While still maintaining that scaling cannot abrade the enamel to expose the dentin, I would like to tell you that the possibility of vigorous toothbrushing was one of the options that I explained to you based on the description that you mentioned. All the suggestions are based on the description that you have mentioned without even having a single look at the clinical condition of the tooth or the X-ray of the tooth. The best thing would be to visit a dentist for a proper evaluation of the case and the objective treatment according to the diagnosis. And as a practical approach, if Dentin exposure has been clinically identified, more important than trying to figure out the cause of the same should be the action towards covering it up back so that you are relieved of your symptoms. Regards.