Not sure what a dental gap is, but I've had two "closing" experiences...
My son had a split between his two front baby teeth. I was told that's a good sign the adult teeth will fit, but if it's there at age 7 or so, they'd clip the attachment from gum to lip. He ripped it in a minor incident at age 4. No issues.
My daughter had a space between her upper and lower teeth on one side. The dentist wanted her in braces. ($5K) we went to a tongue therapist for a year ($1500) and the teeth grew in fine once the tongue stayed out of there.
at 11:00 AM on Feb. 3, 2010