What should I do about cervical abrasion?

When I brushed my teeth, I experienced sensitivity, so I visited the dentist. It was diagnosed as cervical erosion, and I received a filling treatment, which helped reduce the sensitivity.

However, after some time, the covering quickly fell off.

There are no symptoms of this cold, but when I brush my teeth, I can see that the tooth roots are exposed.

Why is this happening even though I'm not brushing my teeth hard?

I don't know if there's any way other than covering it.

Even if you cover it, it will inevitably fall off quickly due to its position.