Keeping An Eye Out For Zebras

The concept of the zebra diagnosis is credited to Dr. Theodore Woodward, professor at the University of Maryland School of Medicine in the late 1940s.

Bonnie Sue Rauch

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For many of us, the Veterinary Dental Forum has become a homecoming of sorts, an assurance that we will gather with old friends and meet new ones with similar interests every year.

This year’s VDF met in New Orleans, and I am writing as I travel home from the group’s 27th annual conference. It is the nation’s—if not the world’s—largest annual conference dedicated to veterinary dentistry and oral surgery.

The three-day educational experience is presented by the Veterinary Dental Oversight Group, VDF conference management, sponsors, exhibitors, lecturers, lab coordinators, instructors and many more.

This year’s VDF offered fundamental, intermediate and advanced series, original clinical research, wildlife/exotics, equine and technician tracks. Wet labs were offered in a variety of fields, including canine and feline extractions, endodontics, prosthodontics, orthodontics and maxillofacial surgery.

Piezoelectric Surgery

I taught a laboratory on piezoelectric surgery, a relatively new technology in veterinary dentistry and oral surgery. Ultrasonic surgery’s use in dentistry was first documented in 1953.1

Recent advances have allowed for clinical improvements in cutting and shaping bone with piezoelectric technology. The passage of an electric current across ceramic crystals modifies them and causes oscillations. Voltage applied to a polarized piezoceramic causes it to expand in the direction of and contract perpendicular to polarity.

A frequency of 28-36 kHz is used because the movements created at this frequency (ranging from 60 to 210 µm) cut only mineralized tissue; neurovascular tissue and other soft tissues are cut at frequencies higher than 50 kHz.2

Think of the piezoelectric surgery unit as a miniature cast-cutting saw, where the blade works by oscillation rather than rotation.

Benefits of piezoelectric surgery include minimal mechanical and thermal damage to soft tissue structures, sterile irrigant delivered to the surgery site, very fine control for precise bone cutting, cavitation of irrigation solutions providing an antimicrobial effect, inducing an earlier increase in bone morphogenetic proteins, controlling the inflammatory process better and stimulating remodeling of bone.3

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Operating times for osteotomies are longer than with traditional saws and burs. The piezosurgery unit is not a replacement for your high-speed dental drill, but rather an adjunctive tool to allow for more precise bone dissection when finesse is important.

I have used the piezosurgery unit for extraction of unerupted teeth, mandibulectomies, maxillectomies and temporomandibular joint surgeries. I’ve found that the best applications are those surgeries that require bone removal in areas of important soft tissue structures, such as neurovascular bundles.

I also presented a lecture titled "Zebras You’ll Want to Know Better.” This was not a lecture about the zebra diagnosis.

Hearing Hoofbeats?

The concept of the zebra diagnosis is credited to Dr. Theodore Woodward, professor at the University of Maryland School of Medicine in the late 1940s. When instructing his medical interns, Woodward said, "When you hear hoofbeats, think of horses, not zebras.”

Because horses are common in Maryland and zebras are rare, an animal making the sound of hoofbeats is probably a horse. By the 1960s, the term was widely known and taught throughout many medical and veterinary schools.

Woodward was trying to make the point to his interns that the inexperienced clinician fresh from medical school can recall all the details of rare diseases, but does not yet have the experience to put prevalence and common sense into the equation.

Although I agree with Dr. Woodward’s original premise, I have always felt it best to teach my students: "When you hear hoofbeats, think of horses, zebras and any other cloven-hoofed animal that might be responsible for the sound.”

Why do I love zebra diagnoses? If for no other reason, it makes for great dinner conversation. No one ever went home to his/her significant other and said "Honey, I diagnosed a case of periodontal disease today!”

A Real-world Test

Not to diminish the importance of such a diagnosis, but a disease like periodontal disease is so prevalent that the uniqueness of the disease is lost. Of course, every case of periodontal disease may be different and may require a different approach.

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If you closely study the mundane, you soon realize that it becomes anything but mundane.

But the main reason I love the zebras is this: I love testing myself, and the zebra diagnosis is that real-world test that may be lurking behind the door of exam room No. 1. Are you going to see it, or is it going to see you and go unnoticed?

I am excited to share that, starting this month, the Dental Pearls column will be offered in every issue of Veterinary Practice News instead of every other month. Starting with the December issue, we will explore some of these zebra diagnoses in dentistry and oral surgery.

Meanwhile, let me know if you see a zebra. My new email is jlewis@northstarvets.com.

Dr. Lewis, FAVD, Dipl. AVDC, practices veterinary dentistry and oral surgery at NorthStar Veterinary Emergency Trauma & Specialty Center  in Robbinsville, N.J. 


1. Catuna MC. Sonic surgery. Ann Dent 1953;12:100.
2. Labanca M, Azzola F, Vinci R, Rodella LF. Piezoelectric surgery: twenty years of use. Br J Oral Maxillofac Surg 2008;46:265-269.
3. Preti G, Martinasso G, Peirone B, et al. Cytokines and growth factors involved in the osseointegration of oral titanium implants positioned using piezoelectric bone surgery versus a drill technique: a pilot study in minipigs. J Periodontol 2007;78:716–722.


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