Post on 18-Mar-2018
Good Morning
Orthopantomogram(OPG) with Landmarks
Introduction
History
• Dr H Numata of Japan in 1933 and later, Dr YV Paatero of Finland in 1948: techniques of rotational panoramic radiography.
• In 1985, Kashima et al reported the implementation of computed panoramic radiography.
Indications
Evaluation of trauma
Impacted third molars
Large lesions
Mixed dentition
TMJ
Dental anomalies
Advantages
• Broad coverage of facial bones and teeth• Low patient radiation dose• Convenience of the examination for the patient• Use in patients unable to open their mouths• Short time required to make a panoramic
image, usually in the range of 3 to 4 minutes• Useful visual aid in patient education and case
presentation
Disadvantages
• Does not display fine anatomic detail available on intraoral periapical radiographs. So not useful in detecting small carious lesions, fine structure of marginal periodontium, or periapical disease.
• Unequal magnification and geometric distortion across the image.
Principles of panoramic image formation
The film and x-ray tubehead move around the patient in opposite directions in panoramic radiography
Rotation center
• Three basic rotation centers used in panoramic x-ray machines-
1. Double-center rotation2. Triple-center rotation3. Moving center rotation
Double center rotation
Triple center rotation
Moving center rotation
Principles of panoramic image formation
Movement of the film and X-ray source about a shifting center of rotation
Panoramic Collimation
Panoramic Imaging: Projection in the Vertical Plane
Panoramic Imaging:Projection in the Horizontal Plane
True intraoral source & focus of projection
Uniform magnification
Effective focus of projection
Rotating beam projected on stationary film
Projection in the Horizontal Plane
Rotating beam and moving film has proportions restored
Image layer (focal trough)
The closer to the center of the trough (dark zone) an anatomic structure is positioned, the more clearly it is imaged on the resulting radiograph
Image layer (focal trough)
Equipment
• Main components of panoramic x-ray units1. X-ray tube head2. Head positioner3. Exposure controls
Main components of the Orthophos XG 5: A, x-ray tubehead; B, head positioner; C, exposure controls
C: exposure controls
B: head positioner
A: x-ray tubehead
The head positioner (notched bite block, forehead rest, and lateral head supports) is used to align the patient’s teeth in focal trough
Exposure controls can be used to adjust exposure
Preparing the patient
Prepare the machine
• Disinfect the machine• Place a new bitestick in the machine
Positioning the patient
Common Errors
• Patient preparation errors• Patient positioning errors
Ghost images
Lead apron artifact
The figure above shows an extensive white area caused by the lead apron. Note the black dots ( red arrow) that represent the stitching on the apron. The thyroid collar should never be used for panoramic radiography since it would routinely cause this same problem.
Positioning of Frankfort plane upward
Chin tipped up too much. Hard palate superimposed over roots of maxillary teeth. Squared-off mandible. “Reverse Smile”.
Positioning of Frankfort plane downward
Chin tipped down too much. Roots of mandibular incisors shortened. V-shaped mandible.
Positioning of teeth anterior to focal trough
Incisors positioned anterior to notch in bitestick. Anterior teeth narrower.
Positioning of teeth posterior to focal trough
Incisors positioned posterior to notch in bitestick. Incisors wider than normal.
Positioning of midsagittal plane
Head turned to the right, moving the teeth closer to the film on that side. The teeth on the left side, being farther from the film, will be magnified more and appear larger.
Positioning of spine
White area in the center of the film represents the shadow of the vertebral column due to patient slouching.
Miscellaneous problems
Static electricity caused by friction when removing film from box or cassette too rapidly.
Failure to remove complete upper denture before exposure. This is usually not a problem since the denture acrylic is not dense enough to block the image of the maxillary bone.
Failure to remove glasses. Also note squared-off mandible and reverse “smile”, indicating chin tipped up too much.
Slight patient movement indicated by notching of mandible at arrow.
Over-exposureUnder-exposure
Normal Anatomic Landmarks
Bony landmarks of maxilla and surrounding structures
Normal anatomic landmarks of maxilla and surrounding structures: 1. mastoid process, 2. styloid process, 3. external auditory meatus,4. glenoid fossa, 5. articular eminence, 6. lateral pterygoid plate, 7.
pterygomaxillary fissure, 8. maxillary tuberosity, 9. infraorbital foramen, 10. orbit, 11. incisive canal, 12. incisive foramen, 13. anterior nasal spine, 14. nasal cavity, 15. nasal septum, 16. hard palate, 17.
maxillary sinus, 18. floor of maxillary sinus, 19. zygomatic process of maxilla, 20. zygomatic arch, 21. hamulus
1. External auditory meatus, 2. pterygomaxillary fissure, 3. infraorbital foramen, 4. orbit, 5. anterior nasal spine, 6. nasal septum, 7. nasal conchae, 8. hard palate, 9.
zygomatic process of maxilla
1. Glenoid fossa, 2. articular eminence, 3. maxillary tuberosity, 4. maxillary sinus, 5. zygoma
Bony landmarks of mandible and surrounding structures
Normal anatomic landmarks of mandible and surrounding structures: 1. condyle, 2. coronoid notch 3. coronoid process, 4. mandibular foramen, 5. lingula, 6. mandibular canal, 7. mental foramen, 8. hyoid bone, 9. mental ridge, 10. mental fossa, 11. lingual foramen, 12. genial tubercle, 13. inferior border of mandible, 14. mylohyoid ridge, 15.
internal oblique ridge, 16. external oblique ridge
1. Soft tissue of ear, 2. submandibular fossa, 3. external oblique ridge, 4. condyle, 5. coronoid notch, 6. coronoid process, 7. mandibular foramen, 8. mental foramen,
9. mental ridge, 10. mental fossa, 11. genial tubercles, 12. lingual foramen, 13. inferior border of mandible, 14. mylohyoid ridge, 15. mandibular canal
1. internal oblique ridge, 2. angle of mandible
Air space images seen on panormic radiographs
Air space images seen on panoramic films: 1.nasopharyngeal air space, 2. palatoglossal air space, 3. glossopharyngeal air space
Soft tissue images seen on panoramic radiographs
Soft tissue images seen on panoramic films: 1. tongue, 2. soft palate and uvula, 3. lipline, 4. ear
1. Uvula and soft palate, 2. tongue, 3. ear lobe
References
• White and Pharoah 6th edition• Haring and Howerton 3rd edition• www.harpercollege.edu• www.monroecc.edu• www.dent.ohio-state.edu• faculty.ksu.edu
Thank you