I had a bump on my gum about a year after a root canal. A dentist checked it out by inserting a probe between the tooth and the gum area an found there as a pocket therethat was about 6 or 8 mm deep and caused by an abcess.The tooth had a crack in it and I just had it remove about 30 minutes ago. Better have the boy\'s dentist check it out again or check with another dentist.