Disease of the oral cavity may be divided up into conditions of the puppy or kitten (Pedodontics), occlusion (Orthodontics), tooth supporting structures (Periodontics), tooth surface (Restorative Dentistry), inside the tooth’s pulp canal (Endodontics), and diseases associated with cancer and medical conditions.
PEDODONTIC DISEASE
The veterinarian may be called upon to examine a young patient for missing teeth, or teeth that are slow to erupt. A radiograph should be taken to identify whether the tooth is missing (missing tooth radiograph) or retained (retained root radiograph). Premolars and incisors are the teeth most commonly found to be missing. This most commonly has an inherited basis.
An additional cause for missing teeth is trauma at a very young age. Retained primary teeth may cause orthodontic or periodontic abnormalities. Extraction of these teeth may help to alleviate orthodontic complications at a later date. Primary teeth may be selectively extracted to remove interlocks (interlocked tooth) to allow the “full genetic potential” of the jaw to develop. This procedure may be useful in cases where there is a minor difference between a correct and incorrect occlusion. It will not work if there is moderate or severe brachygnathic or prognathic occlusion. Genetic counseling and signed, informed consent forms are important prior to proceeding.
Cranial mandibular osteodystrophy is an inherited condition of West Highland White Terriers and other breeds. It is a non-neoplastic exostosis of the caudal mandible and tympanic bulla. Patients with this condition are presented with pain, mild fever, depression, and reluctance to eat. On examination, there is a decreased range of motion in opening the mouth. Often times the exostosis is palpable.
Fractured canine teeth occur fairly frequently. The fracture can result in abscessation and stoma formation. Rather than risk the development of enamel hypoplasia of the adult tooth, extraction of the primary tooth is recommended. Supernumerary teeth occur mainly in the incisors, however they can occur in any of the teeth.
ORTHODONTIC DISEASE
In the normal occlusion, the maxillary and mandibular incisors overlap slightly so that the occlusal edge of the mandibular incisors rests on the cingulum of the maxillary incisors. The mandibular canine interdigitates evenly between the maxillary corner (third) incisor and canine tooth. In evaluating the premolars, the mandibular premolars occlude mesial (rostral) to their maxillary counterparts. The premolars interdigitate with each other in the center of the interproximal area. The molars occlude with each other on the grinding surface.;
In Class 1 Malocclusion there is an overall normal occlusion, however one or more teeth are out of occlusion. One or more of the maxillary incisors are displaced palatally or one or more of the mandibular incisors are displaced labially. Otherwise, there is a normal occlusion. Base narrowed canines may be due to a structural narrowing of the mandible, or failure of the primary teeth to exfoliate prior to the eruption of the adult canine teeth. Spearing or lancing canines are maxillary canine teeth that are tipped in a rostral position by the mandibular canines. They occur most often in Shelties and Persian cats. Often times the problem starts out with spearing primary canine teeth which direct the adult teeth into mal-occlusion. Extraction of the primary teeth may prevent the problem in the adult teeth. Extraction or orthodontic correction is the treatment options. The lateral incisors may erupt in a buccal direction. Most of the time, the incisors will re-direct downward.
CLASS II OCCLUSION
In mandibular brachygnathism (Class II Occlusion), the mandible is shorter than the maxilla. The mandibular incisor teeth occlude palatal or caudal to their normal position on the cingulum of the maxillary incisor teeth. Often times these incisors may occlude against and irritate the hard palate or nasal bulbar gland. The canine teeth may indent or perforate the hard palate. The occluding mandibular teeth may cause wear of the palatal surface of the maxillary canine teeth at a later age. The premolar teeth may occlude caudal to their normal position.
The patient with mandibular prognathism (Class III) has maxillary incisors occluding lingual or caudal to the mandibular incisors. The mandibular canine may occlude anterior to the maxillary incisors.
In maxillary brachygnathism, the jaw is normal length and without crowding. The maxilla is shorter than normal and the teeth are rotated. Excess “freeway space” may be noted caused by bowing of the mandible. A wry bite is noted when the centerline between the central incisors of the mandible and maxilla do not match. It may be caused by mandibular or maxillary asymmetry.
PERIODONTAL DISEASE
Periodontal disease is described as Healthy, and Stages 1 through 4. The stage of periodontal disease qualifies the degree of disease and the type of treatment. Healthy gingiva has a knife-like margin and is coral pink or a pigmented color. It is important to note the smooth gingival topography (surface features of the gingiva as it flows from tooth to tooth). Generally, as periodontal disease progresses the surface features become irregular and the even flow from tooth to tooth is lost. Healthy gingival tissue is firm. Close observation will reveal that blood vessels can be seen out to the margins. When probing with a periodontal probe there is a normal minimal sulcular depth of 2–3 mm in dogs and 0.5–1mm in cats. There may or may not be evidence of previous disease.
In Stage 1, a redness of the gingiva at the crest of the gingiva and a mild amount of plaque are noted. There is loss of visualization of the fine blood vessels at the gingival margins. Radiographically, there is no change from
healthy periodontium. The condition is reversible with treatment. Stage 1 can appears two to four days after plaque accumulation in previously healthy gingiva and is localized to the gingival sulcus, including the junctional
epithelium and the most coronal part of the connective tissue.
Stage 2 is similar to the early stage in that it is still reversible; there is an increase in inflammation including edema and subgingival plaque development. Amounts of supragingival plaque and calculus are increased. The
gingival topography has started to become irregular, but is still good. Root exposure has not yet occurred. Radiographically, there is little noticeable change. Plaque induced gingivitis can be reversed with the initiation of
plaque control measures (dental scaling and prophy, home care, etc.).
In Stage 3, there is a moderate loss of attachment or moderate pocket formation with 10–30% loss of bone support. Furcation exposure may be present as well as inadequate gingival topography, recession and or hypertrophy and there may or may not be mobility. The gingiva will bleed upon gentle probing at this stage. Radiographically, subgingival calculus may be visualized and a rounding of the alveolar crestal bone at the cervical
portion of the tooth can be seen upon careful examination.
In Stage 4, established periodontitis there is advanced breakdown of the support tissues with severe pocket depth or severe recession of the gingiva. Some of the signs that may be associated with Stage 4, or advanced
periodontal disease, are the presence of severe inflammation, deep pocket formation, gingival recession, bone loss, pus, and mobility. The gingiva usually bleeds easily upon probing. There is loss of gingival topography.
Radiographically, subgingival calculus and bone loss are noted.
DISEASE OF THE TOOTH SURFACE
Stains can occur as the result of occlusal wear and exposure of dentin. They are not necessarily pathological, although many clients will ask for a consultation when they think caries are present. Abrasions occur as the result of abnormal wear of the tooth against an external source, such as chewing hair, due to pruritis from allergies, or from chronically chewing foreign objects. Table wear may occur from chewing tennis balls. This may be due to dirt being trapped in the cloth adding to the abrasiveness of the ball. Attrition occurs as the result of teeth wearing against other teeth. This is of great concern in the incisor region and when a canine is involved.
Enamel hypoplasia can result from infectious diseases that cause high fever. It can also result from the extraction of primary teeth or other traumatic events. The two most common types of caries in the dog are Class I and Class V. Class I caries occur on the pits and fissures of teeth on the occlusal surfaces. Class V caries occur on the gingival third of the tooth on the buccal or labial surface.
ENDODONTIC DISEASE
The incisors commonly fracture. A Class A1 fracture involves only a chip of the enamel. A Class A2a fracture involves a chip of enamel and includes dentin but has not exposed the pulp chamber. Class A2b fractures involve the enamel and dentin and have involved the pulp as well. Special attention should be paid to the mandibular incisors on physical exam as fractures of these teeth can be overlooked due to being covered by the maxillary teeth when the mouth is closed and by the tongue then the mouth is open. Many types of trauma can damage the canine teeth. The trauma can cause a small chip or may cause a more severe fracture below the gumline. The same classification system applies to the canine teeth. Slab fractures of the fourth premolar often result from chewing hard objects such as bones, rocks, and hooves. Often, the slab remains attached for months until when detached, hemorrhage may occur alerting the client to the problem. Fractures can occur on the molar teeth. The occlusal partner of the maxillary fourth premolar tooth, the mandibular first molar, may fracture. Similar to the mandibular incisor teeth, fractures of the mandibular molars and premolars may be difficult to detect because of the overlap of the tongue and because they frequently occur on the lingual side of the tooth.
A tooth that is discolored with a purple discoloration and later becomes tan colored has had pulpal hemorrhage. This hemorrhage is usually caused by trauma to the tooth. As a result of this hemorrhage, the intrapulpal pressure has increased, resulting in death of the odontoblasts that line the pulp chamber and root canal. Red blood cells leak into the dentinal tubules and cause the discolored tooth. As oxygen is released from the hemoglobin, the tooth changes from purple to a tan color. A tooth may become pink secondary to internal inflammatory resorption. This usually occurs in older patients. If bacteria have successfully invaded the pulp chamber, the exposed tip (which was the former pulp chamber) may become black and endodontic therapy is indicated. If tooth wear/pulpal exposure occurs slowly enough, the odontoblasts inside the tooth have a chance to produce secondary dentin. In this case, the tip of the tooth appears brown.
ORONASAL FISTULAS
Oronasal fistulas result most commonly from advanced periodontal disease on the palatal side of the canine teeth. As the plate of bone between the canine tooth and nasal cavity breaks down the fistula develops. It is often present, but not diagnosed prior to the extraction of the canine tooth.
UREMIC ULCERATION
Patients with advanced renal disease may develop ulcerations on the tip of the tongue. Increased calculus formation and periodontal disease may also be associated with uremia.
ORAL NEOPLASIA
Benign
Benign granulomas are common and are usually the result of periodontal disease or other irritation. They are responsive to local excision and removal of the originating cause. The formation of hyperplastic gingiva is common among some breed lines. Pocket formation and periodontal disease may be the result of this hyperplastic tissue. Epulides are characterized by the presence of tumor arising from the periodontal ligament. The fibromatous epulis contains periodontal ligament stroma as the primary cell type. They are responsive to excision. An ossifying epulis contains large amounts of osteoid matrix. This gives it a bony feel while excising.
Malignant Neoplasms
The acanthomatous epulis is composed primarily of epithelial cells associated with the stroma. Tendency of the acanthomatous epulis is to invade bone, which makes dental radiographic evaluation mandatory for complete evaluation.
Malignant melanomas can form in many sites in the oral cavity (gingiva, buccal mucosa, hard and soft palate, and tongue) and are locally invasive and highly metastatic to the lungs and regional lymph nodes as well as bone. They may appear either darkly pigmented or nonpigmented. Clients may complain about halitosis or oral bleeding. Loose teeth may result from bone involvement. Surgical excision, electrocautery, cryotherapy, radiation, chemotherapy and immunotherapy have been used in treatment. Malignant melanomas carry a poor prognosis, as reoccurrence is common.
A frequent site for fibrosarcoma is the maxillary gingiva or hard palate. They appear as a fleshy, protruding, firm mass which may be friable. They may be ulcerated and infected.
The most common site of squamous cell carcinoma is the tonsillar crypt and the gingiva. They are usually a nodular, grey to pink irregular mass. They may invade bone and cause tooth mobility. Generally, the farther away from the tonsils or floor of the mouth, the better the prognosis.