periodontics
noun [ U ] medical specialized uk/ˌper.i.əʊˈdɒn.tɪks/ us/ˌper.i.oʊˈdɑːn.t̬ɪks/
牙周病学
the area of dentistry (= the work of a dentist) concerned with the gums (= the pink flesh in the mouth into which the teeth are fixed) and other tissues around the teeth