Periodontology is a branch of dentistry that studies the tissues of the periodontium (peri = around; odons = tooth) and related pathologies.

The periodontium is constituted

1 gum
2 alveolar bone
3 root cement (tissue covering the root of the tooth)
4 periodontal ligament.

Periodontology therefore deals with the set of soft tissues (the periodontal ligament and the gum) and hard tissues (cement and alveolar bone tissue) that surround the tooth and ensure its stability in the alveolar arch (in healthy conditions).

Periodontology also deals with diseases affecting the periodontium, these are generically called periodontal diseases or periodontal diseases, or pyorrhea (a historical term still used today in the population). They are periodontitis and gingivitis.