Chapter 5

Question 1

Compton effect

Answer 1

occurs when an x-ray photon collides with an outer-shell electron, causing ionization and scattering of the x-ray photon with reduced energy. (This is the most frequent interaction with dental radiation.)

Question 2

Thomas scatter

Answer 2

involves low-energy x-ray photons that interact
with an atom, causing it to vibrate and scatter without ionization or
energy loss.

Question 3

Photoelectric effect

Answer 3

occurs when an x-ray photon is completely
absorbed by an inner-shell electron, causing ionization. This contributes to image contrast but occurs less frequently.

Question 4

Direct effect

Answer 4

Ionizing radiation directly hits DNA or critical cell targets,
causing immediate damage.

Question 5

Indirect effect

Answer 5

Ionizing radiation interacts with water molecules, leading to
the formation of free radicals, which then cause cellular damage.

Question 6

What does radiobiology study?

Answer 6

The study of the effects of ionizing radiation on living organisms, including the mechanisms of radiation-induced damage and the body’s response.

Question 7

Define the term dose.

Answer 7

The amount of radiation energy absorbed by tissues.

Question 8

Describe a free radical.

Answer 8

An uncharged molecule with an unpaired electron, making it highly reactive
and capable of causing cellular damage.

Question 9

What is background radiation?
What contributes to it?

Answer 9

Natural radiation from cosmic rays, the earth’s crust (radon), and internal body sources. It contributes to the majority of annual radiation exposure.

Question 10

List stochastic radiologic effect.

Answer 10

Effects that occur by chance and increase in probability with dose, such as cancer and genetic mutations, with no threshold dose.

Question 11

Stochastic Effects

Answer 11

Probability increases with dose but severity is
independent of dose (e.g., cancer).

Question 12

Deterministic Effects

Answer 12

Severity increases with dose and has a threshold
(skin erythema, cataracts).

Question 13

What are the direct effects of radiation.

What areas are affected?

Answer 13

Direct damage to DNA or cellular structures.

Question 14

What are the indirect effects of radiation?

What areas are affected?

Answer 14

Damage from free radicals formed by radiation interacting with water molecules.

Question 15

List traditional units of radiation.

Answer 15

• Roentgen (R)
• Rad
• Rem

Question 16

Define latent period.

Answer 16

Time between radiation exposure and the appearance of clinical symptoms.

Question 17

Define period of injury.

Answer 17

The time when cellular damage is visible or measurable.

Question 18

Define radioresistant.

Answer 18

Tissues or cells that are less sensitive to radiation (e.g., muscle, nerve cells).

Question 19

Define radiosensitive.

Answer 19

Tissues or cells that are more sensitive to radiation (e.g., lymphocytes,
bone marrow).

Question 20

What tissue is considered radiosensitive?

Answer 20

Bone marrow, reproductive cells, and lymphoid tissues.

Question 21

List critical organs.

Answer 21

Thyroid gland, bone marrow, skin, and eyes.

Question 22

What is artificial radiation? Sources?

Answer 22

Man-made radiation from medical procedures, nuclear industry, consumer products (examples, CT scans, nuclear power plants)

Question 23

Human tissue is composed primarily of ___, which affects how the x-ray energy is absorbed.

Answer 23

Water

Question 24

What surface of caries are most often seen on radiographs?

Answer 24

Proximal surfaces (mesial and distal)

Question 25

What is the output of a dental x-ray machine expressed in?

Answer 25

Expressed in milliamperes (mA) and kilovolts (kV).