The failure of endodontic treatment is commonly caused by errors in preoperative, operative, and postoperative endodontic treatment. Inadequate final restoration of post-endodontic treatment would impact the success of the treatment. Loose restoration is an example of restoration failure caused by inadequate retention, which leads to penetration of saliva along the root canal. This could dissolve the luting cement and cause microleakage to constantly reach the periradicular areas. If neglected, this situation will result in a periradicular lesion. Endodontic treatment was performed to resolve the failing restorarion. The restoration failed due to inadequate retention. The treatment was needed to prevent more problems to occur sometime in the future.