(i) Ivory

(ii) Shen (8127) - from 8150; a tooth (as sharp); specifically (for 8143) ivory; figuratively, a cliff:

Shanan (8150) - a primitive root; to point (transitive or intransitive); intensively, to pierce; figuratively, to inculcate: - also used for 'to teach diligently'!

Pure, sharp (cutting edge)

Same Hebrew used as for Teeth.

(iii) Teaching others with purity and sharpness in the Spirit.

(iv) (a) 5:4; 7:4