13/14: Film Mounting

Transcribed by Amit Amin August 01st, 2014

[Class] [13/14] – [Film Mounting and Radiographic Anatomy] by [professor]

[1] – [Title][Dr. Chan] – Hello, we're going to change the lighting a bit. We're going to wait 5-10 more minutes. Don't worry, this lecture won't take the whole two hours ok? You guys have your laptops right? You'll type in your PDF notes right? Ok, we'll just do this. We all want to go home early on Friday. I'm Dr. Chan and I'm the directory of Radiology at the dental college. This lecture I don't want to spend two hours on it, b/c I can't talk for that long. It's radiographic anatomy. The reason we need to know it is b/c this is how you read radiographs. Traditionally it is taught by introducing the small films first. Well, I'm not a traditionalist and I'll talk about panoramic imaging first b/c if you know the key features on a panoramic image, you'll naturally master the anatomy on the intra-oral images. We'll zoom in and master the intra-oral images (the anatomy). We'll zoom out first and know all the bones of the maxio-facial complex (midface, maxilla, mandible) and then we'll zoom in and look at the teeth. As dentist, I know you will never forget to look at the teeth but remember, the bones support the teeth. So even if the teeth are decayed, but there is no bone supporting the teeth, the bone has other kinds of disease, there is no point of restoring the tooth. You need to address the bone issue first before addressing the teeth. In this lecture we'll go into the details of the anatomy on a panoramic image first and it actually gives you a brief introduction to OMPR (3rd year course). It'll prepare you for that course.[2] – [Panoramic Units][Dr. Chan] – These are examples of the panoramic units. These are examples of units. You have the stand, a base, and a C arm. Here is another one here. Some units have a cephalometric extension but you can ignore that for now. Some allow patients to be seated in wheel chairs and they too can be scanned. The C arm is composed of two sources, the X ray source and the image receptor (sensor). There's some difference b/w a panoramic unit and an intraoral unit. Intraoral unit, you just place and shoot. You place the film behind the tooth you want to image and just point and shoot X-ray to where you place the film. Here, b/c the patients head is in the middle and this thing will rotate around the head, you'll get more artifacts on the panoramic image. Dr. Freidman has a physics lecture on panoramic view next time. He'll go through all the physics behind the panoramic technology.[3] – [Panoramic Imaging][Dr. Chan] – So simplifying that set up. We've got the patients head, the X ray source, and the image receptor sensor. As we're imaging the right side of the mandible, b/c in radiographs we're always looking at the patient. Your left arm will be the patient's right. Here we are imaging the patient's right side. As we're imaging the right side in the focal trough of the panoramic unit, we will also need to expose the left, so the beam also passes the left side of the image. As it is doing that, the X-ray being is inclined 7-13 degrees off the horizontal. As we image the right side clearly, b/c the beam is on an incline and passes through he left side of the mandible, the left side of the mandible will also be projected over and as a blur on the right side of the mandible. This concept is called ghosting. On panoramic imaging, you'll give ghost

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images b/c of this principle right here. Just keep in mind what ghosting is and we'll go through the anatomy later on. [4] – [The Focal Trough][Dr. Chan] – In intraoral units, b/c of point and shot devices, there are no ghosting, you're directly capturing the left molar b/c you don't need to go past the right side to capture the left molar, but you do for panoramic. The focal trough is the image layer where everything inside the trough will be imaged clearly. Dr. Freidman will have 50 minutes on the topic alone so we'll let him do that.[5] – [Panoramic Imaging][Dr. Chan] – So this is what a panoramic image looks like. You've got physically, a large part of patient's face. You've got the mid-face (maxilla, zygomatic bone, parts of the temporal bone). You also have the mandible. The teeth don't make up that much of the image. If you have some pathology here, the teeth are floating in air anyways, you need to address the teeth before you look at the carious lesion. You need to look at the bone first before you look at the teeth. How I've been teaching the 3rd year students is, is when you do a panoramic survey, you start on this corner, you move to the periphery to look at the anatomical structures, move down, move again at the periphery and up again, and finally during your second run move and look at the teeth. You always do the periphery first and then you look at the center. This concept of periphery and center also applies to intraoral imaging but we'll talk later. For those of you that understood what ghosting means, this fuzzy hazy line is the ghost of the left mandible as the right mandible imaged. Here is the ghost of the right mandible as the left mandible is imaged. On panoramic imaging, you'll always have markers to distinguish R/L sides. Again, you're facing the patient's face as if you're talking to them. Once you've done the periphery and centered survey, what's interesting about head and neck anatomy is that it'll always be symmetrical. You can zoom out and compare and see what you see on the right side is similar or identical on the left side. That's the quick and dirty method. For the purposes of communication, when you need to refer someone to oral surgery for care, you need to communicate by anatomy. It's a form of communication b/w different specialties in the dental profession.[6] – [Open Skull View][Dr. Chan] – Now, as the patient is standing/ sitting in the machine, and the X ray unit tube head and sensor rotates around, what it's doing is actually unrolling, ironing out a spherical head and putting it on a 2D plane. This open skull view is actually someone unrolling a spherical head and putting it on a 2D plane. These are the exact structures you'll encounter and see on a panoramic image. Here you start from one side, to the left. Go here, here, and finally the teeth.[7] – [No Title][Dr. Chan] – If we simplify this, you guys have ortho before or no? Well in orthodontics, you'll encounter another film called laterocephalometric film. Panoramic images consists of two laterocephalometric and one posterior/ anterior cephalometric film. From the cervical spine and the posterior part of the right side of the mandible to the canine that's kind of a cephalometric region there. Canine to canine you're looking at the patient front on in an anterior/posterior view. From canine to the left side, you're looking at a laterocephalometric. This is saying that a

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panoramic image is not just about a teeth. You may order a panoramic image for sinus pathology, tooth implant, but the teeth shouldn't be your focus when you read or review a panoramic image. Make sure you look at the bones before you look at the teeth.[8] – [The Midface][Dr. Chan] – Ok. How do we start? Well there are names to these images. Different structures. I start from here and here. This is not marked. This hole here is the external auditory meatus. if you move anteriorly, you have (some word) of sphenoid and you move anteriorly still and you have the articular eminence of your temporal bone (temporal component of TMJ). Mandibular portion is the condylar head. Those are the two bones that make up the TMJ. Here you have the articular eminence and move forward and you have the temporal process of the zygomatic bone. It will be a diamond shaped thing. I'll have it in other skull views. Here you have to check the inverted teardrop structure called the pterygomaxillary fissure. It's important landmark on panoramic imaging. If you see any change in the contour of the inverted tear drape or door hole structure, you need to think of something serious. I'll go over that when we actually go look at that structure in detail. To make sure you look at the cortices are thick, uniformly intact and radiopaque, the posterior wall of this fissure is the anterior border of the sphenoid bone. The anterior wall of the fissure is the posterior wall of the maxilla.. As you drop down, you have maxillary sinus. Here you have the sinus floor. As you come up, this part of the image, the panoramic image is imaging the medial part of the patient. Instead of calling this the anterior wall, it's not the anterior wall, it's the medial wall of the sinus b/c the patient is right here and the x-ray source and receptor is rotating around the patient's head. You're getting the medial wall of the sinus. Depending on how big or long patient's head is, you'll see the orbital floor, inferior nasal concha smeared across the sinus like this, you'll see the nasal septum, hard palate, interior nasal spine, sinus floor. Check the R/L sides are the same. Orbital floor, zygomatic process of the maxilla. Look at the left pterygomaxillary fissure. Make sure the lines are thick and opaque. Everything intact, nothing broken/ cloudy. Then you go to the zygomatic complex you have the articular eminence of the left temporal bone and then you complete the survey of the midface. Then you drop down to look at the condylar head/ neck. Here you'll see the soft tissue of the ear. Then you drop down to see the ramus, inferior alveolar canal, mandibular canal. The inferior mandibular cortex, we'll actually go over in a few slides.[9] – [Pneumatized Articular Eminence of the Temporal Bone][Dr. Chan] – Sometimes on panoramic imaging, you'll have anatomic variance. Again, whenever you have an image you start from this corner and move across the screen. Here you see something that's not present on the other side. See the articular eminence of the right temporal bone right here, and left temporal bone. There is a well-defined radiolucency right here. Everyone see that? This is not pathology. The fact is, that it's black telling you its air. Only air on radiographs are black. This is a rheumotized articular eminence b/c if you remember from anatomy, a temporal bone has a mastoid process and inside there are mastoid air cells. Sometimes they like to move anteriorly to rheumotize the articular eminence of the temporal bone. Just as you will encounter in clinic, sometimes in edentulous areas, maxillary sinus

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floor will drop down to rheumotize the edentulous bone right here. That's the same concept. Air cells from the mastoid air cells are rehumotizing the articular eminence. Do nothing. Do not go in to biopsy. I know you can get in trouble doing that. A surgeon went in and biopsied air and the dentist lost the lawsuit. Know if you see well-defined radiolucency that is black as air right here in the articular eminence you write rheumotized by the air cells and don't treat. Everyone clear?[10] – [Pneumatized Alveolar Process ][Dr. Chan] – Similarly, here we've got your rheumotized alveolar process. Your sinus floor on the right process drops down to air out the bone b/w the second premolar and first molar on the upper right jaw. This is from an oral surgeon and he was wondering why there is air here as well. Its just rheumotizing the zygomatic bone right here by the maxillary sinus. Again, normal finding. No need to biopsy.[11] – [Pterygomaxillary Fissure][Dr. Chan] – Here we talk briefly about what the pterygomaxillar fissure look like. Upside down teardrop. You want to make sure the cortices are radiopaque. This is what it looks like anatomically. Here's the posterior wall of the left maxilla. Here you see the humeral process of the medial pterygoid plate of the sphenoid bone, here you've got the pterygoid plate of the sphenoid bone, here you have the tear drop structure. Here you've got your zygomatic bone. You see kind of how it's like a diamond shaped. This is the pterygomaxillary fissure. It's actually a lateral doorway (axial cut of a CT scan) to the pterygopalatine fossa. Has anyone heard of the PPF? What's in there? All the nerves and vessels right? If for instance you have a tumor somewhere here and the teardrop is actually breached, fractured or clouded, there's something in the PPF. B/c the PPF, all of those nerves connects the regions of the head. Eye w/ the nose, nasopharynx, oral cavity. It's basically like the grand central station of the head and neck. If you tumor in any of these spaces, it has the potential to travel via the nerves and vessels in this area to spread to other parts of the head. Always check to make sure this is intact. I always do this on pans and cone beam CTs. This is a key structure that radiologist check. If you see a fracture here or a cloudy sinus and a change in contour you needed to suspect 3 things: Malignancy from the maxillary sinus, LeFort fractures which are fractures involving the midface but always fracturing the pterygoid plate of the sphenoid bone. Remember that the posterior wall of the pterygod maxillary fissure is actually the anterior wall of the pterygoid plates of the sphenoid bone. So if this fractured here or here suspect LeFort fracture. The last thing is, is that if you have a cloudy sinus, you can consider a true sinus mucoseal. Those are very destructive lesions. Not the same as the mucoseals that you get on the lower lip. It turns the sinus into a bag of mucous. Whenever you see something that is destroying this fissure, suspect something nasty. Always take a quick look and then you're safe.[12] – [Soft Tissue Mass][Dr. Chan] – Here's an image I got when I was in a pathology residency. Here you've got the pterygomaxillary fissure on the right side. Something has expanded the fissure on the left side. The sinus is not cloudy so I know this thing is outside the sinus b/c if you expand the contour of walls of the fissure. This turned out something that developed inside the PPF. Don't worry about the diagnosis. Just worry about the size, shape of the fissure. If you see this, you would want to take

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this out yes, but refer the patient for further studies. Then this patient needs to be further worked up to determine what this thing is. You can ignore the teeth first. This takes precedence. Does that make sense? All it takes, is comparing symmetry. What you want to see on the right side is what you want to see on the left side. You use an anatomical landmark to work w/ your colleagues. You can say "oh' there's asymmetry. Where is it? It's in the left pterygomaxillar fissure. You tell this to the oral surgeon and they know where to look and how to plan what steps to take.[13] – [The mandible][Dr. Chan] – So that's the midface. Any questions? So, the rest is easy. The midface we already did the complicated stuff. There's a lot of bones. The mandible is just one bone. You've got the condylar head, neck, coronoid process. sigmoid notch, ramus. You want to make sure the canal is uniformly thick and radiolucent w/ corticated borders. Compare that on the right hand side. Move down and you will see an area that is radiolucent compared to the rest. It's the mandibular gland fossa. In the 2013 lecture meeting one colleague raised his hand and asked if you needed to do a root canal there since it's radiolucent. It's normal anatomy and completely benign. Doing root canal won't change anything since it's normal pathology. Submandibular gland fossa is a concavity on the medial side of the mandible where the submandibular gland sits. B/c there's concavity compared to the rest of the bone, the bone is thinner and it's not going to attenuate more x-rays. That's why it’s more radiolucent on the image. Here are both sides you want to make sure the inferior mandibular cortex in healthy adults is at least 3 mms thick and uniformly radiopaque. If you see bites or discontinuity in a healthy adult, you need to suspect something. In the elderly population, this cortex may be thinner. That's normal at that age. In healthy adults make sure it's uniformly thick. Swoop up and you see the same thing on the right side. Can you see the mental foramen? Depending on the projection. It's always going to be near the second premolar. Not pathology right? Here's the cervical spine. This is ghosting of the cervical spine b/c as the beam is passing through the head, it also passes through the spine. This is ghosting of the cervical spine. Again a blur right in front of the anterior mandible. If there's swelling of the anterior mandible and for some reason you want to take a panoramic image, make sure you understand that if you take a panoramic image of the interior mandible it may not be clear since you may have ghosting of the spine superimposed of the area. It doesn’t' give you a clear view and you try taking a periapical or occlusial radiograph instead b/c those are point and shoot modalities that don't give you ghosting. For anterior mandibular pathology, there are other modalities to consider. So here is the right side, submandibular gland fossa, everything looks good. It's pretty easy the mandible. Just one bone.[14] – [Epiglottis][Dr. Chan] – Sometimes by the angle of the mandible, since they have flesh and glands, this part (canine to spine area you're imaging the sagittal view of the head), you get structures of the neck such as the epiglottis. Depending on how old the patient is, you will always get calcified fibrocartilage. This is the superior horn of the thyroid cartilage. If it is calcified, you'll see a structure right here just lateral and inferior to the epiglottis. This is the epiglottis b/c this is the base/ dorsal tone and here's the epiglottis. This structure, when you start clinic next year w/ Dr. Freidman,

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he will ask you what this structure is. Can anyone guess? it's above the thyroid. Hyoid. Yes. You have no idea how many people think that's the clavicle. Bravo. You'd be surprised. They'd say clavicle. Awesome. This is a great class.[15] – [Median Sigmoid Depression][Dr. Chan] – There is a rare or not rare uncommon anatomic variant kind of like an inverse Nike sign on the right side and Nike sign on the left side and it's called median sigmoid depression. It's normal variant.[16] – [Median Sigmoid Depression of the Mandible][Dr. Chan] – We have a special guest in the audience. My co-resident. We actually imaged the skull he gave us. Can you appreciate a Nike sign here on the medial side of the ramus just below the sigmoid notch? There's a little Nike depression here. When we imaged it, we also saw that Nike sign depression. It's below the sigmoid notch on both sides of the ramus. Some patients may have this depression on both sides of the ramus. Some just have one. These are all anatomic variants.[17] – [Soft Tissues][Dr. Chan] – Sometimes soft tissues are imaged. Here we've got, permanent tissues that will be on panoramic imaging. The soft palate, the dorsal tongue, the pharyngeal mucosa overlying the cervical spine, the external ear, here we have the hyoid bone, here is the ear lobe. You always see sometimes-inferior nasal concha which we went over when we talked about the midface. Soft palate, dorsal tongue, pharyngeal mucosa. The soft tissue of the ear. Here you also see the nasopharynx, the oropharynx, the black space is air. Here is the rest of the pharynx right here. Remember, when you're imaging a patient the patient has soft tissue as well. Similarly in intraoral when you take your bitewing or periapical you will still see a very parallel rim of mucosa overlying the alveolar ridge or alveolar crest. You will still see soft tissue but there is more soft tissue to see on a panoramic image but there is just more tissue to see in a panoramic image since you're imaging the patient's head.[18] – [Common Incident][Dr. Chan] – Remember those sessions you had in gross anatomy lab w/ cadaver heads. I had to do that w/ dead people's heads. That's where you get your x-ray vision. Sometimes, soft tissue anatomy is not obvious on a radiograph. You won't see a maxillary artery on the radiograph. In the presence of calcified material in the soft tissue elements you won't see them indirectly. You will see them as casts. That's how some dentist notice incidental calcification of the carotid. To know what these calcifications represent you need to remember those cadaver sessions from the anatomy lab.[19] – [Sialolith of the Left Submandibular Glad][Dr. Chan] – Here you've got a calcification in this region. If you remember, your anatomy you'll know that this is where the submandibular gland is. Even though it's not directly projected on the image, you have to estimate and recall what structure is in that space. Once you have potential candidates for that anatomical structure you can say submandibular gland and associate a salivary stone and that's how you make a diagnosis of sialolith. It's in your head when you did your anatomy sessions w/ your vessels and glands.[20] – [Picture ]

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[Dr. Chan] – This is a quick overview. The submandibular gland lies just below the inferior border of the mandible. That's where you want to remember where the gland is on the image. The parotid gland will be hugging the posterior border of the ramus. The sublingual gland I wouldn't worry about it. It's too small and we've got all of this bone so you can't really see anything sub lingually. Just remember where the submandibular gland and the parotid is relative to the osseous structure of the panoramic image.[21] – [Sialolith of the Right Parotid Gland][Dr. Chan] – Here you've got a sialothis of the parotid gland. That's where your parotid gland sits. Hugging the posterior border of the ramus.[22] – [Tonsilloliths of Palatine Tonsils][Dr. Chan] – Here we've got other soft tissue calcifications. This is a very common find on panoramic imaging. These specs of radiopacity superimposed over the ramus like this are stones in your palatine tonsils. if you see multiple specs of calcifications like this overlying the ramus, it may not be on both sides, it may be on one side. Those are tonsillotliths of the palatine tonsils.[23] – [Lymphoepithelial Tissues][Dr. Chan] – Here's a quick overview of where the tonsils are you'll see the palatine tonsils on a pan. The palatine tonsils. they are right by the midramus area. You will not see lingual tonsils unless they are very calcified. Just know where the palatine tonsils are.[24] – [Phleboliths of the Pterygoid Plexus][Dr. Chan] – Phelboliths. You guys don't do block injections right? I'm sure you've heard of pterygoid plexus. Here you have 3 stones superimposed over the right maxillary tuberosity. You know they are stones b/c they are very concentric in appearance in radiopaque material. This is where the pterygoid plexus is. Hugging the border of the posterior wall of the maxilla.[25] – [Pterygoid Venous Plexus][Dr. Chan] – You can write that this is consistent w/ phleboliths of the pterygoid plexus. If you see stones superimposed over the posterior maxilla in the tuberosity areas. [26] – [Calcified Carotid Atheroma][Dr. Chan] – Finally this is the finding that most patients cringe about. Irregular linear calcifications just anterior to the cervical spine. These are calcified carotid atheroma since the bifurcation is at the level of the hyoid bone and that's the site you get calcifications. If you see this, for the conservative practitioner the patient will be referred to a physician to get a carotid ultrasound but currently there's not concreted evidence that the presence of atheroma leads directly to stroke. B/c we are conservative, if we see this they need a medical consult for an ultrasound b/c it's better to be conservative in the absence of concrete evidence.[27] – [Calcified Carotid and Maxillary Arteries ][Dr. Chan] – Here's an example of calcified carotid and maxillary artery. The artery lies deep to the condylar neck.[28] – [Carotid and Maxillary Arteries ][Dr. Chan] – Here's the course of the maxillary artery relative to the bones. Here is the ramus cut out. The maxillary artery lies deep to the condylar neck area. Here's

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the condyle. Here's the condylar neck. Deep to it is the maxillary artery. Just remember these key structures and you'll be fine when you see calcifications. You're to localize the anatomical structures. That's it for panoramic imaging.[29] – [Case 1][Dr. Chan] – I have 3 cases priming you to OMPR that dreaded course in 3rd year. You probably heard horror stories that I give students panoramic images on the exam that drives them mad. This is an example of an exam question. I hope when you do a survey of the periphery you know something is wrong here. If you see ill-defined destruction. Here the pterygomaxillary structure is gone compared to the normal side. This is malignancy. That's your first into to OMPR. If you know how to read a pan you have no problem w/ the exam or your career.[30] – [Case 2][Dr. Chan] – Second example, look at the bone, pterygomaxillary fissure, zygomatic bone, zygomatic process, sinus, hard palate, everything we have on the right is present on the right side. The sphenoid sinus. You know it's the sphenoid sinus b/c the posterior wall of the pterygomaxillary fissure is the anterior border of the pterygoid plates and the pterygoid plates are part of the sphenoid bone. If you have something like air in that part of the plate you know it's the sphenoid sinus. You go here. This is the styoloid process of the temporal bone. If may be long. It may be a common incidental finding. You don't need to do anything about it. It can be thicker, it can be longer. It's normal anatomical variance. If you go down here, patient's in retention. She's a young patient. You say, oh what's going on here. Don't stop the survey. Finish your assessment before you think about what that abnormality maybe. You've got some radiopacity but keep looking for any other problems and then you go back and you're like oh, it's well defined but it's radiopaque but the roots is missing so in the clinical setting you may chose to do vitality tests and you find that the tooth is vital. If you have this pattern of well-defined non-corticated radiopacity that may or may not in this case resorbing the root of the molar, the diagnosis is dense bone island. It's very common. You'll see it often in the clinic. We have 5-6 of these in a week. If you see something well defined that is not really having any other problems w/ it, think its bone island. We'll talk about the diagnosis in OMPR. I hope you pick up something here.[31] – [Case 3][Dr. Chan] – Finally, case 3 compares symmetry. Moves from one side to the next. It's a bit burned out but this is a good copy of a copy of a panoramic image. Then you go down and you see oh the canal looks enlarged on the other side. I hope you can pick up the abnormality. Compare symmetry. Know your anatomical landmarks b/c that's how you're going to communicate w/ the referrals w/ each other. Pick up the symmetry. Here this turned out to be something back. You don’t have to worry about the differential right now. That's panoramic imaging. Once we are going into intraoral you'll realize it's a breeze.[32] – [Time for a break][Dr. Chan] – [33] – [Acknowledgments][Dr. Chan] – Ok. So I'm going to start. The second bit is going to be much more easier b/c we've got the major bone/ soft tissue anatomy out of the way. If you know your

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panoramic imaging you'll be fine. Before we start I want to thank these four people in my career.[34] – [Panoramic Image][Dr. Chan] – so panoramic image. That's that. Aright. Intraoral, we're going to focus in this part. We're zooming in on a panoramic image. We'll still see the coronoid process, part of the ptyergoid plate. We'll still see the spine. The reason I show you the panoramic image and then the intraoral stuff, is b/c it makes it so much easier.[35] – [DXTTR][Dr. Chan] – This is actually a full mount series. In the school a FMS is defined by 6 anterior 6 posterior periapicals and 4 bitewings. If you start from the periphery here's the zygomatic process/ bone, sinus bone, some anatomy is missing b/c it's fake teeth. Here you have your anterior nasal spine. You'll see the floor of the nose right here. We have real patients that we have in our presentation. Here's the sinus on the other sinus wall. Some parts of the submandibular gland fossa more radiolucent. Like reading panoramic imaging, we start from the periphery, we do one swoop through the quadrants (1 thru 4) and then finally look at your teeth for caries. Once you know the landmarks, once you've practiced this many man times, it will be second nature and this process should not take more than 3 minutes max.[36] – [Periphery][Dr. Chan] – The periphery structures. The red line.[37] – [Maxillary View][Dr. Chan] – Ok I'm going to start posteriorly and then move anteriorly b/c that's how you're going to read. And forgive me b/c I know you read from the patient's right side but these examples are right left. Here we have a maxillary view. I'll give you full marks in clinic if you can get this view in patients. You have the pterygoid plate of the sphenoid bone in a maxillary left third molar view. You can see the pterygoid plate and the outline here as well. What is this? The coronoid process. That's good. Not many people can get this view. I know I can't.[38] – [Maxillae: Zygomatic Process and Bone][Dr. Chan] – Moving a bit anterior. You have the maxillary. Here is the first molar, the tuberosity, premolar. This is actually the zygomatic process of the maxillary. This it the bone that hooks up w/ the zygomatic bone. It's reflected in this diagram right here.[39] – [Maxillae: Zygomatic Process and Bone][Dr. Chan] – Ross did an experiment to show you the extent of the zygomatic process of the maxilla right here. Here you can see it's projected similarly on the radiograph. The zygomatic process of the maxilla is that bone that hooks up w/ the zygomatic bone. A very diamond shaped structure right here. This part here is the zygomatic process of the temporal bone. That's called the zygomatic complex in addition to the zygomatic process of frontal bone which is not here. These structures reinforce that cheek bone (diamond shaped zygomatic bone). [40] – [Maxillae: Maxillary Sinus][Dr. Chan] – As we move more anteriorly we've got the zygomatic process of the maxilla. Zygomatic bone. We've got your sinus floor. Make sure it's intact. Here the sinus is clear. It's completely clear. It's black. It's filled w/ air. I hope you can appreciate that it's gray and hazy. If you see a gray and hazy sinus like that it can be

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mucositis. The mucous lining the sinus floor is actually thickened. It could be many reasons including dental infections, allergies. We see a parallel rim of hazy radiopacity lining the floor of the sinus think mucositis. If what you see is completely radiopaque you need to think sinusitis. There may be more of the sinus that is filled w/ this radiopacity. Again, when you start looking, I hope you see the sinus floor varies b/w patients and in patients. What you see on the right side you might not see on the left side. Here is phneumitizing bone b/w the premolar and the molar. It's dropping down pnuemitizng the bone. It's normal anatomical variance.[41] – [Maxillae: Maxillary Sinus][Dr. Chan] – other variation of the sinus floor are these accessory septum. Sinuses are very heterogeneous. What you see in one patient is going to be completely different. Sinuses same thing. In the same patient, you may have one accessory septum on the right side vs. multiple on the other side. They are projected on imaging like this. Straight bony radiopaque septum like this.[42] – [Maxillae: Maxillary Sinus][Dr. Chan] – sometimes you may actually see radiolucent bands in the sinus region. They will be drooping over the apical thirds of the maxillary roots like that. That's not a fracture b/c fractures are contained planes w/in the anatomic structure. They don't extend beyond the structure like this. If you see a radiolucent band, here's another one, and here maybe some more in these sinus area and extending like this, they are neurovascular canals.[43] – [Maxillae: Maxillary Sinus][Dr. Chan] – As we move more anteriorly in the premolar region, you will see the floor of the nose. Where the floor of the nose and the anteriomedial part of the sinus crosses. it's called the inverted Y. It use to be a board question. In this event, what does it represent you can say the Y line or the inverted Y of Ennis. It's an anatomic landmark for edentulous patients. Below this inverted Y is your maxillary canine. If the patient is edentulous and you want to know where the canines are, this is a good guideline.[44] – [Maxillae: Nasolabial Fold][Dr. Chan] – Now that we're hitting the premolar canine/ premolar region, sometimes you'll see a nice oblique diagonal line like this. Crossing over the apical 1/3rds of the root tips. You see a nice oblique line here and here. That’s your nasolabial fold. Everything behind that line will be slightly more radiopaque. There's fat there attenuating the x-rays. This line is not a fracture since it goes from one edge of the film to the other. It's the nasolabial fold. [45] – [Maxillae: Lateral Fossa][Dr. Chan] – Sometimes patients will have very deep concavities along the buccal cortex of the maxillary lateral incisor region. B/c you have a concavity you have thinner bone. Thinner bone you're not attenuating that many photons. You get a more radiolucent projection image. This is called a lateral fossa. Directly superimposed over the mid and apical root fold of the lateral incisor. It's an ill-defined hazy radiolucency right over the lateral incisor’s fossa. You may not see it in every patient but if you do now you now what it's called.[46] – [Soft Tissue Nose]

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[Dr. Chan] – moving anteriorly still you have the soft tissue of the nose. It shows up right here as a line. Again, soft tissue of the nose right here and this droops over the apical 1/3s of the maxillary central incisors. B/c there's soft tissue here, it's going to attenuate some more x-ray beams so that this area is more opaque then the rest b/c you have soft tissue.[47] – [Soft Tissue Nose][Dr. Chan] – Here are other examples of the soft tissue of the nose. Sometimes you may see artifacts since patients can't take off their nose rings and you're stuck w/ it.[48] – [Nasal Fossa][Dr. Chan] – As we're looking at the anterior maxilla you will see that sometimes we can image part of the nose. The nose is captured. Here we have our inferior nasal concha. Here's the bony nasal septum. Nasal septum is the same as nasal cavity or your nose. Here you've got your floor forming a v shaped line of the right/ left nasal fossa. Here you have your anterior nasal spine just like on your panoramic image. This is your anterior nasal spine.[49] – [Incisive Foramen][Dr. Chan] – You also see a well definitely radiolucency b/w the maxillary central incisor. That's your incisive foramen. Here it is on your skull. Depending on where you read pathology or radiology texts there's a discussion on the upper limit of normal on the size of this foramen. The upper limit of normal in pathology is 6mms on the periapical film. In radiology it's 10mm. These are rough ball park figures.[50] – [Anterior Nasal Spine][Dr. Chan] – anterior nasal spine right here.[51] – [Intermaxillary Suture][Dr. Chan] – b/c the maxillae consists of two bones, we've got a right maxilla and a left maxilla. It's connected by the intermaxillary suture.[52] – [Coronoid Process][Dr. Chan] – that's the maxilla. mandible. You all know what this is which is awesome. Here's the coronoid process of the mandible and then on the let side.[53] – [External Oblique Ridge][Dr. Chan] – External oblique ridge is this thick ridge. You can see it right here on the skull. It's actually he continuation of the anterior border of the ramus. As the ramus drops down from the process like so, it becomes the external oblique ridge once it hits the retromolar region like that.[54] – [Internal Oblique Ridge][Dr. Chan] – b/c there's an external oblique ridge there's an internal oblique ridge. Here it is on the radiograph. As you move more anteriorly, the interior oblique ridge gets another name called the mylohyoid ridge.[55] – [Internal Oblique Ridge][Dr. Chan] – Internal oblique and then swoops down into the mylohyoid ridge. This is the attachment point for the mylohyoid muscle. You can see it here as well.[56] – [Oblique Ridges][Dr. Chan] – Finally, thanks to Ross you have the external oblique ridge right here and the internal oblique ridge becoming the mylohyoid ridge right here.[57] – [Submandibular Gland Fossa]

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[Dr. Chan] – again. this is the second time I put this slide up. This is a crop pan image showing you a nice radiolucent and thin submandibular gland fossa. It's radiolucent but it's not pathology b/c this is where the submandibular gland sits right here. Depending on how deep the fossa is it may be more or less radiolucent than this example. Don't do a root canal there[58]- [Submandibular Gland Fossa][Dr. Chan] – Here are more examples on intraoral radiographs showing the submandibular gland fossa. In a subsequent slide I'll go over the detail on how to determine if you have pathology that will tell you if you need endo or not. You can go back to revisit this slide when I go over it. You can see the periodontal ligament space surrounding or hugging the apices are intact and outside the space is something called lamina dura. This cortex is intact. B/c these are intact you know the teeth are not diseased. There's no way this can be pathology b/c you know the teeth are normal. This is just normal anatomy ok?[59] – [Mandibular Canal][Dr. Chan] – another normal anatomy that we have to be aware of is the mandibular canal. Even in implant surgery we have to make sure the implant is far from the mandibular canal. It's also known as inferior alveolar canal. We call them canals since they contain nerves and vessels. Most people call them canals in radiology. Here it is again, the superior cortex of the canal, the inferior cortex of the canal, and here's the canal proper.[60] – [Mental Foramen][Dr. Chan] – It comes out buccally and distally. The nerve comes out of the mental foramen like this in a buccal and distal manner via the mental foramen. Sometimes to the untrained eye, there are a periapical radiolucency here. This premolar needs a root canal. No it doesn't. B/c the periodontal ligament space and the lamina dura are hugging this tooth symmetrically. Even if you don’t believe that I tell you radiographically you can always test the tooth for vitality.[61] – [Mental Foramen][Dr. Chan] – Here's the foramen on different patients hooking out buccal and distally exiting out the mental foramen. Again this was not needed. Things like this happen. This is not needed b/c you check PDL space and the lamina dura. They are hugging the tooth very nicely. Nothing is blurred, nothing is broken. Everything is normal. This root canal should not have been done. This dentist was smart enough b/c he realizes lamina dura and PDL space are normal and are hugging the root tip of this premolar. This is the mental foramen not periapical radiolucency. Root canal not needed. [62] – [Inferior Cortex][Dr. Chan] – sometimes you may see the inferior cortex no an intraoral film. Depends how big the mandible is. This is something called periostitis. It's a periosteal membrane reaction to inflammation. It's from inflammation of these carious molars. Here is an example of a truly periapical pathology b/c you have no lamina dura and the PDL space is widened. This is purely inflammation. it then pushes the pus periosteum lining the outer cortices of the bone outward and stimulate the periosteum a new layer of bone. In addition of making sure that the thickness of the inferior mandibular cortex is 3mm thick and uniformly radiopaque make sure you

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don't have a layer of bone like this. If you see it, think pathology. We'll go over it in D3.[63] – [Mental Ridge][Dr. Chan] – As we move more anteriorly you may see in some anterior periapical images (incisal region) 2 pointy lines like this which are the mental ridges. Right there.[64] – [Mental Fossa][Dr. Chan] – Then I don't know why there is no title here. Um that's ok. Here we are dealing w/ the mental fossa. See here you have a concavity. Whenever you have a concavity you have less bone to attenuate the x-ray photon explaining why you have more radiolucency. Mental concavity or mental fossa.[65] – [Genial Tubercles][Dr. Chan] – Genial tubercles. In real life. There's something different about text book examples and real life. Text books will give you beautiful examples of long slender and pointy. In real life that never happens. Just a little bump on the lingual side. It's' the attachment for muscles in the tongue. This is the lateral occlusial of the left side of the mandible. Here are the genial tubercles. Very pointy, very nice example. B/c we're actually learning about periapical image right here, you'll see that pointiness as a more radiopaque blur. There's more bone here. You've got more bone attenuating the x-ray beam giving you a blur. If you see b/w the mandibular central incisors and apical to that, a nice well defined radiopaque blur those are the genial tubercles. Attachment for muscles of the tongue.[66] – [Lingual Foramen][Dr. Chan] – sometimes you may be lucky enough to see a radiolucency in that white blur. You may not see this in every patient but sometimes if you see a radiolucency like this in the genial tubercle that's the lingual foramen.[67] – [Nutrient Canals][Dr. Chan] – Just as we saw, neurovascular, nutrient canals superimposed over the sinus cavities when we did the maxilla we may see also see that in the anterior mandibular body right here. These are nutrient canals (small neurovascular canals) supplying the bone of the anterior mandible. Sometimes they go directly into the bones of the teeth. These are nice nutrient canals. You should know what these represent since we see a lot of students confusing these as fracture lines. These are nutrient canals feeding the bone of the anterior mandible.[68] – [Center][Dr. Chan] – that's the periphery. Almost done. Almost done. Now we will look at the teeth.[69] – [Bone Pattern][Dr. Chan] – before looking exactly at the teeth we need to know what the bones b/w the teeth. Once you know these anatomical structures, it should not be laboring process to look at all the bone. The posterior maxilla should be a nice network. In fact the anterior and posterior maxilla, the pattern of networking of the bone is very similar. Some patients may have slightly larger marrow spaces showing the radiolucency b/w the radiopaque lines. Sometimes posterior maxilla may have larger marrow spaces on the anterior maxilla but as long as you see a nice network it's good.

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[70] – [Bone Pattern][Dr. Chan] – Here the marrow spaces are smaller on the patient but you can see a nice network of trabeculatoin.[71] – [Bone Pattern][Dr. Chan] – I want you to remember that the step latter pattern is consistent w/ anemia. Don't listen to it. In rare patients you may see it. in many times you will see that pattern in normal patients w/ diagnosis or symptoms of anemia. Anatomic variance, you just have to train your eyes to knowing that in the posterior mandible you will see a step ladderish bone patter like this. The marrow space is the largest ok. If you do see a step ladder patter like this do not make the overcall of anemia. it's most likely anatomic variance. In an anemic patient they will have other radiographic signs. That's the key point you need to remember. The step ladder pattern alone, think normal. Of the bone pattern in all parts of the jaw, there will be largest in the posterior mandible. They may be devoid of trabeculae since this is the submandibular gland fossa.[72] – [Bone Pattern][Dr. Chan] – Sometimes the bone marrow spaces will be so large that they mimic pathology but they are not. It's just marrow space. This may be nice for the exam alright? Marrow spaces know what they look like. Don't overcall it. They are normal anatomic variance. The former name is called focal osteoporotic marrow defect. If you put large marrow space, same thing.[73] – [Bone Pattern][Dr. Chan] – At the other end of the spectrum, the bone may be very dense. Just like case 2 of the pan image I showed you. You have well definited non-corticated homogenous radiopacity and you have this and nothing else, the PDL space and everything else looks normal, this is dense bone island. In the other end of the spectrum, instead of having a large marrow space you have more bone being formed so much that it mimics cortico bone. That's why it's so radiopaque. These are dense bone islands. They do not represent any manifestations of systemic inflammatory agents. Dense bone island.[74] – [Bone Pattern][Dr. Chan] – Sometimes mimicking a dense bone island would be a mandibular tori. You can very easily make this differential by looking into the patient's mouth clinically. The like to hang out over the midroot, apical 1/3rd of the premolar area. They are not as homogenously radiopaque, they are more radiolucent then dense bone island. But if you have that in your differential and you want to know if it's a dense bone island or tori you look in the patient's mouth .[75] – [Bone Pattern][Dr. Chan] – Here just showing you the bone of the interior mandible. Nice network.[76] – [Lamina Dura][Dr. Chan] – Now we are talking bout lamina dura. The radiopaque line that hugs all the root surfaces of the teeth. That's the lamina dura. The PDL space, the radiolucent black line, immediately adjacent to the roots of the teeth. It's black b/c it's the periodontal ligament. The fibrous tissue don’t' attenuate. In radiology land they call it PDL space. Sometimes, depending on the tooth morphology, you may have a concavity and giving you a slightly double PDL space right here and here. Like that.

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[77] – [PDL Space][Dr. Chan] – When you're in the clinic next year I hope you review this slide. It shows you what a true periapical inflammatory lesion looks like. The PDL space is widened and the lamina dura is lost. If you have this, almost always you will have some kind of decay here. 95% of the time, these are the two conditions that will give periapical inflammatory disease. Loss of lamina dura and widening of PDL space is commonly associated w/ periapical inflammatory disease. This is actually an example of condensing osteitis. The bone is inflamed. Condensing is b/c if you remember systems path. The steps of inflammation, once it begins to become chronic it starts to produce product that stimulates bone formation. When you have more bone, the bone on the radiograph will be more white. That's why it's called condensing osteoitis. Dr. Shah likes to put that on the competencies. You can remember widened PDL space and loss of lamina dura will point you to periapical inflammation.[78] – [title of slide][Dr. Chan] – Skip[79] – [Alveolar Crest][Dr. Chan] – This is what normal alveolar crest looks like. It actually continues w/ the lamina dura. You check the level of alveolar crest for periodontal disease.[80] – [Alveolar Crest][Dr. Chan] – Here you've got molar vertical periodontal bone loss. A normal alveolar crest should be 1-2mm below the CEJ. It should be intact like that.[81] – [Root Apices][Dr. Chan] – In addition to mental foramen superimposing over the root tips of the premolar, to trick your eyes to think its periapical disease when it's not, developing roots may also trick you. You now know that this is an intact lamina dura which is continuous w/ the follicular space so you know this is normal and not a periapical lesion. If ever in doubt test the tooth for vitality.[82] – [Root Apices][Dr. Chan] – Here again showing you how they need be mimics. This is not mimic b/c lamina dura is intact but here you've got a similar presentation but a loss of laminar dura. Here the lamina dura is blurred, here it is gone. The PDL space also widened. These are additional examples of periapical disease, not developing tooth or roots. If you're in doubt you can check for vitality but after this lecture you will be fairly confidently make the diagnosis by looking at the PDL space and the lamina dura. You can always compare. Look at the key details. We are dentist.[83] – [Tooth Follicle][Dr. Chan] – What do I want to say about tooth follicle? Tooth follicles again, you want to make sure are uniformly thick and radiopaque. Deep to the follicular cortex you have a thin and uniform radiolucent space.[84] – [Tooth Follicle][Dr. Chan] – If the space is enlarged like this it's a hyperplastic follicle. If it's got bigger and bigger the you can say it's a dentigerous cyst. Dentigerous cyst is a well definited unilocular radiolucency pericoronal to a tooth of an impacted tooth and connected to the tooth at the CEJ b/c a dentigerous cyst is basically fluid accumulation in the follicular space. That's a dentigerous cyst. We'll go more into that in OMPR. Just so you have a reference of what normal tooth follicle should look

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like, this is it. It should be no bigger than 2-3mm. If it's around 4-5mm you can call it a hyperplastic follicle. If it's larger than 4-5mm you can call it a dentigerous cyst.[85] – [Tooth Structure][Dr. Chan] – This slide is self explanatory. You've got your enamel, your dentin, pulp, cementum which we can't really see.[86] – [Tooth Structure][Dr. Chan] – So this tooth is caries. Normal tooth structure. Everything is smooth and continuous. Your dentin is very uniformly one shade of grey. The pulp is like this. In fully developed teeth, you will not be able to see the pulp at the end of the root tip. If you do, that means its widened and there is disease there. Caries, if you see ill-defined radiolucency that has a gradient like this, and the enamel is breached like this, think caries. Here are examples of caries. Cariology will do a thorough lecture w/ you on how to diagnose caries on radiographs. The other thing you have to keep in mind is this right here called artifacts. It's called cervical burnout. It happens b/c there's less tooth structures at the lateral surfaces of the teeth where the neck is.[87] – [Cervical Burnout][Dr. Chan] – Ok, this is a birds eye view of the tooth. Here's the pulp, here are x-ray beams. At the lateral surfaces of the tooth there is less tooth structures so it's not going to attenuate many photons. More X-ray beams pass through and that's why there's radiolucent right here. These are not caries but artifacts. They always appear at the necks of the teeth like this. Cervical burnout. If you don't remember where it is, but you know the name it's going to always be at the neck of the tooth right here. Not caries but artifacts b/c there is less tooth structure attenuating the photons of the x-ray beam.[88] – [Report Form][Dr. Chan] – This is the radiographic form that we will be using in clinic. We ask that you do a quick survey of all the bones before you look caries. It should be the last thing you check for since you will not forget about that. So in the maxilla and mandible just do your periphery swoop to make sure your sinus floor is intact and the sinus is clear. The pterygoid maxillary fissure is there. TMJ is normal. Overlying soft tissues on a pan, soft palate, dorsal tongue. On the intraoral, if the patient is edentulous on the maxillary molar region you should see a nice thin rim of mucosa overlying the alveolar crests. Lets see if I can find an example. I don’t' think so. Right here. Kind of you see how this part is not as black as this part. It's different b/c whenever we project an image some of the resolution is lost. If you look at Chapter 10 or 9, the anatomy chapter, you'll see mucosa overlying the alveolar crest. Always look from the periphery to the center.[89] – [Key Point][Dr. Chan] – The key point of the lecture is bones before the teeth b/c the bones are what support the teeth. Alright?

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