I recommend Seoul Yeonchi Dental Clinic in Sangnam-dong.

I've been going to Seoul Yeon Dental Clinic for orthodontic treatment for two years. The dentists are very thorough and attentive. The nurses are also very attentive and patient, making sure my teeth are comfortable.

I even went to get my impacted wisdom tooth extracted, and they did a great job! The price is about average for a typical dental clinic. ^^ I think it's worth a visit~