In dentistry charts, the letter "M" symbolizes this major tooth type
T. S. R. Q. P. K. L. M. O
. N. [DOC] [TLE] The Dental Chart - DentalVet.com [PAR] When choosing one to be used in your dental practice, look for ease of ... 
Charting shorthand-letters are placed over a tooth to indicate type of pathology 
noted.