Endodontics: Care for the Fractured Tooth

The days of observing and neglecting fractured teeth should be over. Our patients may not "complain" to their owners or us about fractured teeth until lesions have progressed, sometimes to the untreatable.

All teeth are susceptible to fracture, however, in the mature dog or cat, the maxillary canines are most commonly broken, followed by the mandibular canines, the maxillary fourth premolars, and incisors. In the immature dog, deciduous canine teeth commonly fracture.

How do small animals fracture their teeth? Commonly from chewing on cage doors, airplane crates, or chain-link fences. Also implicated are hard chew toys, ice cubes, and horse hooves. Auto accidents, aggressive Schutzhund training, and dog fights can additionally lead to fractures.

What happens to a tooth when a fracture occurs? The lesions that develop vary. Many times a tooth fracture will occur that does not enter the pulp chamber and only the enamel or dentin is affected. Even so, trauma that caused the enamel and dentin to fracture may be sufficient to cause direct vascular damage and hemorrhage that can lead to inflammation and tissue destruction. Bacteria can then move in through anachoresis (the process of bacteria lodging in an area of previously damaged tissue), causing a myriad of problems ranging from internal inflammation to an apical abscess.

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Recently fractured
canine
Therapy decisions depend on which parts of the tooth are exposed. If the fracture involves only enamel, the treatment of choice is to smooth the sharp edges with fine white stone burs and sanding disks, in order to prevent trauma to the lips and tongue. Intraoral radiographs should be taken to get baseline images of the apex and to check for apical fractures The tooth should be re-radiographed at six and twelve months for evidence of periapical pathology.

Vertical fracture
through the
crown and root
of a cat's canine

If the crown fracture involves enamel and dentin, bacteria have a direct pathway to the pulp through the dentinal tubules. Either direct or indirect pulp capping, or root canal therapy is performed to save the tooth. Restoration of the tooth with amalgam, acrylic composite, or metallic crowns follow. Follow-up radiographs should be taken at six month intervals after the injury for several years examining the pulp chamber for internal resorption and the periapical structures for pathology.

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Left upper incisor
fractured, exposing pulp
Right upper incisor
enamel fractured with
near exposure of pulp

Often the crown fractures and pulp is exposed. This will be visually evident as a red or brown dot on the cut surface of the fracture. If the dot is black and shiny there may not be a pulp exposure, but an area of sclerotic or reparative dentin. A method to diagnose pulpal exposure is to insert an explorer tip into the suspected exposed pulp. If the explorer tip does not penetrate, then a pulp exposure is probably not present. An intraoral film should be taken, and, if the pulp chamber, the periapical, and periodontal structures appear normal then, no further therapy is necessary, other than possible crown restoration. Follow-up radiographs are recommended.

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Repair of above, with
crown restoration

If an exposure of the pulp exists, endodontic therapy must be performed, or the tooth must be extracted. An untreated exposed pulp can lead to pulpal necrosis and abscess formation from bacterial infection.

Two variables that enter into the decision making process when the pulp is exposed, are:

  1. the age of the patient and
  2. the time between the fracture and treatment
caoh.jpg (31001 bytes)
Calcium hydroxide placed on
top of live pulp to save the
tooth

Immediately after pulpal exposure, and for up to two weeks, inflammation of the pulp exists less than two millimeters from the exposure site. When superficial necrosis does occur, healthy pulp tissue is usually found several millimeters deeper within the pulp. If superficial layers of the pulp are removed, healthy pulp tissue is usually encountered that will respond to vital conservative pulp procedures. If the fracture is recent (less than two weeks old) and the patient is less than one and a half years old, a vital pulpotomy, also referred to as apexogenesis. One to four millimeters of pulp tissue are removed with a high speed drill and a direct pulp cap, with calcium hydroxide is applied as a dressing on top of the vital pulp. The hope is that calcium hydroxide will stimulate dentinogenisis forming a new dentinal bridge over the fracture site.


Zirconium crown matching tooth color

The primary goal in conventional endodontics is sealing the apex to prevent transmission of harmful bacteria to the periapical structures. If the dog or cat is less than one and a half years old, the root apex has not completely closed, making an effective seal via the non-surgical root canal procedure uncertain. When an immature patient is presented with an older fracture an apexification treatment can be performed that allows the apex of the root to continue to mature so a conventional root canal procedure can be performed at a later time. Apexification is accomplished by performing a conventional endodontic procedure with the exception of calcium hydroxide paste is used to fill the canal. Follow-up radiographs are taken every two months to evaluate apical closure. Once the root tip is closed, the calcium hydroxide is removed and the canal filled with gutta percha and zinc oxide-eugenol.

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X-ray of completed root canal
therapy to repair two fractured
lower canine teeth

In the mature patient with recent fracture, a vital pulpotomy with follow-up radiographs can be performed, but may not be as long term effective as conventional endodontics. In cases that the owners do not know when the fracture occurred, or if the fracture is greater than two weeks old, then a conventional root canal procedure should be performed to remove the effected pulp, seal the apex, and restore the crown. In cases where intraoral radiographs show marked periapical lysis, retrograde surgical endodontics or extractions are indicated.

impression.jpg (56623 bytes)
Rubber-based impression material
used to send to laboratory for
crown fabrication

Materials chosen for crown restoration depend on how the crown was fractured. An acrylic composite is easy to apply as a restoration and approximates the appearance of the tooth. Unfortunately acrylic does not hold up well to occlusal trauma. A better choice would metallic crowns fabricated from nickel and chromium.1.gif (807 bytes)

How to do Root Canals

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Three root canal files used to
remove infected pulp

Indications

Fractured teeth with
pulpal exposure --
more than 24 hours
old, fractured
segments coronal to
gum line
Discolored teeth --
usually indicates pulpal
death from trauma.
Can result in periapical
abscess if untreated
Periapical abscesses
with or without fistula
formation
Prior to post placement
for crown restoration

Instrumentation

"Hardware"

Delivery system to make access-high speed air drill with water
Lentulo filler-helps delivering apical sealing cement to root apex
Dental x-ray machine-conventional machines can be used at 10 Mass 50-70 kvp 12"FFD
Light cure gun-for restoration of access hole (optional)

"Software"

Barbed broaches-used to remove pulp
Endodontic files-diameter sizes 10-80 length sizes 21, 25, or 55 mm
Paper points-for drying canal-same size and diameter as files
Gutta percha-inert filling material for root canal
Zinc-oxide Eugenol-liquid-paste sealer for root apex
Composit or amalgam for restoration

Procedure -- Seven steps to a successful root canal:

  1. Make access opening over each root as close to gum line as practical
  2. Use barbed broach to remove root
  3. Use files to ream out root canal and remove necrotic debris. Between each larger file size irrigate canal with Chorox and saline. Take intraoral radiograph to make sure you are working 2 mm from the apex
  4. Dry out canal with paper points
  5. Mix zinc-oxide eugenol place on spiral filler and fill canal
  6. Pack appropriate sized gutta percha points into pulp chamber, radiograph
  7. Restore access opening composite or amalgam

There are variations of different steps and instruments used to complete the conventional root canal procedure.

 



This page last updated on October 31, 2000
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Jan Bellows, DVM
All Pets Dental Clinic
17100 Royal Palm Blvd.
Weston, FL 33326
(954) 349-5800
dentalvet@aol.com