Oral Pathology
World Small Animal Veterinary Association World Congress Proceedings, 2013
Brook A. Niemiec, DVM, DAVDC, FAVD
Southern California Veterinary Dental Specialties, San Diego, CA, USA

Malocclusions

An occlusion that is not standard for the breed. It may be purely cosmetic or result in occlusal trauma. There are several different potential etiologies for orthodontic problems, which are broken into two categories, genetic and nongenetic. Therapy for malocclusions is relative to type and severity of the disease process. Options include: No therapy (if purely cosmetic), extraction of the offending tooth or teeth, orthodontic correction using appliances, and coronal amputation and vital pulp therapy.

Deciduous Malocclusions

In some cases, the patient may be genetically programmed for a normal bite and only temporarily maloccluded. In these cases, the alignment problem is typically mild. These temporary malocclusions occur when the maxilla and mandible grow at varying rates during development due to an independent jaw growth surge.

In many cases, the deciduous dentition is trapped by a tooth or the soft tissues on the opposite arcade, which interferes with programmed jaw growth and subsequent self-correction. This is called an adverse dental interlock.

Depending on the class of malocclusion (especially class II and base narrow) palatine/gingival/lip/tooth trauma may occur. Occlusal trauma is traumatic and painful, regardless of the lack of clinical signs; therefore, expedient therapy is mandated.

If occlusal trauma is present, extraction of the offending deciduous teeth should be performed as quickly as possible. Even if there is no current occlusal trauma, selective extraction of the deciduous teeth should be performed to remove the adverse dental interlock and allow jaw movement.

Deciduous extractions should be performed as soon as the problem is noted (ideally at 4–8 weeks).

Root fracture is a common occurrence during extraction attempts. If this occurs, every effort should be made to remove the piece(s). A retained root tip may become infected, or more commonly act as a foreign body and create significant inflammation. There are rarely any clinical signs associated with this, but the patient suffers regardless. Retained roots are best extracted utilizing a surgical approach. Dental radiographs should be exposed following extraction, to confirm complete removal of the deciduous tooth.

Persistent Deciduous Teeth

Persistent deciduous teeth are very common, especially in small and toy breed dogs. They create both orthodontic and periodontal problems if not treated promptly. It has been reported that orthodontic problems begin within two weeks of the permanent canines starting to erupt. This is due to the deciduous tooth being in the place that the adult wishes to occupy.

The periodontal issues occur due to a disruption of the normal maturation of the periodontium. When there is a persistent deciduous tooth, one area of the periodontium is not attaching to the permanent, therefore the periodontal attachment in that location will not be normal. It has been reported that the damage begins within 48 hours of the permanent teeth starting to erupt! Therefore, the adult tooth does not need to be completely erupted for these problems to occur, and they should be extracted as early as possible.

Fractured Teeth

The two main types of crown fracture seen in veterinary medicine are complicated and uncomplicated. Both types require therapy.

There are 45,000 tubules per mm2 in coronal dentin. This means that a defect 1 cm in diameter will result in the exposure of 1,000,000 odontoblasts. Each one of these dentinal tubules has what amounts to a nerve, resulting in significant sensitivity. Also, the exposed dentinal tubules may act as a conduit for bacterial infection of the pulp, thus initiating endodontic disease.

All teeth with direct pulp exposure (complicated crown fractures) should be treated with endodontic or exodontic therapy; ignoring them is not an option. Uncomplicated crown fractures are also a very common finding on oral exam, particularly in large-breed dogs. These fractures will result in direct dentinal exposure, creating significant pain for the patient. It is recommended that these teeth be radiographed to ensure vitality. If the teeth are nonvital, endodontic or exodontic therapy is required. If the teeth appear vital, the application of a bonded sealant is recommended to decrease sensitivity.

Intrinsically Stained Teeth

Endodontic disease is also manifested by intrinsic staining. This can appear as pink, purple, yellow, or grey. A study by Hale showed that only 40% of intrinsically stained teeth had radiographic signs of endodontic disease; however, 92.7% are nonvital. Therefore, do not rely on radiographic appearance to determine vitality; all teeth should be definitively treated via root canal therapy or extraction.

Enamel Hypocalcification (Hypoplasia)

Enamel is a very thin (< 1 mm) material on the surface of tooth crowns. It is formed and deposited on the dentin by the enamel-forming organ which consists of cells called ameloblasts. Enamel is only formed prior to tooth eruption and cannot be naturally repaired.

Areas of enamel hypocalcification will generally appear stained a tan to dark brown (rarely black) color, and may appear pitted and rough. The tooth surface is hard, however, as opposed to the soft/sticky surface of a caries lesion.

Dentin exposure will result in significant discomfort for the patient. The roughness of the teeth will also result in increased plaque and calculus retention, which in turn leads to early onset of periodontal disease.

Treatment is aimed at removing sensitivity, avoiding endodontic infection by occluding the dentinal tubules, and smoothing the tooth to decrease plaque accumulation. The most efficient and effective way to accomplish these goals is placement of a bonded composite restoration.

Feline Tooth Resorption

TRs are a very common malady. Reports vary as to their incidence, but approximately 60% of cats over 6 years of age have at least one, and those that have one typically have more. These lesions are caused by odontoclasts which are cells that are responsible for the normal remodelling of tooth structure. There are currently two recognized forms of resorptive lesions, type 1 and type 2. Clinically, they appear very similar, as dental defects that are first noted at the gingival margin. The best diagnostic tool for differentiating between types is dental radiology. With type 1 lesions, there is no replacement of the lost root structure by bone, whereas with type 2 there is generally marked replacement of the lost tooth structure. Extractions can be very difficult in these cases due to tooth weakening and ankylosis. Recently, crown amputation has been suggested as an acceptable treatment option for advanced type 2 lesions, as it results in significantly less trauma and faster healing than complete extraction. Crown amputation should only be performed on teeth with radiographically confirmed advanced type 2 TRs which show no periapical or periodontal bone loss. Crown amputation should not be performed on teeth with: type 1 TRs, radiographic or clinical evidence of endodontic or periodontal pathology, inflammation, or infection; or in patients with L/P stomatitis. Those practitioners without dental radiology capability should not perform crown amputation.

Missing Teeth

There are several reasons that teeth may be missing. These reasons include: congenitally missing, previously extracted, fractured (or extracted) with retained roots, or impacted. If dental radiographs reveal retained roots and evidence of inflammation or infection (clinical or radiographic), the teeth should be surgically extracted. If they are "quiet," the owners should be informed and given the option of having the teeth surgically extracted.

Impacted teeth are defined as any tooth that has not erupted by its normal time. Impactions occur most commonly in the premolar teeth (especially PM1). They also occur most often in toy and small breeds as well as brachycephalic dogs. These patients generally have no overt clinical signs other than a missing tooth in a young animal.

On occasion, an unerupted tooth may lead to the development of a dentigerous cyst. Definitive diagnosis can be achieved with histopathologic analysis of the cystic lining. Surgical removal of the offending tooth and careful debridement of the cystic lining will prove curative. It is important to avoid leaving any of the cystic lining behind.

Oral Neoplasia

The oral cavity is the fourth most common place to encounter neoplastic growths. They range from very benign to quite malignant. The only way to know for sure what type of growth is present is to perform a biopsy.

Caudal Stomatitis

The best description is a severe immune-mediated reaction to dental tissues, but we really don't know. Some feel that this may actually be a group of disease processes that look the same clinically, which is why they can be very frustrating to treat.

Medical Therapy

Most medical therapies will work for a while; however, in general, resistance will start within a year or less. In addition, most therapies have side effects worse than the disease process in and of itself. In general, medical therapy is very frustrating to the practitioner and client.

Surgical Therapy

Extraction is currently the only effective long-term treatment for this disease process in cats. In our experience, the sooner this is done the better; cats do well postoperatively and long term.

For extractions to be successful, the teeth must be completely removed. Therefore, postoperative radiographic confirmation of complete extraction of the tooth roots is recommended.

  

Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker)

Brook A. Niemiec, DVM, DAVDC, FAVD
Southern California Veterinary Dental Specialties
San Diego, CA, USA


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