Radiology – Paralleling, Bisecting,
Bitewing
 Everything
lines up to long axis
 Film is placed parallel to long axis of
tooth being radiographed
 Central ray is perpendicular or at a right
angle to the film and long axis of the
tooth
 Achieve
parallelism between film & tooth
– Film must be placed away from the
tooth and toward middle of mouth.
 Increase the object to film distance to
keep film parallel with long axis of tooth –
increased object to film distance = more
magnification
 Increased
magnification causes loss of
definition
 To compensate increase the target film
distance (16” PID)
Accuracy- Produces an image that has
dimensional accuracy
 Simplicity- Use of the film holder and
beam alignment device elminates
guessing placement
 Duplication- It is easy to standardize and
can be accurately duplicated

 Film
placement- difficulties may be
encountered w/ children or w/ adult
patients who have a small mouth or shallow
palate
 Discomfort- the XCP may impinge on the oral
tissues and cause discomfort for the patient
 Also
called the bisecting angle technique,
bisection of the angle technique, and shortcone technique
 Another method used to expose periapical
films
 Bisecting
the angle between film & tooth
– rule of isometry.
 Based on two imaginary equal triangles
 Film
placed along the lingual
 Point where film contacts the tooth – the
film and the long axis of the tooth form
an angle.
 Visualize a line that divides in half
(bisects) the angle formed by the film &
long axis of tooth. Line = imaginary
bisector
 Not good for pt. w/bone loss – distorts
level of bone
 Angulation
of the PID is critical with the
bisecting technique
 Angulation is used to describe the alignment
of the CR on the horizontal and vertical
planes
 This is important with the snap-a-ray or
finger holding method
 Film
placement
 Film position
 Vertical angulation
 Horizontal angulation
 Film exposure
 Can
be used w/o a film holder when the
anatomy of the patient precludes the use of
a film-holding device
 Decreased exposure time, a 8” PID is
preferred with the bisecting technique
 Image
distortion- occurs when a short PID is
used, it causes image magnification
 Angulation problems- w/o a film holder and
aiming ring visualizing the imaginary bisector
can be difficult, image may result in
distortion
 Unnecessary exposure- with the finger
holding method the patient’s hand is
unnecessarily exposed to the primary beam
 Also
know as the interproximal technique
 Method used to examine the interproximal
surfaces of the teeth
 Used
to diagnose caries between the teeth
and bone levels
 Film
placement – teeth to be examined
 Film position – parallel to crowns of both
arches
 Vertical angulation – central ray of beam
directed through contact areas
 Horizontal angulation – central ray of beam
through contact areas
 Film exposure – beam centered on film so all
areas are exposed – failure – cone cut or
partial image