Through and Through
Little Bella.

A Welsh pony mare bought at sale is saved by Colorado State University. Her issues included periodontal disease and deep infundibular cavities eroding into her nasal passage as well as a chronic hind limb lameness.

Previously published in modified form in EQUUS magazine, #417, 2012

When Little Bella danced into the exam room, eyes askance at all the equipment hanging on the walls and the people gathered around the stocks, my first words were, "fancy. With chrome." My husband and partner, Dr. Jim Latham, and I had been helping out with teaching equine dentistry at CSU's College of Veterinary Medicine and were invited to take a look at a dental case coming into the hospital that morning. Little Bella was more than just a dental case.

Jan and Clyde Canino bought the Welsh Mountain Pony at an Amish driving sale in Northern Colorado in July of 2011. They were already driving two mares -- a big paint and a bigger Clydesdale—but they thought Little Bella was just grandkid size. She was about twelve years old, a little chubby, and a rich sorrel with a flaxen mane and tail, with a perfect blaze down her forehead, and four white stockings. Clyde had taken her out under harness and knew already that she was a hand full. She was going to be a project for quite a while before she would be kid safe. 10 days after Little Bella came to her new home, she developed a foul smelling white nasal discharge, a raspy breathing sound (stridor) coming from her left nostril, and weepy eyes. The Caninos called out their local veterinarian who examined her mouth, put her on antibiotics, and requested a consultation up at CSU.

At CSU, staff surgeon Dr. Katie Seabaugh and resident Dr. Ali Daniels ordered facial x-rays on Little Bella and set up the video endoscope. They could visualize a large amount of fetid hay packed in the left nasal passage approximately above the #206, the first large upper cheek tooth on the left.
Endoscopic view of feed in nasal passage
We moved Little Bella into the stocks to take a look. She had feed stuck in the discharge from her left nostril and she couldn’t move her lower jaw side to side without opening her mouth. We sedated Little Bella and looked in her oral cavity with the full mouth speculum in place.

Our oral exam confirmed a very worn #206 with deep grade 3 coalescing infundibular cavities and a 30 mm deep periodontal pocket on the cheek side (buccal aspect) of the tooth. This pocket formed an open tract or fistula into the nasal passage.

Infundibular cavities are present in over 70% of horses over the age of fifteen. The infundibulae are cone shaped structures (cups) made from enamel infoldings and are found in all incisors and in the upper (maxillary) cheek teeth where there are two—front and back (mesial and distal)--infundibulae. Prior to tooth eruption, infundibulae are filled with a tissue called cementum from the occlusal (chewing) surface all the way to the root tip, the apex, though some cementoblast cells continue to fill the more apical aspect as the root develops. Sometimes the infundibulae are irregular or are not completely filled and those in the first true molars commonly are not.

Inadequate filling, called cemental hypoplasia, may occur during tooth development especially if the caps are lost prematurely causing disruption of the nutrient artery to the infundibulum. As cheek teeth wear,cavities in the infundibulae are exposed. Erosion of the surface of the cavity from carbohydrate fermentation and acids may lead to decalcification of cementum (stage 1 cavity). Further erosion may progress through the enamel cup (stage 2) and then into dentin and pulp horns (stage 3). Deep infundibular cavities, especially those involving pulp horns, predispose the tooth to sagittal fracture, apical infection, and root abscess.

Overgrowth malocclusions like ramps, steps, or waves on the lower teeth or prior performance of an overaggressive bit seat in the first cheek teeth may cause excessive wear into infundibular cavities and pulp horns in the upper teeth. Management will require cleaning out the cavity and repeated equilibration of the dominant opposing teeth at least every six months to relieve pressure and arrest further wear on weakened teeth.

The #106 tooth on the right was abnormally worn with a grade 3, 10 mm deep rostral infundibular cavity and it was just slightly mobile. Ramps were present on the lower #306 and #406 teeth probably caused by a slight underbite malocclusion and the ramps in turn were contributing to the abnormal wear on the upper teeth. Several of the remaining upper teeth also had grade one infundibular cavities and some gingival recession from food packing and periodontal disease.

The left oblique x-ray of Little Bella’s nose showed a large abscess above her 206 tooth with infection of the bone around the tooth. It had to come out.

Senior students were adept at inserting an intravenous jugular catheter and starting fluid therapy and a constant rate infusion (CRI) of detomidine and butorphanol providing long term sedation and pain relief. The IV fluids would maintain hydration during the procedures to follow and they would balance the diuretic effect of the sedatives.

Dr. Jim Latham performed a regional maxillary nerve block on the left side using a long spinal needle and a combination of local anesthetics that would last for several hours.

The maxillary regional nerve block desensitized all the teeth in the left upper arcade, including the #206 and the surrounding bony structures, much like a human dentist will use an injectable anesthetic before painful procedures. However, the approach to the nerve in the horse is from the outside. A 2008 modification of the block by Dr. Carsten Staszyk has made it safer, and regional nerve blocks are the standard of care for equine extractions. Dr. Latham also used a long, narrow syringe to inject local anesthetic around the gums (gingiva) of the diseased tooth in preparation for the extraction. Little Bella would be comfortable and calm.

Dr. Latham used gingival elevators to release the gum tissue from around the tooth and periosteal elevators to disrupt the strong periodontal ligament that holds the tooth in the bony alveolus. Molar spreaders were used behind the tooth to apply pressure away from the premolar next in line, and the diseased tooth was extracted orally.

The alveolus was curetted, lavaged and swabbed before packing with Splash Dental Impression material to prevent further movement of feed into the nasal passage. Little Bella stayed on antibiotics with phenylbutazone added for discomfort and softened senior pellets provided as her only feed. She spent the night at CSU.

On the following morning, Dr. Seabaugh scoped Little Bella and extracted large plugs of necrotic hay from her left nasal passage. Little Bella went home on antibiotics, daily oral flushing of dilute chlorhexidine solution, and soft feed. A Follow-up visit was scheduled to recheck the tooth packing, the fistula, and to debride cavities in other teeth. We would also float sharp enamel points and perform an occlusal equilibration to reduce the ramps that further compromised her ability to chew. To avoid exposing the sensitive pulp tissue of the overgrown teeth at any one time, we discussed scheduling equilibrations every 3-4 months until the teeth could be brought into a more normal state and the remaining infundibular cavities could be debrided on a regular schedule. Some equine dental specialists are attempting posterior hybrid composite restorations of deeper infundibular cavities after debridement with air abrasion and long endodontic files to help preserve the weakened tooth from fracture, even if the decay is not completely arrested. Cavities in equine cheek teeth may be too deep and the pulp chambers too complex for current instrumentation, and to date compelling evidence is lacking that supports the efficacy of this therapy. Time will tell.

But Clyde and Jan had an additional worry with Little Bella. They had also noticed a slight favoring of one hind leg as they worked her a few days after her homecoming. But that’s another story.

After Jan Canino broke her ankle while loading her Clydesdale mare in a wind storm, we made a trip down to their ranch to save them an additional haul up to CSU. Little Bella’s nose was clear and she was eating senior pellets and grass. Dr. Jim completed the prescribed floating and equilibrations and debrided the multiple cavities we’d noted previously. Intraoral x-rays (like bite wings) showed that Little Bella’s cavity on her right second premolar (tooth #106) extended into the pulp horns and through the tooth root. We scheduled another extraction. A few days later, using the same methods as before, we extracted the #106. However, we also noted a slight odor from the left nostril with only a clear nasal discharge and explored the healing alveolus from the initial extraction on the left. Probing with a polyethylene catheter confirmed our fears—the fistula was still present. We attempted to curette the tract with a small spoon curette and picked grass stems out with long handled alligator forceps. After flushing we changed the antibiotic to doxycycline. Clyde would continue to flush Little Bella’s mouth daily and we restricted her feed once again to soaked pellets. She was due back up at CSU in a month's time.

On October 24, Jan and Clyde once again presented Little Bella at CSU’s Veterinary Teaching Hospital. Again, there was a faint fetid odor from her left nostril and a scant clear nasal discharge. Little Bella headed straight to the endoscopy room. With Dr. Daniels manipulating the fiber optics scope, Dr. Seabaugh could see the wide, funnel-like opening of the fistula in the nasal passage.

The alveolus of the tooth appeared to be sealing, but it was obvious that feed was finding its way from the oral cavity to the nose. Dr. Seabaugh explored the small opening from the mouth to the nose first with a pipe cleaner and then with a spoon curette. She was able to scrape the lining of the fistula on all sides and flush the nasal passage through the scope and through a catheter until it appeared clear.

For three more weeks, Little Bella would be restricted to soaked senior pellets without access to hay or grass but she would remain off antibiotics. Prognosis was guarded because long standing fistulae can be difficult to obliterate without open nasal surgery, but we were hopeful.

In January of 2012, Little Bella returned to CSU for a final scope. Her nose was clean and sweet, and her endoscopic exam confirmed closure of the fistulous tract. Little Bella would begin to enjoy a regular diet and a clear nasal passage. CSU dealt with her lameness issues, and Little Bella was finally freed from confinement to begin reconditioning.

In October, Little Bella attended the Rocky Mountain Carriage Club’s annual Halloween party and at last we got to experience the exuberance of Little Bella as she explored the marathon course with Clyde and Jan. She is truly a joy.

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