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 cross- infection 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