Considering that children lose about 20 baby teeth between the ages of 5 and 12, it's hard to remember each one (the tooth fairy is a busy lady, after all). If you do forget, here are strategies that will dry the tears.
Chuck Smith, who created the Web site 123toothfairy.com, suggests enlisting the help of an older sibling who has outgrown the sparkling fairy. Have the older sibling come out of her room with the loot, and say, "Gee, it must have been delivered to the wrong room."
Use the strategically placed crumpled bill routine, advises Dawn Savaria, a dental hygienist in Massachusetts and creator of toothfairyshoppe.com. Tuck a dollar in the palm of your hand and pretend to check around the bed. Surreptitiously drop it on the floor and blame its misplacement on your child's restless sleep. Suggest that the fairly must not have had room in her sack for the tooth.
Say the tooth fairy must have had a "molar emergency" and is sure to return the following night. Then write a note from the tooth fairy explaining what happened (Savaria and Smith offer tardy tooth fairy letters on their Web sites, or you can write your own): "I got stuck in a cobweb and couldn't get out until morning." End the letter by praising your child for taking good care of his teeth, and leave a smattering of glitter on the note.
So that this doesn't happen again, tie a string -- dental floss works nicely -- around your toothbrush as a reminder of the night's delivery.