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38 ch review
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Question | Answer |
---|---|
Radiographs enable the dentist to see | conditions that are not visible in the oral cavity and to identify many conditions that might otherwise remain undetected |
many dental diseases and conditions have no clinical signs or sympstoms and are typically discovered | only through the use of dental radiographs |
____ has teh ability to cause damage to all types of living tissues | radiation |
Any exposure to radiation no matter how small has the potential to | cause harmful biologic changs in the operator and the patient |
who discovered the x-ray on Nov 8 1985 | Wilhelm Conrad Roentgen |
what does the x in x-ray stand for | represents the unknown |
what represented the first radiograph of the human body | Roentgen's wife's hand |
what were x-rays first referred to as, and what was radiology referred to as, and what were radiographs known as | roentgen rays and roentgenology, and roentgenographs |
who made the first dental radiograph | Otto Walkhoff |
how long did the first dental radiograph take to expose | 25 minutes |
who is credited with the first practical use of radiographs in dentistry | C. Edmund Kells |
C. Edmund Kells dedication to the development of dental radiography eventually cost him his | fingers, later his hand, then his arm and after enduring much pain and being faced with the prospect of becoming a burden to his family he committed suicide in 1928. |
dense core of the atom that is compromised of particles known as protons and neutrons. | nucleus |
___ carry positive electrical charges | protons |
___ carry no charge | neutrons |
Dental x-rays _____ make atoms radioactive | can not |
patients _____ give off x-rays after the x-ray machine stops producing x-rays | do not |
tiny negatively charged particles that have very little mass | electrons |
electrons remain stable in their orbit around the necleus until | radiograph photons collide with them |
x-rays belong to a group classified as | electromagnetic radiation |
what things are also classified as electromagnetic radiation | visible light, radar, radio, and television waves |
Electromagnetic radiation is made up of photons that travel | through space at the speed of light in a straight line with a wavelike motion |
the ______ the wavelength of the x-ray the _____ is its energy | shorter, greater |
which wavelengths are especially usefull in dentistry | shorter |
what are the 3 primary components that x-ray machines all have | tubehead, extension arm and control panel |
parts of the tubehead | xray tube, metal housing, anode, insulating oil, unleaded glass window of xray tube, lead collimator,PID, aluminum discs, tubehead seal, filament circut, cathode |
metal body that contains the x-ray tube | tube head housing |
fills the housing and surrounds the x-ray tube, this prevents overheating by absorbign the heat created by the production of x-rays | insulating oil |
made of leaded class or aluminum keeps the oil in the tubehead and acts as a filter to the x-ray beam | tubehead seal |
where x-rays are produced | x-ray tube |
alters the voltage of incoming electric current | transformer |
metal disk with a small opening in the center it is located inside the PID in the path of the x-ray beam, it limits the size of the x-ray beam | lead collimator |
when the size and shape of the beam are changed to a rectangle only slightly larger than the film the amount of tissue exposed to radiation can be | reduced by more than 1/2 |
The PID is the | open ended lead lined cylinder that extends from the opening of the metal housing |
the x-ray tube is the ____ of the x-ray generating system. | heart |
the ____ or ____ electrode, consists of a tungsten filament in a focusing cup made of molybdenum. the purpose of this is to supply the electrons necessary to generate x-rays | cathode, negative |
the ___ the filament becomes ,the ___ electrons are produced | hotter, more |
the focusing cup keeps: | electrons suspended in an electron cloud at the cathode |
the ___ or ___ electrode acts as the target for the electrons, it is composed of a tungsten targetthat is embedded in the larger copper stem | anode, positive |
the copper around the tungsten target does what | conducts the heat away from the target, reducing the wear on the target. It serves as a focal spot and converts the electrons into x-ray photons |
what % of the x-rays generated are absorbed by the oil | 99% |
what # of the x-rays generated exit the tubehead through the opening as a divergent beam toward the patient | 1 % |
what 2 shapes can the PID be | cylindrical or rectangular |
which PID shape limits the size of the beam to that of a dental film | rectangular |
means to move in a side to side motion | horizontally |
means to move in an up and down motion | vertically |
what must a dental assistant or patient never do to the tubehead | hold it in place during exposure |
what is the abreviation for milliamperage | mA |
what is the abreviation for kilovoltage | kV |
the milliamperage selector controls what | the number of electrons that are procuded |
the kilovoltage selector controls what | penetrating power of the x-ray beam |
dental x-ray machines generally operate at what kVp | 70 or 90 |
characteristics of the x-ray beam are described as | the quality , quantity and intesity of the x-ray beam |
structures that radiation can easily pass through appear | radiolucent ( dark ) on a radiograph |
examples of things that will show up radiolucent on a film | air spaces, soft tissues, abcesses, tooth decay, and dental pulp |
structures that radiation does not easily pass through appear | radiopaque ( white or light gray ) on a radiograph |
examples of things that will show up radiopaque on a film | metal restorations, tooth enamel, dense areas of bone |
the range of shades of gray to black to white is called | contrast |
___kilovoltage produces more penetrating radiographs and ____ radiographic contrast | higher, lower |
___ is the overall blackness or darkness of a film | density |
the degree of density is controlled by the ___ seconds | milliampere |
if the radiograph is not exposed for a suffiecient amount of time or is exposed with a low milliampere setting, the resulting radiograph will not have the correct overall density or will be: | light in appearance |
other factors that influence the density of the radiograph include: | distance from the x-ray tube to the patient, developing time and temperature, and body size of the patient |
if the operator lengthens the source-film distance without changing the exposure settings, resulting radiographs will be | light or less dense |
If the processing time is too long, the radiograph will appear | dark |
A patient who is very small or thin requires___ radiation than a husky, heavy boned person | less |
which 3 geometric characteristics affect the quality of the radiograph | sharpness, magnification and distortion |
___ refers tohow well the radiograph reproduces the fine details or distinct outlines of an object, is sometimes referred to as detail, resolution or definition. | sharpness |
the sharpness of an image in influenced by what | focal spot size, film composition and movement |
a machine with a___ focal spot results in a sharper image than a machine with a ___ focal spot size | smaller, larger |
fast film speeds result in __ ___ detail because of the ___ crystal size | less sharp, large |
any movement of the patient or the film, no matter how slight will __________ of the image | degrade the sharpness |
___ refers to the disproportionate change in the size of images on radiographs that is caused by excessive or insufficient vertical angulation | distortion |
______ refers to the proportionate enlargement of a radiographic image | magnification |
the cumulative effect of radiation exposure can be compard with the cumulative effect from what | repeated exposure over the years to the rays of the sun |
which organs are considered critical organs | skin, thyroid gland, lens of the eye and bone marrow |
two sets of systems are used to define the ways in which radiation is measured, the older system is referred to as ____, the newer system is ____ | the traditional system or standard system, the metric equivalent known as the susteme internationale |
the maximum permimssible dose is defined as | the maximum dose equivalent that a body is permitted to receive in a specified period of time |
The current MPD for persons occupationally exposed to radiation is | 5000 millirem or 5.0 rems/year |
for non occupationally exposed persons, the MPD is | .1 rem/year |
dental personnel should strive for an occupational dose of 0 by | adhering to strict radiation protection practices |
back ground radiation comes from natural sources such as | radioactive materials in the ground and cosmic radiation from space |
when dental radiographs are prescribed and properly taken, the benefit of disease detection _____ the risk for biologic damage associated with receiving small doses of radiation | far outweighs |
when radiographs must be retaken because of poor operator technique the patient is exposed to | unnecessary additional radiation |
the decision to expose new radiographs must be base on what | how recently previous films were taken and the clinical need for additional films |
radiographs should never be taken on a | "routine basis" |
what is the purpose of the aluminum filter | to remove the low engery long wavelength, least penetrating x-rays from the beam |
what is the collimator used for | to restrict the size and shape of the x-ray beam to reduce patient exposure |
what is the PID | position indicator device, used to direct the x-ray beam, has a round or rectangular shape |
the PID is available in which two lengths, why is it available in two lengths | 8 inch and 16 inch, a long PID is more effective in reducing exposure to the patient than a short one because it causes less divergence of the beam |
what must you not do to the lead apron when storing | fold |
what is the main factor in determining film speed | the size of the silver bromide crystals |
in reference to film speed the _____the crystals the ____ the film | larger, faster |
a fast film requres _________ to produce a quality radiograph | less exposure |
_____ film is the most effective method of reducing a patients exposure to | fast, x-radiation |
film holding devices are used for what purposes | to keep the patients hands and fingers from being exposed to x-radiation, holds the film in a stable position and assists the operator in properly positioning the film and PID |
a setting of ______ keeps patient exposure to a minimum | 70 to 90 kVp |
in reference to taking x-rays on pregnant patients the ADA and FDA state that | dental radiograpic procedures "do not need to be altered because of pregnancy" |
what are the 3 types of monitoring devices used to determine the amount of radiation exposure to personnel | film badge, pocket dosimeter ( pen style ) and thermoluminescent device |
the ________ is most commonly used to measure the amount of occupational exposure | film badge |