OPG.pptx

OPG BY DR. KIRAN KUMAR, NAVODAYA DENTAL COLLEGE, RAICHUR

1. Dr KIRAN KUMAR K R Professor DEPARTMENT OF ORAL MEDICINE & RADIOLOGY NAVODAYA DENTAL COLLEGE

2. Contents Indications Principles of OPG Focal Trough Limitations Advantages Disadvantages

3. PANORAMIC IMAGING

4. INDICATIONS To establish site, size and extent of lesions. e.g. cyst, tumour.

5. To detect the middle 1/3 rd of fracture of face and mandibular fractures. To investigate TMJ dysfunctions.

6. To evaluate development anomalies. To evaluate tooth development and mixed dentition.

7. To assess the underlying bone before CD construction.

8. To assess impacted/supernumerary teeth. To assess the age estimation.

9. Prior to any surgical procedure. To assess the progress of lesions and post operative bony healings.

10. To evaluate vertical height of alveolar bone before placing implants. To assess the alveolar bone loss in PDL disease.

11. To assess the orthodontic treatment

12. LIMITATIONS Not suitable for patient who cannot stabilize head. Not suitable for children under 5 years. Not suitable for handicapped patients.

13. PRINCIPLES OF PANORAMIC RADIOGRAPHY

14. Paatero and Numata - The first to describe the principles of panoramic radiography . Movement of the film and objects(A,B,C,D) about two fixed centers of rotation.

15. PROJECTION IN THE VERTICAL PLANE

16. +

17. Vertical dimension of panoramic image is unaffected by the horizontal rotation of the beam. The vertical dimension of panoramic image is result of conventional radiographic projection. Focal spot in x-ray tube anode serves as a functional focus for vertical aspect.

18. Slight negative angulation of beam so, x-ray beam will pass beneath the occipital portion of skull. Angle is -4 to -7 °.

19. PROJECTION IN THE HORIZONTAL PLANE

20. PROJECTION IN THE HORIZONTAL PLANE Stationary sources compared with moving source.

21. The horizontal dimension of the panoramic image is affected by the horizontal rotation of the beam X-ray appear to diverge from an intraoral source although they really originate outside the patient at the focal spot of the x-ray tube. This apparent intraoral x-ray source – “ center of rotation” or “Effective focus of the projection” for the horizontal dimension of the x-ray image. Center of rotation serves as “ functional focus”

22. Movement of the film and x-ray source about one fixed center of rotation.

23. Movement of the film and x-ray source about a shifting center of rotaton.

24. Movement of x-ray source and beam.

25. MOVEMENT PATTERN OF XRAY BEAM

26. IMAGE LAYER OR FOCAL TROUGH It is a zone in an object defined as containing those object points depicted with sufficient detail to be distinguished. The vertical and horizontal dimensions match only when the object lies within a particular plane – central plane or sharply depicted plane .

27. FOCAL TROUGH

28. Objects outside this sharply depicted plane but still within the image layer will always be somewhat distorted in shape and will appear unsharp or fuzzy.

29. PRINCIPLES OF IMAGE LAYER FORMATION

30. WIDTH OF IMAGE LAYER

31. POSITION OF IMAGE LAYER

32. ADVANTAGES Broad coverage of the facial bones and teeth Broad anatomical coverage in a single film. The procedure -simple and rapid. The procedure – patient’s convenient Low patient radiation dose (FMX=170.7, OPG =24.3 microSV ) Less time required > IOPAR Useful - trismus & gagging patient. Infection control minimum Useful as a teaching or visual aid.

33. Useful for mass screening. Decrease superimposition of anatomical structures. Helps- localization of object along with IOPAR/occlusal Easy to compare condylar heads.

34. DISADVANTAGES Poor anatomical details. Overlapping of proximal surfaces of premolars. Overlapping of cervical spine in lower anterior region. Poor visualization of areas of diagnostic interest( if they are outside focal trough)

35. Not useful in detecting incipient caries > IOPAR. Ghost images, artifact, shadows can overlies-structures in focal trough. Artefacts can easily misinterpreted. Soft tissue & air shadows can overlies the required hard tissue. OPG machine is costly!