hey everyone ryan here and welcome back to our oral radiology series this video will be all about the types of radiographs that you can take and how to read them so we can break down the types of x-rays that we can take into two big categories so over on the left we have our direct or intraoral images and these are taken with the receptor inside the mouth so x-ray photons are directly interacting with the receptor examples of these are the periapical or pa the bitewing or bw and the occlusal image over on the right we have our indirect or extra oral images and these are images that require a specialized screen placed outside the patient's mouth which the x-rays contact before interacting with the film so examples of extraoral images are panoramics or pans cephalometrics or cephs and then we'll also put in our 3d image called the cone beam computed tomography we'll cover all of these different radiographs in this video we're going to start though with the periapical so periapicals are used to capture the roots of the teeth including their apices and this enables you to look for any manifestations of pulpal or periodontal disease the periapical radiolucency which is a dark spot at the root apex is a good sign of an endodontic condition for example they're all they're also used almost exclusively for detecting radiographic presence of caries in the anterior region and notice how the periapicals are positioned vertically in the anterior and horizontally in the posterior and this is so that they're in the the most ideal and optimal position for capturing those root apices so let's talk about some normal anatomy we can show you what some of this will usually look like for a normal tooth so we have our enamel layer on this premolar we can see very clearly that transitions into the dentin layer which is a little bit more radiolucent not quite as radio-opaque as the enamel and then we have the pulp tissue which is more radiolucent yet over on the molar here we have a rather large amalgam restoration and this metallic filling will attenuate almost the entire x-ray beam which means that none of those x-ray photons are getting through to the receptor so it remains a blank canvas like we talked about in the last video we also have speaking of not normal anatomy some interproximal caries i might also argue that this looks like some occlusal carries over on this molar but we'll talk more about carries detection a little bit later in the next video we also have uh this thin radio opaque line this is called the lamina dura and that's a dense border of the alveolar bone that the periodontal ligament attaches to this is a sign of a healthy periodontium the very thin radiolucent line that's hard to point to it's right inside the lamina dura that's the periodontal ligament space where the actual ligament resides so that's just some of the normal things that we look at when we see an x-ray alright so the bitewing by contrast does not show root apices it instead focuses more on the crowns and the bone height the alveolar bone height and bite wings are usually better for posterior carries detection especially between teeth and for checking bone levels as well as calculus deposits so we can see clearly our bone levels and those are fairly accurate because the bitewing is taking these in a parallel direction periapical is coming more at a vertical angle so bone levels aren't quite as reliable on the pas that's why we usually like to take these bitewings and rely more on that for reliable bone level reading also you can see a little bit of radio pake that radio peak spec is some calculus deposits now the bitewings are usually exposed horizontally but they can be vertical as well all right next we have our occlusal films and these are taken with the receptor lying flat on the occlusal plane and they should capture from k9 to k9 and it provides a different angulation to shed some light on perhaps an alveolar bone fracture maybe an impacted tooth a missing tooth or a supernumerary tooth like in this mandibular occlusal film we can see this premolar that is completely impacted and crossing the midline and you can get a really good view of it in this occlusal from this angulation thanks to the occlusal film now the nice thing about the occlusals is that they're generally easier for pediatric patients they'll tolerate them a bit better because the receptors are less likely to pinch down at their floor of their mouth or by either the upper or lower lip all right so let's go to the extraoral images and the panoramic x-rays spin around the patient's head hence the name panoramic and they're incredibly useful for screening for pathology of the jaws and also locating third molars so this is an excellent diagram for listing out the various landmarks for a pan now i won't go over all of these 21 numbers but let's hit the highlights real quick so whenever i look at a panoramic i have a systematic way to approach it and you can develop whatever method you want but i recommend using the same approach every time and it's good to start global and then go local so the temptation is to immediately zoom in on the teeth first but i start up here at the right condyle i look for any irregularities trace down the articular eminence look at the maxillary sinus the lateral wall and then you come down the floor look at the medial wall go to the nasal cavity and then you can go to the other condyle look at the left compare it to the patient's right side trace that articular eminence go through this sinus area the nasal cavity etc so i usually start kind of looking at that part and then i would go down to the right a gonial angle look in here this is probably one of the most common places for pathology of the bone to manifest then i would trace the inferior border of the mandible look for any again irregularities any thinning or thickening go to the other gonial angle again compared to the other side look symmetrically and at this point after we trace around all the teeth then i would go to the teeth and i would first count all of them see how many teeth there are if there's anything missing anything extra then you can look at the crowns look at the bone levels and then look at the roots of all the teeth and after all of that you have a pretty good idea of what's going on encephalometrics gather information on the patient's entire head ceph means head after all and the lateral ceph is the most common cephalometric x-ray and gives you a side profile look at everything and it's most used for determining the relationship of teeth and the jaws to one another and to the rest of the cranium you can also superimpose two lateral ceph tracings on top of one another usually on the anterior cranial base area because it's the most stable area and that would be to compare a before and after look either before and after orthodontic treatment before and after surgical treatment or changes during normal growth and then we have the posterior anterior or pa cef which gives you a front back view it's not really used that much anymore since it's mostly been usurped by the cone beam but it does or it was used for looking at transverse asymmetry because the transverse dimension is the one thing that's missing from the lateral ceph view but in the pacef we can clearly see this asymmetry of the mandible and so that's really what this was historically used for so we have the cone beam computed tomography image the cbct is an extremely valuable three-dimensional radiographic image and we get three different views from it we have the axial view which gives you a top bottom view the sagittal which is a side to side view and the coronal which is the front to back view and we can physically scan through each of these views to look at hundreds of different slices through the patient's tissue and so the software also provides a 3d volumetric render where you can twist this around you can zoom in on certain areas of interest and see what's going on in a very clear 3d way which is really cool implant planning is the most common use for cbct imaging you're able to check bone quality the quantity of bone how high and how wide a certain alveolus might alveolar ridge might be you can look at where vital anatomy is so where the inferior alveolar nerve is where the lingual artery is and then you can even make a template from a 3d printer to figure out where exactly we want to place this implant where we can avoid any vital structures for instance endodontics can use cone beams as well to look at things like root fracture root resorption and to better understand complex canal anatomy orthodontics uses cbcts to look at tooth impaction the exact location and orientation of an impacted tooth and its relation to other tooth roots tmj i can look you can look at things like the condylar head the fossa and the articular eminence however if you're looking at soft tissue you need to have an mri heart tissue is really the only thing that you're looking at if you're taking a cbct zoomed in on the tmj and then of course pathology so you can get a really good look at certain pathological lesions that maybe might be obfuscated by a regular two-dimensional radiographic image now let's talk about some specialized views that can appear on the board exam so the waters view is the standard x-ray of choice for showing an anterior view of the paranasal sinuses and midface and orbits so it basically frames everything really nicely around the cranial vault so it's a pacef but it's taken on an angle and that angle is about 45 degrees to the orbito medial line and so you're going to have the patient's face lying against the film and the x-ray source is going to come from behind the patient's head so this is again the best film for a radiographic diagnosis of mid facial fractures sinus infections and lesions of the maxillary sinus because they're framed so nicely for you within that cranial vault town's view is another angled pa cef of the skull but it's coming from the opposite direction this time the film is under the head and the source is from the front this time it's directed right at the condyles at about a 30 degree angle to the orbital medial line this one is the best film to visualize the condyles and the neck of the mandible and that's because um it eliminates the superimposition of the mastoid and zygoma over the condylar neck that you would often get in the straight pa sef which makes interpretation of that region very very difficult the town's view by angling that x-ray source lets you get that con and get a better look at the condyle anatomy the submento vertex view or submental vertical view is a base projection of the skull with the source below the mandible and the film above the head so basically you lean your head all the way back and then the x-ray source comes in under your chin and this is the best x-ray for diagnosing basilar skull fractures and it provides some information about the zygomatic arches and the mandible so it can be used when you suspect a fracture of the zygomatic arch as well all right let's talk about two techniques for taking intraoral images now so the first one we'll talk about that can come up on the board exam is the bisecting angle technique and this is where the central ray of the x-ray beam is aimed perpendicular to the imaginary bisector between the long axis of the tooth and the long axis of the image receptor so here we have drawn the long axis of the tooth long axis of the image receptor and this is that imaginary line that's bisecting those two other lines and so if we're able to angle the primary ray of the x-ray beam perpendicular to this imaginary bisector we have a very cool geometric phenomenon that happens because if the central ray is positioned in this way you end up with two equal triangles both of those triangles that are formed are equal because they share the same bisecting line and so this hypotenuse here and this hypotenuse here are going to be exactly the same length because that's true you're going to have theoretically the image on the film being equal to the length of the tooth so both of those should be the same length now however the problem with this is that the x-ray image may still be distorted because the image is not a true reproduction of the object because there's still some angulation going on you may still be getting some stretching or distortion of the actual true anatomy and that's where the paralleling technique comes in and so this is where the receptor is placed parallel to the long axis of the tooth so this time both the long axes of the tooth and the image receptor are parallel with each other and the receptor and i should say the source is placed so that the central rate of the x-ray beam is aimed perpendicular to both of those axes the tooth and the receptor and so in this case an xcp or which stands for extension cone paralleling device basically just a film holder it fill it holds the film packet or digital sensor in place one of those must be used in order to ensure that the position indicating device that's this part here is pointing at the right in the right direction and so that everything is lined up perfectly well because if anything is just slightly off here you're going to get some distortion and it's going to defeat the purpose of going through the effort of doing the paralleling technique so if it's carried out properly there's less distortion and you get an overall better image but the one downside here is that the object to image distance that oid is increased look at how small it is for the bisecting angle technique it's a lot longer here because well especially in the upper arch this part that palatal that palatal wall area where it's sloping is going to get in the way of the receptor so you have to push that receptor to work to where the palatal vault is the highest and so you're going to have some inherent distance there so what does that mean well if that object image distance is increased that means the image is going to be a bit more magnified but that's okay so in the last video we talked about troubleshooting some problems specifically with film but now since we've gone over those imaging techniques let's talk about some of the other common errors that we can get more so with digital imaging so elongation is the most common error in radiology and it can be due to an angulation error or if the receptor is being bent while the image is captured and remember a radiograph is a two-dimensional image of a three-dimensional object so some distortion and overlapping is to be expected but these all are examples of operator errors that can be avoided the cone cut oh and this is an example of elongation you can see how long these roots are and likely that film was or the digital receptor was being bent while the image was taken a cone cut which is seen over here means that the x-ray beam and the receptor were not lined up properly either the xcp device that a film holder wasn't being used or just things weren't lined up for some reason and so the actual x-ray beam was probably shooting more up in this direction and so all this part of the receptor was was just completely missed and not exposed and so it remained a blank canvas so with a circular collimator you're going to see something like this where the line is rounded if you used a rectangular collimator you'd have a straight edge that's being cut off again we can have underexposed which appears like a grainy image it's too light and that's that could be due to any number of wrong settings that we talked about in the second video the exposure times too short low ma low kvp or the distance is too far then we can have the opposite where the image is overexposed again wrong settings the exposure time could be too long a high m a a high kvp etc you can also have a double exposure and this is where two images are exposed on the same psp plate so that's before the psp plate was red and before it was cleared so it had already had an image stored on it and then you exposed another image on top of that so you can kind of see where these inner proximal contact areas are being overlapped on this new fresh image and so this is just non-di not diagnostic and would have to be cleared and retaken now some errors exclusive to panoramics and so motion is most often seen in a panoramic because it's spinning around the patient's head for several seconds and if they're swallowing or kind of physically moving around shaking their head a little bit you could have some motion errors and so lines that should be sharp like the inferior border of the mandible could appear wavy and irregular and that's a pretty good sign that they were swallowing while this thing was spinning around also for panoramics if the chin is tilted too far down the occlusal plane shows an excessive upward curve what i call a big smile and if the chin is tilted too far up you can see a flat or even a reverse occlusal plane so it looks more like a frown and to remember this and keep these two straight just look at yourself smiling in the mirror and if you tilt your chin up and then down you'll see what i'm talking about how you kind of create a big smile or a frown because again this is a two dimensional representation of a three-dimensional object and last but certainly not least we have ghosting and no i'm not talking about online dating i'm talking about image detector lag and this is something again exclusive to panoramics where a radio opaque artifact gets projected to the other side of the image and can obfuscate the anatomy so things like jewelry glasses dentures with metal in them any of that can cause this ghosting effect and so this pan is actually from one of my patients and it's the first time i've ever seen this but they left not only their earrings in place but also an air pod in their left ear so you can see how these image these images get ghosted over to the other side so here are the three earrings here's the air pod and then they also had an earring on their right side that got ghosted looks like up here and so a ghosted image will be translated to the other side it'll be slightly higher up and it'll also be magnified and enlarged and so these things can really block some of the anatomy that you want to look at luckily we were looking for the third molars here but this can certainly be a problem especially if they have something intra oral or close to their oral cavity where it could ghost in an unfortunate location alright so that's it for this video guys thank you so much for watching if you like this video please give it a like give it a thumbs up and subscribe to this channel for much more on dentistry if you're interested in supporting this channel and what i do please check out my patreon page thank you to all of my patrons here for all their support you can unlock extras like access to my video slides to 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