Medical term for inflammation of the tissues surrounding the teeth, including the gums and bone.
If periodontitis progresses, teeth may fall out.
歯槽膿漏 is an older, more colloquial term for advanced periodontitis with pus discharge; 歯周炎 is the modern medical term.
Compound of 歯周 (shishū, 'periodontal') + 炎 (en, 'inflammation'). The term is a modern medical coinage.