The Case of the Dog With Holes in His

Sandra L. Waugh VMD, MS - Windsor Pet Dental

Well, not exactly holes in the head, but holes inside the mouth that connect the mouth to the inside of the nose (nasal cavity). Such a hole is called an “Oronasal Fistula”, ONF for short. (Oro refers to the mouth, nasal to the nasal cavity, and a fistula is an abnormal passage.) In the dog, the upper canine, or fang, tooth has a very long and broad root, which slants inward from the side of the mouth towards the nasal passage. There is a thin shelf of bone that separates the end of the root from the inside of the nose (nasal cavity). This thin bone can be weakened or even destroyed by periodontal disease, creating a hole connecting the tooth socket to the nasal cavity. When the canine tooth is removed, either by extraction or by falling out on its own, the hole is then exposed to the inside of the mouth. If the gum is not carefully sutured closed, a permanent hole can be created.

Why permanent? The body wants to heal tissues together. Ideally, the tissue lining the nose would heal together to close the hole on the nasal side, while the tissue lining the mouth would heal together to close the hole on the mouth side of the bone. With a large enough hole, there is no scaffold for the cells to stick to in order to seal the hole. Instead, the tissue on the mouth side heals to the tissue on the nasal side all around the hole, making the hole permanent unless it is repaired surgically.

Upper right side of dog’s mouth. The ONF is located approximately where the end of the root of the upper canine had been originally.

Upper left side of the same dog’s mouth.

The ONF is located approximately where the end of the root of the upper canine had been originally. 26 4 Legs & a Tail

A hole in this position will cause the dog a great deal of distress and pain. Image if food or water went into your nose every time you ate or drank. These poor dogs suffer with chronic infections of the nasal passage, constant nasal discharge and the danger of inhaling food particles, which can cause pneumonia. Typically these dogs sneeze after eating or drinking, and rub their faces excessively on the floor or paw excessively at their nose. I imagine that they must have headaches all the time.

These holes can occur on one side only or on both as in this Dachshund, a breed that is known for having ONF’s. Dog breeds with noses that are long in relation to their skulls are at risk for ONF’s.

There are a variety of surgical procedures described for closing these holes. They can be difficult to repair, and may take several attempts to fully close. The repair requires that the two sides, mouth and nasal cavity, be separated by incising the two tissues apart. With a large hole, providing some

Symptoms of an oronasal fistula can include a chronically runny nose, with or without bleeding, and persistent sneezing. It can occur in both cats and smaller dogs, ten pounds or smaller. Causes of ONF include:

• Trauma • Bite wounds • Oral cancer • Electrical shock • Periodontal disease • Traumatic tooth extraction • Mandibular canines (the fang-like teeth) positioned toward the tongue • Upper jaw overbites, which causes the canine teeth in the bottom jaw to pierce the hard palate (roof of the mouth)

The gum is then sutured closed over the barrier membrane.

support for the sutured tissues is ideal. With each breath in and out, the repaired tissue is going to be pulled into the nasal passage and then pushed out toward the mouth. This movement puts extra strain on any sutures that have been placed.

A barrier membrane of cartilage or demineralized bone can be placed over the hole after the tissues have been separated. This provides a barrier between to two sides and another layer to resist motion. While small holes do not require this, large holes need the extra support.

This Dachshund was a rescue dog and had been in his new home for 2 months. Before the oral surgery, he lay around all day and moved only when necessary. He was discharged the afternoon of his surgery and the next day was moving around the house more than the owner had ever seen. As each day went by, he became more and more active, running up and down stairs and poking his nose into everything. The owner was delighted with her “new and improved” dog, as he was now healthy and pain free enough to enjoy his new home and owner.

He was also much more amenable to oral examination. The first day I examined him, he was growling and trying to bite when I got my hands near his mouth. Ten days after the oral surgery, I could lift his upper lip and touch the gum which had been sutured over the ONF, although he was still suspicious. I expect that over time he will become much less guarded about his mouth. Henry is a rescue and had been in his new home for 2 months when treated for ONF.

Dr. Waugh is a graduate of the

University of Pennsylvania School of

Medicine. She also holds a Masters

Degree from Washington State University of Veterinary Medicine and is owner of Windsor Pet Dental, PLC. Spring 2022 www.4LegsAndATail.com 27