Can a root canalled tooth with a crown get decayed?

Recurrent Caries: RCT on a tooth removes the tissues inside the canal(s) of the tooth, which is then filled with a thermoplastic material. It has no effect on whether a tooth can or will develop caries. A crown protects most of the tooth, generally above the gum line. However, decay can still develop past the crown margin on the tooth structure itself. Therefore, still need exams, x-rays & proper tooth brush\floss!

It can...: Dental restorations, whether it be fillings, crowns, inlays, or dentures, should not be expected to last forever. Many factors go into the longevity of your dental restorations, including your diet and proper home care, as well as regular dental cleanings. A crown with recurrent decay is usually replaced.

Yes: You can get decay under your crown and the crown may need to be replaced. Because you have had a root canal you would not have pain or sensitivity if there is decay in the crowned tooth so make sure you have regular dental care so any problem can be detected early and be fixable so you do not loose your tooth.