Thanks for posting your query.
Since the tooth which is mobile is root canal
treated,its non vital in nature.
A thorough clinical and radiological evaluation is required for retaining the tooth.
splinting can be done to make the tooth firm again.
If too shaking,it has to be extracted.
Maintain good oral hygiene
Brush your teeth twice daily using soft-bristled toothbrush and dental floss.
Please avoid hot,spicy foods.
Biting on hard objects has to be avoided.
Use chorhexidine mouthrinses to gargle.