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