Radiography of caries Flashcards
describe role of radiographs
what is caries definition?
- multifactorial disease
- infectious disease
- lactic acid produced by bacteria causing demineralisation
- Step mutant
- balance between de and re mineralization
- Demineralisation may extend well into dentine before cavitation occurs,
how can you describe carious lesions
- enamel
- dentine
- root
- primary
- secondary
- residual
- active caries (early childhood, rampant)
- arrested or inactive
describe blacks classification of dental caries
Class I - pit/fissure
Class II- interproximal areas of the posterior teeth
Class III- interpoximal surface of anterior teeth
Class IV- interporximal surface of anterior tooth involving the incisor edge
Class V - lesion affecting the cervical third of tooth
Describes Pitt’s Classification
D1- White/opaque or won lesion but surface hard and occlusal surface hard on probing
D2- slight loss of surface,s sticky issues, no dentine involvement
D3- Dentine involvement but not pulp
D4- possible or definite pulpal involvement
D1 and D2 lesions often managed with preventative measures
D3 or D4 will likely require restorative treatment
Describe diagnosis and detection of caries lesions
need to establish both presnce and activity of lesion
- primary detection method is visual inspection
(direct vision of clean, dry teeth under good lighting)
- additional detection methods
temporary tooth separation
fiberoptic transillumination
laser fluorescence
radiography
what is temporary elective tooth separation
- interproimal surfaces
- can’t see surface clincially
- separated using bands placed between contact points
- left for 1/2 weeks
- separated teeth and allow clear vision
what is fire optic trans-illumination (FOTI)
technique
- white light shone into contact points through a 0.5mm diameter probe
- normal tooth scatters light
- caries reduces spread of light so appears darker than sound tooth
Limitations
- better for detection of approximate caires than occlusal
- cannot be used near restorations
describe how laser fluorescence is used to detect caries
- light of a known wavelnthg is shown onto an obejct
- the light scatters through the material
- some of the light waves are absorbed
- some lose energy and are emitted as waves with longer wavelength
- fluorescence changes with density
- lower density of demineralisation and caries will alter fluorescnce
- observed using digital imaging software
how is radiography sued to detect caries
- use of ionising radiation to create an image demonstrating differences in tissue density
- demineralisation in caries reduces enamel /dentien density
- can reveal lesions otherwise undetectable by clinical exam; pre cavitation, approximal surface
- BUT early lesions are difficult to detect
(40% mineral loss required before visible on a radiograph
what type of radiographs are used for caries detection?
Bitewings - small imaging detector on tongue side of teeth and placed in holder
patient bites on block
Periapical
Oblique lateral
Dental panorami
Extroral bitewings
Describe bitewing radiography?
- gold standard radiograph for caries assessment
- advantages
- maximum coverage of ‘ at risk areas’ for lowest dose
- high resolution image
- minimal superimposition of other anatomical structures
-reproducible tehcniqe
Features of a good quality bitewing - should see medial contact point of first premolar to the most distal contact point
-in adults, 2 radiographs may be required to cover all contact points on each side - no or minimal overlap of enamel
Describe other dental radiographs for caries detection
Periapical
- same resolution. to bitewing and minimal superimposition of adjacent anatomy
-however, fewer teeth shown on each film for a similar dose of ionising radiation
Oblique lateral
- extraoral image with lower resolution than bitewing
- useful for caries diagnosis in young children
Dental panoramic
- not indicated purely for caries diagnosis, unless unable to tolerate intraorals
-extraoral image with lower resolution
- Artefacts related to the moving x ray source and image receptor
describe extroral bitewings and the advantages
- more comfortable for patients
- better interproximal separation between contacts than a panoramic
- 50% dose reduction than normal panoramic
Describe the disadvantages of extra oral bitewings
- compared with intramural bitewings
- higher dose
lower resolution
increased artefact less reproducible
Describe the appearance of caries
- demineralisation of the inorganic portion of dental tissues
- destruction of the organic portion
- results in a decrease ind density compared with normal tooth and a more radiolucent appearance in the radiograph
what is occlusal caries
- related to food debris and bacteria accumulating in pits and fissues
- begins with decalcification of enamel
- poorly seen on radiographs
- when dentine is reached, caries appears to spread laterally- seen as triangular shape on radiographs
describe approximal caries
- medial and distal surfaces
- early lesions may involve enamel only
- spreads laterally In dentine
- need good quality image to separate contact points and reveal low contrast lesions
describe buccal and lingual surfaces
- can arise in pits and fissures
- when small lesions are usually round becoming more elliptic or semilunar when large
-D not widen to occlusal surfaces
describe root surface caries
- usually detected clinically
- lesions involve cementum and dentine and are associated with gingival recession
- beware cervical burnout artefact
describe recurrent caries
- secondary caries
- occurs adjacent to an existing restoration
overhanging margins
-deep to enamel
describe process of reporting caries
- systematic approach simialr to charting
- assess each tooth individually
-full crowns, enamel and dentine density - cervical margins
- existing restoration
- pulp chamber
-reactive dentine - direct involvement
what are the probes. with using radiographs for caries detection
Ionising radiation
- damaging effect on tissue
-use must be justified - benefits outweigh risk
technique/projectional issues
- clinical progression of caries versus radiograph appearance
-caries mimics
describe techqieu and projectional issues in radiographs
- film faults/processing
projectional issues related to beam angulation - overlapping contact points can obscure early lesions
- superimposition of restorations
- localisation to buccal/lingual surfaces
- accuracy of depth of carious lesion
describe technique erros/film faults in x rays
faults which can reduce image quality and make it harder to see caries
- film positioning so some contact points are missed
-poor contrast0 image too pale/toot dark
incorrect exposure settings
processing errors
artefact obscuring crowns
foreign object, chemical splash
- radiograph orientation for viewing
why are adjacent restorations difficult to project
- superimposition of high density restoration will obscure low density caries
- caries in adjacent sites and secondary caries may not be visible in the radiograph
how is localisation a projections issue?
- cannot localise lesion to the buccal or lingual surface form a single radiograph
both will look same - cannot assess bucco-lingual depth
how is caires depth a projection issue
depending on beam angle, a superficial lesion can be projected deeper eg. an enamel lesion can appear into dentine
describe the visibility of depth of lesion
- 40% Mineral loss before a lesion becomes visible on a radiograph
- lesions usually larger clinically than radiographically
- very early lesions not evident at all
describe diagnosis of active or arrested carries
- a single radiographic shows area of demineralisation but gives no din cation on whether caries is currently active
- follow up radiographs can show progression or stability of the lesion
stable = arrested caires
progression = active caries
to assess change, radiographic technique must be reproducible
describe caries mimics
- cause of radiolucency on radiogprah which can be mistaken for caries
- tooth substance loss not related to caries
(attrition/abrasion/erosion
cracked cusp
lost restoration - radiolucent lining materials - smooth radiolucent band deep to a large restoration
- artefact - cervcial burn out artefact. mach effect artefacts
- corrosion products
describe cervical burnout artefact
- evident at cervical margin of tooth
- caused by x rays oevrpentrating the thinner dentine at the tooth edge
-superior to the alveolar bone and inferior to the enamel - triangular in shape, gradually less apparent towards too centre
- cervical root edge should be intact albeit dark
- usually all teeth in the radiograph with be affected
- premolars most pronounced as they are smaller
what is the Mach band Effect
- visual illusion
- when uniformly dark area meets uniformly light area
describe corrosion products
- radiolucency deep to amalgam restoration
- can mimic caries
- deposits of heavy metal ions eg. tin, zinc in softened dentine
when to image?
- impotence of early caries detection
preventative management and conservative treatment options - image shows current state of deminerlisation
remineralisation only occurs at surface
a single radiograph cannot distinguish between active or arrested lesion
second image at a later time can reveal whether disease was active - decline in caires prevalence in recent decades
fewer people with rapidly progressing lesions
interval between examinations should be customised on basis of caries risk
describe radiographs for caries in children
high caries risk group
moderate caries risk group
low caries risk group
describe FGDP selection criteria
High risk
- posterior bitewings at 6 monthly intervals until no new or active lesions or patient changes into different risk category
Moderate risk
- annual posterior bitewings unless risk status alters
Low risk - posterior bitewings at 12-18 monthly intervals in primary dentition
2 years intervals in permanent dentition
what questions should be asked prior to radiograph
has it been done already
do I need it now
is it the best investigation
are they all needed
