What is the reason behind of greyish teeth?? Any history of trauma or injury of teeth previously in childhood. If yes than, shoot a X-ray and checked for any pathology on root tip. If yes then required a surgery (apicoectomy) with rct.
Next Steps
please consult an oral and maxillofacial surgeon to diagnosed the problem.
Health Tips
if pathology at root then please go with surgery otherwise it will further grow and form a large cystic lesion.