arh dental radiology workshop
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Dental Radiology Workshop
Dr Christine HawkeVeterinary Dental Consultant
29th April 2012
Would you do orthopaedics without rads?
At least 2/3 of each tooth is below the gumline and
not visible without radiographs!
Why is dental radiology so important?
• For diagnosis of pathology– In animals with abnormal findings on clinical oral
examination, full mouth radiographs showed other undetected pathology in 50% of dogs and 53.9% of cats.
– In those with no clinical findings, radiographs showed
clinically-important pathology in 27.8% of dogs and 41.7%
of cats
Verstraete et al. Am J Vet Res 1998 59:
692-5
• For treatment planning, monitoring, follow-up and screening
Make the most of the opportunity!
• Many owners are concerned about
the anaesthetic, and the cost
associated with dental treatment
• We need to be thorough when we
have the opportunity to assess
and treat the mouth, so we can do
everything that is needed to
remove infection and relieve pain
Lamina Dura(Crestal bone)
Enamel
Pulp
Alveolar bone
Dentine
Cementum
Lamina lucida (PDL)Lamina lucida (PDL)
Everyday dental radiology
Periodontal disease is the most common condition we see in small
animal practice, and the real action is happening below the gumline
Assessing periodontal disease
http://www.avds-online.org
Looks can be deceiving…….
Dental extraction planning
Very common in cats, and very painful
Radiographs are critical for assessment
and treatment planning
Retained roots
Resorbing roots
Tooth resorption
Missing teeth
Missing teeth
Fractured teeth
Discoloured teeth
Periapical lucencies - normal or not?
Look for the lamina lucida (PDL)
Compare with the contalateral side
Correlate with clinical presentation
Crown integrity, discolouration, transillumination etc
Monitor radiographically
Periapical lucencies - normal or not?
Compare with contralateral side
Worn teeth
Oral tumours and swellings
Courtesy Dr A Caiafa
Interpreting dental radiographs
Orientation
Looking from outside the mouth
Roots up for maxilla, down for mandible
Left or right from dental anatomy
QUESTIONS?
We need an xray source Dental xray machine
Smaller focal spot so more detailed images
than standard machines
More versatile as can adjust the angle of the
head in many directions (horizontal and
vertical)
Usually have fixed kV and mA so use the timer
to adjust exposure (may have preset times)
Courtesy Dr A Caiafa
Portable dental xray machines
We need an xray source
Standard xray machine
Settings for a 30-40 cm focal-film distance (FFD) are around 100
mA, time of 0.1or > sec.
Range of KVp from 50 (cat or small dog) up to about 85 (large dog)
Can use 100cm FFD and adjust using the inverse square law
(double distance = fourfold increase in time)
We need an xray source
We need to capture and process the image Film processing facilities
Wet chemicals in darkroom or chairside darkroom
Rapid developer and fixer solutions - shortening the
developing time to 20 seconds (normally 4 minutes) and
fixing time down to 2 minutes (normally 10 minutes)
Automatic processors
Image capture and processing - digital
DR and CR systems are available
More expensive but eliminates need to process films in chemicals
Can adjust images onscreen to optimise viewing
Much easier to jump onto the steep part of the learning curve
Taking intraoral radiographs
What makes a diagnostic radiograph?
Minimal distortion of length or aspect
Adequate periapical tissue included
No confounding superimposition
Parallel Technique
Standard method used in veterinary
radiography where the film is
placed parallel to the object being
radiographed
This can only been used in the
caudal and mid mandible in dogs
and cats (due to the shape of the
oral cavity)
Lateral recumbency, side of interest
towards the xray machine
Taking intraoral radiographs
Bisecting Angle Technique
Shoot perpendicular to the
bisecting angle (halfway
between the film plane and
the long axis of the tooth) to
give an image that is of a
similar dimension to the object
VERTICAL angulation
Taking intraoral radiographs
Bisecting Angle Technique
If the beam is angled too vertically, perpendicular to film (ie too
acute or vertical), the image is foreshortened.
Taking intraoral radiographs
Bisecting Angle Technique
If angle beam perpendicular to tooth (ie too flat or horizontal),
the image will be elongated.
Taking intraoral radiographs
Problems with maxillary premolars and molars due to
superimposition of the zygomatic arch
Come in more horizontally (~30o)
Extraoral parallel or near-parallel view
need to reverse the
orientation when
‘mounted’
Taking intraoral radiographs
Differentiating the roots of the maxillary PM4s - the SLOB rule
Lateral view has mesial (rostral) roots overlying each other
Shift machine horizontally, about 30 degrees rostrally, and shoot
rostrocaudallyBuccal root
Palatal (lingual) root
Overlying roots
Taking intraoral radiographs
PLAYTIME