Introduction to Radiographic Interpretation

Question 1

Why can we see caries on radiographs?

Answer 1

1. Caries results in area of demineralised enamel/dentine
2. Demineralised tissue is less effective at attenuating X-ray beam
3. More X-rays photons are transmitted & reach receptor
4. Creates darker area on radiograph (i.e. radiolucency)

Question 2

What is radiography necessary for?

Answer 2

detection of approximal caries in posterior teeth (unless large lesion), but also improves detection of occlusal caries

Question 3

What are benefits of radiographs for caries diagnosis?

Answer 3

• Can visualise lesions in inaccessible areas e.g. approximal surfaces, base of fissures, under restorations, etc.
• Can help identify lesions earlier → treatment can be less invasive
• Able to show extent of lesions → aids treatment planning

Question 4

What are the downsides of radiographs for caries diagnosis?

Answer 4

• Exposure to ionising radiation (particularly in children)
• Cannot directly show whether caries is active or inactive/arrested*

*unless you compare radiographs of same patient taken months apart

Question 5

When to take radiographs?

Answer 5

Radiographs of clinically-evident carious lesions can aid treatment planning by showing extent * e.g. pulp involved → will require RCT or XLA

Radiographs of posterior teeth can aid early diagnosis
* Taken at specific intervals based on patient’s caries risk
* Risk assessment reviewed at each appointment
* Interval length must be based on evidence-based guidance

Note: can vary between guidelines

Question 6

What is the intervals for children of high, medium and low risk?

Answer 6

• High risk: 6 months
• Medium risk: 12 months
• Low risk:
• 12-18 months (if primary dentition)
• 24 months (if secondary dentition)

Question 7

What is the intervals for adults of high, medium and low risk?

Answer 7

• High risk: 6 months
• Medium risk: 12 months
• Low risk: 24 months

Question 8

What does a bitewing radiograph show?

Answer 8

• Provides low-dose, high-resolution,
  reproducible image of many teeth
• Only for posterior teeth

Question 9

What is the default choice for caries?

Answer 9

bitewing

Question 10

What does a periapical radiograph show?

Answer 10

• Shows fewer teeth but can check periapical status if suspect tooth has pulpal involvement

Question 11

What does a panoramic radiograph show?

Answer 11

• Higher dose & worse resolution but able to show entire dentition

Question 12

When do caries appear on radiographs?

threshold

Answer 12

Caries will only appear on radiographs if there has been sufficient demineralisation of enamel/dentine
* ~40% demineralisation required

Question 13

What extent of a lesion is visible radiographically?

Answer 13

roughly 2/3s

Question 14

What is dentine split into to evaluate the depth of the caries?

Answer 14

• Outer third
• Middle third
• Inner third (next to pulp)

Question 15

What are the two classifications of caries?

Answer 15

Primary caries
* Not associated with a dental restoration

Secondary caries
* Associated with a dental restoration
* a.k.a. recurrent caries

Question 16

Where do primary caries often arise?

Answer 16

predictable areas (e.g. approximal surfaces of posterior teeth & at the base of dental pits & fissures) & forms characteristic shapes

Question 17

What other radiolucences can be misdiagnosed as caries?

Answer 17

cervical burnout
deficient restoration margins

Question 18

Where do atypical patterns often arise?

examples

Answer 18

atypical oral environments
* Exceptionally poor oral hygiene
* Extreme hyposalivation
* Abnormal diet

Question 19

What is the position/shape of secondary caries influenced by?

Answer 19

• Shape of restoration
• Integrity of restoration margins
• Complete/incomplete removal of original caries

Question 20

What should you beware of when looking for secondary caries?

Answer 20

Beware of residual caries under restorations
* Left deliberately during placement

Question 21

be

How to differntiate between secondary caries and deficient margins on a radiograph?

Answer 21

• Secondary caries: soft-edged radiolucency of uneven thickness
• Deficient margin: well-defined radiolucency with angular edges

Remember: deficient margins can become carious

Question 22

What are things mistaken for caries commonly?

Answer 22

• Deficient margins
• Superimposed anatomy
• Cervical burnout
• Mach band effect
• Excessive digital manipulation

Question 23

What is superimposed anatomy?

what radiographs is it most commonly seen in?

Answer 23

Superimposed anatomy occurs when two or more structures overlap on a radiographic image.

Rare on bitewing & periapical radiographs but more common on panoramic & occlusal radiographs

Question 24

What is cervical burnout?

Answer 24

Artefactual radiolucency occurring at the neck of the tooth
* Always present but usually too subtle to raise concern
* Can be enhanced by artificially increasing contrast

Created by a combination of the tooth’s structure & the peri-radicular bone

Question 25

What are features of cervical burnout?

Answer 25

• Located at cervical region of tooth
• Gradually fades away towards middle of tooth
• Apical margin of radiolucency follows alveolar crest
• Coronal margin follows cemento-enamel junction
• May extend slightly past CEJ (where enamel is thin)
• Usually affects multiple teeth

if uncertain, check clinically

Question 26

What is mach band effect?

Answer 26

Optical phenomenon where the human visual system enhances the interface between 2 contrasting areas

Light edge appears lighter & dark edge appears darker

Question 27

What are the features of mach band?

Answer 27

• Thin radiolucent band of uniform thickness
• Located directly adjacent to restoration
• Often spans entire underside of restoration

Question 28

What image alterations are avaliable with radiographs?

Answer 28

brightness, contract, edge enhancement

Question 29

What are shortcomings of radiographs?

Answer 29

Active caries looks identical to arrested caries
Residual caries looks identical to secondary caries
Radiolucent linings under restorations can mimic secondary caries
Cervical burnout can mimic root caries

Question 30

What is the solution to these shortcomings?

Answer 30

check clinically + check progression over time on radiographs