The only scary thing about this movie is the thought that whoever made it might make a sequel.
From start to finish "The Tooth Fairy" was just downright terrible. It seemed like a badly-acted children's movie which got confused, with a "Wizard of Oz" witch melting and happy kiddies ending combined with some bad gore effects and swearing.
Half of the cast seem completely unnecessary except for conveniently being there to get murdered in some fashion. The sister of the two brothers, Cherise the aura reader and Mrs. McDonald have entirely no point in the film - they could have included them in the main plot for some interesting side stories but apparently couldn't be bothered. The people watching the film know the characters are there for some bloody death scene but come on, at least TRY and have a slight plot for them. The story in general is weak with erratic behavior from the characters that makes you wish they all get eaten by the witch.
Add the weak plot and the weak acting together (the children are particularly wooden) and the movie ends up a complete failure. If only MST3K could have had a go at this one ...