Questions and Answers
What is the basic principle of the paralleling radiographic technique?
The film is placed parallel to the long axis of the teeth being radiographed.
To achieve parallelism, film must be placed away from the tooth, toward the ________ of the oral cavity.
middle
What does an increase in object-film distance (OFD) do to magnification?
What is the most common type of film holding device used for the paralleling technique?
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Using the paralleling technique, the film must be placed directly against the teeth.
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What should clients do after establishing two points of contact when using XCP instruments?
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Which of the following is an advantage of the paralleling technique?
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What is the recommended film size for anterior radiographs in the paralleling technique?
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What do the letters X, C, and P stand for in XCP?
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A common error in radiographs results from faulty film __________.
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What should be ensured regarding the white side of the film during imaging?
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Increasing the vertical angulation is not required for clients with a shallow palate.
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Study Notes
Basic Principles of Paralleling Technique
- Film is placed parallel to the long axis of the teeth during radiography.
- Central ray is directed perpendicularly to both the tooth's long axis and the film.
- A film holding device is essential to maintain film parallelism with the long axis of the tooth.
Achieving Parallelism
- The film must be positioned away from the tooth, toward the center of the oral cavity.
- Increased object-film distance is required to compensate for the oral cavity's curvature.
Magnification Factors
- Increasing object-film distance (OFD) leads to greater magnification.
- Increasing target-film distance (TFD) results in reduced magnification.
Object-Film-Beam Alignment
- Proper alignment (film parallel to the tooth and beam at 90º) minimizes distortion in images.
Film Holding Devices
- XCP (Extension Cone Paralleling): The most commonly used film holder designed to simplify the paralleling technique.
- Precision Film Holder: Features metal collimating shields to restrict beam size.
- EEZEE Grip Film Holder: Also known as Snap-A-Ray.
- Stabe Bite Block: Made of disposable styrofoam for single-use.
- Hemostat: Utilized with a rubber bite block for stabilization.
Usage of XCP Instruments
- Simplifies paralleling procedures and minimizes distortion.
- Adjustable for patient positioning.
- Anterior images use size 1 receptors, placed high in the palate or floor of the mouth.
- Posterior images utilize size 2 receptors in a horizontal position, ensuring proper coverage of the area.
Rules for Using XCP Instruments
- Establish two points of contact (palate/floor of mouth and teeth) for accurate placement.
- Use the bite block length to achieve film parallelism.
- Align the PID to the film to prevent cone cuts.
Advantages of the Paralleling Technique
- Directing vertical angles away from the thyroid gland and lens of the eye.
- Produces images with minimal dimensional distortion and maximum detail.
- Offers a straightforward learning experience with the aid of XCP instruments.
- More reliable comparison radiographs when a series is needed.
Disadvantages of the Paralleling Technique
- Requires film holding devices, which could be challenging for some clients.
- Potential discomfort caused by the film holder or the film edge impacting oral tissues.
- Long PID necessary to compensate for increased object-film distance.
Film Sizes and Individual Radiographs
- Size #1 film is used for anterior periapicals, while size #2 is used for posterior periapicals.
- Full Mouth Series (FMS) includes 8 anterior images (4 maxillary and 4 mandibular) and posterior images.
Common Errors in Paralleling Radiographs
- Issues arise from poor film placement leading to vertical angulation problems and result in foreshortening.
- Ensuring the white side of the film faces the teeth is crucial.
- The bite block needs to be stabilized by teeth, rather than lips.
Modifications for Anatomical Variations
- Shallow Palate: May require use of cotton rolls to increase vertical angulation for better periapical coverage.
- Bony Growths: Film should be placed strategically around growths, like maxillary or mandibular tori, to avoid obstruction.
Closing Notes
- Anticipate upcoming review sessions, quizzes, and tests related to this unit to consolidate knowledge.
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Description
This quiz focuses on the paralleling technique in dental radiography, highlighting its basic principles. Participants will explore the correct positioning of the film in relation to the teeth and the role of the central ray and film holding device. Mastering these principles is essential for accurate dental imaging.
