I recommend Hambak Smile Dental Clinic in Ilsan, Ilsan-dong.

You can tell just by looking at the teacher's resume in the photo, right?

The director, a graduate of Seoul National University College of Dentistry, personally provides treatment based on his extensive clinical experience. Opened in 2001, the practice has been in operation for 20 years. It has expanded and relocated once, but the facilities have improved since then.

The staff are all friendly and helpful. It's conveniently located right in front of Ilsan Station.