Dental Radiology for Dental Assisting Exam Practice Problems (page 2)

Updated on Jun 23, 2011

Practice Answers and Explanations

1. d. The effects of repeated exposure to radiation are cumulative and can result in many different disorders such as cancer, cataracts, leukemia, and genetic abnormalities.

2. c. The lead apron must be impregnated with 0.25 mm of lead to be effective in shielding out the radiation.

3. e. If you have a patient with concerns about radiation exposure, you should explain that you are using a lead apron and lead thyroid shield, you are using the long cone paralleling technique, and you take radiographs only when a need is indicated by clinical examination and not based on an arbitrary time schedule.

4. e. Aluminum filters are used in the PID to filter out the long waves. Only the short waves are useful in making an image on a film. Therefore, the filter removes the long waves and the patient receives less radiation.

5. b. The X-ray photons produced in the tube head have many different wave lengths.

6. b. The recommended collimation or restriction of the size of the X-ray beam at the patient’s face is 2.75 inches.

7. a. As Low As Reasonably Achievable is the concept for all radiographers to keep in mind by controlling the amount of radiation the patient receives. Using fast film, at least 60 kV, the aluminum filter, lead collimator, long cone PID, and utilizing the paralleling technique, proper processing, and minimal retakes are all ways to adhere to the ALARA concept.

8. e. Film badges, pocket dosimeters, and film rings are all examples of personnel monitoring devices that measure the dose of radiation received by the members of the dental team.

9. d. The energy of the X-ray beam is transferred to the material through which it passes. This transfer of energy is called absorption.

10. b. Collimation means that a lead disc is used for the elimination of the peripheral portion of the X-ray beam. The lead disc is called the collimator. It restricts the size of the X-ray beam at the patient’s face.

11. e. When a living organism is struck by photons, the molecules are broken into smaller pieces, they form new bonds within themselves and with other molecules, and some molecular bonds are disrupted.

12. b. +10 degrees vertical angulation is the correct vertical angulation for taking bitewing radiographs to produce minimal geometric distortion and open the contacts between the teeth.

13. d. In the bisecting the angle technique, the vertical angle of the beam is directed perpendicular to the line that bisects the angle made by the film and the long axis of the tooth being radiographed.

14. a. A full-mouth X-ray series always has periapical and bitewing films.

15. d. In dental radiography, the Snap-A-Ray film holders and XCP film holders are sterilized, and the treatment room is disinfected. No antiseptic agents are used.

16. b. Standing behind the lead barrier is the safest place for the operator while exposing intraoral films.

17. b. Exposed film packets should never be immersed in a disinfecting solution. Immersing them in any liquid will destroy the image. However, it is acceptable to wipe the exposed films with a dry paper towel to remove any saliva or blood.

18. d. Covering the exposure button with a plastic barrier is part of the infection control protocol for exposing X-rays.

19. b. Thermionic emission, which is when the electrons are boiled off of the tungsten filament, takes place in the cathode at the tungsten filament.

20. c. The periapical intraoral film records the most accurate image of crowns, roots, and supporting structures.

21. b. Proper film placement for the bicuspid/premolar bitewing radiograph must include the distal half of the mandibular cuspid. This way the bicuspids will appear in the center of the radiograph.

22. e. The primary diagnostic use of a bitewing radiograph is to check for interproximal decay and examine the crestal bone levels.

23. a. In a 20-film mount full-mouth set of X-rays, the central incisors, lateral incisors, and cuspids are radiographed using a size-1 film.

24. c. If the operator places the film backwards, the resulting image is one with low density and a herringbone pattern on the film.

25. c. The size of the silver halide crystals determines the speed of the film. The fastest film speed available is F speed.

26. a. For manual processing in the darkroom with the developing tanks, the proper sequence for immersion of the films is develop, rinse, fix, and wash.

27. c. Ammonium thiosulfate is the chemical found in fixer solution that clears the unexposed silver halide crystals.

28. d. Metol or hydroquinone is the chemical found in the developer that is responsible for building the black and gray tones.

29. d. Density is the degree of darkness or blackness on the film.

30. c. When the same film is exposed twice, a superimposed image will be the result. This operator error is called a double exposure. To prevent this error, the operator should align the unexposed films on a clean paper barrier. Once the film is exposed, it should be placed into a disposable cup.

31. c. Ionization is the term used to describe a substance losing electrons. Ionization is one of the many results of molecular change caused by radiation.

32. c. Lead is the most resistant material to the penetration of ionizing radiation. This is why the patient is draped with a lead-lined apron and thyroid collar.

33. a. Ninety-nine percent of the energy produced by the collision between electrons from the cathode and the anode is actually converted to heat. Only 1% of the energy produced is converted to X-ray photons.

34. d. On an edentulous patient, the maxillary tuberosity and the outer corner of the eye would serve as the landmarks of the maxillary molar radiograph.

35. b. If developer splashes on a film prior to processing, the result will be a black spot. Splashes of fixer would cause white spots.

36. c. Soft substances such as the dental pulp will appear dark on an X-ray film and are therefore radiolucent.

37. e. Underexposure, underdevelopment, and low mA and kV will all cause a light film.

38. b. A radiolucent structure appears dark on a radiograph.

39. d. Gold and amalgam appear radiopaque on an X-ray film. Both gold and amalgam are solid metal substances. Composite is a form of plastic called resin, which can be filled or unfilled. The filled composite shows radiopaque, just not as bright white as gold or amalgam.

40. d. A full-mouth X-ray survey appears in an upward curve similar to a smile. This curve is called the curve of Spee.

41. a. The resultant image of the operator using too much vertical angulation is foreshortening. The X-ray image is shorter than the actual size of the tooth in the mouth.

42. c. The occlusal radiograph is designed to show the complete arch of teeth, either maxillary or mandibular. Foreign bodies such as tumors or cysts are more readily identified in an occlusal radiograph. 

43. b. Intensifying screens contain phosphors that emit blue or green light and are used only in extraoral films. Therefore, extraoral films require less radiation since the intensifying screens are present.

44. b. If the patient does not place his or her tongue on the hard palate, a dark image will appear above the apices of the maxillary anterior teeth.

45. c. A periapical abscess is the result of the death of the dental pulp. This occurs after eruption of the tooth into the mouth and therefore is not a developmental abnormality.

46. e. A charged coupling device (CCD) is made of silicon. This is used in the sensors of digital radiology.

47. d. An exaggerated curve of Spee will be the resultant image on a panoramic X-ray if the patient’s chin is too low. Therefore, the operator must make sure that the patient’s Frankfort plane is always parallel to the floor.

48. c. Prior to placing a dental implant, the operator needs to examine the bone quality and bone quantity, and locate anatomical structures. The panoramic radiograph is best for this purpose. A patient may be sent to the hospital for medical clearance and an MRI prior to implant placement.

49. A X-ray Tube B Tungsten Target C Metal Housing of X-ray Tube Head D Anode E Insulating Oil F Unleaded Glass Window of X-ray Tube G Lead Collimator H Position Indicating Device I Aluminum Filter J Tube Head Seal K Tungsten Filament L Cathode

50. k. Andibular left bicuspid periapical

51. c. Maxillary left bicuspid periapical

52. l. Mandibular left molar periapical

53. e. Right molar bitewing

54. d. Maxillary left molar periapical

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