Teeth of a dragon

Solution 1:

Indeed, as you so reference, the OED provides 5 sample sentences with various iterations of (D)dragon('s)(s) teeth:

• 1644 J. Milton Areopagitica 4 They are as lively, and as vigorously productive, as those fabulous Dragons teeth.

• 1853 J. B. Marsden Hist. Early Puritans (ed. 2) 290 Jesuits..sowed the dragon's teeth which sprung up into the hydras of
  rebellion and apostasy.

• 1943 J. L. Hunt & A. G. Pringle Service Slang 28 Dragon's teeth, a form of anti-tank obstacle.

• 1944 Times 28 Nov. 4/2 Extensive minefields, road blocks, dragons' teeth, tank ditches, [etc.].

• 1971 Oxf. Univ. Gaz. 18 Feb. 671/1 ‘Dragon's teeth’, that is to say, sharp hinged teeth which..protrude from the ground but can be
  made to sink into it for a car to pass.

I agree 1644's punctuation may not be an example of modernity. As for the mid sentence 'D', my sense is that is is un-necessary. As Wikipedia uses primarily 'dragon's teeth', as do both the 1944 and 1971 citations, that would be my vote too. (ecp: capital D at beginning of sentence)