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38 ch review
whole chapter for test reveiw
| 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 |
Created by:
cynthia.fryer
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