Tooth enamel, the outer layer of teeth, is the hardest substance in the human body, even tougher than bones, protecting teeth from damage and decay, according to a nutritionist.

Q: Penny, my middle-aged indoor cat, chews her dental treats only on the left side of her mouth. Is this normal? A: I confess ...

The Mosura fentoni, or "sea moth," is a newly discovered type of arthropod that would have lived in the deep sea more than 500 million years ago.