Oral radiology: intro to radiation biology

what is radiation

energy released in the form of waves or particles and can penetrate materials.

what is ionizing energy

energy that can remove electrons from orbit, making the atom charged or ionized.

what percentage of ionizing radiation is background radiation

52%

what are examples of background radiation

radon, cosmic, internal radionuclides, and terresterial

where does radon come from

it is emitted from the uranium in the soil

when is cosmic radiation exposure high

In higher altitude. and doubles every 6,000 ft

On land, where is cosmic radiation the highest

at the north and south poles

what amount of cosmic radiation exposure occurs when flying from london to new york

0.032mSv of cosmic radiation

what is an example of internal radionuclides

brazil nuts that contain radon and potassium-40

what are examples of artificial ionizing radiation

CT, nuclear medicine, interventional radiology, radiography, dental and consumer products

what percentage of artificial ionizing radiation does dentistry contribute

2.6%

compton scattering radioation

ionizing radiation where an electron is ejected and the photon has lower energy and changes the direction it travels

photoelectric absorption

ionizing radiation where the electron absorbs all the energy from the photon and is ejected

coherent scattering

non-ionizing radiation where the photon doesn’t have enough energy to eject an electron but the direction of the photon changes

what is the main interaction occurring between an x-ray and tissue

compton scattering

what interaction occurs the least between an x-ray and tissue

coherent scattering

what is the direct effect of x-rays on living tissue

the photon from the x-ray directly hits critical areas of a cell

what is the indirect effect of x-ray on living tissue

when the photon from an x-ray is absorbed by water and forms free radicals that go on to damage critical areas of a cell

radiolysis of water

forms free radicals of hydrogen and hydroxyl

what can the free radicals from the radiolysis of water form

hydrogen peroxide and hydroperoxyl free radical and other free radicals

how is a DNA helix held together

through weak hydrogen bonds between the nucleotide base pairs

what happens when a single strand of a DNA helix is damaged

the intact second strand is used as a temple for repair

what happens if both strands of the DNA helix are damaged

cell death or mutation that can lead to cancer or an inheritable gene

what is deterministic

the higher the dose the higher the severity of side effects

stochastic

the higher the dose the higher the probability of having side effects

what does radiotherapy damage

oral mucosa, teeth, bones, muscles, taste buds, salivary glands

what are the effects of radiotherapy on teeth

radiation caries due to the altered environment of the oral cavity (low pH, low buffering, low calcium ions)

how are children’s teeth impacted due to radiotherapy

altered development such as delay, small, or lack of teeth. eruption is not effected

what is radiotherapy’s effect on bone

damage to the vessels of the periosteum leading to lack of osteoblast/ osteoclasts, increased chance of infection. Osteorradionecrosis

during radiotherpy what are the likely side effects

tase loss, mucositis, and xerostomia

after radiotherapy what are the likely side effects

tase loss, mucositis, xerostomia, radiation caries, trismus, and osteoradionecrosis

what model does the stochastic effect follow

the linear non-threshold model

what are the modify factors for the stochastic effect

dose, dose rate, age, and radiosensitivity

what is effective dose

the proper dose of radiation for a specific tissue to allow proper medical treatment

what increase radiosensitivity

high mitosis and low maturity (differentiation)

what tissue has high radiosensitivity

testicles and mucous membranes

what tissues have intermediate radiosensitivity

salivary glands and thyroid glands

what tissue have low radiosensitivity

muscle cells, mature red blood cells, and neurons

how does age alter the risk of radiosensitivity

the yonger the patient the higher the risk for cancer