A horse's teeth should be checked yearly. As a horse chews, he grinds his teeth, creating sharp edges on the outside of his upper teeth and the inside of his lower teeth. Normally, teeth will need to be floated (grinding the sharp edges off) about once a year. However, some horses need attention more often. If you see a horse dropping feed from his mouth, holding his head sideways when he eats, or slobbering a lot, have his teeth checked. Young horses lose teeth in their first three years, and they can experience problems with teeth erupting or retaining caps. Check young horses every 6 months.