hey everyone this is Ryan here and welcome back for this next series on endodontics one of the main clinical topics that appears on part 2 of the dental board exams it's actually tied with pharmacology with having the least amount of questions of all the sections there are only 31 questions out of a total 500 so with that being said like all of my videos I'm gonna be focusing only on the highest yield things you need to know while I'm gearing these videos for exam preparation they are also designed to give you a nice overview of these topics for clinical application and general knowledge so first we're going to go over the biology of the dental pulp because much of endodontics is focused on Popol health since endodontics literally translates to the knowledge of what's within teeth so the Pope is obviously very important so the Pope is the innermost part of the tooth is generally very soft and vascular so let's talk about what specifically is contained within this tissue so the Pope contains a loose fibrous connective tissue with nerves blood vessels and lymphatics again very vascular it contains fibroblasts which secrete fibrous connective tissue it also houses the odontoid blasts which secrete dentin now the type of dentin depends on the stage of root formation so it's considered primary dentin before root formation is complete and secondary dentin after root formation is complete but odana blasts secrete both types of dentin it also contains undifferentiated mesenchymal cells which can differentiate into a specific type of cell which we'll revisit later called secondary Azonto blasts so the confusing thing here is that secondary odana blasts do not secrete secondary dentin they actually form tertiary dentin to protect the pulp from injury but these undifferentiated mesenchymal cells are basically stem cells that can later on divide and become new cells so the pulp is also surrounded by hard dentin so that's what those add onto blasts have secreted as the tooth was forming and after it has after it has completed formation and so this hard dentin creates a pressure system which limits its ability to expand so the pulp if it's if pressure is building up and some infection has taken place it has a lot of trouble expanding against this horrid dentin also it lacks collateral circulation which limits its ability to cope with infection so basically there's one one way in one way out for a two rooted to Tighe s it has two ways in and two ways out but there are less avenues for immune cells to reach the pulp so the pulp tissue as compared to say the skin of your face is already compromised structurally in terms of being able to fight an infection one for the pressure buildup and two for less avenues for immune cells to reach that component so the pulp is already anatomically more driven to infection at least more easily so let's talk about that the dentin and poke defense what can we do for or what can the pulp do rather to fight off or defend itself from an infection so sclerotic dentin is basically very hard dentin the calcification has occurred of dentinal tubules in response to slowly advancing caries or just aging just a physiological process of this dentin getting harder over time so sclerotic dentin would be a Popol response to slowly advancing caries now we have this thing called reactionary dentin which is a reaction two minor damage so reactionary reaction to minor damage and some sources would call this another word for another word for secondary Tenten now reparative Venton is repair for major damage and some textbooks and some sources will refer to this otherwise as the tertiary dentin and this makes sense because minor damage wouldn't be enough to destroy the original add-on to blasts that are pleasant that are present so it allows them to lay down some dentin while major damage would destroy the original danta blasts and so then those undifferentiated mesenchymal cells need to step up and become secondary Odense blasts and lay down tertiary dentin as basically a last resort however many sources just refer to both of these together as tertiary dentin but I wouldn't worry too much about these details it's not too too important more important is to know that reactionary is for minor damage whereas reparative is for major damage that's much much more important to know than all the secondary and tertiary stuff so in endodontics and operative dentistry there's this technique referred to as poke capping where you place a calcium hydroxide liner which irritates a danta blasts and they'll form either this reactionary or reparative dentin depending on how close you are to the pulp so this sort of dynamic response of Odense blasts and the secondary of danta blasts you lay down new dentin sort of to form this dental wall that forms a barrier and defends the pulp so the tooth is very alive as long as it's not necrotic and it can respond dynamically to infection which is pretty cool and now of course we have Popol necrosis where the tooth is dead the pulp has been compromised and that's the response to rapidly advancing caries or other severe damage and the tooth has lost the battle and the pulp is now dead so in all of these cases the main cause of serious Popol injury is always bacteria so bacteria can come from a plethora of sources mostly from let's think dental caries or cavities and the bacteria are small enough where they can penetrate beyond the obvious caries and cavities through dentinal tubules to reach the pulp and that's when problems can start occurring the patient can be in pain and the pulp can become infected and can die eventually all right so now let's talk about more specifics of the histology of the dental pulp so from outside to inside we have well first we have dentin that's this darkest layer right here and then the pre dentin is the innermost portion of dentin that's the lighter portion here and it's lighter because it's not mineralized and it's located directly adjacent to what we would consider the actual pulp so do danta plastic layer is where all of these nuclei are these are the ADAAA blasts that are laying down dentin right on the outside just adjacent to the pulp tissue so the ADAAA blasts again are actually part of the pulp but they are forming the dentin just outside of it now right next to or right inside the ADAAA blastic layer is the cell free zone of whale and that's this zone right here where there are almost zero nuclei present and that's because there are no cells there in this region you'll often see nerve bundles and we'll talk more about nerves in the next coming slides and then right inside of that is the cell rich zone and that's where we have a lot more nuclei and then inside of that would be the pulp core the central part of the Pope and we will talk more about that as well when we were referring to nerves okay so we have this thing called dentinal pain and so this is conducted by these a delta fibers so that's a problem you are that's extremely important and I would definitely definitely know that for the exam this one D a delta fiber is large its myelinated and it's an afferent nerve which means or afferent nerve that means it's carrying nervous information from outside the body it's carrying it peripherally towards the center so it's bringing information into the body and so it's as you can see in this picture it's large it's at least larger than this one that we're going to talk about in the next slide it's myelinated that's what these darker red portions are and the nodes of ranvier between these myelinated sheaths and it's Afrin so the dentinal pain that's conducted by these a delta fibers is a sharp transient first pain so if you stub your toe that's the initial really sharp pain that you would feel from that these fibers coarse Corona Lee through the pulp so they're Corona Li as opposed to say centrally which is where the C fibers are going to be and dental pain is more often than not associated with cold temperatures and now the second type of pain is pulpitis pain and that's conducted by the C fibers so when we compare them to the a delta fibers they're small they're unmyelinated and they're also afferent nerves they're carrying this pain information as I said before they course centrally in the pulp stroma this one is involved with dull throbbing ii pain so after you stub your toe and it hurts a lot initially and then it kind of is sore and achy a little bit later that would be the second pain and this is more often associated with heat so now that we talked about both of these you can see this this chart here or this graph with time on the x-axis and that a delta axons are transmitting this first pain super painful and then the second pain is sort of creeps up later and it's a lot longer maybe not quite as intense but it's managed a lot later so those are the two different types of pain and the two different types of fibers associated with each of those pains now I'll go back one slide real quick because I wanted to mention that the a delta fibers are transmitting dentinal pain because they are associated with the popo dentinal complex and so that means where the pulp and the dentin meets it's a bit more easily provoked because dentinal pain is further on the outside you can say and because the fibers aren't central to the Pope they're more coronal they're more on the outside along the outside border they're more easily provoked than the C fibers which are located more central and so you can think of it the progression of Popol inflammation can change a pain response from this first pain with a delta axons to become second pain transmitted by these C axons all right next time talk about these two really important terms for pain sensitization and there are some graphs and drugs you can check out for these terms but I actually thought they were very confusing so I'll try to explain these important terms as best as I can first we have hyperalgesia which is a heightened response to pain and then that's compared to allodynia which is a reduced pain threshold so that's pain due to a stimulus that does not normally provoke pain so hyperalgesia would be where you have inflammatory mediators in the pulp that can increase the intensity of a pain stimulus in other words something that's usually painful becomes even more painful and for allodynia I have a great way to remember this and a great example of allodynia is sunburn so usually touching your skin doesn't hurt but when it's badly sunburned it physiologically hurts when you touch your skin and aloe is something you often use to treat symptoms of sunburn so I think of it like sunburned skin is an example of allodynia and aloe being again the thing that you would often grab when you're experiencing these terrible symptoms of a bad sunburn so hopefully that can help you differentiate and remember between these two important pain sensitization terms and last I just wanted to review the concept of referred pain which is important in all of dentistry and particularly endodontics so pre auricular pain often refers from mandibular molars since both share v3 innervation okay so what does this all mean and why is it important for endodontics so pretty auricular is referring to the region in front of the ear and you'd think pain in front of the ears maybe referred from say maxillary molars because well they're anatomically much closer but with how the innervation of the face works as we can see in this diagram although they may be anatomically closer they share or this area in front of the ear shares v3 innervation with the mandibular molars since V 3 is the mandibular nerve of mandibular nerve that is what shares innervation with this part of the ear these molars are often innovated by v2 or the maxillary nerve and that's not associated with the preauricular region the reason I bring this up is because this itself can be a test question it's something that you could easily think well just because the maxillary molars are closer to the ear maybe that could be some referred pain where you feel pain in this region because those molars are acting up but really it's more to do with how the innervation is mapped out onto the face so that's it for this video I hope you found it helpful in our introduction to endodontics and how pain is transmitted from the teeth please leave a like if you enjoyed this video and subscribe to my channel for more on antibiotics and all things dentistry thanks so much for watching and I'll see you guys in the next video