periodontitis
noun [ U ] medical specialized uk/ˌper.i.əʊ.dɒnˈtaɪ.tɪs/ us/ˌper.i.oʊ.dɑːn.ˈtaɪ.t̬ɪs/
牙周炎
a condition in which the tissue around the teeth becomes swollen and the gums (= the pink flesh in the mouth into which the teeth are fixed) move away from the teeth