14th President: Franklin Pierce, 1853
Tar = 14 (Pierce was the 14th president)
Pierce with a drill = Pierce
Film = 853 = 1853 became president
Frankenstein = Franklin
The tar(tar) (14) on the patient's teeth was so thick the dentist couldn't pierce (Pierce) it with his drill; it was a solid film (853).
Connect Pierce to Franklin
The patient whose tartar the dentist couldn't pierce (Pierce) was actually Frankenstein. Frankenstein has a scar, like a line, on his forehead (Frank + line = Franklin).
NOTE: The way Mammoth Memory remembers Frank is to think of Frankenstein.