thanks for posting query.
well as per your past dental history, loosening of seal leads to re - infection of treated root cnals because of saliva penetration. now following points to be considered:
1. if your restoration is lost for more tahn 1 month or so you should opt for re- rct.
2. x- ray can show the status of previously done rct whether it was properly done or not,
3. if seal loosening is less than 2 weeks and x ray
is showing no pathology beneath the antibiotica nad re- filling may also help.
yes x ray can be done without putting paltes inside. you have to go for OPG the; but taht too can only be used for diagnostic purposes only as if re- rct is required the u have to get an iopa ( x ray with film in mouth ) done for the procedure purposes.