Radiographic techniques 2 - bitewings

Question 1

the x-ray beam should always be what? and what happens if it isnt?

Answer 1

• Should be at right angles to the tooth and the receptor to avoid distortion of the image
• any upward angulation will cause the teeth to be elongated
• any downward angulation will cause the teeth to be fore-shortened
• remember image geometry can also be affected by the angle of the receptor

Question 2

Why would you request a bitewing radiograph?

Answer 2

• Will help detect caries or monitor caries progression
• assess periodontal status and also assess existing restorations

Question 3

Answer 3

Question 4

how many radiographs do you take if u do a vertical bitewing?

Answer 4

In vertical bitewings as the long axis of the receptor is in the vertical plane, 2 radiographs are required to cover the desired teeth. Again you want to see from the 4 to the 8. You will demonstrate more of the root but you will still not see the apices

Question 5

If you require to see more of the root and supporting bone then you should request?

Answer 5

vertical bitewings. However, vertical bitewings involve irradiating your patient 4 times compared to only twice with horizontal bitewings and also vertical bitewings can be much more difficult to tolerate as size of the receptor will be uncomfortable for the patient.

Question 6

What are the positioning requirements for bitewing radiographs?

Answer 6

the receptor and object should be parallel. The receptor should be as close as possible to the object. And the x-ray beam should be perpendicular to both the object and the receptor

Question 7

How do we achieve good positioning?

Answer 7

Always use a holder

Question 8

What colour holder is for the bitewing?

Answer 8

red

Question 9

Answer 9

Sometimes you may have to use only a paper tab if the patient cannot tolerate the holder. The tabs have an adhesive side and can be stuck directly to the receptor with a wing sticking out for the patient to bite on. It is much more comfortable for the patient but there is no guide ring to help you position the tube so you have no control over image geometry or even whether you are going to hit the receptor at all.

Question 10

pitfalls to look out for when positioning in the horizontal plane are?

Answer 10

• Not following the dental arch ( in other words having the film in squint)
• or not having the tube correctly positioned against the ring
• you can see only 2 corners are touching

Question 11

describe horizontal overlap

Answer 11

• Sometimes difficult to avoid
• crowing or tilting of teeth
• acceptable if less than half of enamel superimposed
• will miss early carious lesions
• must show enamel dentinal junction and dentinal half of enamel

Question 12

what is a benefit of the holder?

Answer 12

Allows you to keep the source to object distance long, and the image receptor close to the object, thus reducing magnification

Question 13

what size of bitewing do you use for each patient?

Answer 13

size 2 = always for adults, and children over 10
size 0/1 = on children under 10 depending on their size

Bitewings on children can be extremely difficult, they find it extremely uncomfortable. If a child refuses to co-operate you must then change to lateral oblique mandibles but the detail on the teeth is greatly reduced, but it is still better than nothing

Question 14

Why use a rectangular collimation?

Answer 14

can reduce the dose to the patient by up to 50%