Medical/dental term for the third molar. In everyday conversation, 親知らず (oyashirazu) is much more common.
See also: 親知らず
知歯が生えてきて痛みがある。
My wisdom tooth is coming in and it hurts.
歯科医に知歯の抜歯を勧められた。
The dentist recommended extracting my wisdom tooth.
Standard kanji spelling for 'wisdom tooth'.
Variant kanji spelling; 智 is an older form of 知.
From 知 (chi, 'wisdom') + 歯 (shi, 'tooth'), a calque of the English 'wisdom tooth' or similar Western term.