chapter 5

Question 1

x rays have the ability to detach and remove electric charges from the complex atoms that make up the molecules of body tissues; delicate balance of structure is altered, and a cell may be damaged or destroyed

Answer 1

ionization

Question 2

what are the two theories for how radiation damages biological tissues

Answer 2

direct and indirect

Question 3

one third of biological alterations from x radiation exposure result from a direct effect; most dental x ray photons probably pass through a cell with little or no damage

Answer 3

direct theory

Question 4

x ray photons collide with important cell chemicals and break them apart by ionization, causing critical damage to large molecules; a healthy cell can repair any minor damage that might occur

Answer 4

direct theory

Question 5

based on the assumption that radiation can cause chemical damage to a cell by ionizing the water within it; before it enters the cell

Answer 5

indirect theory

Question 6

two thirds of biological alterations from x radiation exposure result from___ effects

Answer 6

indirect

Question 7

radiolysis of water

Answer 7

indirect theory

Question 8

indicates threshold amount of radiation, below which no biological response would be expected

Answer 8

threshold dose response curve

Question 9

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

Answer 9

non threshold dose response curve

Question 10

As low as reasonably achievable

Answer 10

ALARA

Question 11

sequence of events following radiation exposure

Answer 11

latent period , period of injury recovery period

Question 12

following initial radiation exposure, and before the first detectable effect occurs

Answer 12

latent period

Question 13

follows latent period
stoppage of mitosis
breaking or clumping chromosomes
abnormal mitosis
formation of multinucleated cells associated with cancer(giant cells; large tissue clumped together, could be cancerous)

Answer 13

period of injury

Question 14

following exposure to radiation, recovery can take place(short term effects);
may be a certain amount of damage from which no recovery occurs(later or long term effects)

Answer 14

recovery period

Question 15

greater dose, more severe the probable biological effect

Answer 15

total dose

Question 16

a given dose will produce less effect if it is divided than if it is given in a single exposure

Answer 16

dose rate

Question 17

larger exposure area, greater injury

Answer 17

area exposed

Question 18

LD50/30

Answer 18

the lethal dose, dose required to kill 50 % of the individuals in a large population in a 30 day period

Question 19

most sensitive to radiation

Answer 19

lymphocytes and blood forming cells reproductive cells

Question 20

moderately sensitive to radiation

Answer 20

GI tract, skin cell, and lens of the eye

Question 21

least sensitive to radiation

Answer 21

mature bone, cartilage, nerve, brain, and muscle cells

Question 22

when the severity of the change is dependent on the dose

Answer 22

deterministic(nonstochastic) effect

Question 23

when a biological response is based on the probability of occurence rather then the severity of the change; when dose of radiation is increased, the probability of the stochastic effect occurring increases, but not its severity

Answer 23

stochastic effect

Question 24

occurs when a biological change or damage occurs in the irradiated individual, but is not passed along to offspring(all except reproductive cells)

Answer 24

somatic effect

Question 25

describes changes in hereditary tissues that do not manifest in the irradiated individual, but show up in the individuals offspring

Answer 25

genetic effect

Question 26

when a very large dose of radiation is delivered in a very short period of time, the latent period is____

Answer 26

short

Question 27

ARS

Answer 27

acute radiation syndrome

Question 28

symptoms for ARS

Answer 28

``` erythema, nausea vomiting diarrhea hemorrhage hair loss ```

Question 29

primary risk from dental radiography is a ____ effect

Answer 29

stochastic

Question 30

critical tissues for dental radiography

Answer 30

skin of head and neck bone marrow in mandible thyroid gland