This document discusses various extra oral radiographic techniques used in dentistry. It begins by defining extra oral radiography and medical radiography. It then describes several maxillofacial radiographic projections including true lateral skull, PA skull, PA jaws, oblique lateral mandible, and occipitomental views. It also discusses TMJ radiographic projections and recent advances in extra oral radiography such as tomography, panoramic radiographs, cephalometry, CT, CBCT, MRI, and their main indications.

1. DR NWAHAJIOKE CHINONSO
DENTAL DEPARTMENT,
UATH.

2.  Introduction
 Main maxillofacial Projections
 TMJ Radiographic Projections
 Recent advances in Extra Oral Radiography
-Tomography, Panoramic x-rays,
Cephalometry, CT, CBCT, MRI etc
 Conclusion
 References

3.  Medical radiography is an imaging technique
that uses x-rays or gamma rays (a form of
electromagnetic radiation) to view the internal
structures of the body. To create the image, a
beam of x-rays is produced by an x-ray
generator and is projected towards the body
onto a radiographic film.
 Extra oral radiographic examinations include
all views of the orofacial regions with films
positioned extraorally.

5. Most views are named according to the
direction the X-ray beam is travelling.
Head positioning is facilitated by the
radiographic baseline or the canthomeatal
line. This is a line from the outer canthus of
the eye to the ipsillateral external auditory
meatus.

6. These maxillofacial views include
 True lateral of the skull
 Posterior Anterior view of the skull (PA skull)
 Posterior Anterior view the jaws ( PA jaws)
 Oblique Lateral of the mandible
 Occipitomental views - Standard 0°, 30°, 45°,
28° OM Waters projection
 Submentovetex (SMV) – jug handle view

7. • This projection shows
the skull vault and facial
skeleton from the lateral
aspect. The main
difference between the
true lateral skull and the
true cephalometric lateral
skull taken on the
cephalostat is that the
true lateral skull is not
standardized or
reproducible.
• This view is used when a
single lateral view of the
skull is required but not
in orthodontics or growth
studies.

8. Main indications
• Fractures of the cranium and the cranial base •
Middle third facial fractures, to show possible
downward and backward displacement of the
maxillae
• Investigation of the frontal, sphenoidal and maxillary
sinuses
• Conditions affecting the skull vault, particularly:
— Paget's disease
— multiple myeloma
— hyperparathyroidism
• Conditions affecting the sella turcica, such as:
— tumor of the pituitary gland in acromegaly.

9. Technique and positioning
1. The patient is positioned with the head
turned through 90°, so the side of the face touches
the film. In this position, the sagittal plane of the
head is parallel to the film.
2. The X-ray tube head is positioned with the
central ray horizontal (0°) and perpendicular to
the sagittal plane and the film, centered through
the external auditory meatus .

12.  This projection shows
the skull vault,
primarily
 the frontal bones and
the jaws.

13. Main indications
• Fractures of the skull vault
• Investigation of the frontal sinuses
• Conditions affecting the cranium,
particularly:
— Paget's disease
— multiple myeloma
— hyperparathyroidism
• Intracranial calcification.

14. Technique and positioning
1. The patient is positioned facing the film with the
head tipped forwards so that the forehead and
tip of the nose touch the film — the so-called
forehead-nose position. The radiographic
baseline is horizontal and at right angles to the
film. This positioning levels off the base of the
skull and allows the vault of the skull to be seen
without superimposition.
2. The X-ray tube head is positioned with the
central ray horizontal (0°) centered through the
occiput .

17.  • This projection shows
the posterior parts of the
mandible.
 It is not suitable for
showing the facial
skeleton because of
superimposition of the
base of the skull and the
nasal bones.

18. Main indications
• Fractures of the mandible involving the
following sites:
— Posterior third of the body
— Angles
— Rami
— Low condylar necks
• Lesions such as cysts or tumors in the
posterior third of the body or rami to note any
medio-lateral expansion
• Mandibular hypoplasia or hyperplasia
• Maxillofacial deformities.

19. Technique and positioning
1. The patient is in exactly the same position as
for the PA skull, i.e. the head tipped forward,
the radiographic baseline horizontal and
perpendicular to the film in the forehead-nose
position.
2. The X-ray tube head is again horizontal (0°),
but now the central ray is centered through the
cervical spine at the level of the rami of the
mandible.

22.  Oblique lateral
radiograph of the
mandible is an extra
oral view of the jaw
that is produced when
the x-ray beam is
oblique to the sagittal
plane of the patient.

24. Main indications
• Assessment of the presence and/or position of
unerupted teeth
• Detection of fractures of the mandible
• Evaluation of lesions or conditions affecting
the jaws including cysts, tumours, giant cell lesions,
and osteodystrophies
• As an alternative when intraoral views are
unobtainable because of severe gagging or if
the patient is unable to open the mouth or is
unconscious
• As specific views of the salivary glands or
temporomandibular joint

25.  • This projection
shows the facial
skeleton and maxillary
antra., and avoids
superimposition of the
dense bones of the
base of the skull.

26. The main clinical indications include:
 Investigation of the maxillary antra
 Detecting the following middle third facial fractures:
— Le Fort I
— Le Fort II
— Le Fort III
— Zygomatic complex
— Naso-ethmoidal complex
— Orbital blow-out
—Coronoid process fractures
 • Investigation of the frontal and ethmoidal sinuses
 • Investigation of the sphenoidal sinus

27. Technique and positioning
1. The patient is positioned facing the film with
the head tipped back so the radiographic
baseline is at 45° to the film, the so-called
nose-chin position. This positioning drops
the dense bones of the base of the skull
downwards and raises the facial bones so
they can be seen.
2. The X-ray tube head is positioned with the
central ray horizontal (0°) centered through
the occiput .

30.  • This projection also
shows the facial
skeleton, but from a
different angle from
the 0° OM, enabling
certain bony
displacements to be
detected clearly.

31. Main indications
Detecting the following middle third facial
fractures:
 — Le Fort I
 — Le Fort II
 — Le Fort III
 • Coronoid process fractures.

32. Technique and positioning
1.The patient is in exactly the same position as
for the 0° OM, i.e. the head tipped back,
radiographic baseline at 45° to the film, in
the nose-chin position.
2. The X-ray tube head is aimed downwards
from above the head,
with the central ray at 30° to
the horizontal, centered through the lower
border of the orbit.

35.  37° OM (Water’s
projection)- commonly
taken by the ENT
surgeons to view the
sinuses. X-ray beam is
travelling from the
occipital region to the
mental region. With
maximum mouth
opening ensured by a
bite cork
 ,

37.  examination of the maxillary sinuses with
bilateral comparison
 Examination of depressed fracture of the
zygomatic bone.

38.  • This projection
shows the base of the
skull, sphenoidal
sinuses and facial
skeleton from below.

39. Main indications
• Destructive/expansive lesions affecting the
palate, pterygoid region or base of skull
• Investigation of the sphenoidal sinus
• Assessment of the thickness (medio-lateral)
of the posterior part of the mandible before
osteotomy
• Fracture of the Zygomatic arches

40. Technique and positioning 1
1. The patient is positioned facing away from the film. The
head is tipped backwards as far as is possible, so the
vertex of the skull touches the film. In this position, the
radiographic baseline, is vertical and parallel to the film.
2. The X-ray tube head is aimed upwards from below the
chin, with the central ray at 5° to the horizontal, centered
on an imaginary line joining the lower first molars .
Note: The head positioning required for this projection
means it is contraindicated in patients
with suspected neck injuries, especially suspected
fracture of the odontoid peg.

44. The main projections include:
• Transcranial view
• Transpharyngeal view
• Reverse Towne's view
•Transorbital view (rarely used)

45. Main indications
• TMJ pain dysfunction syndrome and internal
derangements of the joint producing pain,
clicking and limitation in opening
• To investigate the size and position of the disc
— this can only be inferred indirectly from the
relative positions of the bony elements of the
joints
• To investigate the range of movement in the
joints.

46. 1. The patient is placed in the craniotome
with the head rotated through 90°, so the TMJ
under investigation is touching the film and the
sagittal plane of the head is parallel to the film.
Initially the patient's mouth is closed while another
one is taken with the patient’s mouth open.
2. The X-ray tubehead is positioned with
the central ray aimed downwards at 25° to the
horizontal, across the cranium, centring through
the TMJ of interest

49. Main indications
 TMJ pain dysfunction syndrome
 To investigate the presence of joint disease,
particularly osteoarthritis and rheumatoid
arthritis
 To investigate pathological conditions
affecting the condylar head, including cysts
or tumours
 Fractures of the neck and head of the condyle

50. 1. The patient holds the cassette against the
side of the face over the TMJ of interest. The film
and the sagittal plane of the head are parallel. The
patient's mouth is open and a bite-block is
inserted for stability.
2. The X-ray tubehead is positioned in front of
the opposite condyle and beneath the zygomatic
arch. It is aimed through the sigmoid notch,
slightly posteriorly, across the pharynx at the
condyle under investigation. Usually this view is
taken of both condyles to allow comparison.

53.  This projection shows
the condylar heads and
necks. The original
Towne's view (an AP
projection) was designed
to show the occipital
region, but also showed
the condyles. However,
since all skull views used
in dentistry are taken
conventionally in the PA
direction, the reverse
Towne's (a PA projection)
is used

54. Main indications
• High fractures of the condylar necks
• Intra capsular fractures of the TMJ
• Investigation of the quality of the articular
surfaces of the condylar heads in TMJ
disorders
• Condylar hypoplasia or hyperplasia.

55. Technique and positioning
1. The patient is in the PA position, i.e. the
head tipped forwards in the forehead-nose
position, but in addition the mouth is open.
The radiographic baseline is horizontal and at
right angles to the film. Opening the mouth
takes the condylar heads out of the glenoid
fossae so they can be seen.
2. The X-ray tube head is aimed upwards from
below the occiput, with the central ray at 30° to
the horizontal, centered through the condyles.

58.  Over the past few years, a couple of other
extra oral radiological imaging techniques
and technologies have been introduced into
the clinical dental practice, and this has no
doubt greatly improved clinical investigation
and diagnosis

59. They include
 Cephalometric projections
 Panoramic X-rays (OPG)
 Tomography
 Sialograms
 Digital Imaging
 Computed Tomography (CT)
 Cone Beam Computed Tomography (CBCT)
 Magnetic Resonance Imaging (MRI)

60.  Introduced in 1931 by B. H. Broadbent
 This is a standardized and reproducible form of
skull X-ray
 Used extensively in orthodontics to assess the
relationship of the teeth to the jaws and the jaws
to the rest of the facial skeleton
 Made with a cephalostat that helps maintain a
constant relationship among the skull, the film
and the X-ray beam
Main radiographic projections include:
1. True cephalometric lateral skull
2. Cephalometric posterio-anterior (PA) of the
jaws

62.  The image receptor is parallel to the sagittal
plane of the patients head
 The X-ray beam is perpendicular to image
receptor and the sagittal plane
 used primarily in the important differential
diagnosis encompassing cephalometric
analysis.

64.  This is a standardized and reproducible form
of PA skull X-ray
 For documentation of skeletal asymmetries.
 For preoperative and post operative
comparison in orthognatic surgery involving
the mandible

66.  Initial diagnosis- confirmation of the under
lying skeletal and or soft tissue abnormalities
 to examine and clarify dysgnathias.
 treatment planning.
 accurate measurements of skeletal and
dentoalveolar relationships within the myriad
of different types of dysgnathias, and permits
precise classification
 Monitoring treatment progress , e.g to assess
anchorage requirements and incisor
inclination

67.  Preoperative evaluation of skeletal and soft
tissue patterns.
 To assist in treatment planning
 Postoperative appraisal of the results of
surgery and long –term follow –up studies.

68.  Specialized technique for producing radiographs
showing only a section or slice or tomograph of a
patient
 Each tomograph shows the tissues within that
section sharply defined and in focus.
 This section is referred to as focal plane or focal
trough
 Production requires controlled, accurate
movement of both the X-ray tube head and the
film during exposure.
 This form the basis of most of the modern
imaging modalities such as OPG, CT, CBCT, MRI

69.  a – linear, b – circular, c – elliptical,
d – hypocycloidal, e - spiral

70.  Also panthomography ,ortho-pantography
(OPG) or panoramic tomography
 Technique for producing a single
tomographic image of the facial structures
that includes both the maxillary and
mandibular dental arches and their
supporting structures
 X-ray source and film holder move clockwise
around the approximately elliptically shaped
dental arches.

74.  Diagnostic problem requiring broad coverage
of the jaws.
 As initial evaluation image that can provide
the required insight or assist in determining
the need for other projections.
 For patients who do not tolerate intra oral
projections well.
 For forensic dentistry – identification, age
determination.

75.  A large area is imaged and all the tissues
within the focal trough are displayed,
including the anterior teeth, even when the
patients is unable to open the mouth.
 The image is easy for patients to understand,
and is therefore a useful teaching aid.
 Positioning is relatively simple and minimal
expertise is required.
 The overall view of the jaws allows rapid
assessment of any underling , possibly
unsuspected, disease.

76.  The tomographic image represents only a
section of the patient. Structures or abnomalities
not in the focal trough may not be evident.
 Soft tissue and air shadows can overlie the
required hard tissue structures.
 Ghost or artefactual shadows can overlie the
structures in the focal trough.
 The tomographic movement together with the
distance between the focal trough and image
receptor produce distortion and magnification of
the final image.

77.  A sialogram is a contrast study performed to
diagnose blockage of the salivary flow due to
stones or strictures in the salivary gland duct.
This examination is done by introducing a
very thin tube into the gland duct opening
and injecting a small amount of a
radiographic dye before a radiograph is
taken.

79.  Digital dental radiography is a type of X-ray
imaging that uses digital X-ray sensors to
replace traditional photographic X-ray film,
producing enhanced computer images of teeth,
gums and other oral structures and conditions
 The images can be enhanced, enlarged, stored or
printed. It can also be sent electronically to
another dentist or a specialist.
 Digital imaging uses less radiation than X-rays

81.  CT is today commonly used in the imaging of the
maxillofacial area. However, a relatively new
technique named Cone- Beam Computed
Tomography (CBCT) or Digital Volume Tomography
(DVT) has now become available for dental purposes.
 The major difference between a CT and a CBCT is the
way the images are taken, while the CBCT machine
rotates around the patients head capturing all the
data in a single rotation, the CT scan collects thin
slices of images as the machine makes several
revolutions around the patient’s head.
 The advantage with this technique is a lower radiation
dose compared to conventional CT

84.  Diagnosing the position of impacted canines and
suspected root resorption of the adjacent lateral
incisor.
 Preoperative planning of implant treatment and
examination of periapical areas when intraoral
radiography has given uncertain information
 Other indications include dentoalveolar traumata,
TMJ problems, cystic lesions and tumours, in
general, all types of problems for which 3
dimentional information is of essence

85.  A non-erupted lower
molar has caused
extensive reorption of
the distal root of the
adjacent 2nd molar. A
volume rendered image
with some of the thinner,
marginal bone digitally
removed shows the
position of the 3rd molar
underneath the distal
part of the crown

86.  A coronal CT view
shows a small blow-
out fracture of the left
orbiatal floor. The
inferior rectal muscle
has herniated into the
left antrum

87.  An MRI scan is a radiological technique that
uses magnetism, radio waves and a computer
to produce images of body structures. It is
excellent in investigation of soft tissues and
soft tissue lesions.

89.  All radiological examinations must be based
on clinical information and relevant clinical
questions that should be answered. A useful
investigation is one in which the result-
positive or negative- will alter patient
management or add confidence to the clinical
diagnosis.

91.  Eric Whaites;Essentials of Dental Radiography
and Radiology; 3rd Edition; Churchhill
Livingstone, 2002
 Dr Olutayo James; Extra Oral Radiography
Presentation
 Arne Peterson, Hans- Goman; Computed
Tomography in oral and maxillofacial
Radiology; Tidende, 2009
 https://my.clevelandclinic.org/health/articles
/typesofdental-x-rays