chapter 5

Question 1

What are the two kinds of radiation?

Answer 1

Natural , Manmade

Question 2

X-rays collide with cell chemicals, breaks them apart, create ionization and therefore, cell damage. Which biological theory is this?

Answer 2

Direct-HIt (target)

Question 3

Radiation causing chemical damage of the water within a cell through ionization.
Which biological theory is this?

Answer 3

in-direct action (poison water)

Question 4

Explain the law of B & T.

Answer 4

Actively dividing cells are more sensitive than slowing dividing cells.
The more specialized the cell, the more radio-resistant it is.

Question 5

Rank the order of the cell sensitivity.

Answer 5

White blood cells
Red blood cells
Endothelial cells
Bone cells
Muscle cells

Question 6

What is the dose-response curve?

Answer 6

A relationship between an administered dose and the response produced.

Question 7

What is a threshold does-response curve?

Answer 7

It indicates that there is a “threshold” amount of radiation which no biological response would be expected.

Question 8

What is a nonthreshold dose-response curve?

Answer 8

It indicates that any amount of radiation no matter how small, has the potential to cause a biological response.

Question 9

What are the radiation injury factors?

Answer 9

Total dose
Dose rate
Area exposed
Variation in species
Individual sensitivity
Variation in cell sensitivity	
Variation in tissue sensitivity
Age

Question 10

What is the radiation injury factor total does?

Answer 10

The total dose of the radiation depends on the type, energy, and duration of the radiation. The greater the dose, the more severe the probable biological effect.

Question 11

What is the radiation injury factor dose rate?

Answer 11

The rate at which the radiation is administered or absorbed is very important in the determination of what effects will occur. Because a considerable degree of recovery occurs from the radiation damage, a give does will produce less effect if it is divided (thus allowing time for recovery between dose increments) than if it is given in a single exposure.

Question 12

What is the Event Sequence After Radiation Exposure?

Answer 12

Latent Period, Period of Injury, Recover period.

Question 13

Explain short-term effects of radiation.

Answer 13

seen within a reasonably short amount of time after exposure.
Acute radiation syndrome (ARS) is associated with.

Question 14

Explain why short- term ARS is not seen in dentistry.

Answer 14

because dental x-ray machines cannot produce the very large exposures nessessary to cause it.

Question 15

Explain the long-term effects of radiation.

Answer 15

it is seen years after the original exposure. The latent period is much longer than associated with ARS. Delayed radiation effects may result from previous acute, high-exposure that the individual has survived or from chronic low-level exposures delivered over many years.

Question 16

What are the long-term effects related to dentistry?

Answer 16

Cancer
Embryological defects
Low birth weight
Cataracts
Genetic mutations – changes in genetic material.  
Small dental contribution

Question 17

Risk varies depending on what three factors?

Answer 17

speed of film, collimation, and the technique used.

Question 18

Explain risk vs. benefit.

Answer 18

Radiographs are to be taken only when the benefit outweighs the risk of injury.

Question 19

What conditions determine a cell’s sensitivity to radiation exposure?

Answer 19

As the law of B & T points out , cells with a potential for rapid division are more sensitive to radiation than those that do not divide.

Question 20

What role does effective dose equivalent play in comparing a medical chest x-ray with a dental periapical radiograph?

Answer 20

According to table 5-3 a periapical is equivalent to .2 days of natural exposure. While the chest x-ray is equivalent to 10 days.

Question 21

What is the difference between stochastic and deterministic (non-stochastic) effects?

Answer 21

Deterministic is used when referring to a tissue response whos severity is directly related to the radiation does, while the Stochastic is the tissue response based on the possibility of occurence.

Question 22

What are examples of Deterministic, and Stochastic?

Answer 22

Deterministic- Erythema (redness of skin) would not be expected to occur just from seconds of sunlight.
Stochastic - the occurence of cancer because it is an all or nothing response.

Question 23

Explain the cumulative nature of radiation exposure.

Answer 23

Much of the low-level radiation damage we receive is repaired within the cells of the body. Some repeated radiation damage remains unrepaired and accumulates in the body.

Question 24

Retaking a radiograph because of a technique or processing error causes an increase in radiation exposure for the patient. Discuss ways a retake radiograph affects the factors that determine radiation injury.

Answer 24

Total Dose- so the greater the dose the more sever the probable biological effect.
Dose rate- the rate at which the radiation is administered.