Tooth Extraction Complications in Dogs and Cats

One of the most commonly performed oral surgery procedures in general practice is exodontia, or tooth extraction. Indications for extraction, grouped by patient age, are shown in BOX 1. Your objective with extraction is to remove the entire tooth and root without unnecessary damage to the surrounding soft tissue or bone. The easiest way to avoid surgical complications is through adequate preparation. Completing extractions in a consistent, orderly manner will decrease the incidence of complications.

Extraction Basics

When oral surgery is performed to remove teeth, controlled forces and proper technique—including use of a short finger stop (FIGURE 1)—are essential. Before attempting to elevate the tooth roots, section all multirooted teeth, and for open extractions, remove adequate buccal bone to visualize the tooth root. Visualization is crucial for successful surgical extractions. The tooth is held in the alveolus by the periodontal ligament. The key to tooth removal is stretching and breaking down the periodontal ligament by placing the dental elevator into the periodontal ligament space and using slow rotational pressure to fatigue the periodontal ligament.

Figure 1. Short finger stop.

After tooth removal, always inspect the extracted root to be sure the apex is smooth and round. A rough or jagged root edge indicates the probability of a root remnant remaining in the alveolus. Always take postoperative radiographs to document complete extraction of the entire tooth root without unnecessary damage to the surrounding bone. The following list provides tips and guidelines to help you avoid complications when extracting teeth. See also BOX 2.

• Always consider your skill and knowledge. If a procedure is beyond your capability based on your knowledge, skill, and/or the pathology that is present, it is best to refer the patient to a board-certified veterinary dentist.
• Understand basic anatomy, including tooth anatomy, location of neurovascular bundles, the mandibular canal, nasal cavity, and the orbit. This knowledge is critical for avoiding key structures during extractions.
• Always take preoperative intraoral radiographs. Preoperative radiographs enable you to carefully evaluate the entire tooth, the periapical area, and the surrounding bone (FIGURE 2), as well as to formulate a treatment plan. 
  

  Figure 2. Radiographic abnormalities that may alter the approach to extraction. (A) Supernumerary root of tooth 207.

  

  Figure 2. (B) Curved roots of tooth 309.

  

  Figure 2. (C) Type 2 tooth resorption of teeth 304 and 404.

  

  Figure 2. (D) Dens invaginatus, periodontal and endodontic disease of tooth 309.

• Consider all information. Combine what you see clinically, what you see radiographically, and clients’ commitment to their pet’s oral healthcare to make an appropriate treatment decision about each tooth.
• Use preemptive multimodal pain management to provide oral surgery patients with a more comfortable intraoperative and postoperative period. Use of intraoral regional nerve blocks decreases minimum alveolar concentration of isoflurane needed by the patient without affecting cardiovascular parameters or causing observable adverse effects.² Nerve blocks provide analgesia in the postoperative period, improving patient comfort and decreasing the need for additional analgesics.²
• Use controlled forces and proper technique, including appropriately sized, sharp instruments and the use of a short finger stop. If the elevator slips during extraction, using a short finger stop prevents inadvertent penetration of the sublingual space, mandibular canal, nasal cavity, and orbit.

Complications

Fractured Tooth Roots

Use of excessive force or use of extraction forceps before the tooth is adequately elevated can lead to root fracture. Anatomic variations in root structure (e.g., hooked, curved, or bulbous roots) can predispose the root to fracture during extraction (FIGURE 3). In addition, the mesial root of the mandibular first molar in the dog has a groove along the distal aspect of the root in an apical coronal axis, which makes extraction of this tooth root more difficult.³

Figure 3. Radiograph of tooth 309, showing curved roots and the mesial root in the ventral cortex of the mandible.

Sometimes, however, despite our best attempts, tooth roots fracture during oral surgery and additional surgery is needed to extract the root tip. The first step in root tip retrieval is to take a deep breath! Then follow these subsequent steps:

1. Take intraoperative radiographs. The radiographs will confirm the anatomy of the remaining root, the adjacent structures, and the pathology associated with the surrounding bone. Keep in mind the anatomy of the area, particularly the location of the neurovascular bundles, the mandibular canal (FIGURE 4), the nasal cavity, and the orbit.
   

   Figure 4. Dog cadaver (A) with bone overlying the neurovascular bundle (arrow) and tooth roots removed showing the proximity of the roots of teeth 308 and 309 to the mandibular canal

   

   Figure 4. Dog cadaver (B) with the neurovascular bundle removed showing the root tips of 309 (arrows) lingual to the neurovascular bundle and closely adjacent to the ventral cortex of the mandible.

2. Visualize the root tip. Creating an open exposure to retrieve a fractured root tip makes the procedure quicker and less traumatic for the patient.⁴ Your objective is to visualize the root tip before attempting to remove it. Visualization can be improved by removal of additional buccal bone, magnification, and adequate lighting. Never dig blindly for root tips.
3. Remove alveolar bone. To expose the remaining root structure and identify the periodontal ligament space, use a small bur to remove additional buccal alveolar bone. Perform this procedure with care because tooth roots can be located on the lingual or vestibular aspect of the mandibular canal.⁵ You can use a smaller round bur to create a groove in the mesial and distal periodontal ligament spaces to allow insertion of the dental elevator in these locations (FIGURE 5). If needed, a small bur can be introduced into the alveolus to create a circumferential “moat” around the root to allow introduction of a root tip elevator into this expanded periodontal ligament space.³ Do not remove excessive bone, and always consider the location of the neurovascular bundles, nasal cavity, mandibular canal, and orbit.
   

   Figure 5. Dog cadaver, showing fractured mesial root of tooth 206 with buccal bone removed.

4. Mobilize the root. After bone removal, place a small dental elevator into the periodontal ligament space of the root tip on the mesial and distal sides. Gently rotate the elevator to stretch the periodontal ligament. Do not use apical pressure because excessive apical pressure can displace the root tip into the mandibular canal, nasal cavity, or maxillary sinus. After the tooth root is mobile, it can be removed through the newly created buccal bone window. Root tip extraction forceps with fine tips may be used to assist in the removal of the mobile tooth root from the alveolus.

Do not blindly pulverize a fractured or resorbing root by using a bur on a high-speed handpiece. Potential complications of root pulverization include air embolism,⁶ subcutaneous emphysema, inadvertent penetration of the nasal cavity, damage to the neurovascular bundle in the mandibular or infraorbital canals, and displacement of the root apex into the nasal cavity or mandibular canal.

Very seldom is it appropriate to leave a root tip in place. Do so only if the risks of surgery to remove the root tip outweigh the benefits of removing the root tip. The surgical risks include: a patient who is not stable under anesthesia; the possibility that continued attempts at root tip removal may affect vital structures (nerves and blood vessels within the mandibular canal, the nasal cavity, or orbit); and the potential for significant destruction of surrounding bone or soft tissues or displacement of the root tip into the mandibular canal, nasal cavity, or retrobulbar space.⁴

Do not leave a root tip in place if you see any clinical or radiographic evidence of periodontal or endodontic disease associated with the tooth. Do not leave root tips in cats and dogs with stomatitis. For a fractured root tip to be left in place, the root tip must be small and deep within the alveolus.

If you decide that the benefit of fractured root removal does not outweigh the risks and the root tip will remain in place, take intraoral radiographs to document the remaining root structure. Referral to a veterinary dentist is recommended. Inform the client of the decision, the reason for the decision, and the possible clinical sequelae. Document the decision in the patient’s medical record. For follow-up, take radiographs of the retained root tip each year to look for any pathology associated with the remaining root fragment. If pathology is found, root tip retrieval is necessary.

In summary, fractured root tips are frustrating and sometimes difficult to remove. Intraoral radiographs must be obtained before extraction to evaluate the tooth structure and surrounding alveolar bone. Proper extraction technique minimizes the chances for fracturing root tips. Removal of buccal alveolar bone and proper sectioning of teeth facilitates extraction. Use of proper, sharp instruments and slow, controlled forces are recommended. Above all, be patient!

Displacement of Root Tips

While attempting to retrieve fractured root tips, you might displace a tooth root into the mandibular canal, nasal cavity, or maxillary sinus.⁷ Root displacement can be avoided by removing alveolar bone to enable visualization of the root tip and carefully elevating fractured root tips with minimal apical force. If displacement occurs, it is desirable to remove the root tip or tooth fragment. Removal is usually facilitated by removal of additional bone and careful evaluation to identify the displaced root tip. When removing root tips from the mandibular canal, avoid the mandibular neurovascular bundle. Root retrieval from the nasal cavity can be difficult because of the large space and potential for tooth fragment migration. These procedures are often beyond the ability of the general practitioner, and referral to a veterinary dentist for evaluation is recommended (FIGURE 6).

Figure 6. (A) Preoperative radiograph of retained tooth roots resulting from fractured tooth 408 at cementoenamel junction.

Figure 6. (B) Mesial root of tooth 408 displaced during attempted removal, now overlying the distal root of tooth 407 (orange arrow). The distal root fractured during extraction because the buccal bone removal was mesial to the tooth root (white arrow) and the root was not clearly visualized before removal.

Figure 6. (C) The distal root of tooth 408 and periodontal ligament were not identified before removal of the distal root, and apical pressure applied while attempting elevation displaced the distal root into the mandibular canal (arrow).

Hemorrhage

Excessive bleeding may originate from the extraction site or from trauma to vascular structures or soft tissue during the extraction. If hemorrhage originates from the mandibular canal or nasal cavity, direct ligation of the vessels is usually not possible. In most instances, hemorrhage can be controlled by direct pressure with a moist gauze sponge. If the bleeding originates from the alveolus, closing the oral surgery site over the alveolus will mechanically put pressure on the area of bleeding and should lead to clot formation. Other techniques to control intraoperative bleeding include ligation of the lacerated vessel, use of electrocautery, or application of a hemostatic agent.

Trauma to the Flap

Tearing of the mucoperiosteal flap may result from penetration of the flap by the periosteal elevator during flap preparation, damage to the flap by the high-speed bur, an inadequately-sized flap, or excess tension on the flap during the extraction procedure. If the tear is very small, it may be possible to suture it, depending on its location. In most cases, suturing the tear will result in adequate but delayed healing.¹ If the perforation is large, trimming the tissue at the area of the perforation and redesigning the flap may be required to ensure tension-free closure.

Trauma to Adjacent Teeth

Teeth adjacent to the tooth being removed can be damaged during sectioning, removal of buccal bone, or elevation of the diseased tooth. The formerly healthy, now damaged, tooth should be evaluated visually and radiographically. Appropriate treatment will be determined by the extent of the damage.

Fractured Alveolar Bone

Occasionally, if too much force is used or if extraction forceps are used before the tooth has been adequately elevated, a piece of buccal alveolar bone may be removed with the extracted tooth. If this occurs, smooth the remaining bone and close the oral surgery site. Alternatively, you may see a small fissure line in the buccal alveolar bone (FIGURE 7) or a fractured segment of buccal bone after tooth extraction. If the fracture is incomplete and there are no loose bone fragments, you can smooth the rough edges of the fracture with a diamond bur. Always remove any loose bone fragments before closing the oral surgery site.

Figure 7. Cadaver, showing incomplete fracture of alveolar bone that occurred during extraction of tooth 104.

Iatrogenic Jaw Fractures

The mandible is most commonly inadvertently fractured during extraction of the mandibular canine tooth in dogs and cats or the mandibular first molar in small-breed dogs^8,9 (FIGURE 8). The large contribution of the first molar and canine roots at their respective locations in the mandible indicates the need for careful planning when performing extractions and raises awareness of a potential cause of iatrogenic fractures.¹⁰ Iatrogenic jaw fractures may result from preexisting periodontal or endodontic disease (FIGURE 9), excessive force used by the operator, or a combination of both.

Figure 8. Radiograph showing fractured mandible after removal of tooth 304.

Figure 9. Radiograph showing advanced periodontal disease affecting teeth 408, 409, and 410.

In small-breed dogs, the ratio of first molar height to mandibular height is higher than that in large-breed dogs, which increases their risk for pathogenic or iatrogenic fracture.¹¹ In this anatomic circumstance, the periodontal ligament space extends from the alveolar bone margin to near the ventral cortex of the mandible. In dogs, presence of periodontal or endodontic disease at the level of the mandibular first molar can lead to bone loss in the area, increasing the susceptibility of the mandible to fracture.¹²

If a mandibular canine tooth is diseased, evaluate the stability of the mandibular symphysis before removing the tooth. Some cats and dogs have symphyseal laxity, which should be noted before starting oral surgery.

If an iatrogenic fracture occurs secondary to extraction, contact your local veterinary dentist for treatment recommendations.

Dehiscence

Dehiscence at the oral surgery site usually results from lack of a tension-free closure. Other causes for flap dehiscence include poor flap design, sutures not supported by bone, occlusal interference from the teeth opposing the oral surgery site, and inappropriate postoperative care of the extraction site (e.g., patient chewing on hard objects or pawing at the mouth). The keys to a tension-free closure are creation of a well-designed, wide-based mucoperiosteal flap and release of the periosteum.

Treatment for dehiscence depends on its location and the state of the alveolus before closure. When the alveolus is intact and no necrotic bone is present, the site can be allowed to granulate by second intention (FIGURE 10). However, in the presence of an oronasal fistula, it is never appropriate to try to allow a defect to heal by second intention. If after 2 weeks the oral surgery site shows no evidence of healing, an examination under general anesthesia is indicated to rule out neoplasia as a potential cause.

Figure 10. Extraction site at tooth 304 (A) 7 days postoperatively

Figure 10. Extraction site at tooth 304 (B) after healing by second intention.

Oronasal Fistulas

Oronasal fistulas may be preexisting and associated with any maxillary tooth that is affected by severe periodontal disease. Most commonly, oronasal fistulas develop in small-breed dolichocephalic dogs, secondary to advanced periodontal disease associated with the palatal aspect of the maxillary canine teeth. An oronasal fistula may be visible in the area of a previously extracted maxillary canine tooth when a mucoperiosteal flap was not used to close the extraction site (FIGURE 11). In addition, an oronasal fistula may be iatrogenic, created during extraction by removal of a piece of bone on the palatal aspect of the root with the tooth root itself.

Figure 11. Oronasal fistula (arrow) in area of previously extracted tooth 204.

In each instance, closure of the resulting oronasal defect with a tension-free flap is indicated. Debride the margins of the defect, create a well-designed mucoperiosteal flap, and release the periosteum to allow for tension-free closure. Most of the time, an oronasal fistula can be repaired with a single mucoperiosteal flap.¹³ Occasionally, to repair a large or nonhealing oronasal fistula, use of a double-layer mucoperiosteal flap, an allograft membrane, or auricular cartilage may be needed.^14,15

If at the postoperative recheck examination you find a defect in the area of the previously repaired oronasal fistula, a new mucosal flap must be created to close the defect. A defect that overlies the nasal cavity will not “granulate in” or heal by second intention.

Ophthalmic Damage

Extraction of teeth in the caudal maxilla of dogs and cats may be associated with damage to the surrounding tissues, including the orbit and globe, especially if the patient has concurrent periodontal disease.¹⁶ The apices of the maxillary fourth premolar and first and second molars in the dog and the maxillary fourth premolar and first molar in the cat lie in close proximity to the ventral floor of the orbit, and only a thin shelf of alveolar bone surrounds these tooth roots (FIGURE 12). The bony orbit of the dog and cat is incomplete; the floor of the orbit is composed of soft tissues, including the zygomatic salivary gland, orbital fat, and medial pterygoid muscle.¹⁷ Inadvertent penetration of the orbital floor during caudal maxillary tooth extraction is often multifactorial and may be associated with the regional anatomy, periodontal pathology, and improper or aggressive extraction techniques.¹⁶ If the tooth is affected by periodontitis and if a short finger stop is not used during extraction, the orbit can easily be penetrated with a dental elevator. Penetration of the globe may result in panophthalmitis and may ultimately require enucleation.

Figure 12. Caudal view of the orbit in a dog.

You can help prevent this complication by being familiar with the regional anatomy, understanding the extent of periodontal disease, using controlled forces, and using a short finger stop.¹⁸ Traumatic brain injury has been reported as an iatrogenic complication of extractions, resulting from the dental elevator slipping during removal of the maxillary molars in the dog and penetrating the retrobulbar space into the brain.^18,19 Use of a short finger stop and controlled forces in the caudal maxilla during tooth extraction cannot be overemphasized.

Lip Entrapment

Lip entrapment is a potential complication of maxillary canine tooth extraction and is most commonly seen in cats. The mandibular canine tooth contacts the upper lip or rests on the outside of the upper lip and may result in an ulcer (FIGURE 13). Lip entrapment can be avoided by paying close attention to flap positioning and by not removing excess bone during extraction of the maxillary canine tooth. If this condition doesn’t self-correct, then treatment is indicated. To eliminate the contact, treatment may be coronal reduction and endodontic treatment or extraction of the mandibular canine tooth.

Figure 13. Lip entrapment in a cat.

SUMMARY

During every procedure, have a silent conversation with yourself about what you are doing and how you are doing it. Create your own checklist or use the one in BOX 3. Atul Gawande and his research team have developed checklists (written guides that walk them through the key steps in any procedure) that have been successfully used in hospitals and operating rooms around the world to decrease patient morbidity and mortality.²⁰ Mental conversations and written checklists can help create muscle memory and consistency in your approach to oral surgery, which will help you avoid complications.

Your goal with all extractions is to extract the entire tooth and root without damage to surrounding structures. Unfortunately, we all encounter complications during tooth extraction at some point in our career. Recognition of potential complications and their causes and knowledge of appropriate treatment methods for those complications help minimize pain and discomfort for our patients. The easiest way to avoid surgical complications is through adequate preparation and use of a checklist. Finally, if a particular case or circumstance is beyond your ability, referral to a veterinary dentist is in the best interest of the patient.