歯齦 is read as しぎん (shigin) and means gums.
しぎん
shigin
しぎんえん
gingivitis
はどめ
brake
はむかう
to strike back at
しか
dentistry
は
support (of a geta)
はぐるま
cog (in an organization, company, etc.)
はぶらし
toothbrush
はみがき
dental brushing
はいしゃ
dentist
はがゆい
(feeling) impatient
はごたえ
challenge (e.g. work, book)
しつう
toothache