Dental Radiology Workshop Dr Christine Hawke Veterinary Dental Consultant 29 th 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 : 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)

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  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

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 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 (~30 o )  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 rostrocaudally Buccal root Palatal (lingual) root Overlying roots Taking intraoral radiographs

PLAYTIME