and the apex of the triangle points towards the distal aspect of the tooth and you need to be very aware of this because clearly very clearly they're not interchangeable okay and if you do accidentally get these mixed up then there's a very high chance that you're going to perforate one of these t's right so that's the the general outline form uh the triangles that we talked about but where are the canals right so in an auxiliary molar the mesio buckle one canal is going to be found in relation to your mesial buckle cusp it's not at the cusp tip it's usually slightly distal a little bit more towards the center and slightly distal of the cusp tip the disto buckle canal doesn't sit by the distant battle casp okay it's usually just a a relatively short distance away it's it's distal and lingual of your mesial battle canal and it's situated at around about the position of the buccal groove and you can see that quite well in this image have a look at the buccal groove there on the side and that's more or less the position of the distort back or cusp the palatal canal is usually in relation to to the palatal cusp it's it's usually a little bit a distal obviously a little bit further back uh from the level of the mesiobuccal one canal then in maxillary molars remember we mentioned that there's almost always additional anatomy the additional anatomy is in the mesiobaccal root so then the canal that we're talking about is the mesiobattle ii canal so the mb2 canal is usually situated between one and three millimeters palatal from the mb1 and it's usually situated a little bit more mesially than the mbu one canal and we can actually gauge this and have a look at it i'm going to show you in the next slide where we normally look for for an mb2 canal and remember it might seem like it's a little distance off but remember the root of the tooth is is really quite ovoid it's not it's not a round root so it's it's quite a fat ovoid root uh that sort of resembles the roots of a primo and this is why we have that that kind of anatomy there right so there's uh just another picture of the maxillary molar so the mb2 uh is is if you draw a imaginary line in your head from the mb1 canal to the palatal canal you'll see that the mb2 canal very often sits mesial to the imaginary line it's then also normally more or less roughly uh in the position where perpendicular line from the disturbed buckle canal joins that imaginary line that's uh that joins the envy and the pedal canal and you can see it relatively well in this example here this is a pretty easy case though so it were it had a relatively large mb canal and these canals have already been prepared with rotary instruments so you can see them very very well so it can be very difficult to find in mb2 you often even need magnification so you need a microscope or loops to find it as well as ultrasonic instrumentation or sort of long long shank burrs that you need to use very very carefully so these canals can be very difficult to find you'll try your your best to to find them in the clinics but don't feel too bad if you if you don't find absolutely all of them they can be very difficult to find it and prepare so what about the mandibular molars so mandibular molars also the uh the canals let's start with the mesia battle canal the mesia battle canal is usually found also in relation to the mesio battle casp and it's usually also slightly distal and slightly towards the center of the tooth compared to that the mesiolingual canal it normally lies in the area of the central groove but it's usually just more towards the lingual side of the central groove and its position as you can see quite well in that picture is slightly distal to the um to the mesiobaccal canal the distal canal is usually found in the area of the central fossa so that's the intersection of your of your buccal lingual and central grooves basically in the middle of the tooth uh although in first manners it can be just beyond that central fossa area and in second molars it usually sits more or less than the middle of the teeth what's important with mandibular molars is that they can have two distal canals some of the time so in this particular case there's only one big large overweight distal canal but in some cases you can find that there's a separate disto buckle and disto lingual canal and that actually does happen about a third of the time so it's not that uncommon in that particular instance your excess cavity is going to be a little bit more rectangular uh or trapezoidal than what it will be triangular but i think again if we focus on the triangular shape it's it's something that you can easily remember for for both teeth and you can just um expand your your excess cavity if you suspect that there's additional anatomy in the distal again as we mentioned before uh it's possible for there to be middle mesial canals or middle distal canals so those are third canals um in either the mesial or the distal root system and if there's an additional middle mesial canal then it usually sits right in the middle of the mesia battle in the mesiolingual or the distobaccelling distilling canals so how do we do an excess cavity on a molar whether it's an upper lower or a low molar the method is going to be more more or less the same i'm going to give you a generic method this is the method that i use there are other methods i'm not saying that my method is superior to anything else but i do find that the method that i was taught in the method that i have used and sort of refined a little bit over the years is quite simplistic and it's easy to to remember so this is what i'm going to teach you so in the method i use step one find the musical right and i and then i hear you ask why so we've just reviewed the anatomy and you'll note that in both the upper and lower first and second motors so in other words all the molars we're going to treat the mesial buccal canal is located slightly distal to the mesial bottle casp so to start here you don't have to think about it you don't have to think about where's my biggest canal or which one will i find easiest or you know sort of what was the uh you know easiest canal for me to find you just look for the museo battlecast whether it's an upper or a ladder then you select your initial access burst so that's either going to be your endo access boom or your diamond cylinder bur and then you position this bur one to one and a half millimeters towards the center of the tooth from this mesiobaccal casper tip so you don't put it on the mesiopetal caster tip you put it just a little bit more towards the center of the teeth right because we know that the mesiobaccal canal is slightly distal to the mesia that will cast and then from that position you sink a hole so then you're going to drill one hole only all the way down six millimeters seven millimeters into the pop chamber you're going to try to keep the stroll relatively parallel to the long axis of the teeth so you're going to drill down one hole until you feel a drop in resistance you're going to feel that there's going to be a lot of resistance a lot of resistance and as soon as you access the pulp chamber you'll feel that sudden drop in resistance once you've reached that point uh you can remove the bird just have a look at the tooth and confirm that that you are in your pulp chamber so that was step one find the museo buckle go a bit more central drop a hole step two is enlarge this initial hole that you've made by very gently stirring the birds a gentle stirring motion almost like how you would stir a cup of coffee but you're just going to stir that bird you're going to place it all the way down into the pulp chamber and you're just going to very gently drag it in a little circle and the idea behind that is just to make that initial hole a little bit bigger so you're not trying to make a big excess cavity you're not trying to find your other canals you're just making that initial hole that you've made a little bit larger and there's a good reason for that the reason is because uh sometimes the initial bur that you use may be the same size or smaller than the endo zed burst so what we're trying to do is we're just trying to make a little bit of space for the end of z bird to actually fit down to the pop floor and then step three is you switch to your endo zebra and with your knowledge of the shape of the pulp chambers that we've just covered you're then going to use only your endo zed bur to extend your access to remove the rest of the roof of that pulp chamber and expose all your other canals and you you do that by placing it onto the pulp chamber floor and then you're just going to drag it laterally so for example if you started in a mandubula mole at the mesio battle casper you're going to insert there then you can just pull that endosed in the direction of the mesiolingual canal and then in the direction of the distal canal and basically complete that triangle and you can almost take it in a bit of a circle as well and and the burr will actually open that that pulp chamber for you there so the only thing that you need in this method is to follow these three steps and to know what the orientation of the triangle is or the outline form of your access cavity let's have a look at it in pictures oh uh yes i've also made a preclinical videos view i will place them on click up i'll also make them available on youtube and these pre-clinical videos will demonstrate the uh technique on both an upper and a lower extracted motor right so in pictures so step one is we said find the mesial buccal casp right i'm going to use exactly the same pictures that we used for the uh for the anatomy so if we have a look at the tooth on the left hand side that's the upper molar so the red arrow indicates the position of the cusp tip so where do we want to go when to go a little bit more towards the center of the tooth so you're going to draw down at the position of the green arrow right if we have a look at the uh at the mandibular molar on the right hand side you can quite easily see the cusp of the mesial buccal casp picture there also indicated by the red arrow so where you're going to make your your initial access with your diamond cylinder bur or your endo excess bur is right there at the position of the green arrow so you're going to go one or two millimeters more towards the center of the tooth and you're going to sink your initial hole there the average distance of the drop or before you feel that drop in resistance is about six millimeters it's six millimeters for the uppers and six and a half millimeters for the lowest so at more or less six millimeters uh you should feel that that initial drop in resistance although bear in mind that we know that age changes to to the pulp or you know very young patients it may be higher in very old patients with very calcified pulps it may be lower this is just the more or less the average drop that you'll find in in a normal youngish to middle-aged patient should be about six millimeters then the average height of the pulp chamber should be about another two millimeters so if you use your your period probe as you're going as well it could it could give you some indication perhaps of how far away you are as well the importance of of looking at this eight millimeters is that you probably don't want to exceed eight millimeters or if you're starting to exceed eight millimeters you might want to start thinking about taking another radiograph or sort of just having another look at the tooth or considering if you're not maybe going a little bit of course because if you haven't reached the pulp chamber after eight millimeters uh this this either something is wrong or perhaps you've missed the drop and you're busy uh drilling through the floor of the pulp chamber which would be catastrophic so after you've made your initial access uh again these are exactly the same pictures you're going to use that same drill so that that dome shaped cylinder drill or the diamond coated cylinder drill or the dome shack fissure or alternatively your endo access boom and you're going to just stir it gently so you're going to take it in a very gentle circle just in order to enlarge that initial hole that you've made a little bit wider and make space for your windows z bird to be able to fit down into the level of the pulp chamber and then step three you'll then switch to windows headburr you'll place the endo zed burr or the tip of it remember it's got a non-cutting tip so it's not going to be able to cut in a vertical direction it can only cut horizontally or laterally you're going to place the tip of your endo zipper onto the pulp floor and you're literally just going to extend that excess cavity towards the other canals so in your in your upper you will extend for your disto buckle canal or alternatively your palatal canal first uh i don't mind which way around you you want to go but you'll basically just extend it in that triangular altine form until you found your three canals and in your lower molar on the right hand side you're gonna start uh at your mesio battle canal and then you can extend towards the mesiolingual and then and then backwards towards the distal canal and again complete that triangular or rectangular uh excess cavity and just uh then have a look with the with the probe or some endo files and make sure that you have all your canals right when you're using the endo zebra to safely remove the roof of the pulp chamber that's essentially what what we're doing and we can use it after we've cut that initial outline form you can have a look at the wall see if there's any undercuts see if there's any sort of rough surfaces and then you can use your windows head bow also just to smoothen out any rough walls and and safely remove the entire roof of the pulp chamber so that we have straight line access please remember in the clinics try not to confuse your zebra with your trans metal burst so you should have access to tron's metal burrs in in the final year when you start doing crime and bridge work as well remember they're designed to cut through metal so if you're going to do an excess cavity with a trans metal bur your chances of perforating or causing serious damage are much much higher so just be careful of that the canal orifice location is then performed as i mentioned with either an endo probe or with a small hand files or something like an eight or a 10k file uh remember molars very often are very small canals they can be very calcified as well so you might even need to drop down to something smaller so remember in molars we always start with something very small don't don't even try to pick up a size uh 15 or a 20 or a 25 or start very very small with them sixes eights or tens when you've found all your canals we can proceed with orifice opening as we as we normally did uh with our anteriors and premolars as well so you can again use your gates glittens uh and your gates glitters are just gently used at the canal orifice or sort of just one or two millimeters into the canal so just use that active cutting tip and for mailers if you've got a very large canal you can use a size three but you mostly use a size two because remember the canals are much much smaller than anteriors and pre matters again we use them on a low speed in a slower hand piece alternatively for orifice opening we could use an sx file as well but we'll talk more about that when we get to the uh the cleaning and shaping part uh when we talk about all the right re instruments we'll give you some information on the sx file but an sx file can also be used in mailers to open up your orifices a little bit right you can also do of course your coronal flaring i forgot to mention that so you can basically use a bit of rc prep on a size 8 or a 10k file and you can pull uh pull those files away from the furcation and just try to open up the top bit of the canal also just to just to do a little bit of coronal flaring so our access is complete once we've opened up the entire pulp chamber so if we remove the entire roof of the pulp chamber we've located all our canals for the given tooth type whether it's a lower or an upper and whether it's a first molar or a second molar once you've ensured that you have straight line access if you can pop a file in and there isn't any sort of dentine impeding the straight line access of the files in the canal and you've performed a little bit of coronal flaring and orifice opening at that point you're in a great position to start with york um you're cleaning and shaping the first part of which is obviously getting your working length and then in molars we will and when using rightly endodontics we'll establish a glide path first and that's going to be the the topic of the next lecture and that needs to be completed before we can actually get to the main cleaning and shaping of the root canal systems so um that's it for the access cavity in the next lecture we're going to be talking about working length we've already covered that in in great detail so probably only be a little bit of information on working length and we'll talk more about how to establish a proper glide path so in the first practical session what you're going to do is you're going to get your extracted teeth let's take some radiographs of the extracted teeth for me to take a nice diagnostic radiograph and then you'll use the endodontic burs that we've discussed to cut excess cavities on both an upper and a lower molar so you are responsible for obtaining these teeth i do have some teeth dr lombard has some teeth um you're not supposed to be taking teeth that you've extracted in in other words because they first need to be sterilized for pre-clean use but you must come in and get a tooth from from me or obtain a tooth on the day it's preferable to get a first or a second molar of course because these are the teeth that we will be treating in the wards but you will find that the extracted teeth that we have are very often third molars so if nothing else can be found you may also bring a third mailer up or lower a third mailer if there's if there's no other serviceable substitute but it's better to have a first or a second motor and then get a watertight container please to store your teeth because we'll be doing um the original treatments over a series of a couple of weeks on these teeth right and uh and that's that for the access cavities thank you for your attention and uh yeah please please contact me if there were any further questions