Review article
Feline odontoclastic resorptive lesions: An unsolved enigma in veterinary dentistry

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Extension of periodontal disease

Chronic inflammation of the periodontium was suggested to be a cause of FORLs [11], [12], [13], [14], [15], [16], [17]. Plaque accumulation can cause inflammation of periodontal tissues, leading to local immune responses and release of inflammatory elements (eg, cytokines) and bacterial products (eg, lipopolysaccharides) that stimulate differentiation and migration of clastic cells [18], [19], [20]. Cytokines, such as interleukin (IL)-1 and IL-6, are secreted locally by epithelial and

Prevalence and predisposition

A significant increase of FORLs has been recognized since the 1960s, with the frequency varying from 2% to 75% depending on the population of cats studied and the investigative methods applied (Table 3). The populations are described as “random,” meaning there was no specific reason for the veterinary examination; “mixed,” meaning that cats were presented to a veterinarian for treatment; and “dental,” meaning that cats were examined during a procedure scheduled for examination or treatment of

Classification

FORLs are clinically and radiographically classified into five stages [52], although earlier reports combined stages 4 and 5 for therapeutic reasons [144]. Stage 1 lesions extend into the cementum only (Fig. 4). They do not enter the dentin and are not sensitive. They may be difficult to detect because of their microscopic size. The authors of the present article think that most lesions diagnosed as stage 1 lesions may already be stage 2. Stage 2 lesions progress through cementum into crown or

Histopathologic appearance

FORLs were first recognized and histologically differentiated from caries in the 1920s [57], [148], but they were not reported again in the veterinary literature until after the mid-1950s, when they were thought to be carious lesions [149], [150], [151], [152], [153], [154], [155]. Two histopathologic studies in the 1970s again revealed that “neck lesions,” now referred to as FORLs, were not caries but a type of tooth resorption [25], [156]. Subsequent studies in the 1980s [10], [80], [157],

Clinical signs

Although cats with FORLs can present with halitosis, dysphagia, ptyalism, anorexia, dehydration, weight loss, lethargy, and discomfort [5], [144], [175], most affected cats do not show distinct clinical signs. Head shaking, sneezing, and excessive tongue movements have also been observed [46]. Cats may sometimes show spontaneous repetitive jaw motions while eating, drinking, or grooming. Signs related to oral pain may include dropping food while eating, refusing to eat hard food, “hissing” and

Comparison with other defects of the dental hard substances

FORLs are often confused with hard tissue defects that are not resorptive in nature [44]. “Attrition” is defined as normal or excessive loss of tooth substance caused by tooth-by-tooth frictional contact, usually as a result of mastication or malocclusion [185]. “Abrasion” is defined as tooth wear caused by frictional contact of a tooth with a nondental material [185], such as that found in teeth in carnivores (common in dogs with untreated pruritic dermatoses; excessive chewing on hard toys,

Tooth resorptions in nonfelidae

There are several reports describing canine odontoclastic resorptive lesions in domestic dogs [1], [189], [190], [191], [192], [193], [194], [195], [196], [197], [198], [199], [200], [201], [202]. In one study, root resorption was reported in 17.9% of randomly selected dogs [203]. In the authors' own experience, the prevalence of canine odontoclastic resorptive lesions is low. Resorptions of permanent teeth have been reported in the dolphin, Montana black bear, and Rocky Mountain elk. Most of

Treatment

The ultimate goal of any treatment option is to provide the cat with a healthy pain-free mouth [177]. Determining the underlying etiology and predisposing factors for FORLs is essential for making future recommendations on preventative measures and successful treatment options. Historically, a common approach for the treatment of FORLs included fluoride treatment of stage 1 lesions, restoration of stage 2 lesions, and extraction of teeth graded stage 3 or higher [15]. Fluoride treatment remains

Conclusion

Approximately one third of all domestic cats may develop FORLs during their life span, and the risk of developing FORLs increases with age. Extraction is the current treatment of choice. The etiology of FORLs remains unknown. Finding the causative factors that alter the resorption-inhibiting characteristics of the outer tooth surface may be the clue to the enigma of FORLs.

Acknowledgements

The authors thank Colin E. Harvey, BVSc, FRCVS, and Sandra Manfra Marretta, DVM, for their time, effort, and contribution in proofreading this article.

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