1. Dental Panoramic Tomography

2. What we will cover… Indications Advantages/disadvantages
Technical principles
Equipment
Technique
Film critique and common mistakes

3. Indications
Large pathologies/un-erupted teeth too big for intra-oral film
Intra-orals not possible
Assessment in:
advanced periodontitis
Extraction of wisdom teeth
Orthodontics
Growth and development
Implants
Grossly neglected mouth
Trauma
TMJ dysfunction

4. Advantages Large area of coverage Bilateral view for comparison
Low dose
Relatively simple to perform
Easy to explain resultant image to patient
Patient movement effects only one section
Rapid assessment method

5. Disadvantages Less sharp than intra-oral Magnification Distortion
Subtle pathology may be missed
Magnification
Distortion
Sectional
More complicated to interpret
Ghost images produced
Intensifying screens result in reduced resolution
Different shaped dental arches

6. Tomography

7. Focal Trough
‘Narrow zone of sharp focus’

9. The technical bit.. Linear tomography Rotational tomography
Flat focal trough
E.g. Gas removal from kidney
Rotational tomography
Arc shaped focal trough
1 centre of rotation
Dental panoramic tomography
How do we achieve a horseshoe shape?
2+ centres of rotation

10. Rotational
Tomography

11. Centres of rotation
Dental
Panoramic
Tomography

12. How does tomography work…
X-ray tube orbits back of head
Cassette holder moves around front of face
X-ray tube and cassette holder move in opposite directions
Cassette moves in same direction as X-ray tube

14. Focal Corridor f=height of film d=focal trough to film distance
x=height of XR beam
Focal Corridor

15. Explain… Why do we need a moving X-ray source?
Why does the cassette carriage move?
Why does the cassette move?

16. Equipment Features Tubehead Control panel Positioning apparatus
Chin support
Bite rod
Light beam markers
Head clamps
mirror
Image receptor

18. The Control Panel What do we need? kV, mA settings
Patient size selection
Height adjustment
AP bite rod adjustment (canine light)
Field limitation options
Range of dental arch shapes

19. Light Beam Markers Mid-sagittal plane - vertical
Frankfort plane – horizontal
Canine light
Position between upper lateral incisor and canine

20. The Image receptor

21. Intensifying screens
Intensifying screens convert X-ray photons to light (UV and visible) to amplify blackening effect
Uses light emitted from photoelectric effect
Less radiation needed to expose film

22. Technique: Preparation
Load cassette and place in carriage
Load cassette and place in carriage
Load cassette and place in carriage
Load cassette and place in carriage
Load cassette and place in carriage
Load cassette and place in carriage
Load cassette and place in carriage
Load cassette and place in carriage
Load cassette and place in carriage
Set exposure factors
Insert bite rod/cover
Set carriage to start position
Remove artefacts

23. Technique: Positioning
Load cassette and place in carriage
Load cassette and place in carriage
Guide patient into unit
Load cassette and place in carriage
Load cassette and place in carriage
Load cassette and place in carriage
Load cassette and place in carriage
Load cassette and place in carriage
Load cassette and place in carriage
Patient holds handles
Place chin on support
Bite upper and lower teeth into groove on bite rod
Patient stands up straight and steps forward slightly

24. Technique: Positioning
Use light beam markers to check position
Explain movements to patient
Patient swallows and places tongue in roof of mouth
Ask patient to keep still
Expose

25. 5 8 1 7 10 4 9 2 12 11 11 3 3 6
Anatomy

26. Normal Anatomy 1.Mandibular condyle 2.Angle of mandible
3.Body of mandible
4.Ramus of mandible
5.Right Orbit
6.Symphysis of mandible
7.Left maxillary sinus
8.Zygomatic arch
9.Mandibular 3rd molar
10.Ear lobe
11.Cervical spine
12.(Root of) mandibular
2nd premolar

27. Film Evaluation 1. Identification 2. Anatomical marker 3. Collimation
3. Area of interest
4. Correct positioning
5. Artefacts
6. Adequate exposure factors

28. Film Evaluation

29. Common Problems Patient movement Ghosting Incorrect positioning
of artefacts
of Cervical spine
Incorrect positioning
AP positioning
Rotation
Chin tilt
Tilting

30. Chin tipped down too much
V shaped smiley mandible
Arching of spine
Condyles high on film
Hyoid bone streaked across mandible

31. Chin up too high.
Flattened occlusal plane
Palate superimposed on roots of maxillary teeth
Broad, flat mandible

32. Patient twisted – right mandibular rami wider than left
Condyles assymetrical
Teeth tend to be wider one side than other
Too far forward on one side, too far back on the other

33. Too far forward
Spine superimposed over rami
Blurred, narrow anterior teeth
Too much spine visible on edge of film

34. Too far back
Ghosting of mandible and spine
Condyles at very edge of film
Blurred and widened anterior teeth

36. Slouching

37. Standing up straight

39. Airway

40. Underexposed

41. Conventional
Digital

42. 3d