week 5

chp 3,11,28,30,31

free radical

* uncharged atom or molecule
* that exists with a single, unpaired electron in its outermost shell
* combines with molecules to form toxins
* highly reactive and unstable

when are free radicals formed?

form when an x-ray photon ionizes with water

what is believed to be involved in degenerative diseases and cancers?

free radicals

What are the two theories of radiation injury?

* direct theory
* indirect theory

direct theory

* this theory suggest that cell damage results when ionizing radiation directly hits critical areas, or targets, within the cell


* direct injuries from exposure to ionizing radiation occur infrequently

indirect theory

* this theory suggests that x-ray photons are absorbed within the cell and cause the formation of toxins, which in turn damage the cell
* ex: when x-rays photons are absorbed by the water within a cell, free radicals are formed. the free radicals combine to form toxins
* indirect injuries from exposure to ionizing radiation occur frequently bc of the high water content of cells

dose- response curve

used to correlate the response or damage of tissues with the dose or amount of radiation received

what kind of curve graph is this?

threshold curve

what kind of curve graph is this?

linear curve

* response of tissues is directly proportional to the dose

non threshold dose response curve suggests

no matter how small the amount of radiation received, some biologic damage occurs

what are the two types of radiation effects?

* stochastic
* nonstochastic

stochastic effects (random)

occurs as a direct function of dose

* effects do not depend on the magnitude of the absorbed dose
* examples: cancer and genetic mutations

nonstochastic (deterministic) effects

* somatic effects that have a threshold and increase in severity with increased absorbed dose
* effects occur only after a threshold of exposure has been exceeded
* examples: loss of hair, cataract formation, decreased fertilityk, radiation sickness, erythema

what is the sequence of radiation injury?

explain each.

1. ==latent period:== time btw exposure to ionizing radiation an the appearance of observable clinical signs
2. ==period of injury:== cellular injuries may result, changes are observable
3. ==recovery period:== depending on factors, cells can repiar the damge caused by radiation
4. ==cumulative effects:== effects of radiation exposure are additive. unrepaird damage accumulates in tissues. Can lead to cancer, cataract formation, birth defects

what does the latent period depend on?

The latent period depends on the __total dose of radiation r__eceived an the __amount of time (rate)__ it took to receive the dose

the more radiation received and the faster the dose rate, the ______ the latent period

shorter

List the 5 determining factors for radiation injury

1. total dose: quantity of radiation received
2. dose rate: rate at which exposure to radiation occurs and absorption takes place
3. amount of tissue irradiated
4. cell sensitivity
5. age

who is more susceptible to radiation damage?

children and elderly

short term effects

\
* associated with __large doses__ of radiation/__short amount of time__
* can be seen within minutes, days, or weeks
* Acute radiation syndrome (ARS) includes nausea, vomiting, diarrhea, hair loss, hemorrhage

long term effects

\
* __small doses__ absorbed repeatedly over a __long period__ of time
* effects can be seen after years, decades, or generations
* cancer, birth abnormalities, genetic defects

somatic cells

all cells except the reproductive cells

genetic cells

reproductive cells

somatic effects

* seen in the person irradiated
* not seen in future generations

genetic effects

* not seen in the person irradiated
* passed on to future generation

somatic or genetic effect?

\
produces poor health in the exposed animal

somatic effect

somatic or genetic effect?

\
does not effect the exposed animal, but can affect future generations

genetic effect

radiosensitive

a cell that is sensitive to radiation

radioresistant

a cell that is resistant to radiation effects

what is the response of a cell to radiation exposure determined by?

* mitotic activity: cells that divide frequently are more sensitive
* cell differentiation: cells that are immature or not highly specialized are more sensitive
* cell metabolism: higher metabolism are most sensitive

radiosensitive **organs**

lymphoid tissue

bone marrow

reproductive cells

intestinal mucosa

What is the **cell** that is most sensitive to radition? It is most susceptible to ionizing radiation

small lymphocyte

radioresistant **tissues**

salivary glands

kidney

liver

radioresistant **cells**

mature bone

muscle

nerve

radiosensitive **cells**

blood

immature reproductive cells

young bone cells

radiosensitive organs are composed of radiosensitive cells and include the

lymphoid tissues

bone marrow

testes

intestines

critical organ

an organ that if damaged diminishes the quality of a person’s life

what are critical organs that are exposed during dental radiographic procedures?

skin

thyroid

lens of the eye

bone marrow

What are the __traditional__ units of radiation measurements?

* Roentgen
* measures radiation exposure by determining the amount of ionization that occurs in air
* Radiation *absorbed* dose (rad)
* amount of energy(x-rays) *absorbed* by tissue
* ==Roentgen equivalent (in) man (rem)==
* used to compare biologic effects of different kinds of radiation

Can roentgen measure the amount of radiation absorbed?

no, limited to measurements in air only

what measurement is only used for x-rays and gamma rays?

Roentgen

__SI (newer)__ units of radiation measurement

* coulombs/kilogram
* gray
* ==sievert==

what does Roentgen measure? Is there an SI equivalent?

* R measures radiation by determining the amount of ionization that occurs in air
* there is no SI equivalent

RAD SI equivalent is _____

Gray

1 gray=100 rad

REM SI equivalent is ____

Sievert

1 sievert= 100 rem

natural background radiation

sources include:

* radon in air
* uranium, radium, thorium in the earth
* cosmic rays from outerspace and the sun


* radioactive potassium in food and water
* radioactive material found w/i human body

what is the single greatest source of exposure to background radiation in the US?

radon gas arising from the soil

In the US, the average dose of background radiation received by an individual ranges from ______ mrad per year

150--300

What is the greatest contributor to human-made (artificial) radiation exposure?

medical radiation

* medical radiographic procedures
* dental radiography
* fluoroscopy
* nuclear medicine
* radiation therapy

ways to decrease pt exposure and dose

film speed

collimation

technique

exposure factors

TRUE OR FALSE

\
anatomic order refers to how teeth are arranged within the dental arches

True

Why is an opaque film mount preferred compared to a clear film mount?

it masks the light around each radiograph

who mounts films?

any trained dental professional with knowledge of the normal anatomic landmarks of the maxilla, the mandible, and related structures is qualified to mount dental radiographs

when should films be mounted?

immediately after processing in a area designated for film mounting

what are two types of film mounting methods?

labial and lingual mounting

Curve of Spee

* maxillary =
* mandibular=

maxillary= convex

mandibular= concave

True or False

\
Use a view box to examine radiographs, avoid holding mounted films ‘up to the room light’ to view

true

radiographs are placed in the film mount with the _____ side of the identification dot facing the viewer

raised (convex-pimple)

\
pimple not a dimple

whos responsibility is it to establish a final or definitive interpretation and diagnosis?

the dentist

two types of bones

cortical bone (compact bone)

cancellous bone (spongey bones)

How does **cortical** bones appear on a radiograph?

radiopaque

how does **cancellous** bone appear on a radiograph?

radiolucent

How do prominences of bone appear on a radiograph? What are examples of prominences?

* __process__
* marked prominence or projection
* __ridge__
* linear prominence or projection
* __spine__
* sharp, thorn-like projection
* __tubercle__
* small bump or nodule
* __tuberosity__
* rounded prominence

\
They appear radiopaque(absorb more of the x-rays)

How do spaces and depressions in bone appear on a radiograph? What are some examples of them?

* __canal__
* tube-like passageway through bone that contains nerves and blood vessels
* __foramen__
* opening/hole that permits passageway of nerves/blood vessels
* __fossa__
* broad, shallow, scooped-out, or depressed area
* __sinus__
* hollow space, cavity, or recess

\
They appear radiolucent (they do not resist passage of x-rays)

Septum

* a bony wall or partition that divides two spaces/cavities
* radiopaque

suture

* an immovable joint
* thin radiolucent line

What does the maxilla form?

floor of the orbit of the eye

sides and floor of the nasal cavity

hard palate

incisive foramen

* hole located at midline of hard palate
* radiolucent

superior foramina of the incisive canal

* two tiny openings in bone on the floor of the nasal cavity
* radiolucent

\

median palatal suture

* immovable joint between the two palatine processes of the maxilla
* radiolucent thin line

lateral fossa

* smooth depressed area of maxilla
* aka canine fossa
* radiolucent

nasal cavity

* pear shaped compartment of bone located superior to maxilla
* radiolucent

nasal septum

* vertical bony wall
* radiopaque

floor of nasal cavity

* bony wall formed by palatal processes
* radiopaque

anterior nasal spine

* sharp projection of maxilla
* radiopaque

inferior nasal conchae

* wafer thin curved plates of bone extend from lateral walls of nasal cavity
* radiopaque

maxillary sinus

* paired cavities of bone located within in maxilla
* radiolucent

inverted y

the intersection of the maxillary sinus and the nasal cavity

radiopaque upside down Y

maxillary tuberosity

radiopaque bulge distal to the third molar region

hamulus

* small hook like projection
* aka hamular process
* radiopaque hook like projection

the mandible

* the only moveable bone of the face
* divided into three parts
* ramus
* body
* alveolar process

where is the coronoid process visualized?

in the maxillary molar PA

lamina dura

* made of **dense** **corticol** bone
* radiopaque

alveolar crest

* radiopaque
* 1.5-2 mm below the CEJ

Periodontal ligament space

radiolucent line around the root of a tooth

what does a normal alveolar crest appear? anterior and posterior regions

==__anterior: pointed and sharp__==

==__posterior: flat and smooth__==

interpret

to offer an explanation

interpretation

an explanation

image interpretation

an explanation of what is viewed on a dental image, the ability to read what is revealed by a dental image

diagnosis

the identification of a disease by examination or analysis g

who interprets images?

any dental professional with training in interpretation can examine images

why should the dental radiographer must have an established sequence in interpretation?

to prevent erros

All interpretation must be be documented and must include:

* description of bone/ supporting structures
* description of artifacts
* indication of any areas that require additional images or evaluation

descriptive terminology allows the dental professional to describe what is seen on a dental image _____ implying a diagnosis.

With out

how to describe lesions

* appearance (most radiolucent lesions appear uni or multilocular)
* location
* size

unilocular lesion, corticated borders

well demarcated radiopaque rim of bone at the periphery

unilocular leson, noncorticated borders

does not exhibit a thin radiopaque rim of bone. instead, the periphery appears fuzzy or poorly defined

inter-radicular location

lesion located ==between the roots o==f adjacent teeth

periapical location

lesion located ==around the apex== of a tooth

pericoronal location

lesion located around the crown

alveolar bone loss

loss of bone in max or mand that surrounds and supports the teth