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Radiology — Occipitomental Skull Projection
Waters View
Dental Radiology · Extraoral / Skull Projections
Calculating…
Maxillary Sinuses
Orbital Floor Fractures
Occipitomental View
Facial Trauma
TL;DR
The Waters view is the cornerstone extraoral radiographic projection for visualising the maxillary sinuses and middle third of the facial skeleton — achieved by a simple but critical head tilt that clears the petrous ridges from the sinus floors.
- The Waters view (occipitomental view, OM view) is an extraoral radiographic projection in which the beam passes posteroanteriorly with the patient’s head extended so the chin is raised, projecting the maxillary sinuses below the petrous temporal ridges for clear visualisation
- It is the single most useful plain film view for assessing the maxillary sinuses — detecting fluid levels, opacification, mucosal thickening, mass lesions, and traumatic changes
- The Waters view is the primary projection for suspected orbital floor “blowout” fractures — the most common orbital fracture pattern following direct orbital trauma
- Positioning: the patient faces the receptor with the chin resting on it (or near it), the nose approximately 1–2 cm from the receptor surface; the orbitomeatal line (OML) is angled at approximately 45° to the receptor; the beam is directed straight posteroanteriorly (horizontally)
- It was described by Charles Alexander Waters in 1915 and remains the standard first-line plain film view for facial and sinus trauma worldwide
Key Facts
Category
Dental Radiology — Extraoral / Skull Projections
Also Known As
Occipitomental (OM) view; occipitomental projection; OM 30°
Beam Direction
Posteroanterior (PA), horizontal (or slightly caudal)
Primary Indication
Maxillary sinus assessment; orbital floor fractures; middle third facial fractures
What Is It?
The Waters view — formally known as the occipitomental (OM) projection — is a posteroanterior radiographic projection of the facial skeleton in which the patient’s head is tilted back so the chin is elevated and the orbitomeatal line (OML) makes approximately a 45° angle with the receptor surface. This head tilt causes the dense petrous ridges of the temporal bone — which would otherwise overlie the maxillary sinuses — to project downward below the sinus floors, leaving the maxillary sinuses clearly visible.
The technique was described by Dr Charles Alexander Waters in 1915 as a dedicated method for imaging the maxillary sinuses and remains, over a century later, the most widely used and most clinically informative plain film projection for the paranasal sinuses, the orbital floors, and the middle third of the facial skeleton.
Why It Matters
The maxillary sinuses are among the most clinically significant anatomical structures in dentistry and oral and maxillofacial surgery. Their proximity to the posterior maxillary teeth, their role in facial trauma patterns, and their susceptibility to inflammatory disease all make reliable plain film assessment essential in both routine and emergency clinical settings.
Clinical Relevance
- Maxillary sinusitis: the Waters view is the definitive plain film for assessing the maxillary sinuses for air-fluid levels (suggesting acute sinusitis), complete opacification (chronic sinusitis or mass), or mucosal thickening (chronic inflammatory change).
- Orbital floor fractures: a direct blow to the eye increases intraorbital pressure, which fractures the thin orbital floor (blowout fracture) — the inferior rectus muscle and orbital fat herniate into the maxillary sinus. The Waters view shows the classic “teardrop sign” — a teardrop-shaped soft tissue mass hanging from the orbital floor into the maxillary sinus.
- Middle third facial fractures (Le Fort fractures): Le Fort I, II, and III fractures all involve the maxillary sinuses to varying degrees. The Waters view is the primary plain film view for Le Fort fracture assessment, though CT has become the gold standard for surgical planning.
- Zygomatic fractures: the body of the zygoma and the infraorbital rim are visible. Disruption of the orbital margin, fluid in the maxillary sinus (haemosinus), and lateral orbital wall involvement can all be detected.
- Dental-sinus relationships: the pneumatised floor of the maxillary sinus lies in close proximity to the roots of the upper premolars and molars — the Waters view can demonstrate root tips projecting into the sinus, oro-antral communications, or sinusitis of dental origin.
Technique & Positioning
Correct positioning is the single most important determinant of image quality for the Waters view. Insufficient head tilt is the most common positioning error and renders the image diagnostically inadequate by allowing the petrous ridges to overlie the maxillary sinuses.
- Explain the procedure to the patient; remove jewellery, glasses, and removable dental prostheses
- The patient faces the receptor (receptor against the face — posteroanterior direction)
- The patient tilts the head back (extends the neck) so the chin is raised and rests on the receptor surface — or is positioned approximately 1–2 cm from the receptor for digital systems
- Correct head tilt: the orbitomeatal line (from outer canthus of the eye to the centre of the external auditory meatus) should make approximately a 45° angle with the receptor surface. This brings the petrous ridges below the maxillary sinus floors.
- The midsagittal plane must be perpendicular to the receptor surface and centred horizontally — essential for bilateral symmetry
- The nose should be approximately 1.5–2 cm from the receptor (chin on receptor, nose away from it due to head tilt)
- The X-ray tube is positioned posteriorly (behind the patient’s head); the central ray is directed horizontally (perpendicular to the receptor) — or with a very slight caudal tilt of 5° in some protocols
- Centre the beam at the level of the lower orbital rims / upper teeth
- Expose; typical kVp: 70–80 kVp; mAs appropriate for facial skeleton penetration
Variation — OM 30° (Modified Waters)
- Head tilt is reduced to make the OML approximately 30° (rather than 45°) to the receptor
- This brings the zygomatic arches and orbital rims into a slightly different projection
- Some radiologists use both the standard OM (45°) and the OM 30° as a series for comprehensive facial assessment
- OM 30°: inferior orbital rims, zygomatic arches, and temporal bones better visualised
- OM 45° (standard Waters): maxillary sinuses optimally projected
Positioning Note
The critical positioning requirement: the petrous ridges MUST project below the maxillary sinus floors. If the patient’s chin is not tilted back enough (insufficient OML tilt), the petrous ridges will overlie the sinuses and obscure the diagnostic image. A well-positioned Waters view has the petrous ridges projected below the antral floors.
Radiographic Anatomy Visible on the Waters View
Understanding the normal anatomy visible on a Waters view is essential for recognising pathological change. The following table summarises the key structures and their clinical significance.
| Structure | Radiographic Appearance | Clinical Significance |
|---|---|---|
| Maxillary sinuses (antral) | Large bilateral radiolucent air spaces below orbits | Fluid level, opacification, mucosal thickening — sinusitis; mass; haemosinus |
| Orbital floors | Thin radiopaque line at inferior orbital margin | Blowout fractures; step deformities; teardrop sign |
| Orbital rims (inferior) | Radiopaque curved lines bounding the orbits inferiorly | Fractures; disruption; Le Fort II fractures |
| Nasal cavity and septum | Midline radiolucent space; septum = thin radiopaque line | Septal deviation; turbinate hypertrophy |
| Frontal sinuses | Bilateral radiolucent spaces above orbits | Opacification; fractures (partially visible) |
| Ethmoid sinuses | Medial orbital wall region | Opacification in pansinusitis; orbital cellulitis |
| Zygomatic body | Curved radiopaque structure at lateral orbit | Zygomatic fractures; soft tissue swelling |
| Infraorbital foramen | Small radiolucency below orbit | Normal structure; infraorbital nerve |
| Hard palate | Radiopaque arch visible inferiorly | Reference structure |
| Petrous ridges | Dense ridges — projected BELOW sinus floors in correct positioning | If above sinus floor → inadequate head tilt (reposition) |
Clinical Applications in Detail
Maxillary Sinusitis
- Acute: air-fluid level (horizontal radiolucent-to-opaque interface in the sinus — the patient must be imaged upright for this to be visible). Mucosal thickening ≥6 mm. Opacification.
- Chronic: complete or near-complete opacification. Loss of scalloped mucosal pattern. May have bony changes.
- Dental sinusitis (odontogenic sinusitis): infection of dental origin extending into the maxillary sinus. Radiographic signs: unilateral sinus opacification or thickening; periapical pathology of adjacent upper molar/premolar roots; disruption of sinus floor cortication.
Orbital Floor (Blowout) Fracture
- Mechanism: direct blow to the orbit increases intraorbital pressure → thin orbital floor fractures into the maxillary sinus below. Contents (fat, inferior rectus muscle) herniate inferiorly.
- Classic sign on Waters view: “teardrop sign” — a teardrop-shaped soft tissue density hanging from the roof of the maxillary sinus, representing herniated orbital fat/inferior rectus.
- Additional signs: opacification of the superior maxillary sinus, disruption of the orbital floor line, enophthalmos (sunken eye clinically), diplopia (inferior rectus entrapment).
- Limitation: plain film may underestimate fracture extent. CT is required for surgical planning.
Le Fort Fractures (Overview on Waters View)
- Le Fort I: horizontal fracture above the teeth through the maxillary walls. Maxillary sinus walls disrupted. Palate/alveolus detached.
- Le Fort II: pyramidal fracture through the orbital floors, infraorbital rims, nasal bones, and lower pterygoid plates. “Floating maxilla.” Best seen on Waters — bilateral disruption of orbital floors and maxillary sinus walls.
- Le Fort III: craniofacial dysjunction — entire face separates from cranial base. Zygomatic arches, orbital walls, nasal bones all fractured. Waters view shows massive bilateral soft tissue swelling, opacified sinuses, disrupted orbital margins.
- Important: Le Fort fractures are clinical diagnoses confirmed by CT. The Waters view is the first-line plain film screening tool.
Clinical Warning
An air-fluid level in the maxillary sinus is ONLY visible if the patient is imaged upright (sitting or standing). A supine or head-tilted patient will have the fluid distribute along the sinus walls, appearing as generalised mucosal thickening rather than a discrete horizontal level. Always ensure the patient is upright before taking the Waters view for sinus assessment.
Clinical Considerations
- Haemosinus: blood in the maxillary sinus following trauma appears as opacification (the sinus is filled with blood). This is one of the most reliable plain film signs of a Le Fort or zygomatic fracture even when bony fracture lines are not visible.
- Dental-sinus relationship: the roots of the maxillary second premolar, first molar, and second molar are in close proximity to the floor of the maxillary sinus. Periapical pathology of these teeth can cause dental sinusitis. The Waters view can show the relationship between root apices and the sinus floor, though CBCT provides far more detail.
- Retention cyst: a dome-shaped soft tissue density arising from the sinus floor — represents a mucous retention cyst. Not clinically significant unless large. Must be differentiated from a polyp, mucous membrane cyst, or tumour by size, location, and clinical history.
- Unilateral sinus opacification: always suspicious in the absence of acute infection. Must be investigated for tumour (squamous cell carcinoma, adenocarcinoma, inverted papilloma) or cyst. CT/MRI is required.
- Symmetry assessment: the two maxillary sinuses should appear approximately equal in size and lucency. Asymmetric opacification or differing sinus volumes may indicate chronic unilateral disease or developmental variation.
Common Mistakes & Misconceptions
These are frequently tested misconceptions in INBDE-level assessments and common errors in clinical practice.
-
Misconception: “The Waters view can be taken with the patient supine to detect an air-fluid level.”
Correction: Air-fluid levels are only visible when the patient is upright (sitting or standing). In the supine position, fluid distributes evenly along the dependent wall and appears as generalised thickening — not a discrete horizontal level. Upright positioning is mandatory for air-fluid level assessment. -
Misconception: “The Waters view is the same as the posteroanterior (PA) skull view.”
Correction: In the PA skull view, the patient’s forehead and nose are against the receptor with the OML approximately perpendicular to the receptor — the petrous ridges overlie the maxillary sinuses. In the Waters view, the chin is elevated so the OML is at ~45° to the receptor — this projects the petrous ridges below the sinuses. The head tilt is the critical difference. -
Misconception: “A normal Waters view excludes a maxillary sinus tumour.”
Correction: Early or small sinus tumours may not produce visible radiographic change on a Waters view. CT and MRI are required for sinus mass assessment. A normal Waters view does not exclude malignancy. -
Misconception: “The teardrop sign in the Waters view always indicates orbital floor fracture.”
Correction: A teardrop-shaped opacity in the maxillary sinus most commonly represents a herniated orbital floor fracture, but can also be caused by a mucous retention cyst, polyp, or inspissated secretions. Clinical correlation (trauma history, diplopia, enophthalmos, diplopia on upward gaze) is essential. -
Misconception: “The Waters view is adequate for surgical planning of facial fractures.”
Correction: The Waters view is an excellent first-line screening view for maxillary sinus, orbital floor, and Le Fort fractures. However, CT with multiplanar reconstruction is required for accurate fracture characterisation and surgical planning in virtually all facial fracture cases.
Related Topics
The Waters view sits within a broader family of extraoral radiographic projections and is closely related to several key clinical areas in dental radiology.
References & Sources
The following foundational texts and peer-reviewed sources inform this article.
- White SC & Pharoah MJ, 2014. Oral Radiology: Principles and Interpretation. 7th ed. Elsevier Mosby.
- Whaites E & Drage N, 2013. Essentials of Dental Radiography and Radiology. 5th ed. Churchill Livingstone.
- Waters CA, 1915. A modification of the occipito-frontal position in the radiography of the accessory nasal sinuses. Archives of Radiology and Electrotherapy, 20:15–17.
- Manson PN, Markowitz B, Mirvis S et al., 1990. Toward CT-based facial fracture treatment. Plastic and Reconstructive Surgery, 85(2):202–212.
- Langland OE, Langlais RP & Preece JW, 2002. Principles of Dental Imaging. 2nd ed. Lippincott Williams & Wilkins.
Summary
The Waters view (occipitomental projection) is the cornerstone plain film projection for the paranasal sinuses and mid-face. Its unique value lies in a deceptively simple positioning manoeuvre — elevating the patient’s chin to tilt the orbitomeatal line to approximately 45° — which projects the dense petrous ridges of the temporal bone below the maxillary sinus floors, rendering those sinuses clearly visible on the radiograph. No other single plain film view achieves this degree of diagnostic utility for the maxillary sinuses and middle third facial skeleton simultaneously.
Despite the widespread adoption of CT for definitive facial fracture characterisation and sinus assessment, the Waters view retains a vital role as an accessible, low-dose, first-line screening tool — particularly in emergency and resource-limited settings. It frequently provides the initial diagnosis of sinusitis, orbital floor fracture, and Le Fort-pattern injuries before CT is available or indicated.
Key Takeaways
- Defining feature: The Waters view (occipitomental projection) projects the maxillary sinuses clear of the petrous ridges by tilting the patient’s chin upward ~45° — making it the best plain film view for maxillary sinus and orbital floor assessment.
- Primary indications: Maxillary sinusitis (air-fluid level, opacification), orbital floor blowout fractures (teardrop sign), and middle third facial fractures (Le Fort I, II, III).
- The teardrop sign: a soft tissue teardrop density hanging from the orbital floor into the maxillary sinus is the classic radiographic sign of an orbital floor blowout fracture.
- Upright positioning is mandatory: Air-fluid levels are only visible in an upright patient — always ensure the patient is sitting or standing before taking the Waters view for sinus assessment.
- Screening, not definitive: Although CT is the definitive investigation for facial fractures and sinus masses, the Waters view remains an accessible, low-dose, first-line screening tool that often provides the initial diagnosis in the emergency setting.
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