 Ranjitha Jiya, conservative dentist and endodontist, today I will be talking about access cavity preparation. All the features of anatomic study in the human system, one of the most complex is the pulse cavity morphology. That means, among all the anatomical studies that you do of all the parts of the body, pulse cavity morphology is the most complex thing to study. Coming to the access cavity definition of access cavity preparation, access cavity is defined as the opening prepared in a tool, it is an opening prepared in a tool to gain entrance to the root canal system for the purpose of cleaning, shaping and obturating. This is given by the glossary of entombed terms in the 8th edition. Now as I already told, studying the pulse cavity morphology is the basic necessity for your access cavity preparation. Your eyes will not be able to see what your mind doesn't know. If you don't know the basic morphology of your pulse cavity, you will not be able to identify your canals. So, they are known the basic morphology of pulse like the root canal, the pulse chamber, a pylchol foramine, islamers, accessory foramines, accessory canals, lateral canals. All these things is of greater importance during the access cavity preparation. Coming to the root canal configuration, there are various types of root canal configurations. Among them, two major types of classification is given, one is given by vertices, the other is given by veins. These are the two commonly used class configurations to identify your root canal system. Among them, vertices root canal configurations have total of 8 types in which type 1 is where it has one orifice with one canal exiting at one apical foramina. Type 2 is where it has two orifice where the two canals merge and exit at one apical foramina. Type 3 is where there are single orifice, then the canal splits into two, but again merges into one and exits at the apical throat. Type 4 is where two separate orifice, when these two canals exit at two separate accessory foramines, two separate foramines, type 5 is where there is only one orifice, and the canal splits into two and exits at two different apical foramina. Type 6 is two orifice, merges into one, then again splits into two and exits at two apical foramina. Type 7 is 1212 that is one orifice, the canal splits into two, then again merges into one, then again splits into two. Type 3 is where the canal has three separate orifice and exits at three different apical foramina. Wains classification is simple in which type 1 is one orifice and one canal exiting at one apical foramina. Type 2 is two orifice where the canal merges and exits at one apical foramina. Type 3 is two separate orifice, exits at two different apical foramina. Type 4 is one orifice, exits at two different apical foramina. This is your basic types of your route canal in this case. Then among the other things, among the other morphology that you mentioned is the most of its great importance. Apical foramina, apical foramina not all the apical foramines will be at the centre of your apical throat. In many times, where your apical foramina will be present easily, distally or laterally of the throat. So, you should always consider that you should never force a bigger file and try exiting at the centre of your apical throat. There are chances that your apical foramina might be exiting at one of the lateral sides, so which radiographically you might feel like the file is shorter, but you will be seeing the exit. If you make it in different angulations, then you will be identified as exiting of the file as drapex. The other thing that you should know is lateral canal and accessory foramina. There are many lateral canals and accessory foramina because of which your indication says an important role in filling base accessory foramina. And the last thing that you should consider is your influence of aging on pulp cavity. For younger patients, the volume of your pulp will be greater amount compared to your older patients. In older patients, because of your secondary dentin deposition, the pulp chimbo volume will be comparatively less and the canals also will be narrower compared to your younger patients. Coming to the objectives of your access cavity preparations, the first objective is to remove all the carious tooth structure. The second objective is to conserve zone tooth structure. You have to remove the carious tooth structure, but at the same time you should be protecting the sand tooth structure and you should completely de-route the pulp chamber. Remove all of the coronal pulp tissue. You should remove the coronal pulp tissue whether it is vital or necrotic. And you should locate all the root canal orifices and you should have a straight line access to the root canal. All these objectives hold good for your traditional access cavity preparations. See these days there are many other modifications of your access cavity preparations which are very conservatively done. So right now the objective holds good for your traditional access cavity preparations. Coming to the laws of access opening, there are nine laws for the access opening. First law is law of centrality. Law of centrality states that the floor of the pulp chamber is always located in the centre of the tooth at the level of your CEJ. What law of centrality tells is that at the level of CEJ the pulp chamber is always located at the centre of the tooth. Law of concentricity states that the walls of the pulp chamber are always concentric to the external surface of the tooth at the level of CEJ. That means the pulp chamber follows the external surface of the tooth at the level of your CEJ. Coming to the law of CEJ, it should be used as a landmark to locate the pulp chamber as it is repeatable and consistent in its position in any tooth. You should always use CEJ as your landmark to locate the pulp chamber. Now coming to the law of symmetry 1, except for the migratory molar, both is law of symmetry 1 and law of symmetry 2. We are excluding the migratory molar. Law of symmetry 1 except for migratory molar, the orifice of the canals are equidistant from a line drawn in a medial distal direction through the pulp chamber. That means imagine you are drawing a line from medial to distal direction. What happens? What they are telling is the orifice of these canals are present at equal distance from this line. Law of symmetry 2 is the orifice of the canals lie on a perpendicular to a line drawn in a medial distal direction across the centre of the pulp chamber. That means imagine you are drawing a line medial distal. So what they said, law of symmetry 1, that your orifice will be equidistant from this line drawn in a medial distal direction. Law of symmetry 2 states that the line that you have drawn in medial distal, you know. If you draw a line perpendicular to this medial distal, line drawn in medial distal direction, your orifice will be located on this perpendicular line. Now coming to the law of colour change, the colour of the pulp chamber floor is always darker in comparison to the vertical surrounding dentine wall. That means there is a colour difference. See the colour of your enamel, the colour of your dentine is always different and the colour of your pulp chamber is little more darker than your dentine colour. Law of orifice location, there are three laws of orifice location. Law of orifice location 1, 2 and 3. Law of orifice location 1 states that the orifice of the root canal are always located at the junction of dentine walls and the floor of the pulp chamber. That means the orifices are located at the junction of your dentine wall and the floor. Law of orifice location 2 states that these orifices are located at an angle. First thing said that it is present at the junction of dentine wall and floor. Second law is stating that it is present at an angle at this junction of dentine wall and pulp floor. And law of orifice location 3 states that the orifice of root canal are located at the terminus of root developmental fusion line. They are basically present at the terminus of your developmental fusion line. See if you see this picture you can see very clearly the developmental group. See this is your Y shaped developmental group. At the terminus of your groups the orifice are present. Now coming to the Arran enterium that is required during your access character preparation. You definitely need a good mouth mirror so that your illumination and magnification is good. Preferably sun surface mouth mirrors are preferred. I am coming to the burst. You can either use ground carbide burst or you can use trans metal burst. If in case you are doing an access opening through the ground. And in case it is calcified too you can use extended long shack burst. You might require endodontic spoon excavator, endodontic explorers. The first picture that you can see here these are your burst. And this is your explorers. This is your bone excavator. This is your dv16. And for an additional age. Or maybe that is what preparation is also done under microscope. And sometimes you might require ultrasonic tips so that you can trough around and find the canal. There is something called micro-openers and micro-dibriders. It is used to locate your orifice. And the most important thing is your radiograph. You definitely need to have iopias that is your periapyrical radiograph in multiple directions. You should not just have one iopia. But it should be in multiple directions both straight and in a medial and distal angulation. And TBCT is also useful in case of complex CTs. To the other eight for determining the pulse phase morphology. You can steam the pulse in the floor with your 1% methanine dye. Which will help you in identifying your orifices. You can also perform a sodium hypochloride bubble test. In which you will fill the tooth pick pulp chamber with a sodium hypochloride. And there will be a bubble generated when the sodium hypochloride reacts with the organic tissue present at the pulp orifice. So when these bubbles start generating at specific spaces, locations you will be able to identify the orifices. If in case the tooth is vital. Then you can locate the orifices by the presence of bleeding points. And if in case the tooth is nectotic. So you will not be able to find this bleeding spots. What so? In that case you should clean and dry the pulse chamber floor. So that you will be able to visually inspect the orifices. The conventional access opening which is also known as your traditional access opening. Mainly follows this principle. That is it should have a straight line access and there should be complete de-oofing of the pulp chamber. If you can visualize this picture. You can clearly see that there is a straight line orifice. There is straight line access to all the orifices. And the roof is completely removed. There is de-oofing of the pulp chamber. So the main principle that is followed during your access cavity preparation is Outline form, convenience form, removal of remaining carious denting and defective restoration. You should always remove the carious denting and also defective restoration before performing your access cavity. The reason behind this. Imagine what happens. You will only remove half of the carious tooth structure or you will only remove half of the restoration. So that you will gain the access. Then you will finish all your root canal. Then before doing your access filling what you will do? You will try removing the remaining carious tooth structure or the defective restoration. There are chances that your tooth might fracture at that particular time. Then if you post and don't take rest. If you are not able to do your post and don't take restoration. The whole point of doing your root canal will be a waste. So you should always remove your carious denting and defective restoration. And toilet of the cavity should also be considered. Coming to the traditional access cavities. These are the various shapes of access cavities that you will gain with different types of tooth. Come to the central incisor. In case of central incisor the access cavity will be in the shape of rounded triangle. With your base at the incisor aspect. See this is your base which is directed incisorily. And this width of the base is determined by the distance between the mucous and distal pulp hairs. So you basically your central incisor will have a rounded triangular access opening. How do you get this access opening? First you should gain the entrance through the middle of the middle third. So if you divide your tooth into nine parts. The middle of your middle third is where you should start your access opening. Initially you should start penetrating at right angle. Once you start only with the NML. After that you can position the burr at 45 degrees. So that you will gain the access into your orifice. And one thing you should remember is you should deroof the pulp chamber completely. So that you will have a straight line access. And you should also be able to remove your lingual shoulder. Always consider the main principle of your traditional access cavity is having a straight line access. So you should deroof the pulp chamber completely and also remove your lingual shoulder. So that you will be able to place the file at a straight line. Coming to the lateral incisor. That's the opening of the lateral incisor. It's almost similar to that of the maxillary central incisor. However that's opening is much more smaller. So that's opening of lateral incisor is also rounded triangle or oval. Depending on the prominence of the mesian and distal pulp horns. Coming to the canine. The access opening of the maxillary canine will be in the shape of an oval or slot shaped. Because there will be no mesian and distal pulp horns present in case of it. So basically your canine will have an oval shaped access opening. Coming to your maxillary first premolar. The access opening of your maxillary first premolar will be oval or slot shaped. It is wide buckwheat linguli and narrow mesiodistally. See you can clearly see it is wider buckwheat linguli and narrow mesiodistally. And centered mesiodistally between the cusp tips. See you can see it is equidistant from your cusp tips. And in case of three canals present. The outline form will become triangular with the base on the buckle aspect. So this is the pictorial representation. The orifice of your buckle canal will be present exactly below your buckle cusp tip. And your pelatal canal will be present below your pelatal cusp tip. This is about your maxillary first premolar. Coming to your maxillary second premolar. If there are two canals present. It is almost identical to your maxillary first premolar. If only one canal is present. Then the buckwheat linguli extension that you gave will be much more lesser than your maxillary first premolar. Coming to the maxillary first molars. These are the most complex because the maxillary first molars almost always has four canals. The axis cavity has a rhomboid shape with corners corresponding to the four orifices. So basically it will be in the shape of rhomboid because of the presence of four canals. Measily you should not extend into your measly marginal ridge. And distally you should not invite your oblique ridge. You should only extend up to involving the measly surface of your oblique ridge. But you should not completely involve your oblique ridge. That is in case of your maxillary first molars. Your MB1, the four canals that is present is your MB1 is meso buccal 1. It is located under your buccal cusp tip. MB2 is located measily and pelletil to your MB1. Disto buccal is located under your central posa. Pelletil is located at the junction of meso pelletil cusp and your oblique ridge. And the point of entry is the center of the occlusal taper. It always start from the center of your occlusal chamber. So that you gain the axis. Coming to the maxillary second molar. If in case there are four canals present then it will be the shape will be in the form of rhomboid. If three canals are present it will be in the shape of rhomboid. If there are only two canals present then it will be in the shape of oval. Where it is white buccal lingualy. Coming to the mandibular central and lateral incisors. The axis opening will be in the form of triangular or oval. Depending on the prominence of your mesial and distal pulpons. Imagine your mesial and distal pulpons are very prominent. Then you will have an axis opening in the shape of rounded triangular. If your mesial and distal pulpons are not very prominent then you will be having an oval type opening. If only two canals are present you should extend the wall into singlum lingualy. Basically it is removing your lingual shoulder. Mandibular canning is also similar to your mencelary canning. Where the axis cavity will be in the shape form of oval or slot shape. Coming to the mandibular first premolar. The axis opening of your mandibular first premolar will be in the form of oval. That means it is wider mesiodistally than its mancelary counterpart. In mancelary first premolar how was it? It was wider buccal lingualy and narrower mesiodistally. But compared to your mancelary first premolar your mandibular first premolar is wider mesiodistally. Much more wider. And mesiodistally the axis preparation is centered between the cusp tips. It is basically at the center of your lingual and buccal cusp tips. Axis opening of your mandibular second premolar is always almost similar to your mandibular first premolar. Mandibular first molar. The axis cavity for the mandibular first molar will be typically in the form of triangular, tracheos or rhomboid regardless of the number of canals that is present. According to your outline form of your mandibular first molar your mesiobuccal canal will be located exactly under your mesiobuccal cusp tip. Your mesiolingual canal will be located on the same line lingual to your central fissure. Your distal canal will be located distal to the central fossa and the point of entry is always your central fossa. There are chances that there is a presence of your fourth canal called your mid mesial canal which will be present between your two mesial canals and sometime there will be presence of two distal canals also. Coming to your mandibular second molar if in case there are three canals present the axis cavity opening will be similar to your mandibular first molar although it will be bit more triangular than less rhomboid if in case there are two canals present it will be rectangular which will be wide mesoid distally and narrow buckling valley if in case there is a single canal present it will be in the form of oval and is lined up in the center of the occlusion surface. So all the traditional axis cavity preparation what design keeping in mind that these extensions are done so that you prevent the procedural errors or any obstructions during your cleaning and shaping so extension work prevention involves removal of your dentine obstruction to extend the straight line access to the apical foramina or to the primary curvature of the root canal basically this was done to facilitate your treatment procedures and to avoid the procedural errors. So the advantages of this traditional axis cavity preparation were the visibility was enhanced and improved clinical exploration for chamber floor anatomy and canal orifice what happens because of the wide axis opening you will be able to locate the presence of an extra orifice or you will be able to easily locate the orifices it facilitates the cleaning shaping and obturation it minimizes the procedural errors and also alters parameters of curvature in a favorable way but there are certain disadvantages also with this traditional axis cavity design that is you will lose the coronal and very cervical dentine of your tooth structure and it compromises the biomechanical integrity of the tooth and there will be early loss of your endodontically treated tooth the main reason for this early loss of your endodontically treated tooth is when we are doing axis cavity with your traditional axis cavity preparation what happens, operator needs and restoration needs are complete that means for operator if it is straight line axis and improved visibility it will be easy for him to do and for restoration also if there is sufficient thickness of your restoration the restoration also will be folded in place but what happens to tooth needs that means there should be sufficient amount of tooth structure to withstand the occlusion forces but here the tooth needs is compromised because of which what happens the extraction of endodontically treated tooth is more and more because of the non-restorability more than the cause of your true endodontic origin the root canals are not failing because of your true endodontic origin that is presence of your bacteria or anything but the failure is more because of your non-restorability see your vertical root tractors are also present in case of tooth so to overcome this the newer axis cavity preparations are designed so that the periservical dentine 3D ferrule and 3D softwood 3D is nothing but your 3 dimensional ferrule 3 dimensional softwood are preserved in case of your conservative axis cavity preparations you might be wondering what is this periservical dentine that ma'am is telling from that time periservical dentine is nothing but the dentine near the alveolar crust this is a critical zone see the 4mm dentine above to your crustal bone and 4mm dentine below to your crustal bone is very crucial in transforming the load from the occlusion table to the root so the more amount of your periservical dentine is retained the capability of your tooth to withstand the occlusion forces is more so what are all the minimally invasive axis cavity preparations or conservative axis cavity preparation is conservative endodontic axis cavity or if I directed dentine conservation axis cavity ninja endodontic axis cavity incisal axis, incisal axis for maxillary central incisor and all what we used to do we used to enter the tooth structure from penitentiary but incisal axis is where you will start the preparation from the incisalate cannally enamel preparation microguided endodontics and dynamically guided endodontics these are all the other types of axis cavity preparations there are truss axis cavity preparations there are many more conservative mode of your axis cavity preparation which you will be studying later thank you