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11) Bite-wing Radiographic Techniques
Introduction:
Bitewing radiographs take their name from the original technique which required the patient to bite on a small wing attached to an intraoral film packet.
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Modern techniques use holders, which have eliminated the need for the wing (now termed a tab), & digital image receptors (solid-state or phosphor plate) can be used instead of film, but the terminology & clinical indications have remained the same.
An individual image is designed to show the crowns of the premolar and molar teeth on one side of the jaws.
MAIN INDICATIONS
● Detection of incipient interproximal caries.
● Detection of interproximal calculus deposits.
● Detection of 2ry recurrent caries below restorations.
● Monitoring the progression of dental caries into the pulp.
● Assessment of existing restorations (i.e., overhanging)
● Detection of pulp stones.
● Assessment of the periodontal status.
● Determine the relation between permanent teeth & deciduous teeth
IDEAL TECHNIQUE REQUIREMENTS:
An appropriate image receptor holder with beam-aiming device should be used.
The image receptor should be positioned centrally within the holder with the upper & lower edges of the image receptor parallel to the bite-platform.
he image receptor should be positioned with its long axis for a or for a
❑ The beam-aiming device should ensure that in the horizontal plane, the X-ray tube-head is aimed so that the beam meets the teeth & the image receptor at right angles, & passes directly through all the contact areas.
❑ The beam-aiming device should ensure that in the vertical plane, the X-ray tube-head is aimed downwards (approximately 5°–8° to the horizontal) to compensate for the upwardly rising curve of Monson.
❑ The positioning should be reproducible.
Note: It is sometimes not possible to use an image receptor holder (with beam-aiming device) & achieve these ideal technical requirements – particularly in children. Clinicians therefore still need to be aware of the original technique of using a tab attached to the film packet or phosphor plate & aligning the X-ray tube-head by eye.
Diagram showing the ideal image receptor position and the approximate 5–8° downward vertical angulation of the X-ray beam (determined by the beam-aiming device) compensating for the curve of Monson.
Using image receptor with beam-aiming devices
everal image receptor holders with different beam aiming devices have been produced for use with film pac ets or digital phosphor plates with digital solid state sensors, held either hori ontally or vertically
A selection of different holders
periapical radiography, the of holder is a matter of personal preference dependent upon the type of image receptors being employed
The various holders vary in cost & design but essentially consist of the same three basic components that make up periapical holders, namely:
● A mechanism for holding the image receptor parallel to the teeth
● A bite-platform that replaces the original wing ● An X-ray beam-aiming device.
The radiographic technique can be summarized as follows:
1. The desired holder is selected together with an appropriate-sized image receptor – typically, a 31 × 41 mm film packet or phosphor plate or the equivalent-sized solid-state sensor. 2. The patient is positioned with the head supported & with the occlusal plane horizontal. 3. The holder is inserted carefully into the lingual sulcus opposite the posterior teeth. 4. The anterior edge of the image receptor should be positioned opposite the distal aspect of the lower canine –in this position the image receptor extends usually just beyond the mesial aspect of the lower third molar 5. The patient is asked to close the teeth firmly together onto the bite platform. (Note: Extra care needs to be taken of solid-state sensor cables.) 6. The X-ray tube-head is aligned accurately using the beam-aiming device to achieve optimal horizontal & vertical angulations 7. The exposure is made. 8. If required, the procedure is repeated for the premolar teeth with a new image receptor & X-ray tube-head position.
Advantages:
● Relatively simple straightforward
● Image receptor is held firmly in position cannot be displaced by the tongue
● Position of X-ray tube-head is determined by the beam-aiming device so assisting the operator in ensuring that the X-ray beam is always at right angles to the image receptor.
● Avoids coning off or cone cutting of the anterior part of the image receptor
● Holders are autoclavable or disposable
Disadvantages:
● Position of the holder in the mouth is operator dependent, therefore images are not 100% reproducible, so not absolutely ideal for monitoring progression of caries.
● Positioning of the film holder image receptor can be uncomfortable for the patient particularly when using solid-state digital sensors. ● ome holders are relatively expensive.
● Holders not usually suitable for children
Using a tab attached to the image receptor
❑ The traditional bitewing technique is particularly suitable when using film packets or digital phosphor plates as the image receptor. ❑ Although, the technique is very operator-dependent & not recommended for adults, it is still widely used for children.
Advantages:
● imple
● Inexpensive
● he tabs are disposable, so no extra cross-infection control procedures required.
● Can be used easily in children.
Film packets and phosphor plates with tabs attached suitable for adult vertical bitewings, adult horizontal bitewings & child’s horizontal bitewings.
The ideal bitewing & film packet position in relation to the teeth for an adult & a child.
Disadvantages:
● Coning off or cone cutting of anterior part of image receptor is common
● Not compatible with using solid-state digital sensors.
P a g e | 96 ● Operator-dependent assessment of horizontal & vertical angulations of the X-ray tube-head.
● Images not accurately reproducible, so not ideal for monitoring the progression of caries
Examples of typical RIGHT and LEFT horizontal adult bitewing radiographs, suitable for the assessment of caries and restorations, with the main radiographic features indicated.
Examples of typical right and left bitewing radiographs of a child with the main radiographic features indicated.
Assessment of image quality
❑ As described in previous lecture, image quality assessment essentially involves 3 separate stages: 1. Comparison of the image against ideal quality criteria 2. Subjective rating of image quality using published standards 3. Detailed assessment of rejected films to determine the source of error.
Ideal quality criteria:
● he image should have acceptable definition with no distortion or blurring
● he image should include from the mesial surface of the first premolar to the distal surface of the second molar – if the third molars are erupted then the 7/8 contact should be included. ● he occlusal plane/bite-platform should be in the middle of the image so that the crowns & coronal parts of the roots of the maxillary teeth are shown in the upper half of the image & the crowns & coronal parts of the roots of the mandibular teeth are shown in the lower half of the image, and the buccal and lingual cusps should be superimposed.
● he maxillary mandibular alveolar crests should be shown
● here should be no overlap of the approximal surfaces of the teeth
● he desired density & contrast for film-captured images will depend on the clinical reasons for taking the radiograph
● he image should be free of coning off or cone-cutting & other film handling errors.
● he image should be comparable with previous bitewing images both geometrically & in density & contrast.
A selection of bitewings showing patient preparation and positioning errors. A→ Image receptor positioned too far posteriorly – the edentulous area distal to the lower second is imaged but not the premolar teeth. B→ Image receptor displaced by tongue – occlusal plane not horizontal. C→ Failure to align the X-ray tubehead correctly in the horizontal plane – coning off of the anterior part of the image. D→ Failure to align the X-ray tubehead correctly in the horizontal plane – overlapping of the contact areas. E→ Failure to align the X-ray tubehead correctly in the vertical plane – buccal and lingual cusps not superimposed and distortion of the teeth. F→ Failure to instruct the patient to remain still – image blurred as a result of movement.
FILL IN THE BLANK
QUESTIONS
1. What does the term bite-wing refer to?
2. What size receptor is recommended for use with the bite-wing technique in the adult patient?
3. What size receptor is recommended for use with the bite-wing technique in the pediatric patient with primary dentition?
4. How is the patient’s head positioned before exposing a bite-wing receptor?
5. What condition is detected by the primary use of bite-wing images?
6. What size receptor is used to include all of the posterior teeth in one bite-wing exposure?
7. What type of angulation is determined by the up-anddown movement of the position-indicating device (PID)?
8. What type of angulation is determined by the side-toside movement of the PID?
9. When the central ray of the x-ray is not directed through the contact areas of teeth, what is seen on the resulting image?
10. When does a cone-cut result?
MULTIPLE CHOICE
Which of the following describes the primary use of the bite-wing radiograph image?
a. examination of the apical areas of teeth b. examination of the apical and interproximal areas of teeth c. examination of the interproximal areas of teeth d. examination of the pulp chambers of teeth
Which of the following is the correct vertical angulation used with the bite-wing technique and the bite tab?
a −10 degrees
b −20 degrees
c. +10 degrees d. +15 degrees
Which of the following describes the relationship of the receptor to maxillary and mandibular teeth in the bite-wing technique?
a. The receptor and teeth are parallel to each other. b. The receptor and teeth are at right angles to each other. c. The receptor and teeth are perpendicular to each other. d. The receptor and teeth intersect each other.
Which of the following about receptor placement is correct?
1. Anterior bite-wings may be placed horizontally. 2. Anterior bite-wings may be placed vertically. 3. Posterior bite-wings may be placed horizontally. 4. Posterior bite-wings may be placed vertically. a. 1, 2, and 3
b. 2, 3, and 4
c. 2 and 3
d. 1 and 4
Which of the following about the exposure sequence for a CMRS that includes periapical and bite-wing exposures is incorrect?
a. anterior periapicals are always exposed first. b. posterior periapicals are exposed after anterior periapicals. c. bite-wings are exposed last. d. none of the above.
