Branch of dentistry (12)
I believe the answer is:
orthodontics
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">branch of dentistry</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for orthodontics that I've seen before include "Treatment of irregular teeth" , "Correction of dental irregularities" , "Branch of dentistry" .)