hey everybody Ryan here welcome to this video on the basics of dental x-rays so whether you're going into the workforce as a dental professional or you're interested in pursuing dentistry or maybe you're a patient who wants to better understand how dental x-rays work well this video is designed to give you a basic understanding of how dental x-rays or radiographs work and how to read them so sit back and relax as we dive into the world of dental x-rays first let's start with a big-picture 30,000 foot view of how x-rays work and produce images so we have a high-voltage power supply that powers up the x-ray unit inside the x-ray tube or tube head we have a filament the filament is heated up and electrons shoot off and contact a tungsten target that then produces the x-rays so essentially we have electricity which turns to heat which turns into electrons which turns into x-rays now x-rays are high frequency high energy waves there between ultraviolet radiation and gamma rays on the electromagnetic spectrum and it's helpful to think of x-rays as similar in some respects to visible light and that they are packaged into these particles called photons so x-ray photons are produced by the x-ray tube and scattered and absorbed by human tissue attenuation of the x-ray beam refers to how the x-ray beam weakens as it travels through matter the thicker and heavier mass tissue there is the less x-ray photons will actually make it through to the other side and on the other side is what we call a receptor traditionally it's a sheet of film that we would process and various chemicals now there are vinyl film packets that can be processed by a scanner and also direct digital sensors that can process the image directly to a computer so let's put it all together we have electricity which turns into heat which becomes electrons which becomes x-rays they shoot out of the x-ray tube and are attenuated through patient tissues and x-ray photons finally strike a receptor that is processed to create the x-ray image that we observe and analyze pretty cool right so there are two main types of dental x-rays intraoral x-rays are taken with the receptor in the patient's mouth their best for evaluating teeth and the supporting structures extra oral x-rays are taken with the receptor outside of the patient's mouth and are best for evaluating the skull and the jaws as well as a bigger picture view of the teeth in the scope of this video we're going to focus primarily on the first two intro or elimin images taken routinely at a dental office so the bitewing image is so-called a bitewing because you bite down on a wing shaped device that holds the receptor between your upper and your lower teeth so this is a diagram showing the tube head and the receptor which is actually being held behind the teeth here between the upper and the lower teeth so bitewing x-rays are commonly taken during routine dental visits and are really good at showing two things cavities starting to develop on your teeth particularly between them and bone loss due to gum disease these are mostly taken between the back teeth on either side of your mouth so different great values on tre are determined in part by the settings of the extra unit so exposure time to potential tube current and other settings but we're going to focus on different gray values that are due to differential attenuation that is some tissues are thicker and more dense than other tissues and those tissues that are more dense appear radiopaque or whiter because less x-ray photons make it through to the receptor on the other hand tissues that are less dense appear radiolucent or darker because more x-ray photons are able to make it to the receptor on the other side so let's look at another bitewing close up now this image has some accentuated contrast but it's helpful to distinguish between the different tissues so in this bitewing we can appreciate a lot of normal healthy tissue so let's first focus on this brightest layer which is the enamel layer it's the most radiopaque tissue in this image because it's the hardest and most calcified most dense tissue of a tooth so we can see the enamel here here and on each of these teeth on the top and the bottom next we have the dentin which is the second hardest and most dense tissue of the tooth it's a little more gray it's not quite as radiopaque but it's still relatively radiopaque in terms of everything we can see on the bitewing image next we have the pulp which is the least dense part of the tooth this is where you have the nerve and the blood vessels that supply the teeth and it's the darkest tissue again because it's the least dense part of the teeth so all of these canals running through the middle of the roots up into around the center of the clinical crown is part of the helped issue the gums are actually very hard to see in this image we'll see them a little bit later but they'd be somewhere at around this level it's a very subtle gray not quite as dark as everything in between the teeth but it would be somewhere in this general vicinity running through here next we have the bone which is a little bit easier to see and it's underneath the gum tissue and you can appreciate how it's a little bit whiter near the borders where it contacts the teeth and this area is called the lamina dura and this is because the bone tissue is a little more dense in these areas where it contacts the teeth and also at the borders inside it's a little bit more porous and it's referred to as the medullary bone the last thing I'll talk about here is the periodontal ligament which is a very thin dark space that is between the lamina dura of the bone and the cementum or the dentin layer of the root so the periodontal ligament or the PDL is this very thin ligament that holds the tooth and the bone together and lastly all of this really dark black area is actually just air it's all the space between the teeth and it's black because x-rays can penetrate through to the receptor essentially unhindered and unattenuated it really only has to travel through your cheek tissue or your lip tissue the soft tissues of the face in order to reach the receptor now when bacteria starts to secrete acid that eats away at the mineral content of enamel that caries or cavity process begins and x-rays are so incredibly you full because a cavity manifests as a radial lucency because some of the mineral has been lost from that part of the tooth and so more x-rays can penetrate it and reach the receptor and in fact this area right here of this upper molar looks suspect for a possible cavity and we can confirm clinically whether that's just an anomaly or in fact a cavitate idli j'en so let's revisit the first bitewing I showed you so here again is the enamel layer this is about a more normal contrast image and then the dentin layer underneath and the pulp here you can see maybe a little bit better the gum tissue coming through around here and then the bone at the bottom running across here so there are a couple things going on here that I wanted to talk about really quickly the bone level is actually pretty low here it's a lot lower than normal so in other words there's a significant amount of bone loss and this patient has or had in the past gum disease there's also a dark spot between the roots of this molar a radiolucency and what we would call the bifurcation area which is a sign of active infection of bone loss or gum disease now you might notice these white blocks that stand out and they're actually more radiopaque van the enamel layer these are actually silver amalgam fillings and they reflect the majority of x-rays because of their metal composition and so they appear very white on the x-ray image as very few photons can make it past this filling material this amount of darkness at the border of the enamel and the root surface is actually normal and we call it cervical burnouts it's not representative of cavities but it's more representative of a concavity of the tooth that's natural Anatomy now maybe if we look really closely there might be a really tiny cavity starting to form over here on this tooth but since it's so small we would simply watch or monitor something like this while alerting the patient making sure they're keeping this area consistently clean following a diet that is not favorable for cavities and so on in our preventative dentistry protocol all right so that's enough about bite wings let's talk about the parry apical it's called a periapical x-ray because it captures the area around which is what peri translates to around the tip of the root of the tooth which is also called the apex so that's how it gets its name the x-ray tube is oriented a little bit more angular ly and the receptor is placed in order to capture the roots of the teeth you can take these x-rays in for the front teeth or for the back teeth they're typically taken vertically in the anterior region and the film is the film packet or digital receptor is oriented horizontally in the posterior region periapical x-rays are also commonly taken during routine dental visits and are used to diagnose an abscess or maybe a cyst which can occur around the roots of the teeth and also any pathology or disease in the surrounding bone however they can also show cavities and bone loss just as we saw in the bite wings with potentially a little less accuracy so here we see a posterior x-ray a posterior periapical x-ray and the important thing with these is to be able to capture the full anatomy of the roots of the teeth you should be able to see the entire root and the apex of each of these routes and so we could see the same thing in this image as well so again here you can see the enamel layer you can see some more silver amalgam fillings and all of these teeth the dentin layer the pulp the gum tissue and the bone and here is actually one of the maxillary sinuses above the roots of the teeth so here in this periapical we can actually see a small triangular radial lucency forming on the side of this tooth and this is something that would be near impossible to see clinically because well it's between two teeth and so for this reason dental x-rays are invaluable for diagnosing cavities especially early on you can also appreciate a fairly large cavity forming over here that's penetrated through the enamel layer into the less dense dentin layer now in this anterior periapical we can see a small triangular radio pasady at the junction between the enamel and the roots and the root is aligned by a thin layer of cementum and then dentin underneath that and so we call in I believe in the first video I did on basic dental terminology I talked about the cej which is the cementoenamel junction that's where the enamel and the cementum layers meet and so typically in this area if a patient has a lot of tartar build-up this is where we would see calculus and so calculus is represented by this little Fleck here and it's mineralized dental plaque and so the reason why it's showing up as a radio pasady it's because it's got some mineral contents in it and so it attenuates some x-rays and shows up a little bit radiopaque so that patient would be in need of a deep cleaning all right so here in this periapical we see a couple of things going on we see two extremely radiopaque structures here and here and these are actually crowns they're porcelain fused to metal crowns or pfm crowns where this extremely radiopaque area is the metal substructure and a little bit less radiopaque area above that is the ceramic outer layer that we can see and here we see a really big cavity that's invaded wave into the enamel into the dentin all the way through to the pulp and it caused infection in the bone manifesting as this radial lucency now if you put a routine collection of bite wings and periapical x' together you get a full mouth series and the full mouth series collectively captures every tooth every root and every contact point between each tooth alright so we have a couple other x-rays i'll just briefly mention we have the occlusal x-ray where the x-ray beam comes from either above or below the teeth and it's good to look for tooth or bone fractures from trauma eruption patterns and other things the panoramic x-ray is an extra oral x-ray and it allows for a frontal view of all the teeth with the patient's right side on the left and their left side on the right it's great for looking at jaw pathology developing and missing teeth evaluating wisdom teeth and many other big picture things that intraoral radiographs just cannot capture here is Assefa lumetri it's also an extra oral x-ray and the patient is looking to the right here with the skull the upper jaw and the lower jaw clearly visible is useful for evaluating the relationship of the upper and lower jaws to each other and to the cranial base it's useful for tracking growth and particularly important in orthodontics and dental facial orthopedics alright so the last thing I want to talk about is something called the buccal object rule I'll admit this is a bit more complicated and involved than everything else we talked about but object localization is an important concept and I wanted to demystify and simplify it a bit in this video so a dental x-ray is a 2d image of a 3d object which means it has some inherent limitations mainly that we don't have any sense of depth but if you take two images of the same spot at slightly different angles you can gain this sense of depth you can gleam where an object is maybe an impacted tooth or a certain root canal whether it's located to the buccal towards the cheek or lingual towards the tongue now the buccal object rule is also known as the slop rule which stands for same lingual opposite buccal and I'll get to that in a moment so the best way to visualize this rule is to hold up a piece sign in front of your face with your fingers just like this so that we're all on the same page I'll refer to this as the index finger and this as the middle finger so do this along with me you'll hold up the peace sign and now rotate your hand so that your index finger and you'll your middle finger are in line with one another so your index finger blocks your middle finger from your view and you can squint one eye if that helps with this part now keep your hand exactly how it is keep one eye closed and move your head slightly to the right so you can see your middle finger peeking out from behind your index finger notice that as you move your head to the right the middle finger appears to move along with you to the right the same thing happens if you move your head to the left the middle finger appears to move left in the direction of your head and this is essentially the buckle object rule as you move the x-ray tube head in one direction the object that's further away from the tube head more lingual moves in the same direction in other words the lingual object moves in the same direction while the buckle object moves in the opposite direction so let's see how that plays out in a real-life radiograph example so let's say we had only this image to the left and we wanted to know which root canal is buckle and which one is lingual well frankly we have no idea just looking at this one image but if we take a second image at a slightly different angle now we have all we need to determine that information so the left image is a canine premolar periapical the right image is a lateral incisor canine image so all we really have to do is determine which direction we moved the to hit the tube head from from this image to this image so let's convert this to a diagram to help so this is another way to visualize essentially what we were just looking at the two canals are right up against each other in the left image and then we move the tube head a little bit change the angle so we can see both root canals clearly separated so the first thing we need to do is determine which direction the tube had moved so this is the patient's right side so we can imagine the tube head would be somewhere over here for this left image and then somewhere over here for the right image so from here to here the tube head moved to the right so once we figure that out holds up your peace sign put the two fingers in line with each other your index finger now represents the buccal root canal that's closer to you the tube head and your middle finger represents the lingual root canal then move your head to the right just like the two pet did between the two images which finger do you see to the left and which one do you see to the right the left one will be this blue arrow one the right one will be this red arrow one so the blue arrow points to the finger that was in the front or the buccal canal and the red arrow points to the finger that was behind or the lingual canal and another way to say it is that the red arrow root canal moved in the same direction as the tube head to the right so same lingual opposite buccal and that's the buccal object rule in a nutshell and you can do this in any direction if you move the tube head left or right even up or down you can do the same thing just holding the peace sign horizontally instead of vertically so hopefully that demystifies a seemingly complex idea and dental ready radiology but it's used all the time and is certainly super useful when used clinically so thanks so much for watching everyone that's it for this video I hope you learned something about dental x-rays how they work and how you read them if you're interested in supporting my channel please check out my patreon page a huge thank you to Michael Raja Wow David Jayden and all of my patrons for all their support you can unlock extras like access to my video slides to take notes on and practice questions for board exams in dentistry so go check that out if you're interested the link will be in the description thanks again for watching everyone I'll see you all in the next video