Introduction to Radiographic Interpretation Flashcards
Why can we see caries on radiographs?
- Caries results in area of demineralised enamel/dentine
- Demineralised tissue is less effective at attenuating X-ray beam
- More X-rays photons are transmitted & reach receptor
- Creates darker area on radiograph (i.e. radiolucency)
What is radiography necessary for?
detection of approximal caries in posterior teeth (unless large lesion), but also improves detection of occlusal caries
What are benefits of radiographs for caries diagnosis?
- 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
What are the downsides of radiographs for caries diagnosis?
- 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
When to take radiographs?
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
What is the intervals for children of high, medium and low risk?
- High risk: 6 months
- Medium risk: 12 months
- Low risk:
- 12-18 months (if primary dentition)
- 24 months (if secondary dentition)
What is the intervals for adults of high, medium and low risk?
- High risk: 6 months
- Medium risk: 12 months
- Low risk: 24 months
What does a bitewing radiograph show?
- Provides low-dose, high-resolution,
reproducible image of many teeth - Only for posterior teeth
What is the default choice for caries?
bitewing
What does a periapical radiograph show?
- Shows fewer teeth but can check periapical status if suspect tooth has pulpal involvement
What does a panoramic radiograph show?
- Higher dose & worse resolution but able to show entire dentition
When do caries appear on radiographs?
threshold
Caries will only appear on radiographs if there has been sufficient demineralisation of enamel/dentine
* ~40% demineralisation required
What extent of a lesion is visible radiographically?
roughly 2/3s
What is dentine split into to evaluate the depth of the caries?
- Outer third
- Middle third
- Inner third (next to pulp)
What are the two classifications of caries?
Primary caries
* Not associated with a dental restoration
Secondary caries
* Associated with a dental restoration
* a.k.a. recurrent caries
Where do primary caries often arise?
predictable areas (e.g. approximal surfaces of posterior teeth & at the base of dental pits & fissures) & forms characteristic shapes
What other radiolucences can be misdiagnosed as caries?
cervical burnout
deficient restoration margins
Where do atypical patterns often arise?
examples
atypical oral environments
* Exceptionally poor oral hygiene
* Extreme hyposalivation
* Abnormal diet
What is the position/shape of secondary caries influenced by?
- Shape of restoration
- Integrity of restoration margins
- Complete/incomplete removal of original caries
What should you beware of when looking for secondary caries?
Beware of residual caries under restorations
* Left deliberately during placement
be
How to differntiate between secondary caries and deficient margins on a radiograph?
- Secondary caries: soft-edged radiolucency of uneven thickness
- Deficient margin: well-defined radiolucency with angular edges
Remember: deficient margins can become carious
What are things mistaken for caries commonly?
- Deficient margins
- Superimposed anatomy
- Cervical burnout
- Mach band effect
- Excessive digital manipulation
What is superimposed anatomy?
what radiographs is it most commonly seen in?
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
What is cervical burnout?
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
