extra oral radiography

1. EXTRA-ORALEXTRA-ORAL
RADIOGRAPHYRADIOGRAPHY
BY BHUPENDER SINGH NEGIBY BHUPENDER SINGH NEGI (MDS 3RD
)
Guided by:-
Dr.Anita Balan
Prof.& H.O.D.
Department Of Oral Medicine &Radiology
Government Dental College, Calicut.

2. Extra oral radiography means that the source as well as film
are placed outside the mouth & an exposure is made in order
to obtain the images on an recording medium.
INTRODUCTIONINTRODUCTION

3. INDICATIONSINDICATIONS
 When it is not possible to place the film intraorally as during trismus,
gagging, loss of consciousness or unco-operative patient.
 To examine the extent of large lesions, especially when the area of
pathology is greater than which cannot be covered by an intraoral
periapical film.
 When jaws or other facial bones have to be examined for evidence of
disease lesions and other pathological conditions.
 To evaluate skeletal growth and development and its disorders.

4.  Pre-operative, intra-operative and post-operative assessment in
orthodontics, orthognathic surgery and implantology.
 To study skull bones for concomitant involvement by disease.
 To evaluate the status of impacted teeth.
 To evaluate temporomandibular joint area and its disorders.
 To detect and assess involvement of jaws by metastasis lesions.
 To study diseases of maxillary sinuses.
 To detect and study extent and nature of oral and maxillo-facial
trauma.

5. DRAWBACKSDRAWBACKS
 Magnification occurs due to the greater object to film distance
used.
 Details are not well-defined due to the use of cassettes and
intensifying screens. For optimum balance between loss of image
detail and reduction of patient exposure medium or high speed
screen film combinations should be used.
 Contrast is reduced as the secondary radiation produced by the
soft tissues is more.

6. Extraoral Landmarks used for PatientExtraoral Landmarks used for Patient
PositioningPositioning
 The Median Plane of the Head: (Midsagittal Plane)
The Infraorbital Line:
The Orbitomeatal Line (Canthomeatal Line):
The Frankfort Horizontal Line:

7. PATIENT PROCEDUREPATIENT PROCEDURE
Explain the radiographic procedure to be performed.
Remove all objects from the head and neck region.
Place lead apron without thyroid collar, lead apron must be
placed low around the back of the neck so that it does not
block the X-ray beam.
The patient must remove eyeglasses, earrings, necklaces,
hearing aids, hairpins and CD/RPD.

8. EXTRAORAL RADIOGRPAHIC PROJECTIONS CAN BEEXTRAORAL RADIOGRPAHIC PROJECTIONS CAN BE
CATEGORIZED INTO:CATEGORIZED INTO:
A)A)Panoramic Imaging:Panoramic Imaging:
B) Posterioanterior Projection:B) Posterioanterior Projection: (also known as occipito
frontal projection of Nasal Sinuses)
 Posterior anteriorPosterior anterior (Granger projection)
 Modified method, inclined Posterior anteriorModified method, inclined Posterior anterior
( Caldwell projection)

9. Radiography of the SkullRadiography of the Skull
 Lateral cephalogram
 True lateral
 PA cephaloaram
 PA Skull
 Towne’s projection

10. Radiography of the Maxillary Sinuses:Radiography of the Maxillary Sinuses:
 Standard Occipitomental projection ( 0 OM)
 Modified method ( 30 OM)
 PA Water’s
 Bregma menton

11. Radiography of the Mandible:Radiography of the Mandible:
 PA Mandible
 Rotated PA Mandible
 Lateral Oblique
 Anterior body of mandible
 Posterior body of mandible
 Ramus of mandible

12. Radiography of Base of the Skull:Radiography of Base of the Skull:
 Submento Vertex projection
Radiography of the Zygomatic ArchesRadiography of the Zygomatic Arches
 Jughandle view (A Modification of submento vertex
view)

13. Radiography of the Temporomandibular JointRadiography of the Temporomandibular Joint
 Transcranial Projection
 Trans Pharyngeal Projection
 Trans Orbital Projection
 Reverse Towne's Projection

14. POSTERIOANTERIOR PROJECTION:POSTERIOANTERIOR PROJECTION:
Indications:
 To examine the skull for disease in trauma or
developmental abnormalities in frontal,
temporal and parietal bone.
 Provides a good record to detect progressive
changes in the mediolateral dimensions of skull,
including asymmetric growth.
 For visualization of facial structures including
the frontal and ethmoidal sinuses, nasal fossae
and orbits

15. Film placement : The cassette is
positioned vertically in a holding device.
Head position: Canthomeatal line
parallel to the floor. For cephalometric
applications the nose should be a little
higher so that the anterior projection of the
canthomeatal line is 10 degrees above the
horizontal plane and Frankfort plane is
perpendicular to the film.

16. Projection of central ray:
Coincident with the midsagittal plane at the level of the bridge of the
nose.
Exposure parameter:
kvp : 84, mA : 13, sec.-1.5.

17. Modified method, inclined Posterior anterior
( Caldwell projection)
 This angulation will cause the petrous ridges to be superimposed on the
maxillary sinuses, thus allowing the accurate examination of the orbits
& ethomidal air cells.
Film placement: The cassette is positioned vertically in a holding
device.
Position of the Patient: The midsagittal plane is vertical and
perpendicular to the cassette. Canthomeatal line is perpendicular to the
cassette.

18. Central Ray:
 Is directed to the 23 to the canthometal line,
entering the skull about 3 cm above the
external occipital protuberance & exiting at
glabella.
Exposure parameters:
 kvp : 70-80 , mA :- 60 to 80 sec. :- 1.6(Bucky
grid.)

19. LATERAL SKULL PROJECTION (LATERALLATERAL SKULL PROJECTION (LATERAL
CEPHALOMETRIC PROJECTIONCEPHALOMETRIC PROJECTION
 To survey the skull and facial bones for evidence
of trauma, disease, or developmental
abnormality.
 Nasopharyngeal soft tissues, paranasal sinuses,
hard palate.
 In orthodontics, to assess facial growth,
pretreatment and post treatment records.
 Conditions affecting the sella turcica such as
tumor of the pituitary gland in acromegaly
 The lateral cephalometric projection reveals the
facial soft tissue profile.

20. Film placement :
Head position:
 Left side of the face near the
cassette and midsagittal plane
parallel to the plane of the film.
 For cephalometric projection:
patient is positioned with in the
cephalostat with the sagittal plane
of the head vertical and parallel to
the film.
 FH plane horizontal

21. Teeth should be in maximum intercuspation
Head is immobilized with plastic ear rods
Wedge filter is placed – absorb some of the radiation in the
anterior region and helps to reveal the soft tissue outlines
Lateral skull projection: cephalostat are not placed and
wedge filter is removed

22. Projection of Central ray
 Distance between the X-ray source and
midsagittal plane is 36-40 inches.
 Central ray is directed toward the
external auditory meatus
 Perpendicular to the film and the
midsagittal plane
Exposure parameter:
kvp of 70-80, mA :- 60-50. sec. :-1.6
(Bucky grid).

23. Water’s ViewWater’s View
 Occipitomental view.
 It is particularly useful for evaluating
maxillary sinuses.
 In addition frontal and ethmoidal
sinuses, the orbit, the zygomaticofrontal
suture, nasal cavity.
 Demonstrates the position of the
coronoid process of the mandible
between the maxilla and the zygomatic
arch.

24. Film placement:
 The long axis of the cassette is
positioned vertically.
Head Position:
 The midsagittal plane should be
vertical & 90 to the plane of the film.
The canthomeatal line should be 37
above the horizontal.

25. Central Ray:
The central ray should be
perpendicular to the film,
through the midsagittal
plane, and at the level of the
maxillary sinus.
Exposure parameters:
kVp: 65 & mA: 10 & Sec: 2-3

26. Bregma MentonBregma Menton
This projection is primarily used to demonstrate the walls
of the maxillary sinus ( especially in the posterior areas),
the orbits, the zygomatic arches & the nasal septum
Also demonstrates medial or lateral deviations of any part
of the mandible

27. Film placement:
 The cassette is placed in a horizontal position
on top of a metal table
 The image receptor is tucked under the chin
as far back as possible.
Position of the Patient:
 The midsagittal plane should be vertical & 90
to the plane of the film & the chin is extended
as far as comfortable to make the lower
border of the mandible as parallel to the
cassette as possible
 Only the chin touches the cassette

28. Central Ray:
Enters at the Bregma & exits at the menton
Exposure parameters:
kVp: 65 & mA: 10 & Sec.: 2-3

29. Reverse Towne'sReverse Towne's
Indications:
 High fractures of the condylar necks
 Medially displaced condyle
 Intracapsular fractures of the TMJ
 Investigation of the quality of the articular surfaces of the
condylar heads in TMJ disorders.
 Condylar hypoplasia or hypertrophy.

30. Film placement:
Position of the patient:
 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.

31. Central ray:
 Is aimed upwards from below the occipit, with the central ray at
30 to the horizontal, centered through the condyles
Exposure parameters:
 kVp: 70-80 & mA: 60-50 & Sec.:- 1.6
(Bucky grid)

32. Submento Vertex ProjectionSubmento Vertex Projection
Structures:
 Symmetrical projection of the petrosa
 Mastoid process
 Spinosum canals
 Foramen ovale
 Carotid canals
 Sphenoidal sinuses

33.  Curvature of Mandible
 Lateral wall of Maxillary sinuses
 Nasal septum
 Odontoid process of the atlas
 Axial inclination of the mandibular condyles

34. Indications:
 Destructive expansile lesions affecting
the palate, pterygoid region or base of
skull.
 Any displacement of a fractured
zygomatic arch.( Jug Handle View).
 Investigation of the sphenoidal sinus.
 Assessment of the thickness (medio-
lateral) of the posterior part of the
mandible before osteotomy.

35. Film placement:
Position of the patient:
 The patient is positioned facing
away from the film. The head is
tipped backwards as far as
possible, so the vertex of the
skull touches film. In this
position, the radiographic
baseline is vertical and parallel
to the film.

36. Central ray:
 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.
Exposure parameters:
 kVp: 50 & mA: 20-30 & Sec.: 0.4

37. RADIOGRAPHY OF THE MANDIBLE:RADIOGRAPHY OF THE MANDIBLE:
 PA Mandible
 Rotated PA Mandible
 Lateral Oblique
A. Anterior body of mandible
B. Posterior body of mandible
C. Ramus of mandible

38. PA MandiblePA Mandible
 Shows the posterio-anterior
projection of the mandibular
body & the ramus. It is not
suitable for showing the facial
skeleton, because of
superimposition of the base of
the skull & the nasal bones.

39. Indications:
Fractures of the mandible involving the:
 Posterior 3rd of the body
 Angles
 Rami
 Low condylar necks lesions such as cysts or tumours in the
posterior 3rd
of the body or rami to note medio-lateral
expansion
 Mandibular hypoplasia or hyperplasia
 Maxillofacial deformities

40. Film placement:
Is centered so that the lips are
centered to the film.
Position of the Patient :
The sagittal plane should be vertical &
90 to the film.
The head is tipped forward so that
radiographic baseline horizontal and
perpendicular to the film in the
forehead-nose position.

41. Central Ray:
Centered through the cervical spine at the level of the rami
of the mandible
Exposure parameters :
kVp: 65-80 & mA: 60-80
Sec.:-1.6(Bucky grid)

42. Rotated PA Mandible
 This projection shows the tissues of one side of the face
and is used to investigate the parotid gland and the ramus
of the mandible.
Main indications:
 Stones/calculi in the parotid glands.
 Lesions such as cysts or tumours in the ramus
to note any medio-lateral expansion.
 Submasseteric infection to note new bone
formation.

43. Film placement:
Position of the Patient:
 The patient is positioned facing the film, with the occlusal
plane horizontal and the tip of the nose touching the film
in the so-called normal head position.
 The head is then rotated 10 to the side of interest. This
positioning rotates the bones of the back of the skull away
from the side of the face under investigation.

44. Central Ray:
Is directed at 90 to the film,
aimed down the side of the face
which is of interest.
Exposure parameters:
kVp: 65-80 & mA:60-80 & Sec.:
1.6(Bucky grid)

45. MANDIBULAR OBLIQUE LATERAL
PROJECTIONS
Two oblique lateral projections commonly used to examine
the mandible, one for the body and one for the ramus.
A dental X-ray machine with an open ended aiming
cylinder is best for these projections.
The film : 13 x 18cm ( 5 x 7” ) or larger.
The patient should hold the cassette.

46. Indications:
 Assessment of the presence and/or position of unerupted tooth
 Detection of fractures of the mandible
 Evaluation of lesions or conditions affecting the jaws including
cysts, tumors, giant cell lesions & osteodystrophies
 As an alternative when intraoral views are unobtainable,
because of severe gagging/if the patient is unable to open the
mouth
 As specific views of the TMJ

47. Oblique laterals are categorized into:
A. Anterior body of mandible
B. Posterior body of mandible
C. Ramus of mandible

48. Structures:
 Anterior body of the mandible
 Position of teeth in the same area
 Helps to evaluate impacted teeth, fractures & lesions located in
the inferior border of the mandible
Anterior body of mandibleAnterior body of mandible

49. Film placement:
 The cassette is placed flat against the
patient’s cheek & is centered over the
body of the mandible overlying the
canine teeth.
 Should be positioned parallel to the
body of the mandible & inferior border
of the cassette should be parallel to the
lower border & below it.

50. Position of the patient:
 The patient is normally seated
upright in the dental chair & is
then instructed to:
• Rotate the head to the side of
interest: to bring the contra lateral
ramus forwards avoiding it’s
superimposition & to increase the
space available between the neck
& shoulder to position the X-ray
set.

51. • Raise the chin: to increase the triangular space between the back
of the ramus & the cervical spine through which the X-ray beam
will pass.
• The sagittal plane is tilted so that it is 5 to the vertical & rotated
30 from the true lateral position.
• The patient must hold the cassette in position with the thumb
placed under the edge of the cassette & the palm against the outer
surface of the cassette.

52. Central ray:
 Is directed from under the mandible
opposite the side of examination from
2 cm behind the angle of the mandible
 The beam is directed upwards (-10 to
-15 ) & centered on the anterior body of
the mandible. The beam must be
directed 90 to the horizontal plane of
the film.
Exposure parameters:
kVp: 65 to 75 & mA: 7-10 & Sec.: 0.8

53. Structures:
 Posterior body of the mandible
 Position of teeth in the same area
 Ramus of the mandible
 Angle of the mandible
Posterior body of the mandible

54. Film placement:
Position of the patient:
 The patient head is so adjusted that the ala
tragus line is parallel to the floor.
 The mandible is protruded slightly to
separate it from the vertebral column.
 The sagittal plane is tilted so that it is 5 to
the vertical & the head is rotated 10 to 15
from the true lateral position.
 The patient must hold the cassette in
position with the thumb placed under the
edge of the cassette & the palm against the
outer surface of the cassette.

55. Central ray:
 Is directed from under the mandible
opposite the side of examination,
from 2 cm below the angle of the
mandible.
 The beam is directed upwards (-10 to
15 & centered on the body of the
mandible & directed 90° to the
horizontal plane of the film.
Exposure parameters:
 kVp: 65 to 70 & mA: 7-10 & Sec.: 0.8

56. Structures:
 Ramus from angle of the mandible to condyles
Film placement:
Position of the patient:
 Ala tragus line
 The mandible is protruded slightly
 The sagittal plane is tilted to 10 to vertical
 Head tilted 5
Ramus of mandible

57. Central ray:
 Is directed from under the mandible
opposite the side of examination, from
behind the angle of the mandible to a point
posterior to the 3rd molar region on the side
opposite the cassette.
 The beam is directed upwards ( -10 to 15 ) &
centered on the ramus of the mandible &
directed 90 to the horizontal plane of the
film.
Exposure parameters :
 kVp: 65 to 70 & mA: 7-10 & Sec.: 0.8

58. HARD TISSUE IMAGING
 Panoramic Projection
 Transcranial Projection
 Trans Pharyngeal Projection
 Trans Orbital Projection
 Convenional Tomography
 Computed Tomography
SOFT TISSUE IMAGING
 Arthrography
 MRI
Radiography of the Temporomandibular Joint

59. Transcranial Projection:
 Sagittal view of the lateral aspects of the condyle and temporal
component.
 Gross osseous changes on the lateral aspect of the joint.
 Displaced condylar fractures
 Range of motion

60. Film placement:
 The cassette is placed flat against
the patient’s ear & centered over the
TMJ of interest, against the facial
skin parallel to the sagittal plane.
Head Position:
 The patient is placed with the head
rotated through 90 so that TMJ
under investigation is touching the
film & the saggital plane of the head
is parallel to the film.

61.  In open view, the patient’s mouth is
opened as far as comfortable & even a
bite block can also be used for
stability.
Central ray:
 The X-ray beam is directed downward
from the opposite side, through the
cranium & above the petrous ridge of
the temporal bone, at a +25
angulation through the joint.

62. Post auricular / Lindblom technique:
Point of entry of the central ray is ½’’ behind & 2’’ above the
auditory meatus
Is directed from posteriorly so that it passes along the long
axis of the condyle i.e. the medial pole of the condyle is more
posterior to the lateral pole.

63. Grewcock approach:
 The central ray enters through a point 2’’ above the external
auditory meatus.
Gill’s approach:
 The central ray enters through a point ½ ’’ anterior & 2’’ above
the external auditory meatus.
 An average 20 anterior angle may be used.

64. Because of the positive beam angulation, the central &
medial aspects of the joint are projected inferiorly & only
lateral joint contours are visible in this projection.
 The image of the condyle, temporal component & joint
space is distorted & condylar position cannot be reliably
determined, particularly if the horizontal beam angle is not
individualized for each patient.

65. Transpharyngeal (Infracranial or McQueen Dell
Technique or Parma )
Structures :
 Lateral projection of the sagittal view of the medial pole of the
condylar head and neck, usually taken in the mouth open position,
so that the joint is projected into the shadow of air containing
spaces of the nasopharynx, which helps to increase the contrast of
the various parts of the joint.

66. Film Placement:
The cassette is placed flat against
the patient's ear and is centered
to a point ½” anterior to the
external auditory meatus, over
the TMJ of interest, against the
facial skin parallel to the sagittal
plane.

67. Position of the Patient:
The patient is positioned so that the sagittal plane is vertical
and parallel to the film, with the TMJ of interest adjacent to
the film.
The occlusal plane should be parallel to the transverse axis of
the film so that the soft parts of the nasopharynx are in one
line with the TMJ.
The patient is instructed to slowly inhale through the nose
during exposure, so as to ensure filling of the naso­pharynx
with air during the exposure.

68.  The patient should open his
mouth so that the condyles move
away from the base of the skull
and the mandibular notch of the
opposite side is enlarged.
Central Ray:
 Is directed superiorly at ­5°
through the sigmoid notch of the
opposite side & 7­8° from the
anterior.
Exposure Parameters:
 kVp­ 70, mA­7 & Seconds­0.8

69. Parma Modification:
The lead lined open ended cone is removed and the tube head
is brought close to the skin surface, producing magnification
of the tube side structures and there by reducing super
imposition.

70. This is the conventional frontal TMJ projection which is
most successful in delineating the joint with minimal super
impositions, leading to the production of a relatively true
'enface' projection.
Structures :
The articular surface (convex) and
the articular eminence (flat or convex).
Transorbital (Zimmer Projection)

71. Film Placement:
The film is positioned behind the patient's head at an angle
of 45° to the sagittal plane & perpendicular to the X­ray
beam.

72. Position of Patient:
 The patient is positioned so that the
sagittal plane is vertical. The
canthomeatal line should be 10° to the
horizontal, with the head tipped
downwards.
 The mouth should be wide open or as an
alternative protrudes the mandible,
thereby positioning the condyle at the
summit of the articular eminence &
avoiding superimposition of the articular
eminence or skull base on the condyle.

73. Central ray:
 The X­ray is directed from the front of the patient through the
ipsilateral orbit & TMJ of interest.
 The point of entry may be taken at:
 Pupil of the same eye, asking the patient to look straight ahead.
 Medial canthus of the same eye.
Exposure Parameters:
 kVp­70, mA­7 & Seconds­0.8

74. Structures:
 Primarily used to observe the
occipital area of the skull. The necks
of the condyloid process can also be
viewed.
Film Position:
 The cassette is placed perpendicular
to the floor in a cassette holding
device. The long­axis of the cassette is
positioned vertically.
Towne’s projection

75. Position of Patient:
 This is an anteroposterior ( AP) view, with the
back of the patient's head touching the film.
The canthomeatal line is perpendicular to the
film.
Central ray:
 Is directed at 30° to the canthomeatal line and
passes through it at a point between the
external auditory canals.
Exposure Parameters:
 kVp:­70­80 & mA:­60­50 & Seconds­1.6(Bucky
grid)

76. CONVENTIONAL TOMOGRAPHY
 Tomography is a radiographic technique that produces multiple
thin image slices, permitting visualization of an anatomic
structures.
 Provide multiple image slices at right angles through the joint.
 Typically are exposed in the sagittal plane with several image
slices in the closed position and usually one image in the
maximal open position.
 Particularly indicated when morphologic abnormalities or
erosive changes of the condylar head are suspected.

77. COMPUTED TOMOGRAPHY
Indications:
 When more information is needed about the three­dimensional
shape and internal structure of the osseous components of the
joint.
 They are useful for assessing osseous deformities of the jaws or
surrounding structures.
 The presence and extent of ankylosis
 Neoplasms

78.  Extent of bony involvment in some arthritides
 Imaging complex fractures
 To evaluate complications from the use of
polytetrafluoroethylene or silicon sheet implants such as erosions
into the middle cranial fossa and ectopic bone growth

79. SOFT TISSUE IMAGING
 It is indicated when TMJ pain and dysfunction are present or
when the clinical findings suggest disc displacement that are non
responsive to conservative treatment.
ARTHROGRAPHY
MAGNETIC RESONANCE IMAGING

80. ARTHROGRAPHY
 Indirect image of the disc is obtained by injecting a radiopaque
contrast agent in to one or both joint spaces under fluoroscopic
guidance.
 A perforation is detected by the flow of contrast agent into
superior joint space from the lower space.
 Adhesions are detected by the manner in which contrast agents
fills the joint space.

81.  After both the joint spaces are filled, disc function is studied
using fluoroscopy during opening and closing movements
Indications:
 Disc position, function, morphology and the integrity of discal
attachments to aid in treatment planning.

82. MAGNETIC RESONANCE IMAGING
 Uses a magnetic field and radiofrequency pulses rather than IR
to produce multiple digital image slices.
Indications:
 Articular disc
 Medial disc displacements
Contraindications:
 Pregnant, who have pacemakers, intracranial vascular clips or
metal particles in vital structures.

83. References:­
Oral Radiology: Principles and Interpretation (Mosby)
(Hardback) By (author) Stuart C. White, By (author)
Michael J. Pharoah
Essentials of oral and maxillofacial radiology ( Freny R
Karjodker)
Essentials of Dental Radiography and Radiology BY
Eric Whaites