Do animals suffer from tooth decay, such as cavities? Is it to the same extent as in humans, or do animal teeth decay more or less? If teeth decay in animals as well, are there natural strategies animals use to heal it? And, lastly, how do animals take care of their teeth?
If this is in comparison to humans, the animals are more or less free from the two common dental diseases by which teeth are lost in humans. These are dental caries (dental decay) and periodontal disease (gum disease).
Common to both the diseases is the biofilm which forms on the teeth known as dental plaque.
If the plaque is colonised by acidogenic (acid producing) micro organisms cavities are produced in the presence of refined carbohydrates.
The gum disease is produced by bacterial toxins from the plaque causing inflammation of the surrounding gum resulting in loss of supporting structures of the tooth including bone resulting in loosening and loss of teeth.
In animals in the wild, plaque accumulation is effectively controlled by the coarse unprocessed diet which has a very good scrubbing effect. Besides wild animals are not exposed to refined carbohydrates like sugars.
Hence wild animals do not have these two diseases. However domesticated animals on human diet are prone to similar diseases.
In wild animals severe attrition (wear) and fracture of teeth are more common.
Wild animals will not survive long without adequate number of functional teeth.
Human tooth decay is mostly from eating foods high in sugar. So animals don't generally get cavities. (Except for humans' pets.) But animals can have other tooth problems. For example, elephants grind down their molars from eating so much plant material. Fortunately for them, they have a supply of new molars that come in regularly. Unfortunately for them, that supply is limited. When an elephant runs out of molars, it dies of starvation. Another example is plaque on dogs' teeth, which can lead to gum disease just like in humans.
Outside mammals animals just let bad teeth fall out and replace them as part of a continuous cycle of losing and replacing teeth, they don't keep teeth long enough for it to be an issue. Mammals are... weird, they only get the two sets. I would go further but Ram's answer covers how this question applies to mammals quite well. Although I should mention humans have relatively thin enamel out diets are rather low demanding in no small part due to the invention of fire.