Radiography of dental caries

Question 1

What 3 types of tooth tissue may be involved in caries?

Answer 1

enamel

dentine

cementum

Question 2

Where does primary caries occur?

Answer 2

at sound tooth surfaces

Question 3

Where does secondary caries occur?

Answer 3

near existing restoration

Question 4

What is residual caries?

Answer 4

demineralised tissue left behind when filling is placed

Question 5

What does active caries describe?

Answer 5

when the disease is in a period of progressing demineralisation

Question 6

What are the recognisable patterns of disease in active caries?

Answer 6

early childhood caries

rampant (generally seen in adolescence)

Question 7

What happens in arrested caries?

Answer 7

when disease is in a period of remineralisation

Question 8

Where are Class I lesions in Black’s classification?

Answer 8

pit or fissure

Question 9

Where are Class II lesions in Black’s classification?

Answer 9

inter proximal of posterior teeth

Question 10

Where are Class III lesions in Black’s classification?

Answer 10

inter proximal of anterior teeth

Question 11

Where are Class IV lesions in Black’s classification?

Answer 11

inter proximal of anterior teeth involving incisal edge

Question 12

Where are Class V lesions in Black’s classification?

Answer 12

cervical third of tooth

Question 13

What is D1 is Pitts’ classification?

Answer 13

white/opaque or brown lesion

surface is hard on probing

Question 14

What is D2 is Pitts’ classification?

Answer 14

slight loss of surface

sticky fissures

no dentine involvement

Question 15

What is D3 is Pitts’ classification?

Answer 15

dentine involvement

but not pulp

Question 16

What is D4 is Pitts’ classification?

Answer 16

possible or definite pulpal involvement

Question 17

How are D1 and D2 lesions managed?

Answer 17

preventative measures

Question 18

How are D3 and D4 managed?

Answer 18

restorative treatment

Question 19

Name the methods of caries detection

Answer 19

visual inspection

radiography

temporary tooth separation

fiberoptic transillumination

laser fluorescence

electrical conductance measurements

research techniques eg MRI (experimental at moment)

Question 20

What happens in fiberoptic transillumination?

Answer 20

white light shone into contact points

with 0.5mm diameter probe

caries reduces spread of light, so appears dark clinically

best for approximal caries

can’t be used near restorations

Question 21

What are the 3 things than can happen to light in fluorescence?

Answer 21

light scatters through the material

some of the light waves are absorbed

some lose energy and are emitted as waves with longer wavelengths

Question 22

How is fluorescence used?

Answer 22

a light of known wavelength is shone onto object

fluorescence changes with density

low density of demineralisation and caries will alter fluorescence

observed using digital imaging software

Question 23

What are bitewing radiographs described as?

Answer 23

gold standard for radiographic diagnosis

as it has maximum coverage of ‘at risk’ areas for lowest dose

Question 24

What should we be able to see in bitewing radiographs?

Answer 24

The mesial contact point of first premolars to the most distal contact point

In adults, two radiographs may be required to cover all contact points

Up to half thickness of enamel overlap in radiographs is acceptable

This is a reproducible technique

Question 25

Describe periapical radiographs

Answer 25

Similar resolution to bitewing but fewer crowns shown on individual film for same dose

Question 26

Describe oblique lateral radiographs

Answer 26

Extraoral image with lower resolution than bitewings Useful for caries diagnosis in young children

Question 27

Describe panoramic radiographs

Answer 27

Not indicated purely for caries diagnosis unless unable to tolerate intraorals Extraoral film/sensor means lower resolution Moving x-ray source and image receptor

Question 28

What are the advantages of extra oral bitewings?

Answer 28

More comfortable for patients Better interproximal separation between contacts than panoramic 50% dose reduction than normal panoramic

Question 29

What are the disadvantages of extra oral bitewings?

Answer 29

compared with intra oral bitewings... - Higher dose - Lower resolution - Increased artefacts - Less reproducible

Question 30

What % mineral loss is required to detect caries on radiographs?

Answer 30

40% via decreased density of dental hard tissues

Question 31

What does caries cause?

Answer 31

demineralisation of inorganic portion destruction of organic portion

Question 32

How does a decrease in density lead to radiographic changes?

Answer 32

decrease in attenuation of x-ray photons area becomes more radiolucent on image

Question 33

Why does occlusal caries occur?

Answer 33

food debris and bacteria in pits and fissures

Question 34

What happens when caries reaches dentine in occlusal lesions?

Answer 34

spread laterally have triangular shape on radiograph

Question 35

Where does approximal caries occur?

Answer 35

medial and distal surfaces early lesions only involve name then spread laterally into dentine

Question 36

Why are good quality images required for approximal caries?

Answer 36

to separate contact points and reveal low contrast lesions

Question 37

How do buccal and lingual caries arise?

Answer 37

from pits and fissures but do not widen to occlusal surface usually round becoming more elliptic or semilunar when large

Question 38

What does root caries consist of?

Answer 38

cementum and dentine associated with gingival recession cervical burnout artefact may mimic caries

Question 39

What must we consider when reporting caries?

Answer 39

full crowns, enamel and dentine density cervical margins existing restorations pulp chamber - reactive dentine - direct involvement of pulp

Question 40

What are the 3 main issues with radiographs?

Answer 40

ionising radiation technique/projectional issues caries mimics/artefacts

Question 41

What are the 2 types of damaging effects that ionising radiation has on tissue?

Answer 41

- Deterministic eg skin erythema - Stochastic/random eg cancer

Question 42

Why do technique and projectional issues occur?

Answer 42

film faults and processing beam angulation overlapping contact points superimposition of restorations

Question 43

What are the film faults and technique errors that reduce image quality and make it harder to see caries?

Answer 43

Positioning of film so contacts points aren’t covered Incorrect exposure settings Processing errors Radiograph orientation of viewing

Question 44

What can occur if the beam angulation is incorrect?

Answer 44

contact points overlap may cause superficial lesion to be projected deeper than it actually is eg enamel lesion appears to be into dentine

Question 45

What is the issue with buccal and lingual caries?

Answer 45

can't localise the lesion from single radiograph both radiographs would look the same unable to assess bucco-lingual depth

Question 46

Are lesions bigger clinically or radiographically?

Answer 46

clinically

Question 47

Name 3 types of caries mimics

Answer 47

cervical burnout artefact Mach effect corrosion products

Question 48

Why does cervical burnout effect occur?

Answer 48

x-rays over-penetrate or burn out the thinner tooth edge

Question 49

How does cervical burnout effect appear?

Answer 49

The cervical root edge will be intact but dark Usually, inner edge is more diffuse and rounded than caries It is bounded by enamel superiorly and alveolar bone inferiorly

Question 50

What is the Mach band effect?

Answer 50

visual illumination when uniformly dark area meets uniformly light area ie dentine and enamel dark shade appears even dark and light shade appears even lighter If either one is masked, then the Mach band will disappear

Question 51

Where may corrosion products appear?

Answer 51

In amalgam restorations there may be radiolucency deep beside it which can mimic caries These are deposits of heavy metal ions eg tin, zinc in softened dentine

Question 52

What is the interval of imaging for a 5 year old according to the European academy of paediatric dentistry?

Answer 52

low caries - 3 high caries - 1

Question 53

What is the interval of imaging for 8-9 year olds according to the European academy of paediatric dentistry?

Answer 53

low caries - 3-4 high caries - 1

Question 54

What is the interval of imaging for 12-16 year olds according to the European academy of paediatric dentistry?

Answer 54

low caries - 2 high caries - 1

Question 55

What is the interval of imaging for 16+ year olds according to the European academy of paediatric dentistry?

Answer 55

low caries - 3 high caries - 1

Question 56

What does the FGDP selection criteria state about high caries risk patients?

Answer 56

Posterior bitewings at 6 monthly intervals until no new or active lesions or patient changes into different category risk

Question 57

What does the FGDP selection criteria state about moderate caries risk patients?

Answer 57

Annual posterior bitewings unless risk status alters

Question 58

What does the FGDP selection criteria state about low caries risk patients?

Answer 58

Posterior bitewings at 12-18 monthly intervals in primary dentition 2-year intervals in permanent dentition