Periodontitis is a set of diseases which usually attacks the tissues surrounding the teeth. Periodontitis in comparison with Gingivitis is a more severe inflammation, because not only it affects the tissues, but also, it affects the bottom of the teeth. If it is not treated at all, it may lead to a loss of teeth.
The word "periodontitis" comes from peri ("around"), odont ("tooth") and -itis ("redness").