Normal Radiographic Anatomy for the INBDE
Every normal landmark on a dental radiograph is either radiolucent (dark: air spaces, canals, foramina, sinuses and fossae) or radiopaque (white: ridges, processes, septa, cortical bone and soft-tissue shadows). The INBDE expects you to name the common landmarks region by region and, more importantly, not to mistake the mental foramen, incisive canal, sinus or a panoramic ghost image for disease.
This guide from The Study Boards covers the tooth, the four intraoral regions, the panoramic view and the look-alikes that cost marks.
How The Study Boards helps you with radiographic anatomy
Anatomy questions on the INBDE rarely ask “name this landmark” in isolation; they hide it inside a case, next to a tooth you might treat. In The Study Boards INBDE course, our faculty-created radiology Module teaches the landmarks region by region, and the Master Test Series, daily tasks and nightly live tests at 9 PM New York time make you read films under time pressure, with explanations by US-licensed dentists.
The course is extremely personalised: red lines and assignments are given to you on the go, the course learns from the way you study, and faculty are there to assist you. Preparing for licensure? The same radiology training is part of our DLOSCE course.
The tooth and its supporting bone
Before any landmark, read the tooth itself. Check every root for two thin lines that should run unbroken around it: a dark one (the PDL space) and a white one (the lamina dura).2
Schematic by our faculty. RO = radiopaque (white). RL = radiolucent (dark).
What normal looks like
- Enamel is the whitest tissue, then dentin; the pulp chamber and canal are dark.2
- PDL space: a fine dark line around the root.2
- Lamina dura: a fine white line outside it.2
- Crestal margin: the top of the bone between teeth.2
- Check the integrity, continuity and width of both lines, and anything dark or white next to an apex.2
Intraoral landmarks by region
Pick a region. The landmark list and the radiolucent or radiopaque label follow the standard teaching set used in a 2026 dental education study.1
Schematics by our faculty, not to scale, following the landmark set in Veerabhadrappa et al.1 Light shapes are radiopaque; dark shapes are radiolucent.
| Landmark | Shows as | What to look for | Why it matters |
|---|---|---|---|
| Incisive foramen and canal | RL | Oval dark area between or above the central incisor roots; its level varies from near the crest to the apices. Average foramen size about 3 mm.9 | Easily mistaken for a lesion of #8 or #9. Over 6 mm wide, suspect a nasopalatine duct cyst.10 |
| Median palatine suture | RL | Thin dark midline line between the central incisors.1 | Not a fracture. |
| Nasal cavity (fossa) | RL | Large dark areas above the incisor apices, split by the septum.1 | Do not call it a cyst. |
| Nasal septum, anterior nasal spine, inferior concha | RO | Vertical white septum; white V-shaped spine at its base; soft grey concha in the fossa.1 | The spine can make a midline cyst look heart-shaped.10 |
| Y-line of Ennis | RO | An inverted Y over the canine region where the nasal floor meets the sinus wall.1 | Marks the sinus and nasal floors on canine films. |
| Lateral fossa | RL | Diffuse dark area between the lateral incisor and canine, where the bone is thin.1 | Can mimic a lateral incisor lesion; test vitality. |
| Shadows of the nose and upper lip | Soft-tissue RO | Faint grey outlines over the crowns and roots.1 | The edge of a lip shadow can look like a cervical lesion. |
| Landmark | Shows as | What to look for | Why it matters |
|---|---|---|---|
| Maxillary sinus | RL | Large dark space above the premolar and molar roots, outlined by a thin white floor.12 | A dome-shaped grey mass in the sinus is often a retention pseudocyst, which is frequently misread on panoramics.13 |
| Sinus septa | RO | Thin white walls dividing the sinus.1 | Not a multilocular lesion. |
| Zygomatic process of the maxilla | RO | U-shaped white band above the first molar roots.1 | Can hide molar apices. |
| Maxillary tuberosity | RO | Rounded bone behind the last molar.1 | Matters for extractions and dentures. |
| Hamular process and pterygoid plates | RO | Small hook-shaped white projection behind the tuberosity.1 | Normal anatomy behind the tuberosity, not a fragment. |
| Coronoid process of the mandible | RO | Triangular white shadow over the tuberosity area on maxillary molar films.1 | It belongs to the mandible; do not call it a maxillary lesion. |
| Nasolabial fold and nasolacrimal canal | Fold: soft-tissue RO | Oblique grey line across the premolars; the canal shows on maxillary occlusal films.1 | The fold line is not a fracture. |
| Landmark | Shows as | What to look for | Why it matters |
|---|---|---|---|
| Genial tubercles | RO | White ring or doughnut below the incisor apices, in the midline.1 | Muscle attachment; often outlines the lingual foramen. |
| Lingual foramen | RL | Small dark dot in the middle of the genial tubercles. Present in 93% of CBCT scans in one study, mostly above the tubercles.11 | Arteries run through it; perforating the lingual plate here during implant surgery can cause serious bleeding.11 |
| Mental ridge | RO | White V-shaped lines below the incisor apices.1 | Normal thick bone of the chin. |
| Mental fossa | RL | Diffuse dark area above the mental ridge, where the labial bone is thin.1 | Can mimic a periapical lesion of the incisors. |
| Nutrient canals | RL | Thin dark vertical lines between the incisor roots.1 | Not fractures or periodontal defects. |
| Landmark | Shows as | What to look for | Why it matters |
|---|---|---|---|
| Mental foramen | RL | Round or oval dark area near the premolar apices: under the second premolar in 67% and between the premolars in 24% of one panoramic study.7 | The classic mimic of a premolar periapical lesion. Usually symmetrical: both sides matched in 80% of patients.7 |
| Mandibular canal | RL | Dark band with thin white borders below the molar roots.12 | Protect it in surgery. A widened canal is not normal: lymphoma, osteosarcoma, nerve tumours and vascular lesions can widen it.14 |
| External oblique ridge | RO | White line running down and forward from the ramus, above the molar roots.1 | Sits higher than the mylohyoid ridge. |
| Mylohyoid ridge | RO | White line lower down, on the lingual side, often crossing the molar roots.1 | Can be mistaken for the canal border. |
| Submandibular (gland) fossa | RL | Diffuse dark area below the mylohyoid ridge under the molars.1 | Normal thin bone. A sharp, corticated hole below the canal near the angle is a Stafne defect instead.12 |
| Inferior border of the mandible | RO | Thick white cortical band.1 | A step in it on a panoramic can come from patient movement.4 |
Panoramic radiograph landmarks
A panoramic view is really three images in one: a posteroanterior image of everything in front of the canines and two lateral images of everything behind them.2 That is why the midline and the ramus look so different.
Try it: find the condyles, coronoid processes, hyoid, hard palate, maxillary sinuses, mandibular canals and the faint ghost of the opposite mandible. This patient is 16 and has impacted wisdom teeth.
Image: Coronation Dental Specialty Group, via Wikimedia Commons, licence CC BY 3.0.
| Group | Landmarks | Appearance |
|---|---|---|
| Mandible | Condylar and coronoid processes, sigmoid (mandibular) notch, ramus, angle, body, symphysis, mandibular foramen, mandibular canal, mental foramen, external oblique line, inferior cortex, submandibular fossa23 | Bone RO; canal, foramina and fossa RL |
| Maxilla and midface | Maxillary sinus walls and floor, tuberosity, hamulus, pterygomaxillary fissure, hard palate, nasal floor, inferior concha, anterior nasal spine, incisive foramen, orbital rim, infraorbital canal, zygoma and zygomatic arch2 | Bone RO; sinus, fissure, canal and foramen RL |
| TMJ and skull base | Glenoid fossa, articular eminence, external auditory meatus, styloid process, mastoid air cells23 | Meatus and air cells RL; the rest RO |
| Neck | Hyoid bone, cervical vertebrae2 | RO |
| Soft tissue | Dorsum of the tongue, soft palate, ear lobe, posterior pharyngeal wall23 | Faint grey (soft-tissue RO) |
| Air spaces | Nasopharyngeal air, palatoglossal air space, nasal meatuses234 | RL |
Ghost images, air spaces and positioning errors
Opposite side, higher, distortedA dense object between the X-ray source and the centre of rotation makes a ghost on the opposite side, higher up and stretched vertically.25
Accepted ghostsA light ghost of the opposite mandibular angle and of the cervical spine is acceptable on a good panoramic; the opposite hard palate also ghosts.2
Common positioning errors and what they look like4
| Error | What you see on the panoramic |
|---|---|
| Tongue not against the palate | A dark band (palatoglossal air space) over the apices of the maxillary teeth, which can hide or mimic apical lesions. |
| Head too far forward | Anterior teeth narrow, shortened and blurred; premolars overlap. |
| Head too far back | Anterior teeth wide and blurred; condyles near the edges of the image. |
| Chin tipped up | Flat or reversed occlusal plane; the hard palate shadow falls over the maxillary roots. |
| Chin tipped down | Exaggerated “smile” curve; lower incisor apices blurred; hyoid may overlap the anterior mandible. |
| Head turned to one side | Teeth wider on one side and narrower on the other; rami and condyles look unequal. |
| Patient moved | Blurred areas and a step in the inferior border of the mandible. |
Landmarks that look like lesions
Three tools settle almost every case: test the tooth, trace the PDL and lamina dura around the apex, and take a second film at a different horizontal angle.
Schematic by our faculty, applying the AAE definition of apical periodontitis and the tube-shift rule.68
| Normal structure | What it mimics | How to tell |
|---|---|---|
| Mental foramen | Periapical lesion of a mandibular premolar | Vital tooth, unbroken lamina dura, shifts with a second angle, usually matched on the other side.67 |
| Incisive foramen | Periapical lesion of #8 or #9, or a nasopalatine duct cyst | Test the incisors. A canal up to 6 mm is normal; wider, suspect a cyst. A cyst is round, oval or heart-shaped and pushes the roots apart, with vital teeth.10 |
| Maxillary sinus recess or septum | A cyst or multilocular lesion over premolar or molar roots | Follow the thin white sinus floor; it stays continuous.1 |
| Submandibular fossa | A cyst under the molars | Diffuse, poorly defined thin bone. A Stafne defect is sharper, corticated and below the canal; neither needs treatment.12 |
| Mental fossa and lateral fossa | Anterior periapical lesions | Diffuse borders, intact lamina dura, vital teeth.1 |
| Palatoglossal air space | Maxillary apical lesions | A band across several teeth; retake with the tongue on the palate.4 |
| Ghost of an earring | A calcification or foreign body | Appears higher on the opposite side; disappears when jewellery is removed.45 |
| Anterior loop and incisive canal of the mandible | Missed on a panoramic | Plain radiographs give many false positives and negatives here; use CBCT before implants in the area.16 |
When the dark or white area does not match any landmark, describe it as a lesion and work through our guide to radiolucent and radiopaque jaw lesions for the INBDE.
Three quick questions
Original questions by our faculty, not real exam items.
What is it most likely to be?
What is the most likely cause?
Show answer
C Air between the tongue and the palate (the palatoglossal air space) shows as a dark band over the maxillary apices.4
What is the best management?
How to prepare: our full plan
Radiographic anatomy is one slice of the exam. Here is the rest of the plan.
The Study Boards INBDE courseBuilt by US-licensed dentists:
- 12 sequenced course sections and 35,000+ focused questions
- Master Files, Master Test Series and 8-hour Grand Test mock exams
- A surprise live test every night at 9 PM New York time
- Students who complete the course pass on their first attempt 99% of the time
Build your own scheduleFit radiology into a full plan:
- The month-by-month INBDE study plan
- INBDE study materials that are worth your time
- Free INBDE practice questions
- Sitting the DLOSCE instead? See the DLOSCE course blueprint
Frequently asked questions
What are the radiolucent landmarks on intraoral radiographs?
What are the radiopaque landmarks on intraoral radiographs?
How do you tell the mental foramen from a periapical lesion?
What is a ghost image on a panoramic radiograph?
How does The Study Boards help you prepare for radiographic anatomy on the INBDE?
Not sure what you are looking at?
Send us your question. Our Admin Team with Dr. T and Dr. Kaur will contact you over WhatsApp.
References
- Veerabhadrappa SK, et al. Study of teaching methods for intraoral radiographic anatomy among dental students. BMC Oral Health. 2026 (landmark set by region, radiolucent and radiopaque). PMC13270581
- Suomalainen A, et al. Dentomaxillofacial imaging with panoramic views and cone beam CT. Insights Imaging. 2015. PMC4330237
- Maeda N, et al. Dental students’ levels of understanding normal panoramic anatomy. J Dent Sci. 2018. PMC6388826
- Rondon RH, et al. Common positioning errors in panoramic radiography: a review. Imaging Sci Dent. 2014. PMC3972400
- Ramos BC, et al. Formation of ghost images due to metal objects on the surface of the patient’s face: a pictorial essay. Imaging Sci Dent. 2016. PMC4816774
- Manne R, et al. Impacted canines: etiology, diagnosis, and orthodontic management (tube-shift / SLOB rule). J Pharm Bioallied Sci. 2012. PMC3467862
- Afkhami F, et al. Radiographic localization of the mental foramen and mandibular canal. J Dent (Tehran). 2013. PMC4025417
- American Association of Endodontists. Endodontic Diagnosis. Endodontics: Colleagues for Excellence, Fall 2013. aae.org
- Al-Amery SM, et al. Cone beam computed tomography assessment of the maxillary incisive canal and foramen. PLoS One. 2015. PMC4332502
- Lake S, et al. The Incisive Canal: A Comprehensive Review. Cureus. 2018. PMC6166911
- Aoun G, et al. Lingual foramina and canals of the mandible: anatomic variations in a Lebanese population. J Clin Imaging Sci. 2017. PMC5433650
- Hisatomi M, et al. Stafne bone defects radiographic features in panoramic radiographs: assessment of 91 cases. Med Oral Patol Oral Cir Bucal. 2019. PMC6344010
- Ha EG, et al. Automatic diagnosis of retention pseudocyst in the maxillary sinus on panoramic radiographs. Sci Rep. 2023. PMC9931752
- Mortazavi H, et al. Common conditions associated with mandibular canal widening: a literature review. Imaging Sci Dent. 2019. PMC6597376
- More CB, Asrani MK. Evaluation of the styloid process on digital panoramic radiographs. Indian J Radiol Imaging. 2010. PMC3056622
- Juodzbalys G, et al. Anatomy of mandibular vital structures. Part II: mandibular incisive canal, mental foramen and associated neurovascular bundles. J Oral Maxillofac Res. 2010. PMC3886037
Current as of October 2026. Schematics are simplified teaching drawings, not to scale. The quiz questions are original and are not real exam items.