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Veterinarian Technician February 2008 (Vol 29, No 2)

Options for Treating a Fractured Tooth

by Jodi Kristel, CVT, VTS (Dentistry)

    CETEST This course is approved for 0.5 CE credits

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    Tooth fractures are common in cats and dogs.1 Teeth may fracture when an animal chews on hard objects, fights with another animal, or experiences an impact injury (e.g., as a result of being hit by an automobile). When an animal has an open tooth fracture, in which the pulp is exposed, the treatment options available are root canal, vital partial pulpectomy, or extraction. Although a pet may be referred to a board-certified veterinary dentist for treatment, understanding the basic anatomy of the tooth is essential for veterinary technicians, who may evaluate a pet that presents to the practice with a fractured tooth.

    Structure of the Tooth

    The teeth of cats and dogs are structurally the same but differ in size and shape. The crown of a tooth refers to the portion that is visible above the gingival margin. The root lies below the gingival margin and is attached to alveolar bone by the periodontal ligament.2 When evaluating a tooth fracture, it is important to determine whether it extends under the gingival margin and into the root or whether only the crown is involved.

    The crown of a tooth is covered with enamel, a dense, smooth material.2 Enamel is the hardest tissue in the body; however, it is susceptible to wear and damage and cannot repair itself.3 During tooth development, ameloblasts are responsible for secretion of the enamel matrix. Enamel, which is usually white, can appear yellow — if the underlying dentin is exposed — and can be stained over time.

    The dentin layer lies beneath the enamel. Dentin is a hard material that is usually yellow in color. It is produced by odontoblasts, which continue to deposit layers throughout an animal's life, resulting in narrowing of the pulp cavity (discussed below) with age. Dentin can be divided into three main types: primary, secondary, and tertiary. Primary dentin is formed before tooth eruption, secondary dentin is formed after the adult tooth erupts, and tertiary (reparative) dentin forms in response to trauma to the tooth.3

    The thin layer of calcified tissue that covers the root surface is called cementum. Cemento­blasts are responsible for producing cementum, which is one of the supporting structures of the tooth.3

    The periodontal ligament, which connects the tooth to the alveolar bone, surrounds and cushions the tooth and is embedded in the cementum. The periodontal ligament contains nerve fibers that transmit sensory information (e.g., pain, heat, cold).3 Radiographic changes in the periodontal ligament (e.g., widening of the periodontal space, periapical lucencies) may indicate periodontal and/or endodontic disease.

    The pulp is located in the pulp cavity, which comprises the pulp chamber and root canal. The pulp is the innermost layer of the tooth and consists of blood and lymphatic vessels, nerves, collagen fibers and other connective tissue, and odontoblasts. Because it contains the nerves of the tooth, the pulp is responsible for pain transmission.3

    The apex, which is the tip of the root, is usually open in animals less than 18 months of age and closes as animals mature.3 Young animals, which have an open root apex and relatively thin dentinal walls, are not good candidates for root canal therapy in the event of a tooth fracture; therefore, procedures such as vital partial pulpectomy or extraction may be better options.

    Oral Examination

    When patients present to the veterinary practice with a fractured tooth, it is important to determine whether the pulp is exposed (i.e., an open fracture). This type of fracture is usually painful and requires immediate medical attention. A fracture in which the enamel and/or dentin is chipped but the pulp is not exposed (i.e., a closed fracture) may not require immediate treatment1; however, the tooth should be assessed radiographically every 6 to 12 months.

    The patient is anesthetized so that a detailed oral examination with thorough charting can be performed. An area of pulp exposure can be found with the use of a fine-tipped dental explorer. When performing dental charting, it is important to check the crowns of all teeth for open pulp cavities. Pulp exposure can be confirmed when the tip of the explorer falls into the exposed cavity. When the pulp is exposed, oral bacteria can enter the tooth, resulting in pulp necrosis, infection, and root abscessation.3

    A common clinical finding is swelling of the alveolar processes of the infected tooth and maxillofacial swelling due to cellulitis. This swelling may be responsive to antibiotics; however, if the fractured tooth is not treated or extracted, the abscess may return after antibiotic treatment is stopped.2 Open tooth root abscesses commonly drain externally through the skin or intraorally at the mucogingival junction of the infected tooth.

    The teeth most commonly fractured are the upper fourth premolars in dogs and the canines in both dogs and cats. Because patients with a fracture of the upper fourth premolar often present with facial swelling ventral to the medial canthus of the eye, they are sometimes incorrectly diagnosed with an eye problem. Therefore, if a patient presents with a facial abscess, its teeth should be checked for fractures.

    A tooth can be worn down gradually over time and appear to be fractured, with a brown spot in the center; however, when explored, the tooth surface has a smooth, glass-like feel. In this case, the tooth may have repaired itself with tertiary dentin and does not likely need further treatment.2 After the oral examination, any findings should be confirmed by radiography.

    Treatment

    When a patient presents to the veterinary practice with an open tooth fracture, the three treatment options are standard root canal therapy, vital partial pulpectomy, and extraction. The option selected depends on the duration of the problem and the age of the animal, as well as the owner's preference.

    By discussing the treatment options and their associated follow-up requirements, veterinary staff can help owners select the most appropriate option for their pet. For example, after patients undergo root canal therapy or vital partial pulpectomy, regular follow-up — including radiographic examination under anesthesia — is necessary. Therefore, an animal that is often stressed or aggressive or that has a systemic illness, such as renal disease, may not be a good candidate for either procedure. In these cases, tooth extraction may be a better option.

    Root Canal Therapy

    The goal of standard root canal therapy is to remove the source of infection — the inflamed pulp — and maintain the function of the tooth.3

    Root canal therapy is indicated in patients with a fractured crown with pulp exposure, a worn tooth with pulp exposure, a carious lesion that extends into the pulp chamber, a nonvital discolored tooth, a tooth crown that appears opaque when transilluminated, or an avulsed tooth that was reimplanted.4 Root canal therapy is also indicated when there is radiographic evidence of a periapical lucency.4

    The root canal procedure is divided into several stages; radiographs should be taken at each stage. Following radiographic confirmation of the tooth fracture, a round carbide bur on a high-speed handpiece is used to access the pulp chamber. A small opening is created through the enamel into the pulp chamber to enable straight-line access to the apex.4

    Cleaning and shaping of the canal involves the use of items such as reamers, Hedstrom files, irrigation syringes, barbed broaches, paper points, a ruler, endodontic stops, and college pliers; endodontic chelating agents such as RC-Prep MicroDose (Premier Products Co.; Plymouth Meeting, PA); solutions such as sodium hypochlorite; and various root canal filling materials.

    Materials used to fill the canal include zinc oxide-eugenol (ZOE) and gutta-percha points. ZOE is a common sealant used in veterinary dentistry.5 It is nonirritating and antimicrobial, with a long working time. ZOE is mixed on a glass slab with a number 5 spatula. When ZOE is mixed to the proper consistency, a half-inch string will form when the spatula is lifted off the slab.5 A spiral filler placed on a reduction gear contra-angle on a low-speed handpiece can be used to insert the ZOE into the canal.4 Gutta-percha is an inert rubbery material derived from the latex of tropical trees such as Palaquium gutta. Most commonly used is the beta form, which is soft and flexible to allow for compaction into the canal.5 Gutta-percha points are available in different sizes to accommodate various canal widths and lengths. Gutta-percha can also be heated in a cannula syringe and injected into the canal.4 Spreaders and pluggers are used to condense the gutta-percha to adequately fill the canal without dead space.

    The final stage of the root canal procedure involves placing restorative material over the access and fracture sites. Three types of restorative material used in dentistry are composites, glass ionomers, and amalgams.5 Composites are commonly used in veterinary dentistry. Some owners may prefer composites for their pet because they produce the most aesthetically pleasing results. They are available in various shades of white to match the tooth color. Glass ionomers are often used as an intermediate layer above the gutta-percha and root canal sealer and beneath the final composite restoration. Amalgams are usually used on the occlusal surfaces of the back teeth because of the compression forces exerted on these teeth. Amalgams are the strongest of the three restoratives, but there are several disadvantages to their use.4 Because they are silver in color, they produce the least aesthetically pleasing results. They also contain mercury; therefore, veterinary staff exposure to mercury is a concern. However, the potential for exposure can be minimized if the amalgam is supplied in capsule form; the capsule contains a protective membrane to prevent personnel from handling the material. Undercut preparation, in which dentin and enamel are removed, is required to hold the amalgam in place. In addition, amalgam placement requires that more tooth material be removed compared with placement of the other restoratives. Amalgam has also been shown to corrode, causing a black line to develop around the margin of the restoration over time.4

    During restoration, dentin conditioner is applied to the dentin, and etching gel is applied to the enamel to remove any tooth debris from the access and fracture sites.5 Conditioning and etching also create irregularities that help the bonding agents adhere. A primer is then applied to prepare the surface for the bonding adhesive. Composite material is placed in layers that are 1 to 2 mm thick; each layer must be cured according to the manufacturer's directions.5 Depending on the material, light curing or chemical curing may be used. More than one layer may be necessary to completely overlap the margins of the access and fracture sites. The tooth surface is then contoured and polished smooth with trimming burs and sanding disks of various grits.5

    In certain situations, a crown may be placed to prevent further destruction of the tooth. The most common material used for crowns is semiprecious metal.4 The decision to place a metal crown involves consideration of the patient's lifestyle. A metal crown should be placed in working dogs (e.g., police, military, prison, guide).4 Metal crown placement requires additional expenses and increased anesthesia time. A disadvantage to applying a metal crown is that more of the enamel or tooth surface must be removed, causing further weakening of the tooth.5 Options include a full jacket crown that covers the whole tooth or a partial crown that covers a portion of the tooth.4 The tooth must be prepared to allow a tight fit, and impressions and models need to be made and sent to a dental laboratory for crown fabrication. A temporary crown is usually created from acrylic or composite material to protect the tooth until the permanent metal crown can be placed.

    In some cases, standard root canal therapy may be unsuccessful. Clinically, the most obvious signs of unsuccessful treatment are continued periapical disease with abscessation, facial swelling, and formation of a sinus tract — an opening in the mucogingival junction or external skin associated with an inflamed or infected area of the tooth root.6 If it is suspected that the procedure was unsuccessful, radiographs should be taken to provide definitive confirmation. A periapical lucency may indicate continued infection.6 If the root canal procedure fails, a second procedure (with better obturation) or extraction may be performed. If the previous technique appears to be adequate, then surgical root canal therapy may be attempted.6

    Surgical root canal therapy, in contrast to standard root canal therapy, involves incising the skin or alveolar mucosa near the affected tooth, performing alveolectomy or apicoectomy, accessing the root canal through the cut apical end of the root, and sealing the canal with a retrograde filling.4

    Vital Partial Pulpectomy

    Standard root canal therapy involves complete removal of the pulp, whereas vital partial pulpectomy involves removal of only the infected pulp.2 In certain situations, vital partial pulpectomy may be performed instead of root canal therapy. For example, vital partial pulpectomy may be performed in a fractured tooth with pulp exposure in an animal younger than 18 months if the fracture occurred within 2 weeks of presentation. An animal older than 18 months that pre­sents with a fractured tooth with pulp exposure may also be a good candidate for vital partial pulpectomy if the fracture occurred within 48 hours of presentation.4 Vital partial pulpectomy allows for further apexogenesis, root lengthening, and narrowing of the pulp cavity. This procedure requires both clinical and radiographic monitoring to check for any signs of failure. The risk of failure is greater for vital partial pulpectomy than for root canal therapy because bacteria present in the root canal may infect the remaining pulp. Standard root canal therapy may be needed if vital partial pulpectomy is unsuccessful.4 Therefore, clients should be informed of this risk when deciding among the treatment options.

    Extraction

    Because of the cost and follow-up care associated with root canal therapy and vital partial pulpectomy, extraction may be the only option. Extraction is usually performed by, or under the supervision of, a veterinarian. Extraction is indicated in patients with a fracture in a primary (deciduous) tooth, a fracture that extends below the gingival margin, a root fracture, a tooth in which more than one-third of the root is compromised, severely worn teeth, or severe periodontal disease, as well as in older animals with extremely narrow and inaccessible root canals.2 Extraction may also be performed in patients with a systemic condition if they cannot undergo the follow-up anesthetic induction needed for radiographic assessment of treated teeth.

    Follow-Up Care

    Postoperative care of patients that undergo root canal therapy, vital partial pulpectomy, or extraction should include the use of pain medication for at least 3 days; patients may also receive a course of antibiotics. Another important part of root canal therapy and vital partial pulpectomy is follow-up radiography at 6 months and yearly thereafter.4

    During follow-up visits, the patient will need to be anesthetized so that intraoral radio­graphs of the treated tooth can be taken. In addition, follow-up visits may be combined with dental prophylaxis, which requires general anesthesia.

    Role of the Technician

    During the oral examination, the technician charts the patient's teeth. When a patient undergoes root canal therapy or vital partial pulpectomy, the technician mixes and prepares the necessary materials, takes radiographs, and provides the veterinary dentist with the appropriate instruments.1 The technician also plays an important role in providing postoperative home care instructions to the client.

    Conclusion

    During the regular patient checkup, the technician should carefully evaluate the pet's oral cavity for any signs of tooth fracture or other abnormal findings. In patients with an open tooth fracture, root canal therapy or vital partial pulpectomy can be a successful treatment option that maintains the function of the tooth while eliminating discomfort and improving the pet's quality of life. In some patients, however, extraction may be the only option. It is important that technicians help clients understand the available options for treatment, as well as the associated follow-up requirements, so that the clients can choose the procedure that is most appropriate for their pet.

    1. Kesel ML: Veterinary Dentistry for the Small Animal Technician. Ames, IA, Iowa State University Press, 2000, pp 167, 233, 235.

    2. Harvey CE, Emily PP: Small Animal Dentistry. St. Louis, Mosby, 1993, pp 156"211.

    3. Wiggs RB, Lobprise HB: Veterinary Dentistry: Principles and Practice. Philadelphia, Lippincott-Raven, 1997, pp 280"321.

    4. Holmstrom SE, Frost P, Eisner ER: Veterinary Dental Techniques for the Small Animal Practitioner. Philadelphia, WB Saunders, 1998, pp 348"407, 462"463.

    5. Holmstrom SE: Veterinary Dentistry for the Technician and Office Staff. Philadelphia, WB Saunders, 2000, pp 252"270.

    6. Niemiec BA: Fundamentals of endodontics. Vet Clin North Am Small Anim Pract 35(4):837"868, 2005.

    Note: Laws regarding who is allowed to perform veterinary dental procedures vary from state to state. Therefore, technicians should check with their local veterinary medical board before performing any dental procedures.

    References »

    NEXT: Picture This! A "Nail" of a Tale

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