Until the last 10 years or so, equine dentistry has been a neglected area of interest. Yet recent postmortem studies reported an 80% incidence of clinically significant undiagnosed dental problems
in equine cadavers (1).
If we don’t discipline ourselves to look for these diseases, we are going to miss them.
To conduct a thorough dental examination, we need to use adequate sedation, appropriate equipment in an appropriate environment for the exam, and record our findings.
Essential Equipment: Full mouth speculum, focused light source, oral flush, cheek retractor, explorer, dental mirror, pick, and probe.
First and Foremost: To maintain the function and comfort of equine dentition as long as possible.
- Equilibrate enamel points where soft tissue abrasion is occurring.
- Manage malocclusions. Overgrowth malocclusions are usually secondary to opposing diseased teeth. Scheduling staged rechecks: Pulp tissue will regress in 2-3 months’ time if 3 mm or
less of overgrowth is removed at a time. Watch floating time on each tooth. Use water cooling with power floats.
- Recognize and manage periodontal disease to prevent pain and tooth loss.
- Recognize and manage occlusal disease to prevent pain and tooth loss from pulp horn exposure and cavities and Infundibular cavities
- Perform extractions as a last resort using sedation and regional and local anesthesia to control pain and ensure patient compliance
EOTRH was first described as hypercementosis by David Klugh, DVM, FACD, in 2004. (3)
- Presentation:
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- Generally stallions and geldings over the age of 15, with thoroughbreds and warmbloods possibly over represented.
- Early, no visible signs, then subtle discoloration and swelling of gingiva over the diseased tooth followed by gingival recession. Corner incisors are usually involved first.
- As the disease progresses, gingival ulcerations, fistulae with eventual purulent discharge may be observed.
- Progressively, extrusion of teeth from the alveoli by bulbous hypercementotic proliferation on the palatal or lingual surface may occur.
- Note: Cheek teeth may develop EOTRH. We have seen one. Microscopic studies are ongoing.
- Oral pain (unable to bite carrots, difficulty grazing, pain on manipulation or percussion of incisors).
- Incisor mobility. Fractures of teeth are common in the middle third, both spontaneously and at extraction, due to lytic lesions. Canines may fracture below the gingival surface and ankylose to the alveolus.
- Radiology: Intraalveolar parts of the involved teeth show a combination of tooth destruction by resorption and bulbous radiopaque masses with accompanying loss of periodontal space and
disaggregation of alveolar bone. Fractures are commonly seen. (2)
- Pathology: Inflammation of periodontal and endodontal cells of canine and incisor teeth leading to both resorption of calcified tissues and subsequent excessive production of irregular cementum internally and
peripherally. The disease is usually limited to the reserve crown and root within the alveolus, primarily on the lingual or palatal surface.
- Etiology: Still in question but possibly related to mechanical stress on the periodontal ligament stimulating clastic cells to resorb tissue and initiating the production of excessive abnormal
cementum by cementoblasts (2).
- Behavior:Progressive
- Treatment: Extraction. Staged or complete extraction of all involved incisors.
Periodontal disease is the number one reason horses lose permanent teeth.
60% of horses over 15-20 years of age have periodontal disease of the cheek teeth (5)usually associated with packing of feed between teeth at sites of diastemata, malocclusions (waves, steps, ramps),
tooth displacement, or overgrowth. Periodontal pain causes abnormal mastication leading to further malocclusions.
Periodontal disease leads to destruction of the periodontal ligaments, inflammation of peripheral cementum and alveolar bone, movement of bacteria and necrotic feed into periodontal pockets,
and eventual progression to tooth loss from destruction of the periodontal ligament and/or apical disease.
There is a mild transient periodontal reaction at tooth eruption in some young horses. There is a mild periodontitis associated with dental calculus on lower canines that can be resolved by
periodic scaling and treatment with chlorhexidine dental rinses. Significant periodontitis is usually secondary to diastemata or malocclusions. Peripheral caries and associated periodontal
disease can occur in geriatric horses.
Causes
- Causes of Diastemata (abnormal spaces between adjacent teeth).
- Primary diastemata: caused by inadequate compression of the occlusal arcade.
- Failure of angulation of 6’s and 11’s to create a sealed occlusal surface
- Congenitally wide spacing of cheek teeth.
- Secondary diastemata: occur especially in mandibular CT 9-10 and 10-11 from slight lingual malpositioning of teeth. You must use a dental mirror to see these.
- Senile Diastemata: occur as fully erupted teeth can no longer maintain the occlusal compression of the arcade because of gradual tapering of the reserve crown and roots.
- “Valve” diastema describes a detectable interdental space at the gingival surface but tight tooth contact at the occlusal surface. Feed is trapped between teeth at the gingival surface creating periodontal disease. “Open” diastema describes a detectable interdental space with parallel sides.
- X-rays should be taken. Periodontal disease leads to apical disease 12% of the time.
Treatment
- Must address predisposing factors: control of waves, ramps, and overgrown teeth. Teeth opposite involved teeth should be taken out of occlusion as possible to reduce compressive forces on diseased teeth.
Staged equilibration of 3-4 mm can be repeated in 3 months.
- Buccal or lingual enamel protrusions on involved teeth should be floated to reduce feed retention.
- A valve diastema may be opened by experienced operators by removing only 1 or 2 mm of the mesial surface of tooth distal to the diastema to avoid pulp exposure.
- Periodontal pockets should be debrided by pick, curette, and pressurized flush or air abrasion and probed for depth, but only after local or possibly regional blocks. Long handled alligator
forceps aid in removal of feed particles.
- Pockets may be packed with Doxirobe Gel and covered with dental impression material for up to 2 weeks. Systemic antibiotics may be used.
Equine teeth have large apical foramina and a large blood supply and they attempt to resist insult by sealing off an area of exposed pulp with secondary dentin from the pulp chamber walls and
tertiary dentin produced by odontoblasts (A dentinal bridge) above vital pulp. Subocclusal dentin is deposited in response to occlusal biomechanical stimulation as the teeth erupt.
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Acute Pulp horn exposure (less than 72 hours old, on incisors, canines or ’06 teeth): a bleeding pulp after fracture or iatrogenic exposure from overzealous equilibration, bit seat or canine reduction.
Field Treatment: Partial Pulpotomy with seal:. Hand scale crown surface to remove organic material and irrigate with chlorhexidine solution. Soak 5 minutes. Minimally debride inflamed pulp to a
depth of 7 mm using small carbide or diamond bit on a dremel tool or high speed dental unit handpiece if you have one (with sterile irrigation). Sterile prep with chlorhexidine. Dry and control hemorrhage
with sterile paper points. Cover pulp with calcium hydroxide powder mixed with sterile saline or Hypocal premixed 2 mm deep. Cover pulp dressing with Dycal calcium hydroxide cement an additional 2 mm deep. Be sure
walls of the pulp horn are clean—use spoon excavators if needed. A final seal with IRM should last for 1-2 years. X-ray in 6 months to check for dentinal bridge. (Alternate pulp dressing with Mineral Trioxide
Aggregate (MTA) under a glass ionomer with a resin composite filling is probably better but significantly more involved and expensive.)
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Pulp horn cavities: Large insult to pulp horns may allow bacterial infection and necrosis that can involve the pulp horns, pulp chamber and lead to apical infection. Cheek teeth apical infection can lead to
fistulous tracts, sinusitis, and nasal discharge. Most cheek teeth fractures involve the pulp horns and pulp chambers. Fractures cause 20% of cheek teeth apical infections. Endodontic therapy (root canal)
in horses is being investigated by some practitioners with mixed results and continuous refinement. Endodontic therapy is much more complex in cheek teeth than with incisors.
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Infundibular cavities:
Present in over 70% of horses over age 15. Infundibulae are enamel invaginations found in incisors and maxillary cheek teeth. Prior to tooth
eruption, infundibulae are filled with cementum primarily from the occlusal to the apical aspect though some cementoblasts continue to fill the more apical aspect as the root develops. Many teeth
are not completely filled and 09’s commonly are not. Cemental hypoplasia may occur during tooth development especially if the caps are lost prematurely with disruption of the nutrient artery to the
infundibulum. Erosion of the surface of the tooth from exposure to carbohydrate fermentation and acids may lead to decalcification of cementum (stage 1) and progression through enamel (stage 2)
into dentin and pulp horns. Deep infundibular cavities, especially those involving pulp horns, predispose the tooth to sagittal fracture and apical infection.
Opposing malocclusions or prior performance of overaggressive bit seat may predispose to infundibular cavities and pulp horn exposure in some cases. Staged, repeated equilibration of the opposing tooth is
important to arrest further wear.
X-rays: to determine extent of infundibular cavity and presence of apical disease (16%).
Treatment
- Stage 1:Pick, debride, flush. Reduce opposing occlusal surface periodically.
- Stage 2,3: Same. Some specialists are attempting posterior composite restorations (Starfill 2B) (11) after debridement with air abrasion and 60 mm
endodontic files to help preserve the tooth from fracture even if decay is not completely arrested. Cavities may be too deep and pulp chambers too complex for current instrumentation,
and to date evidence is lacking that supports the efficacy of this therapy. (12)
A last resort.
Regional Nerve Blocks
Infraorbital and mental foramen blocks are poorly tolerated, may cause damage to nerves, and are only effective if the local anesthetic flows retrograde. However, injection pressure may cause damage to
neurovascular structures in the canals. (6)
The Extraperiorbital Fat Body Insertion (EFBI) technique of the Maxillary nerve block is the safest (7), was described by Carsten Staszyk in 2008 (8), and recent studies have demonstrated
efficacy using 10 cc bupivacaine (Marcaine) (7). 2. 5 cc of lidocaine added would hasten onset of analgesia.
Tuohy Epidural needles are recommended for regional blocks (6) because of their blunted tips that are less likely to lacerate nerves or blood vessels. (3.5” 22 gauge for maxillary , 6” 20
gauge for mandibular, imported by Havel’s—approx. $21 each).
Additional referral surgical extraction techniques have been described:
“Minimally invasive transbuccal surgery and screw extraction”, the Stoll Technique (9). Technique uses an 8mm trocar as a portal for straight elevators, endoscope as needed, and threaded pin to remove
teeth where straight oral extraction is not possible (tooth fractured below gingiva or too worn for forcep grasping)
A modified buccotomy for extraction of mandibular teeth using a high-speed surgical drill with irrigation to precisely remove the alveolar bone plate overlying a diseased tooth. (10)
- Academy of Veterinary Dentistry—equine fellows
- Diplomates, American College of Veterinary Dentistry
- CT
- Endoscopic sinusoscopy
- Root canals
- Restorations
- Surgical extractions
There is a need for evidence-based reports.
- PM Dixon, MVB,PhD,MRCVS. “Acquired Disorders of Equine Teeth”, AAEP Focus on Dentistry Sept 18-20,2011, pgs 93-104
- Carsten Staszyk, Apl.Prof., Dr.med.vet. “EOTRH: Macroscopical and Pathohistological Investigations” AAEP Focus on Dentistry Sept 18-20,2011, pgs 105-108
- David Klugh, DVM, FAVD/equine. “Incisor and Canine Periodontal Disease,” Veterinary Dental Forum Proceedings, 2004; 166-169
- Thomas J Johnson, DVM, 2006 AAEP Dentistry Dry Lab Notes
- PM Dixon, MVB,PhD,MRCVS “Periodontal Disease Research and Treatment—UK Experiences” AAEP Focus on Dentistry Sept 18-20, 2011, pgs 153-159
- Jennifer E Rawlinson, DVM, DAVDC. “Addressing Pain: Regional Nerve Blocks” AAEP Focus on Dentistry Sep 18-20, 2011, pgs 74-81
- Carsten Staszyk, Apl.Prof., Dr.med.vet. “Infraorbital nerve Block Within the Pterygopalatine Fossa-EFBI-Technique” AAEP Focus on Dentistry Sep 18-20, 2011, pgs 82-84.
- Carsten Staszyk, et al, “Simulation of local anaesthetic nerve block of the infraorbital nerve within the pterygopalatine fossa: Anatomical landmarks defined by computed tomography”, Research in
Veterinary Science 85 (2008) pgs 399-406.
- Manfred Stoll, DVM Minimally Invasive Transbuccal Surgery and Screw Extraction
AAEP Focus on Dentistry Sept 18-20, 2011, pgs 170-177
- Jennifer E. Rawlinson, DVM, DAVDC, “Surgical Extraction of mandibular Cheek Teeth via Alveolar Bone Removal, AAEP Focus on Dentistry Sep 18-20, 2011, pgs 178-152
- Chris J Pearce, “Equine Dental Caries” Proceedings of the 47th British Equine Veterinary Association Congress, 2008, pgs 117-118.
- Robert Baratt, DVM, MS, FAVD, personal communication.
Many thanks to the presenters at the AAEP Focus on Dentistry 2011 and at the 25th Veterinary Dental Forum November 11-13, 2011.
