1. Radiology An Introduction
I am going today to introduce you to the field of radiology which is one of the most important field in dentistry.

2. Learning Objectives List the Properties of X-rays
Understand the need for radiology
Explain Radiation Protection
So the learning objectives of our lecture are the followings:
1. Understand the need for radiology
2. List the Properties of X-rays
3. Explain Radiation Protection

3. Introduction Discovery of the x-ray
X-ray picture/ roentgenograph/radiograph
The x-ray was discovered by Professor Wilhelm Roentgen during an experiment with vacuum tube He was awarded the first Nobel Prize for physics in 1901.
Whether the image is called an x-ray picture, a roentgenograph or a radiograph makes no difference.
The patient is best familiar with the word x ray, while scientists and professionals generally prefer radiograph. -

4. Radiation, Radiology and Radiography
Radiation = Emission of energy in the form of EMR or particulate radiation.
Radiography = the techniques involved in producing radiographs.
Radiology = interpretation of radiographs and other images.
Radiograpy
Radiology
Radiation is defined as the emission and movement of energy through space in the form of electromagnetic radiation (x and gamma rays) or particulate radiation (alpha and beta particles).

5. Dental Radiology Dental exams one of most common
survey in UK found:
19 million intra-oral radiographs taken
2.9 million panoramic radiographs taken
In Sweden 15 millions/y
- Dental exams by x ray is one of the most common exams in dentistry.
- A survey between 1997 and 1998 in UK found that 19 million intra-oral radiographs
and 2.9 millions panoramic radiographs was taken.
- In Sweden 15 millions x ray films are sold every year.

6. Properties of x-rays Invisible Have no charge Travel at speed of light
Have no mass or weight
Travel in straight lines
Travel in straight lines: means that we can protect ourselves against unnecessary x rays by avoiding the direction of x ray tube.

7. Properties of x-rays Can cause ionization
Can affect photographic film emulsion
Can affect living tissue
- Atoms that have gained or lost electrons are electrically unstable and are called ions. Ionization is the formation of ion pairs (positive ion and negative ion). When an atom is struck by an x-ray, an electron may be dislodged and an ion pair results.
- Can affect photographic film emulsion: This means that x rays have a capacity to darken a film
- Can affect living tissue: this property is utilized to treat cancer (damage cancer cells).

8. Properties of x-rays Can penetrate opaque tissues and structures
- Can penetrate opaque tissues and structures: The ability to penetrate materials or tissues depends on the wavelength of the x ray and the thickness and density of the object. The composition of the tissues determines whether the x rays will penetrate and pass through it or whether they will be absorbed in it.
- Materials that are extremely dense and have a high atomic number will absorb more x rays than thin materials with low atomic numbers. This partially explains why dense structures such as bone and enamel appear radiopaque (white or light gray) on the radiograph whereas the less dense pulp chamber, muscles, and skin appear radiolucent (dark gray or black).
Radiolucent
(dark)
Radiopaque
(light)

9. Conventional Radiography and Digital Imaging
Conventional radiography uses radiographic film as the image detector/sensor.
Photograph of an open film packet: Waterproof outer package, black paper, film, black paper, lead foil backing.

10. Conventional Radiography and Digital Imaging
Digital imaging uses a charged coupled device (CCD) as the image detector/sensor.

11. Advantages of digital imaging
No use of films, intensifying screens, cassettes etc.
Computer hardware and software allows you to view and store images.
Multiple images are obtained without changing film holder or using new film.
Less exposure to radiation

12. Why do we take radiographs?

13. Role of radiographs Clinical examination phase
Diagnosis (confirm / exclude)
Treatment planning
During treatment
Follow up after various treatment procedures

14. Are all radiographs necessary?

15. Must justify taking any radiographs; not a blanket screening for all patients.
Radiographs do have limitations and should never replace a thorough clinical examination.
There are disadvantages and risks - must weigh up benefits against risks.
Radiographs can indicate the need for further investigation.

16. The uses of radiographs

17. General dentistry: Loss of tooth structure
Carious (occlusal, proximal)
Non - carious (attrition, abrasion, erosion, fracture)
Periodontal disease
Endodontic disease
Impacted teeth
Trauma (root and alveolar fractures, foreign bodies)
Other pathology affecting bone

18. Periodontics: Alveolar bone height Alveolar bone health
Generalised vs localised
alveolar bone loss
Peri-radicular infection

19. Orthodontics: General growth and development Delayed eruption
Ectopic teeth
Eruption paths
Impacted teeth
Supernumerary teeth

20. Oral medicine and oral surgery:
Extractions
Jaw fractures
Tumours
Infections
Foreign bodies

21. Endodontics: Anatomy of the pulp chamber and canal (s)
Presence of peri-radicular and peri-apical pathology
Resorption of roots
Dental trauma
Canal length determination
Root filling
Follow-up/monitor healing (periapical, fracture, resorption)

22. Radiology 3 common dental X-rays: Bitewings Periapical Panoramic
(Univ. Manitoba, 2005)
Intra-oral plain radiography (conventional + digital)
Radiographic film/detector is exposed whilst inside the patient’s mouth
Image of a small area - a few teeth and adjacent supporting structures

23. Types of Radiographs Intra-oral Extra-oral
Other technologies/imaging modalities

24. Intra-oral radiography
Radiographic film/detector is exposed whilst inside the patient’s mouth
Image of a small area - a few teeth and adjacent supporting structures

25. Bitewing: Indications: baseline examination detection of:
- dental caries
- non-carious tooth loss
- monitoring the progress
of any loss of tooth structure
- assessing existing restorations
(defects, contacts)
- assessment of periodontal status.
Image of both upper and lower tooth crowns, cervical portion of the roots and the surrounding periodontal ligament and alveolar bone
Indications:
baseline examination
detection of:
- dental caries (primary and secondary/recurrent)
- non-carious tooth loss
- monitoring the progress of any loss of tooth structure
- assessing existing restorations (defects, contacts)
- assessment of periodontal status.
Usually of posterior teeth but can be anterior teeth.

26. Periapical: Indications: detection of apical infection/inflammation
dental trauma (to the tooth and associated alveolar bone)
assessment of root morphology
endodontic diagnosis, planning,
treatment and monitoring
Image of 1-3 complete teeth and the surrounding periodontal ligament and alveolar bone.
Indications:
detection of apical infection/inflammation
dental trauma (to the tooth and associated alveolar bone)
assessment of root morphology before extractions
endodontic diagnosis, planning, treatment and monitoring

27. Occlusal: Indications: presence/absence of developing teeth
supernumerary teeth
impacted teeth
pathology not fully demonstrated in an intraoral view
contour of buccal and lingual cortical plate
localisation technique (used with another film)
when unable to take intra-oral radiographs
- limited opening of mouth
- uncooperative child.
Image of either the maxilla or mandibular arch including teeth, periodontal ligaments, alveolar bone and some basal bone.
Indications:
presence/absence of developing teeth
supernumerary teeth
impacted teeth
pathology not fully demonstrated in an intraoral view
contour of buccal and lingual cortical plate (usually Mn)
localisation technique (used with another film)
when unable to take intra-oral radiographs
- limited opening of mouth
- uncooperative child.

28. Occlusal:

29. Extra-oral radiography
Radiographic film/detector positioned outside the patient’s mouth.
Can image larger areas of the mandible and maxilla, face, skull.

30. Extra-oral radiography
Skull radiographs:
lateral head

31. Extra-oral radiography
anterio-posterior view
lateral oblique jaw

32. Extra-oral radiography
TMJ

33. Extra-oral radiography
Tomography
Panoramic radiograph
orthopantomograph (OPG)
TMJ
maxillary sinus views
Modern OPG machines can do a range of skull views by altering the extent of the tomographic layer used and by altering the shape of the tomographic layer used

34. Indications for traditional OPG
Assessment of
- wisdom teeth
- TMJ pathology
- maxillary sinus
- jaw bone pathologies
- orthodontic diagnosis
- jaw bone fractures.
NB: A complete diagnosis often requires the use of both intra- and extraoral radiographs to visualise and localise a lesion in its entirety and to detect any similar lesions elsewhere.

35. Other Technologies and Imaging Modalities
Computerised tomography (CT)
Magnetic resonance imaging (MRI)
Ultrasound

36. Computerised tomography (CT)
Radiographic cutting of a region/structure into thin slices
Fairly high doses
Good diagnostic information
Used in oral maxillofacial surgery (diagnosis and treatment planning of tumours, fractures and neuropathies)

37. Magnetic resonance imaging (MRI)
Gives better soft tissue images than CT scans
No radiation - uses magnetic field and sound waves
Very good diagnostic information
Used in oral maxillofacial surgery (diagnosis and treatment planning of tumours, fractures and neuropathies, gold standard for TMJ imaging)

38. Ultrasound Limited uses for dental care Salivary gland tumours
Possibly TMJ
Locating foreign object in soft tissue
Soft tissue cysts

39. Radiation Units Exposure Absorbed dose Dose Equivalent
For radiation measurement, three quantities are used. They are:

40. Radiation Units Exposure: amount of radiation in a beam of x-rays
ionization in air
Coulomb per kg
Exposure: can be defined as the measurement of ionization in air produced by x rays. The units for measuring exposure are coulombs per kilogram.

41. Radiation Units Absorbed dose:
amount of radiation absorbed by the tissues
amount of energy deposited in 1 kg
Gray, Gy (1 joule/kg)
Rad (radiation absorbed dose) equal to 0.01 J/kg

42. Radiation Units Dose Equivalent:
amount of radiation absorbed by the tissues x Quality Factor (QF)
QF relates to biological damage
Sievert, Sv equals 1 Gy
Dose equivalent is a term used for radiation protection purposes to compare the biological effects of the varies types of radiation.

43. Radiation Protection Good technique to avoid re-takes:
use of correct film for the view intended
use of appropriate film holder
correct film placement within film holder
correct placement (angulation) of film holder in patient’s mouth
correct tube angulation
correct exposure time

44. Radiation Protection Protect patient, public and staff
Remember dose is cumulative
Benefit/risk ratio
Dose reduction = time, distance, shielding
High speed film Long exp. cable Lead coats to
reduced exp. time so dentist steps away stop scatter radiation

45. Conclusion X-rays is essential in dentistry Dose is cumulative
Follow radiation protection principles
Each X-ray exam should be justified

46. References
Whaites E (1996) Essentials of dental radiography and radiology, 2nd edition, Churchill Livingstone
de Lrye and Johnson, Essentials of dental radiography for dental assistants
Goaz and White, Oral radiology: Principles and interpretation, CV Mosby