Six common pitfalls in veterinary dentistryand how to avoid them

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Who here has fractured a root during a tooth extraction? Everyone? If you've ever made one wrong move with a dental elevator or had an expletive-inducing suture dehiscence, Matthew Lemmons, DVM, DAVDC, a veterinary dentist at MedVet Indianapolis, wants you to know that you are not alone. In fact, these mishaps are so common that he created a list of the six most common pitfalls in veterinary dentistry, how to avoid them, and how to fix it when things go wrong, which he presented at a recent CVC.

Pitfall #1: Fractured retained roots

Let's face it: roots fracture during tooth extractions-a lot. Fractured retained roots can go undetected in asymptomatic dogs, but these roots are a source of pain and infection in both dogs and cats and of anorexia in cats. Retained roots in maxillary teeth can abscess and be a source of suborbital swelling and draining tracts. In cats, crown amputations are only appropriate when there is bone replacement resorption.

You can avoid fracturing a tooth root by following Dr. Lemmons' tips:

Section multi-rooted teeth before extracting, even if the tooth demonstrates mobility.

Remove adequate buccal bone before elevating.

Use a luxator before an elevator to cut the periodontal ligament.

Use sharp instruments.

When elevating, rotate just a few degrees, and when you feel resistance, hold for a full 10 seconds to fatigue the periodontal ligament and alveolar bone (one one-thousand, two one-thousand, three one-thousand …).

You follow all the rules and the darn root still breaks. Now what?

First, identify the root. Suction any blood and obtain a radiograph to get the lay of the land. Then remove the buccal bone approaching the apex of the root.

You may find root forceps and a root tip elevator helpful in removing the root.

If you're having a hard time accessing the root, a surgical length burr may help, Dr. Lemmons says. Be aware that the longer shaft puts more torque on the handpiece and that the temperature of the burr needs to be monitored.

What do you do if you discover a retained tooth root on radiographs during a “routine” dental prophylaxis?

Dr. Lemmons says to take the root out, especially if there is any lucency around the root. If there's granulation tissue over the root, remove it with a diamond burr before extracting the root.

Pitfall #2: Iatrogenic trauma, otherwise known as “the big oops”

Two possible iatrogenic injuries that may be caused during extraction are mandibular fracture and orbital penetration with an elevator.

Mandibular fracture is caused by forceful elevation of a mandibular canine or molar. Dr. Lemmons has three tips to avoid this pitfall:

Always obtain a radiograph of the jaw before attempting an extraction. This gives the operator an understanding of the anatomy and integrity of the mandible.

Remove enough alveolar bone before attempting extraction-at least two-thirds buccal alveolar bone for mandibular canines and half for mandibular molars. Incisors usually do not require removal of bone.

Be cautious when elevating between the mandibular canine tooth and third incisor.

If the jaw fractures during extraction, complete your extraction before addressing the fracture. Flush the alveolus with sterile saline solution, consider using a natural bone graft, close without tension, and evaluate the fracture. If the fracture is stable and occlusion is good, jaw fractures can be medically managed with soft food and pain medication. If the fracture is not stable, rigid fixation with interdental wiring is recommended. Interdental wiring is less invasive than plates and does not require drilling through the jaw. And Dr. Lemmons reminds us that small breeds don't have a lot of bone to work with in the first place. If you do repair the fracture with a plate, avoid putting screws in tooth roots.

Orbital penetration with an elevator is more likely to occur with improper grip and dull instruments. Most cases require enucleation. Dr. Lemmons says you can avoid this “oops” by using sharp instruments and handling the elevator correctly. Keep your finger near the working end of the elevator so that if you slip, your finger works as a brake.

Pitfall #3: Suture dehiscence

Dehiscence is usually caused by tension on the suture. Rarely, neoplasia is the cause. Consequences include delayed healing, pain and oronasal fistula with possible turbinate atrophy and chronic nasal discharge.

Dr. Lemmons avoids suture dehiscence by using a periosteal-releasing incision to reduce tension. When you reflect your flap, the periosteum of the jaw will adhere to the mucosa. Use scissors to dissect between the mucosa and periosteum and incise the periosteum while leaving the mucosa intact. This will allow the elastin in the mucosa to stretch and reduces tension when the flap is sutured. Dr. Lemmons recommends laying your flap down where you want it to go when it is ready to suture. If it stays put, you are good to go. If it snaps back, then you need to release more tension before suturing. Débride epithelium at the edges of the flap before suturing, and take deep bites of at least 3 mm.

When creating a flap to repair an oronasal fistula, Dr. Lemmons advises using a four-corner mucoperiosteal flap and that you create flaps that are one and half times the size of the defect and the flap should be one and half times as wide as it is long. Dr. Lemmons creates “short, squatty flaps-not long, thin flaps.”

Don't forget: delicate tissue handling is required. The more you mess with the mucosa, the less likely it is to heal correctly. Stay sutures can help with delicate tissue handling.

Pitfall #4: Root transportation

Dr. Lemmons defines root transportation as pushing a root from one place it should be to another place it shouldn't be, such as the sinuses or mandibular canal. Like retained roots, transported roots cause pain and infection.

To prevent root transportation, never push down on a root if you are trying to extract it. Make sure the elevator is between the root and alveolus when pushing in an apical direction. When in doubt, obtain radiographs.

Pitfall #5: Postanesthetic blindness in cats

A retrospective study examined postanesthetic cortical blindness in 20 cats.1 In the study, all postanesthesia cortical blindness cases were dental procedures except one upper gastrointestinal case. The cause? Spring-loaded mouth gags and excessive tension on the temporomandibular joint (TMJ). The main blood supply to the brain, the maxillary artery, runs through the masseter muscle. Spring-loaded mouth gags stretch the masseter muscle, which compresses the artery, cutting off the blood supply to the brain. This transient cerebral ischemia has been linked to the cortical blindness seen after dental procedures in cats.

Dr. Lemmons' advice? Don't use mouth gags.

If you must prop the mouth open, try placing a 1-ml syringe that has been clipped on both sides to three-quarters of an inch long between the canines to avoid extreme extension of the TMJ.

Pitfall #6: Trauma after extraction

If the mucosa is sutured too tightly after extraction of a feline maxillary canine, maxillary lip entrapment and subsequent trauma can occur. This sometimes corrects itself after a week or two, but if it does not, either extracting the lower canine or performing a crown reduction with root canal therapy on the mandibular canine may be necessary. If mandibular mucosal trauma occurs after extraction of the mandibular molar, the maxillary fourth premolar may need to be extracted. An alternative is blunting the tooth followed by restoration to cover exposed dentin. Blunting without treating the dentin can lead to pulpitis.

Reference

1. Stiles J, Weil AB, Packer RA, et al. Post anesthetic cortical blindness in cats: twenty cases. Vet J 2012;193(2):367-373.