Dental Hygienist Practice Test – Obtaining and Interpreting Radiographs

One second equates to 60 impulses, so to calculate impulses, multiply 60 by 1/4 second. Hence, 60 impulses/ second x 1/4 second = 15 impulses.

The three elements used in the x-ray tube are the molybdenum cup, the copper stem and the tungsten filament and target. Silver, Bromine, Iron and nickel are not present in the x-ray tube.

Roentgen is the unit used to measure radiation exposure in the traditional unit of radiation measurement.

Sodium carbonate is the ingredient which provides the required alkaline environment in the developing solution, aiding in the softening of the emulsion.

Concrescence is a rare dental anomaly in which cementum of two adjacent teeth is joined together.

Of the given structures/materials, an amalgam restoration will appear the most radiopaque. It is the densest structure which will absorb or block the most radiation. The area of the amalgam on the image receptor will not be exposed, which will result in an image appearing radiopaque or white.

The lamina dura is cortical bone surrounding the root of the tooth and will appear radiopaque on an x-ray.

A carious lesion on the buccal or lingual surface of a molar will appear as a circular, radiolucent on a dental image.

The mental foramen is a circular radiolucent structure that appears on the mandibular premolar PA image.

The ghost image does not have similar sharpness, but rather is more blurred as compared with the original artifact.

To correct an error regarding cone cutting, one should move the PID to completely cover the image receptor, as this will subsequently allow the x-ray beam to reach each part of the image receptor. By adjusting the PID to cover the entire image receptor, this in turn corrects the error of cone cutting.

Nausea, diarrhea, erythema, hemorrhage and loss of hair are signs and symptoms associated with acute radiation exposure (Acute radiation syndrome – ARS) and are experienced when high doses of radiation are administered within a short time frame. These somatic effects are regarded nonstochastic effects because they have a dose threshold and increase in severity as the dose increases.

When an atom is subjected to the ionization process, it loses an electron and the atom becomes an ion with a positive charge, with the ejected electron having a negative charge.

Contrast is affected only by kVp. The penetrating power of the x-ray beam is determined by kVp. The lower the kVp, the less penetrating is the power of the x-ray beam and the higher the contrast. Whereas the higher the kVp, the greater is the penetrating power of the x-ray beam and the lower the contrast.

The cause of the yellowish-brown stains is due to insufficient rinsing or fixing and exhausted fixer or developer.

In digital imagery, the x-ray photons are captured on a sensor or phosphor plate and are broken into electronic pieces called pixels. Each pixel has one shade of grey. The image is transferred from the sensor and stored on the computer.

The term radioresistant refers to a cell that is resistant to changes induced by radiation. Older, mature cells are considered radioresistant since they divide infrequently and have a lower metabolism. Examples of radioresistant cells include cells of bones, nerves and muscles.

Failure to apply and follow patient safeguards such as a lead apron could potentially harm the unborn child during any trimester. However, the greatest risk for embryologic damage is during the first trimester due to increased mitotic activity, immature cells, and increased cell metabolism.

When the tungsten filament of the cathode portion of the x-ray tube heats up after activation of the filament circuit, the “boiling off” or release of electrons is termed as thermionic emission.

The 8-inch PID creates more divergence of the x-ray beam in comparison with the 16-inch PID, creating more radiation exposure.