Okay, I am correcting this for how it would be written / said in American English.

Dentistry Day

As I do every day, today I went to work to at the University Hospital (or at the hospital on campus). I'm studying as to be a dentist but we already do a lot of clinical training as part of our course work. My today's patient today was a twelve years old twelve-year-old (the word needs hyphens when it is used as an adjective) girl who had have a deep decay in one of her upper molars. The tooth needed endodontic treatment, and although the tooth was already dead, she complainted of imaginary pain. So We tried to anesthetize her but she was crying because of needle'e fear she was afraid of needles. After 30 minutes passed and she was still crying; eventually the physician arrived and calmed the girl. After she was anestethized, we worked very well had no other issues (you could say "problems" instead of "issues" here too) and we saved her decayed tooth.