I went for a scaling of my teeth last week.
I heavily rely on Google ratings when I visit somewhere in Japan, whether they are clinics, restaurants, cafes, etc. Of course, how one finds a place would differ based on their own experiences. But as a foreigner, Google ratings is a helpful indicator that saves unnecessary time & costs as it is highly likely you would experience a satisfactory service at a place with a high rating.
So, as I searched for a good dentist, I found this place had a good rating with genuine recommendations from visitors. I decided to check the place out and it turns out the dentist was extremely informative and friendly. She thoroughly checked my teeth one by one and then scaling, followed by polishing. Some purple liquid was then applied to my teeth all over to check how thoroughly I am brushing my teeth. The dentist explained not only the benefit of flossing but what happens if we do not floss, the correct flossing technique and how to use interdental flossing. She also mentioned how using mouthwash is a great addition to daily dental routine, as the majority of our mouth is in fact the mucosal layer.
I was impressed by how she was extremely caring about her customers, wanting them to have the best dental and oral health possible.
For anyone looking for a good dentist near Shinjuku, below is the Google map link to the dentist I went to. It is right outside Hatsudai Station, and about 20 min walk from the Shinjuku Station.