Hey doctors please my professor ask me to told him what is the shamrouk modification in endodontics, any help please!

Research. Your professor expects you to do your own research, not have someone do it for you. I would suggest you look in Endodontic text books or search Pub Med on your school's library.
Shamrock preparation. In Endodontics it is most important that as much natural crown structure be maintained as possible. Shamrock preparation is modified outline form to accommodate the instrument (e.g. pro-taper file) unrestrained in the severely curved mesial canal to preserve instrument separation. Take care and good luck.