It is important to differentiate between dental caries and resorption cavities:
Caries is demineralization of calcified dental tissues by acid that is created through the bacterial breakdown of refined dietary carbohydrates. Caries in zoo carnivores is virtually unknown.
Resorption is the pathological destruction of mineralised dental tissues through the action of odontoclasts that does not involve demineralization.
External resorption lesions exhibit pain even when probed under a moderate depth of general anaesthetic. According to histopathologists, external resorption is usually related to areas of gingival inflammation. This is often seen in domestic cats, but is relatively rare in large felines outside North America. The reason is almost certainly the soft processed food they are fed on. Resorption cavities cannot be restored predictably and will continue to destroy the teeth. The treatment of choice is extraction of the teeth in question.
Internal resorption is relatively rare. It occurs inside root canals or pulp chambers and is usually a result of blunt trauma to the tooth where the pulp remains alive, but the resultant chronic inflammation initiates an odontoclastic response from the pulp tissues that destroys the dentine from an internal direction.
Cervical resorption cavity. Note the deposit of bacterial plaque on the buccal surfaces. (Amur Leopard)
Cervical resorption cavity clearly visible once the mucogingival flap has been reflected. (Leopard)
Internal resorption cavities perforating the occlusal surface from the pulp chamber. The aetiology was almost certainly excessive occlusal loading initiating a chronic pulpitis. (Sumatran Tiger)