1. Radiation biology and protection in dental radiology

2. Dose units and dosimetry
Radiation-absorbed dose (D)
This is a measure of the amount of energy absorbed from the radiation beam per unit mass of tissue
SI unit: Gray,(Gy) measured in joules/kg
conversion: 1 Gray=100 rads

3. Cont’d Equivalent dose (H)
-This is a measure which allows the different radio-biological (RBE) effectiveness of different types of radiation to be taken into account.
-equivalent dose(H)=radiation-absorbed dose(D)*radiation weighting factor (Wr)
SI unit: Sievert (Sv)

4. Cont’d Effective dose (E)
This measure allows doses from different investigation of different parts of the body to be compared by converting all doses to an equivalent whole body dose
Effective dose(E)=equivalent dose(H)* tissue weighting factor(Wt)

5. Typical effective doses
X-ray examination mSv
CT head
Dental pan
2 dental intraoral films
Using 70 kV rectangular
Collimation and long cone

6. Various sources of radiation
Natural background radiation
Cosmic
Gama form the rocks
Radiation from ingested radioisotops
Radon

7. Cont’d Artificial background radiation
Medical and dental diagnostic radiation
Radiation from occupational exposure

8. The biological effects and risks associated with X-rays
Somatic Deterministic effects
Somatic Stochastic effects
Genetic Stochastic effects

9. Somatic deterministic effects
They are definitely produced by the high dose of radiation
Threshold dose
Examples- skin reddening

10. Somatic stochastic effects
They may develop
Examples- leukemia and certain tumors
No threshold dose

11. Cont’d
Every exposure to ionizing radiation carries the possibility of inducing a stochastic effect
The severity of the damage is not related to the size of the inducing dose

12. Genetic stochastic effects
Mutations result from any change in the chromosome
May result from radiation or occur spontaneously
No threshold dose

13. Effects on the unborn child
Large dose of radiation- congenital
abnormalities
Mental retardation- low doses of radiation

14. Harmful effects important in dental radiology
In dentistry the size of the doses are relatively small
Somatic stochastic effects are the damaging effects of most concern

15. How do X-rays cause damage
Direct damage
Indirect damage

16. Direct damage Incoming X-ray photon An ejected high-energy electron
Effects
Inability to pass on information
Abnormal replication
Cell death
Only temporary damage

17. Factors to be considered
The type and number of nucleic acid bonds
The intensity and type of radiation
The time between exposure
The ability of the cell to repair the damage
The stage of the cell’s reproductive cycle when irradiated

18. Indirect image
The damage to cells result from the free radicals produced by the ionization process
The hydrogen peroxide damages the cell by breaking down DNA or proteins

19. Estimating the magnitude of the risk of cancer induction
Dental intraorals (2)
Dental panoramic in
Lateral ceph
ALARA principle

20. Radiation protection measures
X-ray equipment
Processing equipment
Position and distance from the patient
ALARA
Guidelines for prescribing of radiographs
Digital radiography

21. X-ray equipment Collimation- maximum 6 cm of an x-ray beam
Filtration-aluminium filter to remove long
waves x-rays from the beam
Beam-indicating device (BID)- the legal focus to skin (fsd) distances are:
-200 mm for sets operating above 60 kV
-100 mm for sets operating below 60 kV

22. Inverse square law

23. Ways to reducing radiation exposure to the patients
ALARA concept
As Low As Reasonably Achievable
Digital radiography-80 % dose reduction

24. Guidelines for prescribing dental radiographs
Clinical examination must be performed first
Adhere to departmental protocols for x-raying patients in the School

25. Safety measures for operator protection
Only the operator and patient are permitted in the x-ray room
The operator will stand in a safe place:
-6 feet away NOT in direct beam
-behind an appropriate barrier
-outside the room if you cannot get 6 feet away
Never hold the film or tubehead during exposure