also: うすば
Refers to the back teeth used for grinding food. In everyday conversation, 奥歯 (おくば) is more common; 臼歯 is a technical or anatomical term.
The molars play the role of grinding food.
The dentist treated a cavity in a molar.
Standard kanji spelling for molar teeth, using the reading きゅうし.
Alternate reading うすば is less common and may be encountered in older or specialized contexts.
Compound of 臼 (usu, 'mortar') and 歯 (ha, 'tooth'), referring to the grinding function of these teeth. The reading きゅうし is the on'yomi, while うすば is a kun'yomi-based reading.