Khí-iū-chit (齒釉質;dental enamel) koh kiò-chò hoat-lông-chit (琺瑯質), sī chhùi-khí khí-koan siāng-gōa-têng ê cho·-chit, i-ê ē-kha sī khí-pún-chit. Khí-iū-chit sī iû e̍h-e̍h-kheh-kheh ê hydroxyapatite chiⁿ-thé, enamel prism, kap chiok chió-liōng ê interprismatic substance lâi cho·-sêng, sī lán sin-khu siāng tēng-ngē ê cho·-chit, pí kut-thâu koh-khah tēng-ngē. I-ê inorganic salt sêng-hun chiàm 96%, chú-iàu sī calcium phosphate kap calcium carbonate téng-téng. Khí-iū-chit ê sek-tī pe̍h-bū-pe̍h-bū, sió-kóa thàu-bêng, i-ê piáu-bīn kim-kim-ku̍t-ku̍t, mô·-kńg-khang chiâⁿ-chió.