An overview of common equine dental diseases

Figure 1A. Diastema Between Two Cheek Teeth With Food Accumulation.

Equine dental disorders are common, and horses may present with a variety of clinical signs that do not always correlate to the severity of the disease. Clinical signs observed with dental disease include weight loss, quidding, slow eating, nasal discharge, headshaking, and poor performance or difficulty with the bite.¹

Figure 1B. Diastema After Flushing With Periodontal unit.

Often the veterinarian notices dental abnormalities during routine dental maintenance evaluation, warranting a thorough examination. A dental exam should be performed in adequately restrained horses with the help of standard equipment, including a mouth speculum, a head torch or other light source, an oral irrigator, dental probes and picks, lingual and buccal retractors, an intraoral mirror, and ideally an oral endoscope. Additional diagnostic imaging such as upper airway endoscopy, radiographs, or CT may be required in certain cases. Disease of the upper last 4 maxillary cheek teeth may be associated with sinus disease; therefore, further diagnostics may be helpful in establishing an adequate treatment plan.^2,3

Common equine dental diseases

Figure 2. Midline Sagittal Fracture of Maxillary Cheek Tooth.

Diastemata

Figure 3A. Maxillary CT Infundibular Cemental Caries.

Diastemata is an interdental space between 2 adjacent cheek teeth and can be present in up to 4% of horses. Caudal mandibular cheek teeth are most involved, particularly the interdental (interproximal) spaces between molars 09s and 10s and between 10s and 11s. The presence of space between the teeth usually leads to the accumulation of food material and the development of periodontal disease (Figure 1A). In advanced cases, this can lead to alveolar bone resorption or the formation of an oronasal fistula. Periodontal disease is a painful condition, and quidding is a common associated clinical sign.⁴

Figure 3B. Debridement of Caris Using High-Speed Dental Drill/Burr.

For valve diastemata (where the space is narrower occlusally), one treatment option is to widen the space with a burr to allow for better evacuation of the trapped food material, and this has proved successful in selected cases. Other treatment options for diastemata include flushing the space using a periodontal unit (Figure 1B) and packing the space with dental fillers. In more severe cases, exodontia of one of the teeth may be needed.⁵

Figure 3C. Flushing of Cavity Preparation and Application of Bonding Product. Disinfectant solutions are flushed into the cavity preparation and a layer of a single step-etch bonding product is applied to the walls of the cavity.

Dental fractures

Figure 3D. Cavity Filled With Dual-Cured Flowable Resin Composite.

Fractures can be traumatic in origin, such as following a kick or a collision, or idiopathic. Although mandibular cheek teeth are more commonly involved in traumatic fractures, maxillary cheek teeth, especially the 09s, are frequently found to have idiopathic fractures. Lateral slab fractures through the 2 lateral (buccal) pulp cavities and midline sagittal fractures through both infundibula (Figure 2), believed to be predisposed by infundibular cemental hypoplasia (caries), are common fracture configurations for cheek teeth.⁶ Some uncomplicated crown fractures may not have pulpar involvement, but some more complicated fractures will. These can develop apical infection and, in some cases, secondary sinusitis, depending on the teeth involved. CT can help in determining the extent of the apical and sinus involvement and, therefore, putting in place a comprehensive treatment plan.⁷

Figure 4. Radiographs identifying marked bulbous and heterogeneous remodelling of the roots of all maxillary incisors, and moderate widening of the periapical and periodontal space surrounding these abnormal roots. This horse also presented an acute, open, and completely displaced simple transverse fracture of the left rostral quarter of the incisive bone.

The main treatment for a fractured tooth associated with periapical infection is extraction. This is typically performed orally but, in more complicated cases, can necessitate a minimally invasive buccotomy, where an incision is made through the mucosa for the insertion of specialized equipment to elevate and extract the affected tooth. Oral extraction involves elevating the mucosa surrounding the affected tooth, spreading the affected tooth from each adjacent tooth, and breaking the periodontal ligament using traction and a molar extractor.⁸

Infundibular caries

The most common type of dental caries (occlusal exposure of developmental infundibular hypocementosis) identified in equine teeth is maxillary CT infundibular cemental caries (Figure 3A). If left untreated, this can progress to septic pulpitis or pathological fracture.⁹ In most cases, treatment consists of debridement and filling with dental material to prevent further evolution of the tooth decay. To summarize, necrotic, impacted food material must be removed from the infundibulum using dental picks and a high-speed dental drill or burr (Figure 3B). The infundibular cavity is then flushed, and disinfectant solutions such as dilute sodium hypochlorite or chlorhexidine are flushed into the cavity preparation (Figure 3C). A layer of a single step-etch bonding product is applied to the cavity walls, and the cavity is filled with a dual-cured flowable resin composite.^10-12 (Figure 3D)

Equine odontoclastic tooth resorption and hypercementosis

This condition primarily affects the intra-alveolar aspect of the teeth, most commonly incisors and canines, although cheek teeth can also be affected. Odontoclastic cells have been found to cause resorptive lesions extending into the cementum, enamel, dentin, and even the pulp, causing a marked loss of normal architecture in some teeth.^13,14 This painful condition can present with absent to variable clinical signs, including masticatory problems. The veterinarian often makes the diagnosis by oral examination and radiographs (Figure 4) or advanced imaging. Findings upon oral examination include gingivitis, fistula formation, gingival recession, deposition of calculus, and swelling or abnormal tooth mobility. Tooth resorption and bulbous enlargement are frequent features on radiographic examination. Currently, surgical extraction of the affected teeth is the treatment option of choice. Supportive therapy with systemic antibiotics, anti-inflammatories, and local mouthwash has been shown to provide only short-term relief of symptoms at best.¹⁵

Conclusion

Various pathologies can affect dentition in horses. Most conditions have variable clinical signs, hence the importance of a regular, thorough oral examination in horses, particularly older horses.

References

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2. Dixon PM, Tremaine WH, Pickles K, et al. Equine dental disease: part 3: a long-term study of 400 cases: disorders of wear, traumatic damage and idiopathic fractures, tumours and miscellaneous disorders of the cheek teeth. Equine Vet J. 2000;32(1):9-18. doi:10.2746/042516400777612099
3. Brigham EJ, Duncanson GR. An equine postmortem dental study: 50 cases. Equine Vet Educ. 2000;12(2):59-62. doi:10.1111/j.2042-3292.2000.tb01765.x
4. Collins NM, Dixon PM. Diagnosis and management of equine diastemata. Clin Techn Equine Pract. 2005;4(2):148-154. doi:10.1053/j.ctep.2005.04.006
5. Dixon PM, Barakzai S, Collins N, Yates J. Treatment of equine cheek teeth by mechanical widening of diastemata in 60 horses (2000-2006). Equine Vet J. 2008;40(1):22-28. doi:10.2746/042516407X239827
6. Dacre I, Kempson SA, Dixon PM. Equine idiopathic cheek teeth fractures: part 1: pathological studies on 35 fractured cheek teeth. Equine Vet J. 2007;39(4):310-318. doi:10.2746/042516407x182721
7. Taylor L, Dixon PM. Equine idiopathic cheek teeth fractures: part 2: a practice-based survey of 147 affected horses in Britain and Ireland. Equine Vet J. 2007;39(4):322-326. doi:10.2746/042516407x182802
8. Dixon PM, Barakzai S, Collins NM, Yates J. Equine idiopathic cheek teeth fractures: part 3: a hospital-based survey of 68 referred horses (1999-2005). Equine Vet J. 2007;39(4):327-332. doi:10.2746/042516407x182983
9. Simhofer H, Griss R, Zetner K. The use of oral endoscopy for detection of cheek teeth abnormalities in 300 horses. Vet J. 2008;178(3):396-404. doi:10.1016/j.tvjl.2008.09.029
10. Earley ET. Principles of restorative dentistry: cavity preparation and restoration of the anterior dentition. In: Easley J, Dixon P, du Toit N, eds. Equine Dentistry and Maxillofacial Surgery. Cambridge Scholars Publishing; 2022:694-711.
11. Pearce C, Horbal A. Infundibular restorations. In: Easley J, Dixon P, du Toit N, eds. Equine Dentistry and Maxillofacial Surgery. Cambridge Scholars Publishing; 2022:668-693.
12. Pearce CJ. The equine infundibulum and infundibular disease: background, review, and techniques. Livestock. 2015;20(1):46-51. doi:10.12968/live.2015.20.1.46
13. Moore NT, Schroeder W, Staszyk C. Equine odontoclastic tooth resorption and hypercementosis affecting all cheek teeth in two horses: clinical and histopathological findings. Equine Vet Educ. 2016;28(3):123-130. doi:10.1111/eve.12387
14. Smedley RC, Earley ET, Galloway SS, Baratt RM, Rawlinson JE. Equine odontoclastic tooth resorption and hypercementosis: histopathologic features. Vet Pathol. 2015;52(5):903-909. doi:10.1177/0300985815588608
15. Staszyk C, Bienert A, Kreutzer R, Wohlsein P, Simhofer H. Equine odontoclastic tooth resorption and hypercementosis. Vet J. 2008;178(3):372-379. doi:10.1016/j.tvjl.2008.09.017