Yes you go to fix the crown again , because that tooth is already RCT treated , crown helps it to prevent from further infection , as your son is 4.5 yr old , kids has a diffuculty to keep up the daily oral hygiene .
Next Steps
•visit to your dentist
•Dont wait to teeth to fall , go for a new crown .
Health Tips
•try maintaing oral hygiene of a kid , by cleaning his mouth after every meal .