Contributors: Alex Smithson, Mark Thompson

 Species: Feline   |   Classification: Techniques

Introduction Requirements Preparation Procedure Aftercare Outcomes Further Reading


  • See also dental radiography overview Dental radiography: overview.
  • Extra-oral technique positions the x-ray film outside the mouth.
  • Parallel technique positions the film parallel with the object (tooth).


  • Maxillary pre-molars and molars, particularly in the cat.
    Less useful for mandibular molars/pre-molars because mandible narrower than maxilla   →   more superimposition of tooth images.
  • Good for large lesions such as oral neoplasms.


  • Can use standard cassettes with intensifying screens.
  • Can use non-screen film of varying sizes.
  • Reduces superimposition by the zygomatic arch.


  • Teeth may appear magnified, poor detail.
  • Superimposition of other irrelevant images.
  • Proper evaluation of individual teeth is difficult.

Technical Problems

  • Head shape provides positioning difficulty.

Alternative Techniques


  • 15-30 min depending on the skill of radiographer.


Materials Required

Minimum equipment

  • Standard veterinary X-ray machine.
  • Viewer.

Ideal equipment

  • Mouth gag (soft ends to protect teeth).
  • Foam pad to position head.
  • Film focus distance:
    • Standard x-ray machine: 30-50 cm for non-screen and dental film; 75 cm for standard cassettes.
    • Collimate as much as possible to limit x-ray beam and improve detail.
    • Dental x-ray machine: already set by cone length (around 20 cm); simply place end of cone onto area of interest. Cone also collimates to within its circumference.
  • Suggested standard x-ray machine settings:
    • Small dog/cat: non-screen 60 kV/20 mAs; screened 60 kV/2 mAs.
    • Medium dog: non-screen 65 kV/20 mAs; screened 65 kV/5 mAs.
    • Large dog: non-screen 65-80 kV/25 mAs; screened 70 kV/6 mAs.
  • Suggested dental x-ray machine settings (with dental, non-screen film):
    • Small dog/cat: 0.32-0.40s.
    • Medium dog: 0.40-0.63s.
    • Large dog: 0.63-1.00s.

Minimum consumables

  • Standard cassettes with fast tungstate screens.
  • Non-screen film or dental (sizes 2 & 4) film.
  • Radiographic processing chemicals.
  • Dental radiograph film; many different types including some 'self-developing' which use intra-envelope developing (squeezing injects developer to the film envelope; massage envelope, pull tab on envelope   →   releases film).

Ideal consumables

  • Dental non-screen film sizes 2 & 4 - can be used extra-orally.
  • Dental (rapid) radiographic processing chemicals.


Dietary Preparation

  • Fast animal for 12 hours prior to routine anesthesia to prevent reflux esophagitis.


  • See dental radiography overview link.
  • Radiolucent gag to open mouth wide, eg cut-down hypodermic syringe case.
    Avoid excessive mouth gape, especially for prolonged periods. Relax gape and massage masseter muscles regularly to prevent myositis!
  • Foam pads to position the head.



Step 1 - Set up

  • Place animal in lateral recumbency with the side of interest nearest the table.
  • Use a radiolucent gag to open the mouth wide.
  • Position the head with foam pads so that the long axis of the tooth of interest is parallel to the table.
  • This will often require some rotation of the head about the long axis, ie lateral oblique position created.

Step 2 - Position film

  • Place film under the tooth and angle X-ray beam at 90° to film.
  • With lateral oblique positioning the beam will pass through the palate then tooth area to film.



Potential complications

  • Temporary teeth may have a less distinct root morphology - if in doubt obbtain the opinion of a referral colleague on the radiograph.
  • Cats are especially prone to resorptive lesions Odontoclastic tooth resorption (resorptive lesions), if in doubt re interpretation and treatment obtain the opinion of a referral colleague on the radiograph.


Further Reading


Refereed papers

Other sources of information

  • Smithson A (2006) Oral radiology Part 2. UK Vet 11 (1), 40-44.
  • Smithson A (2005) Oral radiology Part 1. UK Vet 10 (8), 57.
  • Gorrel C (2004) Veterinary Dentistry for the General Practitioner. Saunders.
  • Mulligan, Allen, Williams (1998) Atlas of canine and feline dental radiography. In: Veterinary Learning Systems. Trenton, NJ, USA (Excellent reference for dental radiography).