Why is my tooth still pulsating/throbbing after the root canal retreat that I had done about 3 wks ago? (photos)

My biggest concerns with this tooth is that it was retreated about 3 wks ago to the top molar shown in the picture. The endodontist that retreated it found a missing canal, and also told me (after I asked her ) that there was leakage from my old crown as well. I am going back to her tomorrow to ask her why I am feeling the pulsating.. I know it takes a while to heal, but why didn't she put a temp crown since this one is still leaking? I did get the permanent filling put in like she said..