Veterinary dentistry

Dog with periodontal disease

The most common and significant oral disease is the inflammation of the deeper supporting structures of the tooth and surrounding tissues of the periodontium; it is also called periodontal disease or periodontitis.[6] It begins with the formation of plaque, specifically subgingival plaque within the gingival sulcus or periodontal pocket. This allows a proliferation of bacteria; the subsequent inflammation and the animal's own immune response starts the progression of periodontal disease. The hallmark feature of periodontitis is attachment loss of the tooth from the alveolar bone. Periodontitis is an irreversible process unless the animal is treated with advanced periodontal surgery techniques.[7]

Periodontal disease eventually culminates in tooth loss; however, significant health problems can precede this. Local consequences include the development of an oronasal fistula or periodontal-endodontic lesion, infections or abscesses in the eye, a fractured jaw, osteomyelitis, and oral cancer.[7]

Systemic consequences affect multiple organs. For example, bacteremia from periodontal disease can cause inflammation of the hepatic tissue, portal vein fibrosis, and cholestasis. Chronic stimulation of the immune system can lead to immune complexes in the kidney, causing glomerulonephritis, chronic kidney inflammation and secondary scarring, decreased kidney function and ability to filtrate, and chronic kidney disease. Bacteremia also affects the heart, because circulating bacteria attach to the heart valves, putting the heart at increased risk of endocarditis, hypertension, and roughening of the epithelium of the heart tissue. There may be metabolic changes such as insulin resistance due to the increased inflammatory proteins.[7]

A canine with gingivitis

Gingivitis is the earliest stage of periodontal disease. It is the inflammation of the gingiva and is caused by bacterial plaque, but it is reversible and preventable.

Gingivitis appears as a thin red line along the margin of the gums and may be accompanied by swollen gum margins, bad breath, plaque and tartar.[8] The earliest clinical sign of gingivitis is bleeding on probing, chewing, or brushing.

Radiographs (x-rays) may be needed to evaluate the health of the jaw and the tooth roots below the gum line. Most dental disease occurs below the gum line and is not visible.[3] Some of the indications for dental radiography include:

• Assessment of bone levels and type of bone loss caused by periodontal disease.
• Assessment of endodontic disease including apical pathology, pulp exposures, and draining fistulae.
• Pathology of the oral soft and hard tissues, including tumors and fractures.
• Evaluation of temporomandibular joint dysfunction.
• Crown/root pathology including tooth resorptive lesions, crown or root fractures, extra roots, or dilacerated roots.
• Comparison of pre/post tooth extraction sites.
• Root canal therapy.
• Oligodontia (absence of most teeth) or extra teeth.
• Assessment of tooth development and chronological dental age of the animal.[9]

Malocclusion is the imperfect positioning of the teeth when the jaw is closed. In dogs and cats with normal occlusion, the upper incisors rest in front of the lower incisors, the lower canines fit in the diastema between the upper canine and third incisor, the upper first premolars fit behind the lower first premolars, and the upper fourth premolars overlap the lower first molars. Any deviations are known as malocclusions, and they are separated by class.

Also known as neutrocclusion, MAL/1 occurs when the maxilla and mandible are correctly proportioned, but one or more teeth are misaligned. This type of malocclusion is further classified by type:

• Rostral cross bite (RXB) – one or more of the upper incisors are displaced so they rest behind the lower incisors, rather than in front. May be caused by retained deciduous (baby) upper incisors, preventing normal eruption of adult incisors.
• Caudal cross bite (CXB) – the mandible is wider than the maxilla in the area of the premolars. Instead of the upper fourth premolar resting against the inner cheek (buccal occlusion) and the lower first molar resting against the tongue (lingual occlusion), the positional relationship is reversed. This is commonly observed in dolichocephalic head types (having a long skull).
• Linguoversion (LV) – the lower canines are in the correct anatomic position but are angled inward towards the tongue, which can cause trauma to the palatal tissue (the roof of the mouth).
• Mesioversion (MV) – occurs when a tooth is in the correct anatomic position in the dental arch but is angled more forward than normal.
• Labioversion (LABV) – occurs when an incisor or canine tooth is in the correct anatomic position in the dental arch but is angled towards the lips.
• Distoversion (DV) – occurs when a tooth is in the correct anatomic position in the dental arch but is angled more behind than normal.
• Buccoversion (BV) – occurs when a tooth is in the correct anatomic position in the dental arch but is angled outward towards the cheeks.[10]

Also called distoclusion, brachygnathism, overshot jaw, overbite, and parrot mouth, MAL/2 occurs when the upper teeth rest in front of the lower equivalents. The maxilla is forward (maxillary prognathism) and the mandible is behind (mandibular retrognathism). It is more common in animals with dolichocephalic skulls, such as Collies.[11] It is the most common oral birth defect in horses.[12]

English bulldog with underbite

Also called mesioclusion, prognathism, undershot jaw, and underbite, MAL/3 occurs when the upper teeth rest behind the lower equivalents. The maxilla is behind (maxillary retrognathism) and the mandible is forward (mandibular prognathism). It is more common in animals with brachycephalic skulls, such as pugs. This type of malocclusion is also often associated with rostral cross bite.[11]

• Level bite – end-to-end bite of the incisors. Genetically is a degree of prognathism.
• Wry mouth – refers to a variety of unilateral occlusal abnormalities. Genetically only affects one quadrant of the mandible or maxilla, such as one segment of the jaw being disproportionately sized relative to the other half.
• Oligodontia – only a few teeth are present
• Anodontia – congenital absence of teeth
• Hypodontia – one or a few teeth are missing
• Polydontia – presence of more teeth than is normal (supernumerary teeth)
• Retained deciduous (baby) teeth – occurs when erupting permanent teeth do not push deciduous teeth out. This is common in toy breed dogs.[11]

Some animals will develop oral lesions, masses, or growths, which may be benign or malignant. These may be caused by tooth or gum infections, tumors, or genetic predisposition. Most pets do not show signs of oral masses until it has grown large enough to make chewing and swallowing difficult. Bad breath, excessive drooling, or bloody oral discharge may also be signs of an oral lesion or mass.

• Melanoma – cancerous tumor that spreads to regional lymph nodes and lungs. Bone destruction is usually evident around the tumor. Most commonly observed in dogs; it is rare in cats.
• Squamous cell carcinoma – fast-growing tumor that is often ulcerated. It spreads slowly and invades bone tissue. It is the most common oral tumor in cats and second most common tumor in dogs.
• Fibrosarcoma – occurs at a younger age than other oral malignancies. It metastasizes slowly but is aggressively invasive. It is the second most common tumor in cats and third most common in dogs.
• Osteosarcoma – may affect the bones of the maxilla or mandible. Oral osteosarcoma is more responsive to surgical intervention than the appendicular version.[11]

• Epulis – general term for any gingival mass. A biopsy and radiograph is required in order to differentiate the type.
• Peripheral odontogenic fibroma – grows from the periodontal ligament. It contains no invasion of bone tissue and has a firm, smooth surface. It may cause tooth displacement. It is the most common benign tumor in dogs.
• Peripheral acanthomatous ameloblastoma – a slow-growing tumor that has a raised, cauliflower appearance and may transform into a malignant tumor at a later stage. It is usually invaded by surrounding bone tissue and aggressive surgical removal is required.[4]

Also known as feline cervical neck lesions or feline odontoclastic resorptive lesions, resorptive lesions are most commonly observed in the cat but have been identified in other species as well. The lesion usually starts at the cementoenamel junction and furcation area between the roots of a tooth. They appear as an overgrowth of gingival or pulpal tissue. The lesions erode the dentin within a single tooth (or several simultaneously). It spreads rapidly once it reaches the pulp of the tooth. The crown of the tooth may appear normal, but the tooth may have little to no root left. This is a very painful condition.[13]

Teeth with resorptive lesions are incurable and cannot be prevented. There is no concrete evidence for the cause, but some studies have suggested they are caused by an excess of vitamin D.[14] Extraction is the only method of treatment.

• Gemination – two crowns share one single root canal in an attempt to form two separate teeth from one enamel origin.
• Fusion – two tooth buds grow together to form one larger tooth.
• Impaction – the inability of the tooth to erupt through the gum. This can cause the development of a fluid-filled cyst surrounding the tooth and destruction to alveolar bone.
• Misdirected teeth – teeth that erupt in an abnormal direction.
• Enamel dysplasia – insufficient hardness or amount of enamel due to not properly forming. The enamel is soft, flakes off, stains easily, has a rough or pitted surface, and exposes underlying dentin once chipped away.[4]

Dental instruments are tools used to provide dental treatment. They include tools to examine, manipulate, treat, restore, and remove teeth and surrounding oral structures.

• Curette – used for removing calculus above and below the gumline. It is also used for root planing. It has a U-shaped cross-section and the tip is rounded with up to two sharp edges. The two most commonly used types are the Gracey curette and the Universal curette.[11]
• Sickle scaler – used for removing calculus above the gumline, as well as removing calculus from pits, fissures, developmental grooves, and areas between each tooth. The blade can be straight or curved with a sharp tip and two cutting edges on either side.
• Explorer – used to examine the surface of the tooth to detect any abnormalities, such as resorptive lesions, caries, or fractured teeth. It is also used to assess tooth mobility. The most common type is the Shepherd's hook.
• Periodontal probe – used to measure gingival recession, which ascertains the stage of any periodontal disease. It has a blunted tip that is marked in 1 mm increments. The probe is inserted into the gingival sulcus to measure its depth. Normal sulcus depth in the dog is < 3 mm and < 1 mm in cats.[13]
• Elevator – used to stretch, cut, and tear the periodontal ligament in order to displace the tooth root from the socket. The tip has a rounded scoop appearance with a sharp edge, which may or may not be serrated.
• Luxator – used to cut the periodontal ligament around the tooth; it is not used for leverage. It is similar to a dental elevator in design but has a thinner tip to allow easier access to the periodontal ligament.
• Extraction forceps – used for gripping and removing the tooth after it has been loosened. It can also be used for cracking and dislodging heavy dental calculus.[20]

• Ultrasonic scaler – used for removing calculus above the gumline. It utilizes a removable tip that vibrates at high frequencies by converting sound waves into mechanical vibrations, allowing for more rapid removal of calculus. It generates a substantial amount of heat and may cause thermal damage to the pulp if left on the surface of the tooth for too long.
• Sonic scaler – used for removing calculus above the gumline. It utilizes compressed air and operates at lower frequencies than an ultrasonic scaler. It is also less likely to cause thermal damage.
• Low-speed handpiece – utilizes a rubber tip called a prophy angle that polishes microabrasions and small grooves on the surface of the tooth.
• High-speed handpiece – utilizes a variety of removable dental burs to section teeth and remove alveolar bone during extractions.[20]