A. If you like a big names you can call it dentine hypersensitivity. It can, as you know, be very painfull. The orange paste may be a fluoride varnish which creates a dense surface layer of tooth that insulates you from cold etc. You can help the process by cleaning the tooth gently but thoroughly. Too hard will remove the dense surface that the dentist is trying to build up, too little will leave plaque that dissolves the surface, so its a balance. Also avoid acidic things like fruit / juice/ or fizzy drinks untill the problem improves. if you do have something acidic avoid brushing for an hour after to give the tooth time to “harden up”. Finally try leaving a thin smear of sensitive toothpaste on the teeth at night.
Rob