entry 4: not interested in a tooth being in the logo... I don't think it is needed because I will be talking only to dentists.
Entry 3: I kind of like the duel colors. I think I like the check mark over the i. I mentioned in another comment that I thought the tagline was not important because it may change... but I kind of like the way it looks here. The colors... not too sure about them. I had mentioned some colors that I was looking at... maybe if they were in those colors? Green is a color that more dental companies try to stay way from... not sure why.
I think I like the two level setup, and I think I like the thickness of the font. It seems stable and strong and trustworthy.