Anatomy
& Radiology
Radiographic questions surface across nearly every chapter. The exam isn't testing whether you know the structure exists — it's testing whether you can see it on the right side of a panoramic, name it, and tell it from its lookalikes.
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Cross-cutting
01
Panoramic Anatomy — the 5 Sets
A panoramic film is read top-down: skull base → orbits → maxilla → sinuses → mandible → cervical spine. Booster Prep groups structures into five overlapping sets so the exam can ask "identify" from any region.
Panoramic schematic — key landmarks
1 Condyle
2 Coronoid
3 Max sinus
4 Hard palate
5 Mental foramen
6 IAN canal
7 Cervical spine
The five PAN sets — full structure list
PAN #1
Posterior Skull Base · Sinus · Mandibular Border
- Condyle
- Coronoid process
- Zygomatic process of maxilla
- Hyoid bone
- Maxillary sinus
- Tuberosity
- Incisive foramen
- Ghost image (contralateral mandibular border)
- Mental foramen
PAN #2
Orbit · Zygoma · Soft Palate · Cervical Spine
- Lateral border of orbit
- Zygomaticotemporal suture
- Inferior border of zygomatic arch
- Styloid process
- Hamulus
- Infraorbital ridge
- Middle cranial fossa
- Pterygomaxillary fissure
- Soft palate
- Uvula
- Cervical vertebrae
PAN #3
Mid-face · Nasal Cavity
- External auditory meatus
- Articular eminence
- Nasal fossae
- Nasal septum
- Inferior concha
- Anterior nasal spine
- Pterygoid plate
PAN #4
Hard Palate · Mandibular Canal · Glands
- Infraorbital canal & foramen
- Hard palate
- Tongue
- Mandibular canal & foramen
- Sigmoid notch
- Submandibular gland fossa
PAN #5
Air Spaces · Mandibular Midline
- Nasopharyngeal air space
- Palatoglossal air space
- Glossopharyngeal air space
- Posterior pharyngeal wall
- Ear lobe
- Mental fossa
- Mental ridge
- Genial tubercles
Misc.
Frequent confusables
- Pterygomaxillary fissure — teardrop radiolucency posterior to maxillary tuberosity
- Hamular process — hook-shaped radiopaque projection posterior to tuberosity
- Lingual foramen — small radiolucent dot at mandibular midline
- Nutrient canals — small alveolar channels for vessels/nerves
- Focal osteoporotic marrow defect — benign hematopoietic radiolucency
M
Memory Hook · "Top-to-bottom scanner"
Always read PAN top-down: skull base → orbits → maxilla → sinuses → mandible → cervical spine. Recognise from shape + location, not just name.
!
Trap · Ghost images
Faint blurred shadow on the opposite side of where it actually is, projected upward. Most commonly seen as a contralateral mandibular border ghost. Don't confuse with real anatomy.
02
Radiopaque vs Radiolucent
First step on every "what is shown" question — classify the lesion by density. Then narrow by location and borders.
Radiopaque (white on film)
Bone-dense or calcified
- Calculus — root surface deposit
- Hypercementosis — bulbous root
- Idiopathic osteosclerosis / dense bone island
- Enamel pearl — round at furcation
- Torus palatinus / mandibularis
- Pindborg tumour — mixed (calcifications)
- Cemento-osseous dysplasia (mature)
- Fibrous dysplasia — ground-glass
- Osteopetrosis — generalised ↑ density
Radiolucent (dark on film)
Soft-tissue or destructive
- Caries — enamel/dentin
- Periapical abscess / apical periodontitis (PARL)
- Furcation radiolucency
- Antral pseudocyst — sinus floor dome
- Stafne defect — below IAN canal
- Odontogenic keratocyst (OKC) — well-defined
- Ameloblastoma — multilocular "soap-bubble"
- Odontogenic myxoma — "honeycomb"
- Central giant cell lesion — multilocular
✓
Key · Mixed lesions exist
Pindborg tumour, cemento-ossifying fibroma, and cemento-osseous dysplasia are all mixed radiolucent + radiopaque. Don't dismiss "mixed" as an option in the multi-MCQ.
03
Common Radiographic Findings
Everyday "what is shown" findings on bitewings, periapicals, and panoramics.
| Finding | Recognition |
|---|---|
| Dental caries | Radiolucency in enamel/dentin/cementum, may approach pulp |
| Calculus | Radiopaque deposit on root surface, especially interproximal |
| Attrition | Tooth wear from tooth-on-tooth contact (occlusal/incisal) |
| Pericoronitis | Inflammation around partially erupted tooth — pocket/space around impacted crown |
| Post-extraction socket | Empty socket with possible bony fragments |
| Retained root | Root remnant in alveolar bone post-extraction |
| Furcation radiolucency | Radiolucency in furcation of multi-rooted tooth |
| Horizontal root fracture | Linear radiolucent line across root |
| Ectopic eruption | Tooth erupts in abnormal position or pathway |
| Postsurgical defect / scar | Irregular radiolucency with well-defined margins, no progression |
| Apical scar | Benign fibrous healing at apex after endo or surgery |
| Osteodentin cap | Reparative hard tissue barrier over exposed pulp |
| Ankylosis / infraocclusion | Tooth fused to alveolar bone, obliterated PDL |
| Widening of PDL space | ↑ radiolucent space around root |
| Widening of apical PDL | ↑ radiolucency at root apex (early apical pathology) |
| Antral pseudocyst | Dome-shaped radiolucency on max sinus floor, no corticated border |
| Antral mucositis | Radiographic thickening of max sinus mucosal lining |
| Hypercementosis | Bulbous root enlargement with intact PDL |
| Idiopathic osteosclerosis | Localized radiopaque area, no clinical significance |
04
Developmental & Anatomic Variations
Variants that look pathological but aren't. The exam tests these because students treat them.
| Variation | Description |
|---|---|
| Dens invaginatus | Enamel folds inward into dentin — "tooth within a tooth" |
| Dens evaginatus | Outward enamel/dentin projection — extra cusp |
| Macrodontia | One or more teeth significantly larger than normal |
| Microdontia | One or more teeth significantly smaller than normal |
| Geminization | Single tooth germ splits — two crowns share one root canal |
| Fusion | Two separate germs join — two root canals |
| Concrescence | Teeth joined by cementum only (post-development) |
| Dilaceration | Sharp bend or abnormal curvature of root |
| Taurodontism | Enlarged pulp chamber, apically displaced furcation ("bull-like") |
| Enamel pearl | Small round radiopacity on root surface near furcation |
| Physiologic root resorption | Resorption of primary roots due to erupting permanents |
| Developing tooth follicle | Well-defined radiolucency around crown of unerupted tooth |
| Accessory roots | Extra root, otherwise normal tooth |
| Stafne bone defect | Radiolucency below IAN canal — submandibular gland concavity |
| Pneumatization of max sinus | Sinus expansion into alveolar bone after extraction |
| Transposition | Tooth erupts in another tooth's position |
| Torus | Dense bony growth on palate (palatinus) or lingual mandible (mandibularis) |
| Regional odontodysplasia | Localized "ghost-like" teeth — thin enamel/dentin, large pulp |
| Supraeruption | Overeruption due to lack of opposing occlusion |
| Supernumerary teeth | Extra tooth beyond normal count — mesiodens classic |
| Hypodontia | Congenital absence of one or more teeth |
| Exostosis / Tori | Localized bony outgrowth on alveolar process |
M
Memory Hook · The 3 G/F/C trio
Geminization = "Germ Gets Groovy" — one germ splits, one root canal.
Fusion = "For Friends Fusing" — two germs unite, two root canals.
Concrescence = "Cementum Connects Crowns".
05
Pathologies, Cysts & Tumours
High-yield differentials. The exam likes to give a multilocular radiolucency in the posterior mandible and ask you to pick from the soap-bubble lesions.
Systemic conditions & bone disorders
| Condition | Radiographic features |
|---|---|
| Fibrous dysplasia | Ill-defined radiopacity with ground-glass appearance, bone expansion |
| Osteopetrosis | Generalized ↑ bone density with loss of marrow spaces |
| Florid cemento-osseous dysplasia | Multiple radiopaque lesions with radiolucent borders, several quadrants |
| Osteomyelitis | Ill-defined radiolucent + radiopaque lesion, moth-eaten appearance |
| Periapical cemento-osseous dysplasia | RL → RO at apex of vital teeth |
| MRONJ | Ill-defined RL/RO with bone destruction + sequestra (bisphosphonates) |
| Hyperparathyroidism | Generalized bone loss + loss of lamina dura · "brown tumours" |
| Cherubism | Bilateral multilocular radiolucencies in posterior mandible, childhood |
| Gardner syndrome (FAP) | Multiple osteomas + impacted/supernumerary teeth |
| Ectodermal dysplasia | Multiple missing teeth + conical-shaped teeth |
| Gorlin syndrome (NBCCS) | Multiple OKCs + basal cell carcinomas |
| Cleidocranial dysplasia | Multiple impacted & supernumerary teeth, delayed eruption |
| Neurofibromatosis | Multiple neurofibromas · widened mandibular canal/foramen · café-au-lait |
Cysts & tumours
| Lesion | Recognition |
|---|---|
| Ameloblastoma | Multilocular RL with large "soap-bubble" loculations · expansion · root resorption |
| Pindborg (CEOT) | Mixed RL-RO with scattered calcifications |
| Ameloblastic fibroma | Well-defined unilocular RL · associated with unerupted tooth · young patients |
| Cemento-ossifying fibroma | Well-defined mixed RL-RO · jaw expansion |
| Odontogenic keratocyst (OKC) | Well-defined RL · grows along jaw with minimal expansion |
| AOT (Adenomatoid Odontogenic Tumour) | Well-defined RL with scattered calcifications · "two-thirds rule": 2/3 anterior, 2/3 maxilla, 2/3 female, 2/3 around impacted canine |
| Odontogenic myxoma | Multilocular RL · "soap-bubble" or "honeycomb" |
| Central giant cell lesion | Multilocular RL · bone expansion · often anterior to first molar |
The "soap-bubble" trio
Ameloblastoma
Posterior mandible · expansile · root resorption · adults
Odontogenic Myxoma
Honeycomb · posterior mandible · slower-growing
Central Giant Cell Lesion
Anterior to first molar · expansion · younger patients
!
Trap · Periapical cemento-osseous dysplasia mimics PARL
— but the tooth is vital. Don't suggest RCT. Always check vitality before treating "apical pathology."
✓
Key · Multiple impacted teeth differentials
Cleidocranial dysplasia · Gardner syndrome (FAP). Both feature supernumerary or impacted teeth as a hallmark.