Possible Clues:

• It's trendy in profession of teeth-care
• Its practitioners typically look down in the mouth
• Study of minor car accidents?
• Field dealing with bridges
• Professional care of teeth
• Work on set is requiring effort after evidence of blow
• Medical work is strain with depression coming early
• Impress with one's effort putting on crown, for example
• Boring, excruciating test in filling?
• Specialist medical subject involving oral examinations