Well now lets focus on what he called "retarded". It was your braces not you so that's good.  
As a parent we try to shelter our children from the cruel comments other children make but in truth even as adults we meet up with cruel people who make cruel comments about us. 
Please remember that not everyone we meet will like us nor we them. Isn't that true OP?  While you may not respond  to everyone you don't care for with cruel comments others are not so strong nor classy. 
It's been said that "the person in the room with the most class, is the one who makes the least number of people in the room uncomfortable."  
Don't measure yourself by what others think, cuz  we know everyone can't be right, so choose those that bring out the best in you as being right.  
"I began to feel better when I stopped judging myself through other peoples eyes"   -  Sally Fields (i believe) who suffered with depression. 
Feel better, 
Rancher