My gap was HUGE like you could fit an extra teeth in it HUGE. It filled in alot I still have a small gap but its not that bad. He's only 4 so his gap should fill in. You would really be able to tell when his adult teeth start growing in. my dentist has been trying to get me to try the invisiline thing to correct my gap...but I like my teeth...they're straight except for that and I'm content with it and its apart of me. He thinks I'm crazy but I dont care.