Dentistry Oblique Views

Review Article: Radiography for Diagnosis of Apical Infection of Equine Cheek Teeth

Authors

• C. M. Isgren

• N. B. Townsend (Corresponding author)

• Philip Leverhulme Equine Hospital, University of Liverpool, UKEmail: nt8261@liv.ac.uk

Keywords

• Horse

• Dentistry

• Radiography

• Periapical infection

Summary

• Despite advancements in imaging, radiography remains the most used imaging technique for assessing apical infections in horse cheek teeth.

• Good quality dental radiographs depend on:

  • Radiographic technique

  • Knowledge of normal anatomy

  • Horse compliance

• Interpretation of subtle pathologies can be challenging, particularly for experienced radiologists. Chronic cases tend to reveal dental abnormalities more readily.

Introduction

• Imaging is essential for diagnosing equine dental disorders, especially lesions that are not visible through oral examinations or endoscopy.

• Radiography is the primary diagnostic method for equine practitioners, though alternatives exist like gamma scintigraphy and computed tomography.

• The complex anatomy of the equine skull complicates radiographic interpretation.

• Regular practice and an understanding of anatomy enhance outcomes in radiography of cheek teeth.

• Recognizing common radiographic patterns of dental pathology is crucial for reading images.

Radiographic Technique

• Digital radiography (CR and direct radiography) improves image quality and personnel safety by reducing repeat exposures.

• Use of modern, portable digital units is often sufficient, but a mounted stand can minimize movement blur.

• Radiation safety practices include:

  • Wearing lead aprons and gloves

  • Using cassette holders with long handles to reduce exposure

• Accurate head positioning is critical, and chemical restraint can aid cooperation and reduce repeats due to movement.

• The use of a headstand is recommended for obtaining high-quality radiographs, with alternative options available if necessary.

• Avoid metal head collars during sedation to prevent artefacts.

• Hints for radiography:

  • A grid is generally unnecessary for standing radiography due to low scatter levels.

Radiographic Projections

Views for Maxillary Cheek Tooth Apical Infection

• Standard projections include:

  • Lateral

  • Lateral oblique (latero30° dorsal-lateroventral)

  • Dorsoventral

  • Contralateral oblique for comparison.

• Additional methods may involve placing radiopaque markers for localizing pathology.

Lateral Projection for Paranasal Sinuses

• Position the horse with the affected side next to the plate, ensuring that the plate holder is vertical and close to the head.

• The horizontal primary beam should be aligned with the horse's head's long axis, with careful collimation to minimize scatter.

• Includes assessment of fluid lines or soft tissue opacities in the paranasal sinuses, but superimposition can limit localization of lesions.

Latero30° Dorsal-Lateroventral Oblique Projection

• Positioned similarly, the beam is directed at 30° from the dorsal plane.

• Aims to highlight apices of maxillary cheek teeth while avoiding superimposition.

• Requires precise beam adjustment to avoid distorted images of apices.

Dorsoventral Projection

• Increased exposure needed compared to previous views, directed at the midline of the skull, using careful collimation.

• Evaluates nasal cavities and structures but can obscure specific areas with obliquity.

Latero35–45° Ventral-Laterodorsal Oblique Projection

• Similar procedure, targeting mandibular cheek teeth apices to avoid image distortion.

• Features checking for draining tracts using probes where helpful.

Open-Mouthed and Intraoral Projections

• Open-mouthed oblique projections highlight lesions on clinical crowns. Helpful tools include gags or tubing to keep mouth open.

• Intraoral projections provide detailed views of the interdental bone and alveolar crest without superimposition from the contralateral side.

Normal Radiographic Anatomy

• Key components: enamel, dentine, cementum, and surrounding bone; radiopacity varies with age and condition of the teeth

• Proper detection of periodontal ligament is crucial for assessment.

Eruption and Age-related Anatomy

• Eruption sequence in horses and its implications for radiographic interpretation.

• Distinctions in normal anatomy become evident with age, enabling understanding of lesions over time.

Radiological Interpretation and Diagnosis

• Understanding normal anatomy is critical for interpreting diagnostic images alongside clinical signs.

• Common indications for dental radiography:

  • Diagnosis of apical infection

  • Severe periodontal disease

  • Polydontia and other abnormalities

• Sensitivity and specificity in identifying apical infections improve with experience and use of modern techniques.

• Advanced imaging options include nuclear scintigraphy and computed tomography for unclear cases or concurrent conditions.

Conclusion

• A comprehensive set of diagnostic images and anatomical knowledge are essential for diagnosing equine cheek tooth infections.

• Radiography detects subtle changes associated with periapical infection effectively but with inherent limitations.

Reliability of Radiographic Signs

• Reliable signs include periapical sclerosis and halo formation.

• Some signs may lead to false positives or negatives affecting clinical diagnosis.

Authors’ Declaration of Interests

• No conflicts of interest declared.

Ethical Animal Research

• This article is a review of existing data; ethical review was deemed unnecessary as per institutional guidelines.

References

1. Armbrust, L.J. (2007) - Digital images and capture.

2. Barakzai, S.Z. (2005a) - Use of scintigraphy for equine dental disorders.

3. Brinkschulte et al. (2014) - Sinonasal communication in horses.

4. Buhler et al. (2014) - CT features of apical infection.

5. Casey et al. (2009) - Diagnostic value of computed radiography.

6. Dixon et al. (2000) - Long-term study on apical infections.

7. Gibbs & Lane (1987) - Radiographic examination of sinuses.

8. Tremaine & Dixon (2001) - Study of sinonasal disease.

9. Townsend et al. (2011) - Sensitivity and specificity study.

10. Weller et al. (2001) - Comparison of radiography and scintigraphy.