ilgatto
How inconvenient
OKIt is a bit clunky but I prefer having "trap" in their to make it clear that's what the activated tooth has become.
Er, yes, I liked the difference and the current text is what I was aiming for. Pray forgive the confusion.I thought it made the two forms of trap-setting more distinct if I used "soil" for one and "earth" for the other.
For ploughing, using "soil" is slightly more favored over "earth" (at leas a Bing search got about 71,100 results for "plowed soil" and about 50,700 results for "plowed earth"), while planting favours the other way around (about 6,970,000 results for "plant in earth" and 5,200,000 results for "plant in soil").
So I'm leaving it the way it is, although I'd change "stepping on soil the tooth is buried under" to "stepping on earth or soil the tooth is buried in".
Also planned on adding a size limit to said stepping, so it doesn't attack the first rat or cockroach that walks across it.

OK but note that this excludes sprites and imps (5EMM, p. 6).I'm thinking "is stepped upon by a creature sized Small or bigger."
I suppose specifying size along such lines as "2 1/2 foot or larger" would be undesirable given typical 5E wording?
Maybe "size Tiny or bigger" since 5EMM defines size T as 2.5x2.5 ft?
Hmm..., come to think of it, perhaps it doesn't really matter that DW traps don't activate to attack sprites or imps or similarly small creatures.
Bah! Another one I didn't see earlier, although perhaps it doesn't matter in English.Oh, and I just realized the can/may in the multiple tooth setting actions works better the other way around.
That makes the Dragon Warriors' New Magic Item subsection:
DRAGON TOOTHWondrous item, rarity by dragon: very rare for gold, red and silver; rare for black, blue, brass, bronze, copper, green and white A dragon tooth is a reptilian fang three to six inches long, small enough to fit in a pocket. They are usually found in pairs or sets of four, all canine teeth from a deceased dragon of young age or older,
Starting with "A dragon tooth" singular and then switching to plural in the next sentence is perhaps undesirable?
"A dragon tooth is a reptilian fang three to six inches long, small enough to fit in a pocket. Usually found in pairs or sets of four, dragon teeth are all canine teeth from a deceased dragon of young age or older, (...)"
On the other hand, this doesn't feel as right as I would have thought either.
"dragon warrior"?and their command word is often a nickname of that dragon (e.g. "Emerald Emperor Salvia" for a set of green dragon teeth). Some legendary ancient dragons have had a score or even dozens of dragon teeth harvested from their remains, but the normal limit is four per dragon.When activated by use of its command word, the tooth becomes a living creature, a dragon warrior whose type matches the tooth's dragon (black, blue, brass, bronze, copper, gold, green, red, silver, white). A dragon tooth may be used in one of two ways: it can become a dragon warrior immediately, or it can transform into a trap that becomes a dragon warrior when triggered. See the individual dragon warrior entries for the creature's statistics.The dragon tooth warrior exists for 1 hour.
"warrior"?
"... warrior, and the tooth is wasted"?At the end of this duration, the creature reverts to its tooth form and crumbles to dust, destroying the dragon tooth. It crumbles to dust early if it drops to 0 hit points or if you use an action to speak the command word again while touching it.To use a dragon tooth immediately, you use an action to speak the command word, crush the tooth, and then throw it to a point on the ground within 60 feet of you, where the tooth becomes a dragon warrior. If the space where the warrior would appear is occupied by other creatures or objects, or if there isn't enough space for the creature, the tooth doesn't become a dragon warrior.
Too much?
"dragon warrior"?This dragon warrior is friendly to you and your companions and obeys your spoken commands. It speaks Common and Draconic, but the magic of the tooth allows the dragon tooth warrior
"warrior"?
Pff! Please remind me to never say "good to go" again!

to understand commands given in any of your languages. If you issue no commands, the warrior defends itself but takes no other actions.To use a dragon tooth as a trap, you use an action to speak the command word and then set the trap-activated tooth, either by laying it upon a firm and level surface within 5 feet (floor, table, etc.), planting it into earth within 5 feet, or sowing it onto plowed soil within 60 feet. You can use one action to activate multiple dragon teeth from the same set as traps and lay any number of them upon a surface within an adjacent 5-foot square, but setting them can require additional actions: it takes one action to plant up to four teeth into earth within an adjacent 5-foot square, or one action to sow up to eight teeth onto plowed soil within a 60-foot cone. You may also use an action to move up to your speed and set one tooth, allowing you to set dragon tooth traps from multiple positions. If you are killed or incapacitated, you will drop any trap-activated dragon teeth you have not yet set, laying each upon a random surface within 5 feet.Once planted, a trap-activated dragon tooth will become a dragon warrior if it takes any damage or is stepped upon by a creature sized Small or bigger (including stepping on earth or soil the tooth is buried in, which causes the warrior to sprout from the ground). This dragon warrior ignores you and your orders, and will attack you if its hostility is triggered. The warrior attacks the creature that triggered the trap, fighting to the death. If the triggering creature flees, the warrior pursues it unerringly, sensing its direction as if it was using a locate creature spell. If another creature injures the dragon warrior, the warrior views it as a new triggering creature to fight to the death, although its locate creature ability can only locate the original triggering creature. If no triggering creature is alive, the warrior defends itself but takes no action.