Exposure and Technique Errors

Appearance: The image appears clear (Figure 20-1).

Cause: The receptor was not exposed to x-radiation. Causes include failure to turn on the x-ray machine, electrical failure, and malfunction of the x-ray machine.

Correction: To ensure proper exposure of the receptor, make certain that the x-ray machine is turned on, and listen for the audible exposure signal.

Appearance: The image appears black (Figure 20-2).

Cause: The film was accidentally exposed to white light.

Correction: To protect the film, do not unwrap it in a room with white light. Check the darkroom for possible light leaks. Turn off all the lights in the darkroom (except for safelights) before unwrapping the film.

Appearance: The image appears dark (Figure 20-3).

Cause: The receptor was overexposed to radiation. An overexposed image results from excessive exposure time, kilovoltage, or milliamperage, or a combination of these factors.

Correction: To prevent overexposure, check the exposure time, kilovoltage, and milliamperage settings on the x-ray machine before exposing the receptor. Reduce exposure time, kilovoltage, or milliamperage as needed.

Appearance: The image appears light (Figure 20-4).

Cause: The receptor was underexposed to radiation. An underexposed image results from inadequate exposure time, kilovoltage, or milliamperage, or a combination of these factors.

Correction: To prevent underexposure, check the exposure time, kilovoltage, and milliamperage settings on the x-ray machine before exposing the receptor. Increase exposure time, kilovoltage, or milliamperage as needed.

Appearance: No apices are seen on the image (Figure 20-6).

Cause: The receptor was not positioned in the patient’s mouth to cover the apical regions of teeth. As a result, no apical structures appear on the radiograph, and an excessive margin of receptor edge exists (which appears as a black band). This error occurs with both the paralleling technique and the bisecting technique.

Correction: To make sure that apical structures appear on a periapical radiograph, make certain that no more than one eighth of an inch of the receptor edge extends beyond the incisal–occlusal surfaces of teeth. Such placement ensures adequate coverage of the apices.

Appearance: The occlusal plane appears tipped or tilted (Figure 20-7).

Cause: The edge of the receptor was not placed parallel to the incisal–occlusal surfaces of teeth. As a result, the occlusal plane appears tipped on the radiograph. If the patient is not instructed to close on the bite block to hold the receptor firmly against the tooth, a corner of the receptor may drop or slip.

Correction: To prevent a dropped receptor corner, make certain that the edge of the receptor is placed parallel to the incisal–occlusal surfaces of teeth as the patient bites his or her teeth together.

Appearance: Overlapped contacts are seen on the image (Figure 20-8).

Cause: The central ray was not directed through the interproximal spaces. As a result, the proximal surfaces of adjacent teeth appear overlapped in the periapical image. Overlapped contacts prevent examination of the interproximal areas. This error occurs with both the paralleling technique and the bisecting technique.

Correction: To avoid overlapped contacts on a periapical image, direct the x-ray beam through the interproximal regions. The use of Rinn beam alignment instruments minimizes errors in horizontal angulation.

Appearance: Teeth appear short with blunted roots on the image (Figure 20-9).

Cause: The vertical angulation was excessive (too steep). As a result, images that are shorter than the actual teeth, or foreshortened images, are seen on the radiograph. This error occurs more often with the bisecting technique.

Correction: To avoid foreshortened images, do not use excessive vertical angulation with the bisecting technique. The use of Rinn beam alignment instruments minimizes errors in vertical angulation.

Appearance: Teeth appear long and distorted on the image (Figure 20-10).

Cause: The vertical angulation was insufficient (too flat). As a result, images that are longer than the actual teeth, or elongated images, are seen on the radiograph. This error occurs more often with the bisecting technique.

Correction: To avoid elongated images, use adequate vertical angulation with the bisecting technique. The use of Rinn beam alignment instruments minimizes errors in vertical angulation.

Appearance: A clear (unexposed) area is seen on the image (Figure 20-11).

Cause: The PID was not properly aligned with the periapical beam alignment device, and the x-ray beam did not expose the entire receptor. As a result, a clear, unexposed area resembling the outline of the PID is seen on the radiograph.

Correction: To avoid a cone-cut on a periapical receptor when using a beam alignment device, position the PID carefully. If a beam alignment device with an aiming ring is used, make certain that the PID and the aiming ring are aligned. If an aiming ring is not used, make certain that the x-ray beam is centered over the receptor.

Appearance: A clear (unexposed) area is seen on the image (Figure 20-12).

Cause: The PID was not directed at the center of the receptor, and the x-ray beam did not expose the entire receptor. As a result, a clear, unexposed area resembling the outline of the PID is seen on the radiograph.

Correction: To avoid a cone-cut on a periapical receptor when not using a beam alignment device, position the PID carefully. Make certain that the x-ray beam is centered over the receptor and that the entire receptor is covered by the diameter of the PID.

Appearance: The distal surfaces of canines are not visible on the image (Figure 20-15).

Cause: The bite-wing receptor was positioned too far posteriorly in the mouth; the front edge of the receptor was not placed at the midline of the mandibular canine. As a result, the distal surfaces of the canines are not seen on the radiograph.

Correction: To prevent this error, make certain that the anterior edge of the bite-wing receptor is positioned at the midline of the mandibular canine.

Appearance: The third molar regions are not visible on the image (Figure 20-16).

Cause: The bite-wing receptor was positioned too far anteriorly in the mouth; the front edge of the receptor was not placed at the midline of the mandibular second premolar. As a result, the third molar areas are not seen on the radiograph.

Correction: To prevent this error, make certain that the anterior edge of the bite-wing receptor is positioned at the midline of the mandibular second premolar. Always center the molar bite-wing on the mandibular second molar, even when third molars are not present.

Appearance: Overlapped contacts are seen on the image (Figure 20-17).

Cause: The central ray was not directed through the interproximal spaces. As a result, the proximal surfaces of adjacent teeth appear overlapped in the bite-wing image. Overlapped contacts prevent examination of the interproximal areas.

Correction: To avoid overlapped contacts on a bite-wing image, direct the x-ray beam through the interproximal regions. When the contacts are opened, a thin radiolucent line is seen between the proximal surfaces of teeth. The use of Rinn bite-wing instruments minimizes errors in horizontal angulation.

Appearance: Images appear distorted on the radiograph (Figure 20-18).

Cause: The vertical angulation was incorrect. As a result, distorted images are seen on the radiograph. In this case, a negative vertical angulation was used. Note the occlusal surfaces of maxillary teeth and the apical regions of mandibular teeth.

Correction: To avoid incorrect vertical angulation, always use a +10-degree vertical angulation with the bite-wing technique. This vertical angulation compensates for the slight tilt of maxillary teeth and the slight lingual bend of the upper half of the receptor caused by the hard palate.

Appearance: A clear (unexposed) area is seen on the image (Figure 20-19, A). A cone-cut can also occur with a rectangular collimator and is seen as a clear area on the image (Figure 20-19, B).

Cause: The PID was not properly aligned with the bite-wing beam alignment device, and the x-ray beam did not expose the entire receptor. As a result, a clear, unexposed area resembling the outline of the PID is seen on the radiograph.

Correction: To avoid a cone-cut on a bite-wing receptor when using a beam alignment device, position the PID carefully, and make certain that the PID and the aiming ring are aligned.

Appearance: A clear (unexposed) area is seen on the image (Figure 20-20).

Cause: The PID was not directed at the center of the receptor, and the x-ray beam did not expose the entire receptor. As a result, a clear, unexposed area resembling the outline of the PID is seen on the radiograph.

Correction: To avoid a cone-cut on a bite-wing receptor when using a beam alignment device, position the PID carefully. Make certain that the x-ray beam is centered over the receptor and that the entire receptor is covered by the diameter of the PID.

Appearance: Images appear stretched and distorted (Figure 20-21).

Cause: The film was bent excessively because of the curvature of the patient’s hard palate. As a result, stretched and distorted images are seen on the radiograph.

Correction: To avoid film bending, always check film placement before exposure. If the film is bent because of the curvature of the hard palate, cotton rolls can be used with the paralleling technique, or the bisecting technique can be used. Film-holding devices are helpful in preventing film bending.

Appearance: A thin radiolucent line is seen on the image (Figure 20-22).

Cause: The film was creased, and the emulsion cracked. As a result, a thin radiolucent line is seen on the radiograph.

Correction: To avoid film creasing, do not bend or crease the film excessively. Instead, gently soften the corners of the film before placing it in the patient’s mouth.

Appearance: An image of the patient’s finger is seen on the radiograph (Figure 20-23).

Cause: The patient’s finger was incorrectly positioned in front of the receptor instead of behind it. As a result, an image of the patient’s finger is seen on the radiograph. The term phalangioma was coined by Dr. David F. Mitchell of the Indiana University School of Dentistry; the term refers to the distal phalanx of the finger whose image is seen in the radiograph. (A phalanx [plural, phalanges] is any bone of a finger or toe.) This error occurs when the finger-holding method is used with the bisecting technique; this technique is not recommended by the authors of this textbook.

Correction: To avoid a phalangioma, make certain that the patient’s finger used to stabilize the receptor is placed behind the receptor and not in front of it.

Appearance: A double image is seen on the radiograph (Figure 20-24).

Cause: The same receptor was exposed twice in the patient’s mouth. As a result, a double image is seen on the radiograph. A double exposure is a serious error and necessitates two retakes, one each for the two areas previously radiographed.

Correction: To avoid a double exposure, always separate exposed and unexposed receptors. Once a receptor has been exposed, place it in a designated area (e.g., a disposable cup or bag) away from unexposed receptors. If care is always taken to separate exposed receptors from unexposed receptors, this error will not occur.

Appearance: Blurred images are seen on the radiograph (Figure 20-25).

Cause: Either the tubehead or the patient moved during the exposure of the receptor. As a result, blurred images are seen on the radiograph.

Correction: To prevent movement errors, stabilize the tubehead and the patient’s head before exposing the receptor, and instruct the patient to remain still. Never expose a receptor when a tubehead is drifting or a patient is moving. Reposition the tubehead, the patient, the receptor, or the PID, as necessary, and then expose the receptor.

Appearance: Light images with a herringbone pattern are seen on the radiograph (Figure 20-26).

Cause: The film was placed in the mouth backward (reversed) and then exposed. The x-ray beam was attenuated by the lead foil backing in the film packet; consequently, a decreased amount of the x-ray beam exposed the film. As a result, light images with a herringbone pattern (also known as the tire-track pattern) are seen on the radiograph. The herringbone pattern on the radiograph is representative of the actual pattern embossed on the lead foil (see Chapter 7).

Correction: To avoid a reversed film, always place the white side of the packet adjacent to the teeth. Always note the front and back sides of the film before placing it in the patient’s mouth.

a. elongated

b. foreshortened

c. overlapped

d. none of the above

a. elongated

b. foreshortened

c. overlapped

d. none of the above

a. elongated

b. foreshortened

c. overlapped

d. none of the above

a. elongation

b. overlapped contacts

c. cone-cut

d. phalangioma

a. elongation

b. overlapped contacts

c. cone-cut

d. phalangioma