Heh! Gotta be careful FW, talking about teeth and stones at the same time. Beware! Lest the mad Dentist of Stonehenge picks it up on his strange Denkeian Weirdness Radar ;)
You'd need a hell of a toothbrush for that warrior stone though, it took 'camera-onna-stick' to see the top of it.

Mind, you display a fine bit of synchronicity in the choice of the word extraction, especially coupled with the post of Robin Hoods stride
http://www.themodernantiquarian.com/post/29853

'cos I've been wondering whether stones like the Warrior and Matfen stones, and the one at the Poind and his Man, may have already been quite weathered when they were earthfast, (or even bedrock) quarried for use as orthostats. Even Duddo circle, right at the top of the county, has the toothy silhouette thing going on.

Quite a few bits of Bedrock on the sandstone scraps of Northumerland have bedrock with similar grooves. A good example of this is on the wondrous Simonside near Rothbury, at Dove Crags:
http://www.themodernantiquarian.com/post/29873