A prominent veterinarian says that your cat will be happier and healthier if you take time to brush its teeth regularly. This may fall in the broad category of useful information you wish you'd never received.

It was treated by the media with the jocularity they usually employ in stories about household pets, and it left behind the usual feeling of uneasiness. After the jokes about tabby toothbrushes and so on there remains the nagging thought that you probably should do as the doctor says or you'll add to the world's store of suffering.

The soft-food diet of most house cats does not clean their teeth the way the alley cat's diet of rodents and birds does, says Colin E. Harvey, professor of surgery at the University of Pennsylvania Veterinary School. "The pain that results from erosion of teeth and from spreading soft tissue creates discomfort in eating and drinking. Cats lose . . . weight and refuse to eat and drink." For older cats especially, brushing is a good idea.

The only question is: when? Do you work it in between getting orange juice and corn flakes for the children, or do you forgo your morning jog? You may want to put it off until evening, in which case you wake up at 2 a.m. with the thought: "Uh oh, forgot to brush the cat's teeth." Get out of bed, round up your cat, set him on your lap, force his mouth open, and you'll most likely get a good clawing. Screeches and oaths in the deep of night. This will be the first generation of cats to have its teeth brushed; misunderstandings are inevitable.

You can make things easier by following Dr. Harvey's advice: "Do the front teeth first with the mouth closed, then the outside of the back teeth, again with the mouth closed. The animal is much more comfortable when it is not having its mouth opened." After a while, he says, you can tilt the cat's head back so that the mouth falls open, and then you can do the inside of its teeth. Your cat will thank you, though probably not in this life.