It is pretty ironic that we can reach perfect oralhygiene with toothbrushing many times a day, but we can also traumatize our teeth with it. Surprising, but it is very difficult to learn the correct way of the teeth cleaning. The teeth are not going to be cleaner because of the increasing power of brushing.
As you can see on the picture, the pulp of the tooth is visible due to abrasion. Generally this causes painful inflamation of the pulp, and requires root canal treatment. But in this case the patient just felt sensitivity, so to prevent further complications I covered the pulp with medicine and did an aesthetic filling.