OPG

2.  Panoramic imaging also called pantomography
is a technique for producing a single
tomographic image of facial structures that
includes both the maxillary and mandibular
dental arches and their supporting structures .

3.  To evaluate impacted teeth
 To evaluate eruption patterns, growth and
development
 To detect diseases ,lesions and conditions of the
jaw
 To examine extent of large lesions
 To evaluate trauma and fractures.
 To evaluate periodontal bone loss and
periapical involvement.

4.  Finding the source of dental pain
 Assessment for the placement of dental implants
 Orthodontic assessment. pre and post operative
 Caries detection especially in the inter-dental
region.
 Diagnosis of developmental anomalies such
as Cherubism, Cleido cranial dysplasia
 Carcinoma in relation to the jaws
 Tempero mandibular joint dysfunctions
and ankylosis

5.  Broad coverage of facial bones and teeth
 Low patient radiation dose
 Convenience of the examination of the patient
 Use in patients unable to open their mouth
 Short time required
 In patient education and case presentation

6.  Image quality are not sharp
 Focal trough limitations
 Distortion
 Expensive equipment cost

8.  Numata and Paatero - describe the principles of
panoramic radiography
 Based on the principle of reciprocal movement of x-ray
source and an image receptor around a central point
or plane called the image layer, in which the object of
image is located.
 Object in front or behind this image are not clearly
captured because of their movement relative to the
centre of rotation of the receptor and the x-ray source.

9.  Two adjacent disks rotate at the same speed in
opposite directions as an xray beam passes through
their centers of rotation .
 Lead collimators in the shape of a slit are located at
the x-ray source and at the image receptor to limit
the central ray to a narrow vertical beam.
 Objects A, B, C, and D
present on disk 1 and rotate
past the slit. Their images
are recorded on the receptor,
which also moves past the
slit at the same time.
9

10.  The objects are displayed sharply on the receptor
because they are moving past the slit at the same rate
and in the same direction as the receptor. This causes
their moving shadows to appear stationary in
relation to the moving receptor.
 Other objects between the letters and the center of
rotation of disk 1 rotate with a slower velocity and
are blurred on the receptor. Any objects between the
x-ray source and the center of rotation of disk 1 move
in the opposite direction of the receptor, and their
shadows are also blurred on the receptor.
10

11.  The same relationship of moving film to image is
achieved if disk I is held stationary and the x-ray
source is rotated so that the central ray constantly
passes through the center of rotation of disk 1 and,
simultaneously, both disk 2 and the lead collimator
(Pb) rotate around the center of disk 1.
 In this situation, as before, the objects A through D
move through the x-ray
beam in the same
direction and at the
same rate as the
receptor.
11

12.  Replace disk 1 with the patient, and objects A
through D representing teeth and surrounding bone.
 Structures on the opposite side of the patient (near
the x-ray tube) are distorted and appear out of focus
because the x-ray beam sweeps through them in the
direction opposite that in which the image receptor is
moving. 12

13.  In addition, structures near the x-ray source are so
magnified (and their borders so blurred) that they
are not seen as discrete images on the resultant
image. These structures appear only as diffuse
phantom or ghost images.
 Therefore, only structures near the receptor are
usefully captured on the resultant image.
 Structures located more centrally in the body relative
to the jaws, such as the hyoid bone and epiglottis,
appear on the right, left, and sometimes central areas
of the final image.
13

15.  Also known as focal trough
 It is a three dimensional curved zone where the structures lying
within this layer are reasonably well defined on final panoramic
image.
 The structures seen on a panoramic image are primarily those
located within image layer.
 Objects outside the image layer are blurred magnified are reduced
in size. Even distorted to the extent of not being recognizable.
 This shape of image layer varies with the brand of equipment
used.

17.  The pivotal point or axis around which the cassette
carrier and tube head rotate is termed rotation center
 Three basic rotation center used in panoramic
radiography
Double centre rotation
Triple centre rotation
moving centre rotation
 The location and number of rotational centers influence
size and shape of focal trough

18. a. x-ray tube head
b. head positioner:
chin rest
notched bite block
forehead rest
lateral head support
c. exposure controls

19.  Similar to intraoral x-ray tube head
 Each has a filament to produce electrons and a target to
produce x-rays
 Collimator is a lead plate with narrow vertical slit
 Narrow x-ray beam emerges from collimator minimize
patient exposure to radiation

20.  Tube head is fixed in position and rotates
behind the patient head
 Film positioner is used to align the patients
teeth accurately in focal trough

22.  Dental appliance earrings ,necklace, hairpins, and any
other metallic objects should be removed
 Instruct the patient to stand as tall as possible with
back straight and stand erect .
 Vertical column must be straight
 Instruct the patient to bite on the plastic bite block
tooth must be positioned in edge to edge position in
the groove present in the bite block it is used to align
the teeth in the focal trough

24.  Midsagittal plane
perpendicular to floor
 Frankfort horizontal plane
parallel to the floor
 Tongue must be
positioned on the roof of
the mouth
 Instruct the patient to
remain still while machine
is rotating

25. Due to faults in technique:-
Errors in patient positionening ,
Errors in film exposures and processing
errors.
Errors in handling the film .

26. 1) Anterior teeth positioning errors
2) Midsagittal plane positioning errors
3) Occlusal plane positioning errors
4) Spinal column positioning errror
5) Patient’s shoulder touching the cassette
holder during the movement
6) Distortion due patient movement

27.  For anterior teeth positioning, insert a bite
block between incisal edges of maxillary and
mandibular teeth
 Advantages of using bite block :
a. Places the teeth in image layer
b. Prevents overlapping vertically
c. Prevents undue unsharpness,widenening or
narrowing of anterior teeth

28. Patient positioned too far forward:
Features:- Narrow blurred anterior teeth,
superimposition of spine over the ramus.
Correction :-
 Use bite block.
 Line up the incisal edge of the teeth with
notch,
 Ask edentulous patients to bite about 5mm
behind the groove on the block

31. Patient positioned too far back
Feature:-Wide blurred anterior teeth
Correction ;-
 Use bite block.
 Line up the incisal edge of the teeth with notch

33. Occlusal plane positioning :-
The patients head should be tilted downwards so
that the ala tragus line is about 5 degree
downwards,this will position occlusal plane
slightly downwards towards the floor.
In this plane patients franfurt’s horizontal plane ,
the plane intersecting the lower orbit of the
eyes and ear opening ,is alighned horizontally
with floor level.

34. Chin positioning too low
Feature :-
 Excessive curving of the occlusal plane:loss of image
of roots of lower anterior teeth
 Narrowing of intercondylar distance and loss of head
of condyle at top of film.
Correction;-
 Tip chin down , but ala-tragus line should not exceed
5-7 downwards.
 Use chin rest

36. Chin positioned too high
Features
 Flattening or reverse curvature of occlusal plane.
 Loss of image of the roots of upper anterior teeth
 Lenghtening of intercondylar distance and loss of
head of condyles at the edge of the film hard palate
shadow superimposed on apices of maxillary teeth.
Correction
 Tip chin down 5-7degrees
 Use chin rest

38. Midsagittal plane positioning error
 When the midline of the head is not in center of the
unit, the rami and posterior teeth are unequally
magnified .
 The image of the structures farthest from the film are
magnified ,whereas,on the oppposite,the image of
the structures closest to the film are decreased in size.

39. Patient twisted
Features
 Unequal right –left magnification
 Severe overlap of contact points and blurring
Correction
 Line up the patient’s midline with middle of
incisal bite guide.
 Close side guides

41. Slumped position
Features :-
 Ghost image of cervical spine superimposed on
midline of the film
Correction :-
 Stand up machine –have patient step forward
,or place feet on markers.

42. Spinal column positioning errors
Incorrect vertebral column positioning results in
underexposed area in middle portion of film .
This happens because if spine is not kept erect,the
radiation is excessively absorbed by the spinal
column and surrounding soft tissue sof the
neck, resulting in low density area around the
lower center of the film.

43. spine-shadow ghost

44. Chin not on the chin rest
Features :-
 Sinus not visible on the film
 Top of condyle is cut off
 Excessive distance between inferior border of
mandible and lower edge of the film.
Correction :-
 Position chin on chin rest

46. Tongue not on palate
Features :-
 Relative radiolucency obscuring the apices of
maxillary teeth
 Palatoglossal air space
Correction :-
 Ask the patient to swallow or suck on the tongue and
cheek during exposure

48. Lips open
Features
 Relative radiolucency on coronal portion of upper
and lower teeth.
Correction
 Ask the patient to swallow or suck on the tongue and
cheek during exposure.

50. Patient movement
Features :-
 Wavy outline of the cortex of inferior border of the
mandible
 Blurring of image above the wavy cortical outline
Correction :-
 Ask the patient to hold still and explain the function
of the machine to avoid startling the patient

52. Ghost image

53. Ghost image:
1)Opposite side
2)Higher up in position
3)Larger in size
4)Blurred-more in horizontal dimension

54. Double real images are formed in the central diamond area as the beam
will pass through here twice.
-One image is the mirror image of the other
-Both images are real
-Each image has similar proportions
-Each image has the same location on the opposite side
-Only occurs with midline objects e.g Hard and soft palate, palatal tori,
body of the hyoid, epiglottis, cervical spine

55. Errors in handling the film

57. Static electricity
Features
 Lightning like radiolucency.
 Dot like radiolucencies.
 Other patterns are herring bone, star burst or smudge.
Correction :-
 Dry air in darkroom can be humidified with humidifier
or large bowl of water.
 Avoid rapid pulling of film from envelope type cassette.
 Use antistatic carpet.

61.  Condylar process and TMJ: a bony rounded
radioopaque projection extending from ramus
of mandible
 Coronoid process: triangular radio opacity
posterior to tuberosity region
 Ramus: shadow of other structure may
superimposed over the ramus such as
 Pharyngeal airway shadow
 Posterior wall of pharynx
 Cervical vertebra
 Ear lobe
 Nasal cartilage
 Soft palate and uvula
 Dorsum of tongue
 Ghost shadow

62.  Body and angle : radiopaque bony structure
where the ramus join the body of the mandible
 mandibular dentition and alveolus

63. Individual bones:
 Temporal
 zygoma
 mandible
 frontal
 Maxilla
 Sphenoid
 Ethmoid
 Vomer
 Nasal
 Palate

64.  Cortical boundary of maxilla including
posterior border and alveolar ridge
 Pterygomaxillary fissure : radiolucent area
between the lateral pterygoid plate and maxilla
 Maxillary sinuses: paired radiolucencies
located above the apices of premolars and
molars

65.  Zygomatic complex or buttresses of midface:
includes lateral and inferior orbital rims
zygomatic process of maxilla zygomatic arch
 Nasal cavity and conchae: radiolucent area
above the maxillary incissors
 TMJ
 Maxillary dentition and alveolus

68.  Tongue under the hard palate: radiopaque
area superimposed over the maxillary posterior
teeth
 Lip line: seen in the region of anterior teeth
 Soft palate: extending posteriorly from hard
palate
 Posterior wall of pharynx
 Nasal septum
 Ear lobes
 Nose and nasolabial fold

69.  Teeth and supporting alveolar bone are
evaluated
 Teeth examined for
Gross anomalies of number ,position, and anatomy
Impacted third molars
Endodontic obturations, crowns, fixed restoration

70. THANK YOU