This document provides an overview of orthopantomography (OPG) and lateral cephalometric radiography. It defines OPG as a technique that produces a single tomographic image of the facial structures including the dental arches and supporting bones. The document lists several advantages of OPG including its broad coverage, low radiation dose, and short examination time. It describes the principles of panoramic image formation using reciprocal movement of the x-ray source and image receptor. Key diagnostic regions and structures visible on OPG images are identified. Common errors, artifacts, and positioning considerations are discussed. Lateral cephalometry is introduced as useful for orthodontic diagnosis and treatment planning by allowing evaluation of skeletal and dental abnormalities. References on
2. Content of Presentation
• What is OPG
• Advantages of OPG
• Indication of OPG
• Principles of panoramic image formation
• Focal through / Image layer
• Diagnostic regions in panoramic image and quadrant
• Patient Positioning and Head Alignment
• Structures in panoramic imaging
• Error and Artefacts in producing OPG images
• Lateral Cephalometric & artefacts
• Frequently question asked and terms used in clinical indication
• References
• OT cases pictures
3. What is Orthopantomography?
It is a technique for producing a single tomographic image of the
facial structures that includes both the maxillary and mandibular
dental arches and their supporting structures.
4. Advantages of OPG
• Broad coverage
• Low patient radiation dose (Compared to CT)
(Approx. 76kV, 6mA X 14 sec) = 84mAs
• Convenience of the examination
• Useful in patients who are unable to open their
mouths
• Short time required: 3-4 mins (14-16 sec exposure)
• Useful visual aid
5. Indications of OPG
• A panoramic film is not as
useful as periapical
radiography (occlusal &
bitewing) for detecting
small carious lesions,
periodontal diseases, or
periapical lesions.
• It should not be used as a
substitute for intraoral
films.
• What OPG can do?
6. Indications of OPG
• Impacted teeth and its relation with the mandibular canal.
• Study of sinuses
7. Indications of OPG
• To evaluate eruption patterns @ Tooth development
(for paediatric patient)
8. Indications of OPG
• To detect diseases, lesions, conditions of the jaws and the
extent of large lesions.
15. Principles of panoramic image formation
• 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
(focal through), in which the object of image is
located. (fulcrum plane is clear, outside of
fulcrum become blurring in appearance)
• 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.
16. Principles of panoramic image formation
So why cover only front area, using
single piece of pb shield?
17. Focal Through / image layer
• Is a 3-D curved zone, or “focal trough” where
the structures lying within this layer are
reasonably well defined on final panoramic
image.
• The images seen on the OPG consists largely
of anatomic structures located within the
focal trough
• Objects out of focal trough are blurred,
magnified, reduced or distorted.
• The shape of the focal trough varies with the
brand of equipment used. (normally 2,3
point or moving of rotation centre (fulcrum)
– can choose the pattern of jaw
19. Focal Through / image layer
• Mandible supporting a metal ring positioned at the center of
the focal trough.
• The incisal edges of the mandibular teeth are indexed by a bite
rod-positioning device.
• The Mandible is positioned at the center of the focal trough.
• True size of incisor teeth
20. Focal Through / image layer
• Ring 5 mm anterior to focal through
• Incisor teeth appears small (displaced toward the buccal),
thinner in appearance.
• Closer to IR (smaller)
21. Focal Through / image layer
• Ring 5 mm posterior to focal through
• displaced to the lingual side of its optimal position in the image
layer, the beam passes more slowly through it. The images of the
structures are elongated horizontally thus, appear wider.
• Farther from IR, Closer to tube (magnified) wider appearance
22. Diagnostic regions in panoramic image and
quadrant
TMJ including retromaxillary &
cervical region
Maxillary region
Mandibular regionDentoalveolar region
23. Diagnostic regions in panoramic image and
quadrant (Q)
• The arrangement of Quadrant follows clock wise direction
• 38 impacted tooth refers to Q3 and 8th tooth
Q1
Q4 Q3
Q2
24. Patient Positioning and Head Alignment
• Position heads carefully in the image layer (focal
through).
• Dental appliances, earrings, necklaces, hairpins
and any other metallic objects in the head and
neck region should be removed.
• Demonstrate the machine to the patient by cycling it while
explaining the need to remain still during the procedure.
• Children should be instructed to look forward and to not follow the
tube head with their eyes.
25. Patient Positioning and Head Alignment
• Asked patient to take one step forward, why?
• To extend the cervical spine. To prevent cervical
superimposed with dental/supporting structures.
26. Patient Positioning and Head Alignment
• The patient’s head must be centered
in three different planes.
1.Midsagittal
2.Occlusal @ Horizontal Frankfort Plane
3.Anteroposterior.
27. Patient Positioning and Head Alignment
1. Midsagittal
• Is positioned perpendicular or at a right angle
to the floor and centered right to left.
• Failure to position the midsagittal plane in the
rotational midline of the machine results in a
radiograph showing right and left sides that
are unequally magnified in the horizontal
dimension.
• Tongue must be positioned on
the roof of the mouth
• Instruct the patient to remain
still while machine is rotating
28. Patient Positioning and Head Alignment
2. Occlusal @ Horizontal Frankfort plane
Plane)
• Occlusal plane is angled 20 to 30 degrees
• A general guide for chin positioning is to place the patient so that a
line from inferior margin of orbit and superior margin of External
Acoutic Meatus (EAM) are horizontal (parallel to the floor) known as
HFP
29. Patient Positioning and Head Alignment
3. Anteroposterior.
• is achieved typically by having
patients place the incisal edges of
their maxillary and mandibular
incisors into a notched positioning
device.
• Patients should not shift the
mandible to either side when
making this protrusive movements.
32. Error and Artefacts - Ideal Image
• Smile image produced (shows that the chin is not tipped too high and not too low)
HFP parallel to the floor
• same level of condyle – mid sagittal plane perpendicular with floor – yellow line
• Same distance of ramus red arrow – no rotation of head – red arrow
• Soft palate and tongue not superimposed with the root of maxillary teeth
• Shows clearly hard and soft tissue (all desired structure are in focal area)
33. Condyle and mandible cut-off, what to do?
• Condyle cut-off, what to do?
– 1-Repeat
– 2-Repeat
– 3-Ask to make confirmation to maxillofacial surgeon, paed
dental specialist, periodontics, orthodontics, restorative,
special need dentistry, prosthodontics or forensic dentistry
(more interest to alveolar process-to assess age)
• Why condyle so important even thought impacted tooth?
– Growth centre (fracture will affect growth)
– Stress related sign
– To maintain posterior facial height
34. Error and Artefacts – Error 1
Positioning error – chin tipped too high
• If the chin is tipped too high, the occlusal plane on the radiograph
appears flat or inverted, and the image of the mandible is distorted.
• HFP not parallel with the floor
35. Error and Artefacts – Error 2
Positioning error – chin tipped too low
• The chin is tipped too low, the teeth become severely overlapped, the
symphyseal region of the mandible may be cut off the film and both
mandibular condyles may be projected off the superior edge of the film.
• HFP not parallel to the floor
• Shortened mandibular incisors and a V-shaped mandible.
36. Error and Artefacts – Error 3
Positioning Error –
out of focal area)
• The anterior teeth are positioned behind the notch in the bitestick (farther from
the film), resulting in the widening of the anterior teeth (the maxillary central
incisors are as wide as the molars)
• Also indicated by blurring of structures in the area (out of focal through)
• Widening and blurring of teeth, if in front of bitestick – blurr image + narrowed
of the anterior teeth
37. Error and Artefacts – Error 4
Positioning Error – head turned
• The widening of the ramus is not equal (red arrow), the patient’s head
turned to the left side (closer to film) decreasing width of ramus on that
side
38. Error and Artefacts – Error 5
Positioning error – gown plumbum – cone artifact
• The lead apron was placed too high on the back of the patient’s neck.
39. Error and Artefacts – Error 6
Artefact – patient’s hair
• Pattern on right side of film (patient’s left) caused by excessive oil on
patient’s hair.
40. Error and Artefacts – Error 7
Positioning – spine position
• Shadow caused by the cervical vertebrae due to patient not standing
straight.
• The radiopaque area are not as sharp as those produced by lead apron
• Always happened to those patient with sitting position (sitting on stool)
41. Error and Artefacts – Error 8
Artefact – ghost image
• formed by dense objects located between the tube head and the rotation
center – normally external object or sometimes mandible.
• Remove any jewellery before examination started.
Ghost image (opposite side,
enlarge & distorted
42. Single Real Image
• Only one image results from a given anatomical structure. The structure
is located between the rotation center and the film and the x-ray beam
only passes through the structure one time.
• Most images seen on a panoramic film are of this type.
Double Real Image
• Two images of a single object are seen on the film. Double real images
are produced by structures located in the midline. The x-ray beam
passes through these objects twice as the tube head rotates around the
patient.
• Structures that result in double real images are the hard and soft
palates, the hyoid bone and the cervical spine.
Error and Artefacts – Error 8
43. Error and Artefacts – Error 9
Positioning – tongue and soft palate/hard palate superimposed with root of
maxillary teeth
• HFP not parallel to the floor, the chin little bit tipped up causing the root of
maxillary teeth not clearly appeared
• Instruct to the patient to position the tongue at the roof of palate
44. Error and Artefacts – Error 10
• Positioning – the chin little bit tipped down – HFP not parallel to the floor
• MSP not at the midline – condyle not at the same level and cut-off
• Lower laser not at the chin level – due to wound dressing.
45. USES OF CEPHALOGRAM
• In orthodontic
diagnosis & treatment
planning
• In classification of
skeletal & dental
abnormalities
• In evaluation of
treatment result
LATERAL CEPHALOMETRIC
46. LATERAL CEPHALOMETRIC
Tracing paper hanged on illuminator, measurement and draft were made on it,
HFP parallel to the floor to ease the drawing process
47. Characteristics to pass the
Lateral Ceph. film
• Symmetrical structures must be superimposed for both side
(maxillary, mandible, ant/post clinoid etc.)
• Horizontal Frankfort plane as reference to ensure that true positioning
performed
• Ruler must be placed at Nasion (just to make sure HFP parallel to the
floor)
• Molar and pre-molar teeth for both maxillary and mandible must be
closed each other
• Must include all soft tissue at the facial including throat area (under
chin) or include at least C4
• Print at 100% or less (to prevent the draft/measurement more than
tracing paper)
LATERAL CEPHALOMETRIC
48. Error and Artefacts – Error 11
Rejected cause :
Magnified more than
actual size 150%
49. Error and Artefacts – Error 12
Rejected causes :
• Magnified more
than actual size
119%
• Soft tissue at the
throat area cut off
• Ruler placed higher
than Nasion
50. frequently questions asked and terms in clinical
indication
• What is significant to position tongue at the roof of palate?
• Why need to produce ‘smile image’?
• What is edentulous area?
• Why cant wear cervical collar as protection?
• Meaning of 38, 48 impacted tooth?
• What are the characteristics to pass lateral cephalogram films?
51. • Positioning (common error)
• Position chin tipped up/low
• A slumped position
• The patient positioned forward/backward
• Failure to position tongue against the palate
• Patient movement during exposure
• Pt head tilted
• Head turned to one side
• Artifacts
• Remove jewellery, untighten hair bun
• Stand still and don’t swallow saliva while OPG machine is
moving
Take Home Messages
52. Freny R.Karjodkar :Text book of Dental and maxillofacial radiology 2nd
edition page number :236-255
Laura Jansen ,Joen M.Ianucci Harring :Dental radiography Principles
and techniques of Oral radiology: 3rd edition page number:305-319
White and pharaoh : Oral radiology principles and interpretation 6th
edition; page number: 175-189
References
