[PPT]OPG with Landmarks - Dentistry Notes - DENTISTRY...

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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

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