I recommend Seoul Barun Song Dental Clinic in Sipjeong-dong.

On weekdays, there's usually no wait even without a reservation, but on Saturdays, the waiting time is always longer, and even with a reservation, you'll have to wait at least 30 minutes. While the wait time is a drawback, the staff is very friendly and helpful.

There is no overtreatment, and treatment is given only to the areas that are necessary, and teeth that can be saved are saved as much as possible.
And they even printed out the cost estimate and provided it to me, and they meticulously checked to see if any insurance-related documentation was needed. Most dental treatments aren't covered, so I'm only able to cover a small portion of the out-of-pocket expenses, but they still provided the necessary documentation, which was really appreciated :)