RCT is not a permanent cure for the tooth ache,It can be repeated after root canal treatment also.I shall advise you to use Homoeopathic medicine PLANTAGO MAJOR----Q to apply over the teeth having tooth ache, By dipping a temporary cotton bud in medicine & put it on the tooth & told your son to hold it for 5 minute between the tooth of lower & upper jaw, tooth ache will be revealed. Also give him the KREOSOTE---30 Homo-eo medicine 1 drop in half cup drinking water thrice a day for 15 days.
Check him enjoying toffees,chewing gum,chocolates in excessive. Advise him to brush his teeth after every meal.
I am pretty sure after 15 days use he will not complain for the same.