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.
- Head shape provides positioning difficulty.
- Intra-oral radiographic techniques Radiography: intra-oral parallel and bisecting angle - give much better results where zygomatic arch superimposition can be eliminated.
- 15-30 min depending on the skill of radiographer.
- Standard veterinary X-ray machine.
- 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.
- 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).
- Dental non-screen film sizes 2 & 4 - can be used extra-orally.
- Dental (rapid) radiographic processing chemicals.
- 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.
- 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.
- Recent references from PubMed and VetMedResource.
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).