I did a GOOGLE search for "dental school letter of recommendation" and here are a few ideas.
-A letter of recommendation is a detailed discussion, from a faculty member, of the personal qualities, accomplishments, and experiences that make you unique and perfect for the programs to which you've applied.
-Aim for a set of letters that cover the range of your skills. Ideally, letters should cover your academic and scholastic skills, research abilities and experiences, and applied experiences (e.g., co-operative education, internships, related work experience).
If you do a google search, then I'm sure you'll get much more info than that
okay .. good luck!