Bitewing radiography
Main indications
Detection of interproximal caries
Monitoring the progression of dental caries
Assessment of existing restorations
Assessment of the periodontal status
Ideal technical requirements
The bite-platform should be positioned on
the middle of the film packet and parallel
to the upper and lower edges of the film
packet
The film packet should be positioned with
its long axis horizontally for a horizontal
bitewing or vertically for a vertical bitewing\
The posterior teeth and the film packet should be
in contact or as close as possible
The posterior teeth and the film packet should be
parallel- the shape of the dental arch may
necessitate two separate film positions to achieve
this requirement for the premolars and the molars
In the horizontal plane, the X-ray tubehead should
be aimed so that the beam meets the teeth and the
film packet at right angles, and passes directly
through all the contact areas
I
In the vertical plane, the X-ray tubehead
should be aimed downwards approximately
5 to 8 degrees to the horizontal to
compensate for the upwardly rising curve of
Spee
The positioning should be reproducible
Positioning techniques
Using a tab attached to the film packet and
aligning the X-ray tubehead by eye
Using a holder with beam-aiming device to
facilitate the positioning and alignment of
the X-ray tubehead
Film holders
Basic components of film holders
A mechanism for holding the film packet
parallel to the teeth
A bite platform that replaces the wing
An X-ray beam-aiming device
The appropriate size film is selected as
follows:
- Large film packets ( 31*41mm ) for adults
- Small film packets ( 22*35 mm ) for
children under 12 years. Once the second
permanent molars have erupted the adult
size film is required
The patient is positioned with the head supported and
occlusal plane horizontal
The operator holds the tab between thumb and
forefinger and inserts the film packet into the lingual
sulcus opposite the posterior teeth
The anterior edge of the film packet should be positioned
opposite the distal aspect of the lower canine- in this
position, the posterior edge of the film packet extends
usually just beyond the mesial aspect of the lower third
molar
The tab is placed on to the occlusal surfaces of
the lower teeth
The patient is asked to close the teeth firmly
together on to the tab
As the patient closes the teeth, the operator
pulls the tab firmly between the teeth to ensure
that the film packet and the teeth are in contact
The operator releases the tab
The X-ray beam is aimed directly through the
contact areas, at right angles to the teeth and
the film packet, with an approximate 5-8 degrees
downward vertical angulation
To ensure that the anterior part of the film is
exposed the front edge of the cone should be
positioned adjacent to the corner of the mouth
Advantages of using film packets
with tabs
Simple
Inexpensive
The tabs are disposable, so no extra crossinfection control procedures required
Can be used easily in children
Disadvantages
Operator-dependent assessment of horizontal
and vertical angulation of the X-ray tubehead
Radiographs are not reproducible
Cone cutting is common
The tongue can easily displace the film packet
Advantages of film packet holders
Simple
Film packet held firmly in position and cannot be
displaced by the tongue
X-ray beam is always at right angles to the film
packet
Avoid cone cutting
Holders are autoclavable
Disadvantages
Positioning of the film holder can be
uncomfortable for the patient
Some holders are relatively expensive
Holders are not suitable for children
Ideal exposure factors
Assessment of caries and restoration-high kV
which ensures good contrast to allow
differentiation between enamel, dentin and allow
EDJ to be seen
Assessment of periodontal status- low kV to
avoid burn-out of the thin alveolar crestal bone
In the X-ray machines with fixed kV and mA
these results are achieved through exposure
time