Paralleling technique Flashcards
other names for paralleling technique?
extension cone paralleling technique (XCP), right-angle technique, and long-cone technique
important terminology!!!
- parallel
- intersecting
- perpendicular
- right angle
- long axis of the tooth
- central ray
principles of paralleling technique
- film is places in the mouth to the long axis of the tooth being radiographed
- the central ray of the x-ray beam is directed perpendicular to the film and the long axis of the tooth
- a film holder must be used to keep the film parallel with the long axis of the tooth
different film holders (5)
- rinn XCP instruments
- precision film holders
- state bite-block
- eezee-grip film holder
- hemostat with bite-block
size 1 film is used for…
- used in the anterior region
- long portion in the vertical direction
size 2 film is used for…
- used in the posterior region
- long portion in the horizontal direction
rules for paralleling technique
- film placement: tooth and root
- film position: parallel to long axis
- vertical angulations: central ray perpendicular to film 90 degree
- horizontal angulations: through contacts
- film exposure: avoid cone cut
step-by-step procedures for radiographs
- patient preparation
- equipment preparation
- exposure sequence for film placements
- film placement
how can we prepare the patient?
- explain the procedure
- adjust the chair
- adjust the headrest
- place and secure the LEAD APRON
- remove all object from the mouth
how can we prepare equipment?
- set the exposure factors
- BEFORE PLACING, open the sterilized package containing the film holder
exposure sequence for film placements
- anterior exposure sequence
- posterior exposure sequence
film placement for paralleling technique
- the specific area where the film must be positioned before exposure
- dictated by teeth and surrounding structures
how can we ensure a logical sequence in radiographing?
- anterior first - more tolerable for patient
- posteriors: always premolar before molar due to patient comfort
- lay films out in a FMS mount orientation, as you remove films, put in cup. ensure you do not miss an area or double exposure of a film
- review text sequence and reasoning. reduce changing XCP configuration, but move back and forth from right side
- recommended sequence - next
recommended sequence
- anteriors first: mx and then mn, which side does not matter
- posterior second: do one sextant at a time (premolar and molar), follow arrangement of films
- put films in cup as they are exposed, ex: Q1 - premolar and molar, Q4 - premolar and molar, Q2 and Q3
3 modifications in the paralleling technique
- shallow palate
- bony growths
- mandibular premolar region
what is the shallow palate modifications?
- cotton rolls: 2 cotton rolls can be used, one placed on each side of the bite-block
- vertical angulation: the vertical angulation can be increased by 5 to 15 degrees
what if we cannot get parallel?
no more than 20 degrees is still generally diagnostic
what are bony growth modifications?
- maxillary torus: the film must be placed on the far side of the torus and then exposed
- mandibular tori: the film must be placed between the tori and the tongue and then exposed
in placing film for radiographs…
- film will become parallel as the patient closes
- insert on angle
- floor of mouth will relax as patient closes
mandibular premolar region: film placement
the film must be placed under the tongue
mandibular premolar region: film
the lower edge of the film can be greatly softened to prevent discomfort
advantages of the paralleling technique
- accuracy: the image is free of distortion
- simplicity: eliminated the need to determine horizontal and vertical angulation, elicited chances of dimensional distortion
- duplication: comparison of serial radiographs has great validity
disadvantages of paralleling technique
- film placement: may be difficult
- discomfort: film-holding device may cause discomfort
