With gingivitis, gingiva refers to the gums, and -itis refers to inflammation, so gingivitis is inflammation of the gums.
With periodontitis, peri- means around, and odon-, refers to the tooth, so it’s inflammation and destruction of the supporting structures around the teeth.
Broadly speaking, the two are on a spectrum starting with simple gingivitis on one end, and if the process doesn’t get treated, it can develop into more severe disease - periodontitis, which is on the other end of the spectrum.
Let's start by building a model of a tooth and its surrounding structures.
In the mouth, the bone beneath the bottom row of teeth is the mandible, and the bone above the top row of teeth is the maxilla.
Both bones have an alveolus, or socket, for each tooth.
The socket is lined on the inside by a periodontal ligament.
Protecting the alveolus on the outside, is a layer of soft, supportive tissue called the gingiva, or gums, that sits on top of the bone.
The tooth itself can be roughly divided into two parts.
The first part is the root, and it sits within the alveolus.
The root is covered by a bonelike substance called cementum, and that’s what the periodontal ligament’s fibers attach to.
Next, there’s a short zone called the neck, which is the transition between the root and the crown.
The crown is the visible part of the tooth that protrudes from the gingiva, and it’s covered in enamel.
Enamel has such a high mineral content that it’s the hardest substance in the human body.