Feline Odontoclastic Resorptive Lesions
World Small Animal Veterinary Association World Congress Proceedings, 2001
Yvan Dumais

Feline odontoclastic resorptive lesions (FORL) are the most frequent dental lesions present in cats. During oral examination, FORL is evident by loss of dental tissue on the crown or at the neck of teeth. The lesions are often covered with gingiva, typically more inflamed locally. The crown may be completely resorbed and the retained root covered by gingiva.

FORL may affect the root first, particularly on canine teeth. When this is the case, an early indicator may be a bulbous periodontium. Such a lesion may grow unnoticed until the crown falls, leaving the gingiva inflamed and the alveolus filled with a partially resorbed root.

Touching a FORL may elicit a pain reaction, even when the patient is under general anesthesia (light plane). If many teeth are affected, the cat may hyper-salivate and rub his lips excessively. The feline’s mood and behavior may also be affected. Appetite may decrease, as well as the level of physical activity. The cat sleeps more and may become irascible. These changes, usually attributed to the animal aging, often disappear after successful treatment of the dental disease.

Resorptive lesions are classified from I to V according to their severity. Beyond this classification, primary root resorption is either internal or external.

 Class I: enamel only.

 Class II: enamel and dentin.

 Class III: pulp exposure.

 Class IV: extensive structural damage.

 Class V: the crown is completely resorbed, roots are retained.

FORL cause pain and loss of tooth function and may have adverse local or systemic effects. Osteomyelitis is a possible local complication encountered after loss of the crown of a canine tooth when the root is left untreated. This author has seen cases of osteomyelitis (that were confirmed by histopathologic examination of periradicular bone) associated with partially resorbed retained root tips from canine teeth.

Dental and periodontal diseases have been linked to systemic diseases. According to current scientific thought, seeding of bacteria and bacterial endotoxins in the blood stream is not the only pathological process involving oral disease in the pathogenesis of systemic diseases. A hypothesis considered very favorably by the medical community is that inflammation mediators released from oral infections may play an even greater role in causing systemic diseases.

In this context, the treatment of oral disease in feline patients with systemic diseases such as diabetes and hyperthyroidism could help us more efficiently control these diseases. These are usually older patients who have poor oral health with many resorptive lesions. It is important to consider treating oral disease in these patients’ global treatment plan.

No one has yet identified the etiology and pathogenesis of FORL. The cause may well be multi-factorial. The incidence of the disease is much higher today than it was in the 1950s. The effect of the advent of commercial diets, change in food texture, nutriments, and diet acidification to control feline urologic syndrome are all factors concerning alimentation that should be studied. Hypervitaminosis A or a diet high in calcium and low in phosphorus has been shown to increase the incidence of FORL. A diet higher in fiber, favoring chewing behavior, has decreased plaque formation and calculus build-up in zoo animals.

Viral infections and vaccination should also be regarded as possible contributing factors. More animals are now vaccinated against more diseases. Presence of viruses has been associated with oral inflammation. The incidence of Calicivirus infection is higher among cats with oral inflammatory disease than in the general feline population. Cats with immune system deficiency caused by infection with FIV or FeLV often have chronic oral inflammation, although most cats with FORL test negative for these two viruses.

Other contributing factors to the development of resorptive lesions in cats are the anatomy of the teeth, frequent vomiting, and forces exerted on the teeth during mastication. The anatomy of feline teeth in itself predisposes them to the development of resorptive lesions. Cats that vomit frequently have higher prevalence of FORL, caused by the effect of gastric acid on dental tissues. Physical forces exerted on the teeth during mastication may lead to abfraction, a flexural stress exerted on the buccal or lingual surface of the tooth associated with the development of resorptive lesion in humans.

Periodontal disease is present in most animals affected with FORL. The presence of bacterial plaque and the response by the host immune system cause the release of inflammatory factors responsible for resorption of bone and teeth. With cats, it would appear that cement and dentin are more readily resorbed than alveolar bone.

Association between FORL and periodontal disease as cause to effect has not been proven. Even if inflammatory cells are present in most FORL, they are not necessarily present at the beginning when the lesion is still covered with healthy gingiva. The inflammatory reaction may be a consequence of the development of the FORL, instead of its cause. The rough surface of the FORL increases attachment of bacterial plaque and calculus, leading to gingival inflammation.

Depending on whether periodontal disease is considered the cause or consequence of resorptive lesions, its control could either prevent its development or slow its progression. The control of the progression of periodontal disease is based on yearly oral examination and teeth cleaning and an oral home care regimen.

The diagnosis of resorptive lesions is based on an examination of the teeth using a dental explorator and oral radiographs. All the teeth should be included in the radiographic survey. There is an average of 3.1 lesions per affected cat. The lesions are drawn on the dental chart and a treatment plan is made.

Most teeth affected with FORL should be extracted. Restoration has little chance of success except on very early lesions (Class I or early class II). Restorative materials used are Glass ionomer (fluoride release) and dental composite. The surgical extraction of affected teeth gives the best prognosis. Dental extraction of feline teeth is not easy because their roots are long, thin and diverging. Teeth affected with resorptive lesions are more fragile and often ankylosed to the alveolar bone.

Prerequisites for a surgical extraction are a preoperative dental radiograph, appropriate dental equipment, and time. Extraction of teeth on cats necessitates dexterity, good technique, and patience. After the condition of the affected tooth is determined on a dental radiograph, the best strategy for its extraction is decided. The important points to evaluate are how much resorption is present and on what part of the tooth, is the root ankylosed or curved, is there a swelling (hypercementosis) at the apex of the root, what is the risk of fracturing the root or the jaw or displacing a root tip in the nasal cavity, sinuses or mandibular canal, etc.

A simple extraction technique is sufficient for incisors and upper molars. All other teeth are usually extracted surgically. With surgical extraction, a surgical blade (No. 15, 11 or 12) is first used to incise the attachment of the gingiva to the tooth. A mucoperiosteal flap is elevated with a periosteal elevator (Molt No. 9, Goldman-Fox No. 14, Cislax EX7 or EX9) to expose the alveolar bone. If the tooth has more than one root, the crown is sectioned with a high-speed hand-piece and a bur (FG No. 1 or No.  699) to create sections of crown each attached to a root.

A part of the alveolar bone on the buccal aspect of the root is removed with a bur. Each root is mobilized by stretching the periodontal ligament with a dental elevator (301S, Cislax EX5, EX15, EX 16, Winged Elevators). The blade is introduced between the root and the alveolus and each movement of rotation is maintained for at least 10 seconds. Only once the root is mobile should the extraction forceps be used to complete the extraction.

A post extraction radiograph is taken to confirm that the extraction of each root is complete. The alveolar bone margin is smoothed, the alveolus curetted and rinsed with sterile saline, the edge of the flap trimmed, and the flap sutured with absorbable material and a simple discontinuous pattern.

When a root fractures, the apical fragment can usually be retrieved after removal of more cortical bone and elevation with small root tip pick elevators. What should be avoided is to displace a root fragment into the mandibular canal, nasal cavity, or maxillary sinus. A bur may be used to pulverize a root fragment under direct vision and radiographic evaluation. If a root fragment is left in place, the owner should be informed and provision made for radiographic follow-up. It is important to mention that in case of a gingivo-stomatitis, it is essential that no root fragment be left at all.

Crown amputation with intentional retention of the roots is a controversial procedure. The only indication where this author thinks crown amputation should be used is for the treatment of ghost roots, where the root shadow is almost indistinguishable from the alveolar bone on the radiographs. Even then, the amputation site should be curetted to remove as much root tissue as possible.

Surgical extraction of many teeth affected with FORL is a lengthy intervention. It might be advantageous to consider a two-step procedure to shorten the length of time a cat is under continuous anesthesia (i.e., two shorter periods instead of a long period) and to allow surgical procedures to be made on healthy gingiva. The lack of time, equipment, or expertise available should never compromise the success of the treatment. It is better to reschedule or refer the case if it is in the best interest of the patient.

During the first step, the scaling, polishing, and examination of the teeth is done (and the intra-oral radiographs taken if the equipment is available). After definitive treatment planning, the second step involves doing the surgical procedures including extractions. The length of time between the two steps is typically two to four weeks. Because the patient is anesthetized for a shorter period each time, the body temperature and the blood pressure stay closer to normal values.

The age of the patient should not be considered an obstacle to proper professional dental care. Many preventive measures help safely anesthetize these patients: preoperative blood work, an anesthetic protocol adapted to the patient’s health status, anesthetic monitoring, intravenous fluid administration, a lower anesthetic plane required when using peri-operative analgesia (opiates, NSAIAs, regional anesthesia), etc. High-risk patients would benefit from having a veterinary anesthetist or internist available on-site.


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Yvan Dumais

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