Selection and perception of dental radiographs

Question 1

Biological effects and risks of ionising radiation

Answer 1

Somatic deterministic
Genetic stochastic
Somatic stochastic

Question 2

Somatic deterministic effects

Answer 2

There is a threshold dose below which the effect will not occur
Examples include skin burn and cataract formation
Severity is proportional to dose
Expect these effects with high radiation doses

Question 3

Genetic stochastic effects

Answer 3

Can occur spontaneously or be caused by radiation
DNA damage in reproductive cells may lead to congenital abnormalities or mental retardation
This is why there is a max permissible dose to abdomen during pregnancy.. not relevant to dental radiography

Question 4

Somatic stochastic effects

Answer 4

Stochastic effects are subject to laws of chance
Examples include induction of leukaemia and some other cancers
Any dose, large or small, may produce these effects.. there is no threshold dose
Lower doses.. lower chance but not no chance (think of lottery tickets!)

Question 5

Risk of 30 year old px developing fatal malignancy - panoramic

Answer 5

1 in 1,000,000

Question 6

Risk and age

Answer 6

<10 - multiply by factor of 3
10-20 - 2
20-30 - 1.5
30-50 - 0.5
50-80 - 0.3
80+ - don't worry about it

Question 7

How many fatal malignancies from dental radiography in the UK

Answer 7

Around 10 per year

Keep radiation doses as low as possible

Question 8

Legal stuff

Answer 8

Must examine each px before referring for radiography
Check there are no previous images
Be aware of hospital or dept. guidelines for imagining
If in doubt ask
Provide sufficient clinical info to allow justification of your requiest

Question 9

When should you take radiographs for toothache

Answer 9

Any previous radiographs?

• bitewing where offending tooth not obvious
• periapical if offending tooth obvious and tender to percussin
• periapical if there’s local swelling, and if there is limited opening then sectional panoramic

Question 10

Screening for caries

Answer 10

BW is ‘gold standard’ view
Intervals between subsequent BWs must be reassessed for each new period as individuals can move in and out of caries risk categories with time
High risk: 6 monthly BWs until no new or active lesions are apparent
Moderate risk: annual BWs until …
Low caries risk: 12-18 month in primary dentition, 2 year intervals if permanent dentition

Question 11

Radiographs in periodontal disease

Answer 11

BWs will show bone levels if bone loss not too severe
Periapical required if periodontal/ endodontic lesion is suspected
Panoramic radiograph of good quality may offer dose advantage over large number of intra-oral radiographs, may be considered if available

Question 12

Radiographs in endodontics

Answer 12

Good quality recent periapical radiograph needed before starting
Radiograph needed to determine working length unless other reliable means available
Post-op radiograph necessary to act as baseline for assessment of subsequent bony healing
Durther post-op radiographs are taken usually anually for up to 4 years

Question 13

Radiographs in orthodontics

Answer 13

Panoramic - some of the 5s are not erupted, are they present

Cone beam CT - is the unerupted canine resorbing the lateral?

Question 14

Pre-extraction views

Answer 14

Any previous relevant radiographs?
Is a radiograph necessary?
Always for lower 3rd molars and likely ‘surgicals’
Always for GA cases
Generally periapical will suffice but request full or sectional panoramic for multiple extractions and lower 3rd molars

Question 15

Assessment of lower 3rd molars

Answer 15

A pre-op radiograph mandatory
Use 1/4 panoramic or 1/4 L, or both
Use CBCT if there is overlap between root apices and inferior dental canal

Question 16

TMJ problems

Answer 16

Eliminate dental cause
Is radiograph of TMJ likely to be helpful?
Open-mouth panoramic view will provide overview of mandibular condyles
CBCT can be considered for complex pathology of condyle
MRI might be useful when conservative measures fail for joint dysfunction and disc pathology likely

Question 17

Trauma

Answer 17

Use intra-oral images to detect root #s when possible
Consider ‘soft’ dental view for possible tooth fragments in soft tissue wounds
Don’t forget chest radiograph for ‘missing’ teeth
Full panoramic +/- PA mandible for jaw fracture
OM 10+/- 30 degree views for facial fracture
Cone-beam CT for orbital blow-out fractures

Question 18

Sinus pathology

Answer 18

For acute sinusitis no imaging is needed
If malignancy seems possible an OM view in first instance followed by Cone-beam CT or MRI if more suspicious
Cone-beam CT provides CT provides useful ‘road map’ for ENT in surgical management of chronic sinus conditions

Question 19

Salivary stone disease

Answer 19

Mealtime syndrome
-to detect calculi request lower floor of mouth AND posterior oblique occlusals and submandibular cases
Sialography for mealtime sydnrome once any acute infection has settled
Ultrasound +/- sialography is useful in cases of persistent xerostomia
For discrete lumps request ultrasound in first instance; MRI for deep lobe parotid lesions

Question 20

Implant assessment

Answer 20

Cone beam CT provides excellent images for implant planning

Question 21

How do improve image perception

Answer 21

Have the correct attitude - don’t be rushed
Shut blinds/ turn off lights
Know your anatomy
Develop system for screening whole image-avoid ‘tunnel vision’
Opacities that appear to be in jaw might not be!