Tooth Root Abscesses in Dogs

Introduction

Also called an apical abscess, a tooth root abscess is a fairly common occurrence in the teeth of dogs. It is a painful condition where infection is introduced into the pulp canal of the tooth, travels along it, and forms an abscess at the apex, or tip, of the tooth root. Based on what we know from abscesses in humans, because the abscess can be under pressure, the pain involved can range from low throbbing to intense continuous pain.

Fig 1. This diagram of a single-rooted dog’s tooth shows the pulp (nerve tissue) in the center of the tooth. If the tooth receives a hard blow or is damaged so that the pulp is exposed, an abscess can form.

An abscess is a collection of pus that spreads along the path of least resistance from the apex of the tooth. It can move through the apex of the tooth and the facial bones, and create cellulitis leading to a draining tract through the skin of the face.

Alternatively, it can move through the bone around the tooth, and drainage can occur through the alveolar mucosa above the mucogingival line (parulis) inside the mouth. You may see the former as a swelling on your dog’s face, but the latter is more likely to be found by your veterinarian during an oral examination.

In the vast majority of cases (90%), a broken tooth is the cause of the abscess. Usually a fracture with an open pulp canal is the culprit, although sometimes a tooth with a pulp canal that is still barely sealed can be abscessed.

Although the exact reason for the cause of the abscess may not be known, the treatment remains the same—drainage of the abscessed site. Unfortunately, drainage of the site of an abscessed tooth almost always means extraction of the tooth.

Apical abscesses can involve any teeth, although the majority involve the maxillary fourth premolars. These are major teeth in the upper jaws that are power teeth for tearing, crushing, and chewing food and bones.

For this reason they take the brunt of wear and tear, and unfortunately are prone to injury, particularly slab fractures which can allow bacteria into the pulp canal, inviting an abscess to form.

Fig 2. Dog tooth chart showing the location of the teeth within the mouth and the roots of the various teeth. The most commonly fractured and abscessed tooth in dogs is the upper fourth maxillary tooth; the fourth tooth back from the large canine tooth. This 3-rooted tooth bears the brunt of chewing forces, and when abscessed, often causes swelling below the eye or on the side of the face.

Fig 3. This dog has a slab fracture on their upper left fourth premolar (the fourth tooth from the front (left) on the top), exposing the pulp canal (the dark spot on the tooth). You can see the discoloration of the caudal half of the tooth which suggests bleeding, abscessation, or possible pulp necrosis, or death. This fractured and possibly dying tooth will need to be extracted.

Preoperative antibiotics are recommended in the case of abscessed teeth to help prevent the spread of infection, to help treat the abscess, and treat periodontal disease if present. Antibiotics usually are continued through the recovery phase of the extraction.

If not treated, bacteria can spread to other organs and cause systemic illness, so it is important to take tooth abscesses seriously and use medication as directed.

Occasionally, chronic Phoenix abscesses (non-active abscesses) can become exacerbated and painful, or a pet may have a sterile abscess (without bacteria). These will still need to be drained and treated.

Causes

Risk factors for tooth abscesses include:

• Trauma to the teeth which in turn traumatizes the pulp canals, including direct blows and fracturing the crown of the tooth.
• Chewing hard objects. This commonly causes fourth premolar fractures.
• Fighting with other dogs.
• Severe periodontal disease causing deep gingival pockets.
• Tug-of-war or other ways of pulling on the teeth.
• Bone plating or other dental work that damages the roots.
• Bacteria from dental caries (cavities), exposed dental tubules, or extension into the endodontic system.
  Heat causing pulp injury—electric cord burns, electrocautery, over-polishing, or during drilling.

Fig 4. This terrier lays amongst his favorite toys. Notice there are no tug-toys which can cause teeth to be pulled out, or tennis balls which can cause severe tooth wear. There are also no bones which can cause teeth to break.

Clinical Signs

• A large swelling under the eye is the most common sign noted, since the fourth maxillary premolar is the tooth most commonly fractured and abscessed. Sometimes the abscess presents as swelling of the face.
• The face might be tender, or very painful if there is an abscess that is not yet draining.
• The tooth is broken 90% of the time, or the tooth is barely sealed over from the exposed pulp canal. The doctor can almost always insert the end of the dental probe into the pulp canal.
• There may be a draining tract on the face, commonly seen under one eye due to maxillary fourth premolar involvement.
• The pet may show a reluctance to chew, and an accumulation of plaque and tartar may be seen. They may bite down but release quickly due to pain.
• They may show facial lymphadenitis.
• Deep periodontal pockets may be the cause if no fracture is present.
• The tooth may be discolored which often indicates the nerve has died.
• The tooth may not be sensitive. However, if a tooth was recently fractured it may still be sensitive.
• A parulis (a red, raised lesion seen at the mucogingival line or above) may be noted on oral examination.
• The tooth may be asymptomatic despite the presence of inflammation and bacteremia, but will eventually show signs.
• A mandibular fracture can cause abscesses, especially of the lower canines or first molars.
• Loose teeth are painful and may abscess.
• The pet may show reluctance to eat or stop eating altogether, but most will eat despite the abscess pain.
• Maxillary sinusitis can occur.
• The sense of smell may be affected, which is usually noticed in working dogs.

Fig 5. This maxillary fourth premolar, seen after cleaning, is likely to be abscessed due to the severe periodontal disease present. Even if not abscessed, it is likely that based on radiographic findings, pocket depth, gingival retraction and furcation exposure, this tooth and the third maxillary premolar will need extracting.

Diagnosis

The diagnosis for an apical root abscess is done by oral radiography (X-rays), which must be performed under general anesthesia. Anesthesia is necessary because although most pets are gentle and well-behaved, they cannot help but bite on the X-ray probe, which is expensive, and which must be exquisitely positioned around and between their teeth for their dental X-rays.

(Think about how you must gently bite on the X-ray films during your dental X-rays and how uncomfortable it is holding still for that short amount of time!).

If an abscess is present there will be pus, inflammation, and typically bone resorption at the apex of the tooth. If the tooth root abscess is chronic, it may have a fibrous capsule surrounding it, and a draining tract.

If it is difficult to be sure whether or not there is an abscess or which tooth is affected, the following diagnostic procedures can be done:

• To help determine which tooth is affected if a fistula has developed, gutta percha can be inserted into the sinus tract and a radiograph then taken.
• Transillumination with a strong fiber-optic light can be used to help determine between a healthy or necrotic pulp, and to compare the same tooth on both sides of the mouth.

Differential diagnoses

The differential diagnoses for abscessed teeth include:

• Normal anatomy on x-rays including mental foramen, especially the middle mental foramen just apical to the second mandibular premolar.
• Tooth resorption without apical lucency.
• Tumor including squamous cell carcinoma and fibrosarcoma which can displace teeth.
• Cementomas—enlarged apical roots with a thin radiolucent zone continuous with the periodontal ligament.
• Cysts—large lytic area involving any part of the unerupted crown and or the root.
• Apical periodontal granulomas, radicular cysts.
• Dentigerous cyst—radiograph shows a tooth within the cyst–the follicular cyst of an impacted or embedded tooth (usually the first mandibular premolar in dogs).
• Periapical scar—in an endodontically treated tooth when there is no increase in lucency in the apex more than 6 months after treatment.
• Must be differentiated from the chevron effect–this can be seen radiographically in the small teeth that often abscess.

Treatment

Treatment of an apical tooth abscess involves the following:

• Extraction of the tooth, to provide surgical drainage and remove the focus of the infection.
• Curettage of the apical infected area.
• Chronic abscesses may require surgical removal of granulation tissue and curettage of any draining tract.
• Endodontic root canal or surgical root canal if the apical lesion is large.
• Cold packs on the treated area can help reduce inflammation, if the pet will allow, before and immediately after surgery.
• Appropriate pain control before, during, and after extraction for at least several days.
• Provide oral rest while healing: soft food, no hard chew toys, no bite work for working dogs.
• Broad spectrum antibiotics preoperatively to prevent systemic spread of infection and improve tissue quality for best surgical outcome.

1. Clindamycin is recommended due to its excellent bone penetration.

     2. Amoxicillin/clavulanic acid is another good choice.

Fig 6. This large dog has had their maxillary fourth premolar extracted. A large flap was made in the gingiva, part of the dog’s alveolar bone was removed, the tooth was cut into sections, then was elevated out laterally one piece at a time. Absorbable sutures will be placed to fully close the gingival flap. The dog is anesthetized, with an endotracheal tube in place, through which he receives oxygen and anesthetic gas. This maintains his airway and protects him from aspirating any fluids. The black clip is holding his lips and whiskers out of the way. He also had a small wart excised from his lower lip.

Potential Outcomes

With proper drainage and treatment, the prognosis for an apical root abscess is excellent. Follow your veterinarian’s orders for post-surgical care.

Keep in mind that tooth root abscesses are deep in the tooth, tissue, and bone, and can take an extended period to resolve. Therefore, always use antibiotics as prescribed and use them until they are finished. This helps make sure infections are cured, don’t recur, and helps prevent drug resistance from developing.

Also be sure to take your pet to any recommended recheck veterinary visits. Veterinarians often want to evaluate the post-extractions sites of abscesses to be sure the tissues are healing appropriately.

Sometimes, minor chips in teeth can be treated with a sealant by your veterinarian during dental procedures or by special arrangements, which can protect your dog’s teeth from further damage or abscessation.

But if your dog does develop an abscess, it should be taken care of as soon as it is diagnosed to prevent further pain, and/or damage to your pet’s teeth and oral cavity.

Allowing abscesses to go untreated increases the chances of damage to their facial bones, adjacent teeth, and possibly even their eye on the side of the abscess.

Fig 7. This dog has had a sealant applied to their maxillary fourth premolar. The purpose of the sealant was to protect it from further damage, bacterial invasion, or abscessation after having been fractured.

Maintaining good oral health and preventing injury to your pet’s teeth are the best ways to prevent tooth abscesses.
See our article “How to Brush Your Dog’s Teeth” for more information and some great tips on how to get started with an excellent home care program.

You can help your pet have healthier teeth and gums and hopefully help prevent dental problems in the future. You can’t always prevent tooth fractures but your increased awareness helps you be a better pet owner. Every step you take to improve your pet’s dental health will improve their overall health too. Keep up the good work!

This enzymatic toothpaste helps to clean your pet’s teeth as you apply it by wiping, rubbing, or scrubbing with gauze, finger wipes, or a brush. Just do the best you can as often as you can.

Use whichever end of this double sided brush fits your pet’s mouth and teeth the best, to gently touch, then rub, then scrub, then eventually brush their teeth the best you can, as often as you can. Just do your best!

These little finger wipes are great for reaching along inside the lips of your pet to get to the back teeth. Hold their mouth gently closed, and just rub a little as you get them used to the feeling. Do the best you can to gently rub and scrub those teeth a little more day by day. Even if you never graduate to a toothbrush, you’ll help a lot to keep your pet’s mouth healthy by scrubbing with finger wipes!

This antibacterial chlorhexidine rinse is especially helpful after extractions or dental work. It can be used to flush the extraction sites and/or the whole mouth post op, or to prevent and treat periodontal disease.